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  • 101.
    Moreno, Rodrigo
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Generalizing the mean intercept length tensor for gray-level images2012In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, no 7, p. 4599-4612Article in journal (Refereed)
    Abstract [en]

    Purpose: The mean intercept length tensor is the most used technique to estimate microstructure orientation and anisotropy of trabecular bone. This paper proposes an efficient extension of this technique to gray-scale images based on a closed formulation of the mean intercept length tensor and a generalization using different angular convolution kernels.

    Methods: First, the extended Gaussian image is computed for the binary or gray-scale image. Second, the intercepts are computed for all possible orientations through an angular convolution with the half-cosine function. Finally, the tensor is computed by means of the covariance matrix. The complexity of the method is O(n + m) in contrast with O(nm) of traditional implementations, where n is the number of voxels in the image and m is the number of orientations used in the computations. The method is generalized by applying other angular convolution kernels instead of the half-cosine function. As a result, the anisotropy of the tensor can be controlled while keeping the eigenvectors intact.

    Results: The proposed extension to gray-scale yields accurate results for reliable computations of the extended Gaussian image and, unlike the traditional methodology, is not affected by artifacts generated by discretizations during the sampling of different orientations.

    Conclusions: Experiments show that the computations on both binary and gray-scale images are correlated, and that computations in gray-scale are more robust, enabling the use of the mean intercept length tensor to clinical examinations of trabecular bone. The use of kernels based on the von Mises-Fisher distribution is promising as the anisotropy can be adjusted with a parameter in order to improve its power to predict mechanical properties of trabecular bone.

  • 102.
    Moreno, Rodrigo
    et al.
    Linköping University, Department of Biomedical Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, The Institute of Technology. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Soft classification of trabeculae in trabecular bone2011In: Biomedical Imaging: From Nano to Macro, 2011, IEEE , 2011, p. 1641-1644Conference paper (Refereed)
    Abstract [en]

    Classification of trabecular bone aims at discriminating different types of trabeculae. This paper proposes a method to perform a soft classification from binary 3D images. In a first step, the local structure tensor is used to estimate a membership degree of every voxel to three different classes, plate-, rod- and junction-like trabeculae. In a second step, the global structure tensor of plate-like trabeculae is compared with the local orientation of rod-like trabeculae in order to discriminate aligned from non-aligned rods. Results show that soft classification can be used for estimating independent parameters of trabecular bone for every different class, by using the classification as a weighting function.

  • 103.
    Moreno, Rodrigo
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Techniques for Computing Fabric Tensors: A Review2014In: Visualization and Processing of Tensors and Higher Order Descriptors for Multi-Valued Data / [ed] Carl-Fredrik Westin, Anna Vilanova, Bernhard Burgeth, Springer Berlin/Heidelberg, 2014, p. 271-292Chapter in book (Refereed)
    Abstract [en]

    The aim of this chapter is to review different approaches that have been proposed to compute fabric tensors with emphasis on trabecular bone research. Fabric tensors aim at modeling through tensors both anisotropy and orientation of a material with respect to another one. Fabric tensors are widely used in fields such as trabecular bone research, mechanics of materials and geology. These tensors can be seen as semi-global measurements since they are computed in relatively large neighborhoods, which are assumed quasi-homogeneous. Many methods have been proposed to compute fabric tensors. We propose to classify fabric tensors into two categories: mechanics-based and morphology-based. The former computes fabric tensors from mechanical simulations, while the latter computes them by analyzing the morphology of the materials. In addition to pointing out advantages and drawbacks for each method, current trends and challenges in this field are also summarized.

  • 104.
    Moreno, Rodrigo
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). KTH Royal Institute of Technology.
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Medicine and Health Sciences. KTH Royal Institute of Technology.
    Gradient-Based Enhancement of Tubular Structures in Medical Images2015In: Medical Image Analysis, ISSN 1361-8415, E-ISSN 1361-8423, Vol. 26, no 1, p. 19-29Article in journal (Refereed)
    Abstract [en]

    Vesselness filters aim at enhancing tubular structures in medical images. The most popular vesselness filters are based on eigenanalyses of the Hessian matrix computed at different scales. However, Hessian-based methods have well-known limitations, most of them related to the use of second order derivatives. In this paper, we propose an alternative strategy in which ring-like patterns are sought in the local orientation distribution of the gradient. The method takes advantage of symmetry properties of ring-like patterns in the spherical harmonics domain. For bright vessels, gradients not pointing towards the center are filtered out from every local neighborhood in a first step. The opposite criterion is used for dark vessels. Afterwards, structuredness, evenness and uniformness measurements are computed from the power spectrum in spherical harmonics of both the original and the half-zeroed orientation distribution of the gradient. Finally, the features are combined into a single vesselness measurement. Alternatively, a structure tensor that is suitable for vesselness can be estimated before the analysis in spherical harmonics. The two proposed methods are called Ring Pattern Detector (RPD) and Filtered Structure Tensor (FST) respectively. Experimental results with computed tomography angiography data show that the proposed filters perform better compared to the state-of-the-art.

  • 105.
    Moreno, Rodrigo
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Volume-Based Fabric Tensors through Lattice-Boltzmann Simulations2014Conference paper (Refereed)
    Abstract [en]

    This paper introduces a new methodology to compute fabric tensors from computational fluid dynamics simulations performed through the lattice-Boltzmann method. Trabecular bone is modeled as a pipeline where a synthetic viscous fluid can flow from a single source located at the center of a spherical region of interest toward its boundaries. Two fabric tensors are computed from local velocities at the steady state estimated from the simulations, a tortuosity and a normalized tortuosity tensor.The main advantage of the proposed fabric tensors is that, unlike previous approaches, they intentionally disregard the trabecular termini in the computations, which do not play an important role in the estimation of trabecular bone quality. Thus, the proposed fabric tensors are less prone than previously proposed ones to unnecessary reductions of anisotropy related to the the presence of trabecular termini. The results of experiments conducted on synthetic and micro-computed tomography data in 2D and 3D show the artificial fluid flowing inside the trabecular bone has negligible velocities at trabecular termini, reducing in that way their influence in the estimation of the proposed fabric tensors.

  • 106.
    Moreno, Rodrigo
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping.
    Borga, Magnus
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    On the Efficiency of the Mean Intercept Length Tensor2011Conference paper (Other academic)
    Abstract [en]

    The Mean Intercept Length tensor is one of the most used techniques to estimate microstructure orientation and anisotropy of materials from 2D or 3D binary images. This paper proposes an efficient implementation of this technique. First, the Extended Gaussian Image is computed for the binary image. Second, the intercepts are computed for all possible orientations through an angular convolution. Finally, the tensor is computed by means of the covariance matrix. The complexity of the method is O(n+m) in contrast with O(nm) of traditional implementations, where n is the number of voxels in the image and m is the number of orientations used in the computations.

  • 107.
    Moreno, Rodrigo
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Wang, Chunliang
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Vessel Wall Segmentation Using Implicit Models and  Total Curvature Penalizers2013In: IMAGE ANALYSIS, SCIA 2013: 18TH SCANDINAVIAN CONFERENCE, Springer Berlin/Heidelberg, 2013, p. 299-308Conference paper (Refereed)
    Abstract [en]

    This book constitutes the refereed proceedings of the 18th Scandinavian Conference on Image Analysis, SCIA 2013, held in Espoo, Finland, in June 2013. The 67 revised full papers presented were carefully reviewed and selected from 132 submissions. The papers are organized in topical sections on feature extraction and segmentation, pattern recognition and machine learning, medical and biomedical image analysis, faces and gestures, object and scene recognition, matching, registration, and alignment, 3D vision, color and multispectral image analysis, motion analysis, systems and applications, human-centered computing, and video and multimedia analysis.

  • 108.
    Nilsson, Sven
    et al.
    Uppsala.
    Bergstrand, Lott
    Stockholm.
    Erikson, Uno
    Uppsala.
    Johansson, Jan
    Stockholm.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Walldius, Göran
    Astra-Zeneca .
    Allergic reactions at repeat femoral angiography with ioxaglate.2001In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 42, p. 608-611Article in journal (Refereed)
  • 109. Nilsson, Sven
    et al.
    Bergstrand, Lott
    Erikson, Uno
    Johansson, Jan
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Walldius, Göran
    Allergic reactions at repeat femoral angiography with ioxaglate2000In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 42, p. 608-611Article in journal (Refereed)
  • 110. Nilsson, Sven
    et al.
    Eriksson, Barbro
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Kvantifiering av levermetastaser med datortomografisk arbetsstation2001In: Medicinska Riksstämman i Stockholm/Älvsjö,2001, 2001, p. 253-253Conference paper (Refereed)
  • 111.
    Norén, Bengt
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Prospective Evaluation of a Novel Quantification Method for the Discrimination of Mild and Severe Hepatic Fibrosis Using Gd-EOB-DTPA2012Conference paper (Other academic)
  • 112.
    Norén, Bengt
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Ekstedt, Mattias
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Franzén, Lennart
    Medilab, Täby, Sweden.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Separation of advanced from mild fibrosis in diffuse liver disease using 31P magnetic resonance spectroscopy2008In: European Journal of Radiology, ISSN 0720-048X, E-ISSN 1872-7727, Vol. 66, no 2, p. 313-320Article in journal (Refereed)
    Abstract [en]

    31P-MRS using DRESS was used to compare absolute liver metabolite concentrations (PME, Pi, PDE, γATP, αATP, βATP) in two distinct groups of patients with chronic diffuse liver disorders, one group with steatosis (NAFLD) and none to moderate inflammation (n = 13), and one group with severe fibrosis or cirrhosis (n = 16). All patients underwent liver biopsy and extensive biochemical evaluation. A control group (n = 13) was also included. Absolute concentrations and the anabolic charge, AC = {PME}/({PME} + {PDE}), were calculated.

    Comparing the control and cirrhosis groups, lower concentrations of PDE (p = 0.025) and a higher AC (p < 0.001) were found in the cirrhosis group. Also compared to the NAFLD group, the cirrhosis group had lower concentrations of PDE (p = 0.01) and a higher AC (p = 0.009). No significant differences were found between the control and NAFLD group. When the MRS findings were related to the fibrosis stage obtained at biopsy, there were significant differences in PDE between stage F0–1 and stage F4 and in AC between stage F0–1 and stage F2–3.

    Using a PDE concentration of 10.5 mM as a cut-off value to discriminate between mild, F0–2, and advanced, F3–4, fibrosis the sensitivity and specificity were 81% and 69%, respectively. An AC cut-off value of 0.27 showed a sensitivity of 93% and a specificity of 54%.

    In conclusion, the results suggest that PDE is a marker of liver fibrosis, and that AC is a potentially clinically useful parameter in discriminating mild fibrosis from advanced.

  • 113.
    Norén, Bengt
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Gastroentorology.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Gastroentorology.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Visual assessment of biliary excretion of Gd-EOB-DTPA in patients with suspected diffuse liver disease – a biopsy-controlled prospective study2015In: European Journal of Radiology Open, ISSN 2352-0477, Vol. 2, p. 19-25Article in journal (Refereed)
    Abstract [en]

    Objectives: To qualitatively evaluate late dynamic contrast phases, 10, 20 and 30 min, after administration of Gd-EOB-DTPA with regard to biliary excretion in patients presenting with elevated liver enzymes without any clinical signs of cirrhosis or hepatic decompensation and to compare the visual assessment of contrast agent excretion with histo-pathological fibrosis stage, contrast uptake parameters and blood tests.

    Methods: 29 patients were prospectively examined using 1.5-T MRI. The visually assessed presence (1) or absence (0) of contrast agent for each of five anatomical regions in randomly reviewed time-series was summarised on a four grade scale. The scores, including a total visual score, were related to the histo-pathological findings, the quantitative contrast agent uptake parameters and blood tests

    Results: No relationship between the fibrosis grade or contrast uptake parameters expressed as KHep or LSC_N could be established. A negative correlation between the visual assessment and ALP was found. Comparing a sub-group of cholestatic patients with fibrosis score and Gd-EOB-DTPAdynamic parameters did not add any additional significant correlation.

    Conclusions: In this prospective study with a limited number of patients we were not able to demonstrate a correlation between visually assessed biliary excretion of Gd-EOB-DTPA and  histo-pathological or contrast uptake parameters.

  • 114.
    Norén, Bengt
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Separation of advanced from mild hepatic fibrosis by quantification of the hepatobiliary uptake of Gd-EOB-DTPA2012Conference paper (Other academic)
  • 115.
    Norén, Bengt
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Quantification of the hepatobiliary uptake of Gd-EOB-DTPA can separate advanced from mild fibrosis2012Conference paper (Other academic)
  • 116.
    Norén, Bengt
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Forsgren, Mikael Fredrik
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Romu, Thobias
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Gastroentorology.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Gastroentorology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Separation of advanced from mild hepatic fibrosis by quantification of the hepatobiliary uptake of Gd-EOB-DTPA2013In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 23, no 1, p. 174-181Article in journal (Refereed)
    Abstract [en]

    Objectives

    To apply dynamic contrast-enhanced (DCE) MRI on patients presenting with elevated liver enzymes without clinical signs of hepatic decompensation in order to quantitatively compare the hepatocyte-specific uptake of Gd-EOB-DTPA with histopathological fibrosis stage.

    Methods

    A total of 38 patients were prospectively examined using 1.5-T MRI. Data were acquired from regions of interest in the liver and spleen by using time series of single-breath-hold symmetrically sampled two-point Dixon 3D images (non-enhanced, arterial and venous portal phase; 3, 10, 20 and 30 min) following a bolus injection of Gd-EOB-DTPA (0.025 mmol/kg). The signal intensity (SI) values were reconstructed using a phase-sensitive technique and normalised using multiscale adaptive normalising averaging (MANA). Liver-to-spleen contrast ratios (LSC_N) and the contrast uptake rate (KHep) were calculated. Liver biopsy was performed and classified according to the Batts and Ludwig system.

    Results

    Area under the receiver-operating characteristic curve (AUROC) values of 0.71, 0.80 and 0.78, respectively, were found for KHep, LSC_N10 and LSC_N20 with regard to severe versus mild fibrosis. Significant group differences were found for KHep (borderline), LSC_N10 and LSC_N20.

    Conclusions

    Liver fibrosis stage strongly influences the hepatocyte-specific uptake of Gd-EOB-DTPA. Potentially the normalisation technique and KHep will reduce patient and system bias, yielding a robust approach to non-invasive liver function determination.

  • 117.
    Norén, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Lundberg, Peter
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ressner, Marcus
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Wirell, Staffan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology.
    Almer, Sven
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Molecular and Clinical Medicine, Gastroenterology and Hepatology. Östergötlands Läns Landsting, Centre for Medicine, Department of Endocrinology and Gastroenterology UHL.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Absolute quantification of human liver metabolite concentrations by localized in vivo 31P NMR spectroscopy in diffuse liver disease2005In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 15, no 1, p. 148-157Article in journal (Refereed)
    Abstract [en]

    Phosphorus-31 NMR spectroscopy using slice selection (DRESS) was used to investigate the absolute concentrations of metabolites in the human liver. Absolute concentrations provide more specific biochemical information compared to spectrum integral ratios. Nine patients with histopathologically proven diffuse liver disease and 12 healthy individuals were examined in a 1.5-T MR scanner (GE Signa LX Echospeed plus). The metabolite concentration quantification procedures included: (1) determination of optimal depth for the in vivo measurements, (2) mapping the detection coil characteristics, (3) calculation of selected slice and liver volume ratios using simple segmentation procedures and (4) spectral analysis in the time domain. The patients had significantly lower concentrations of phosphodiesters (PDE), 6.3±3.9 mM, and ATP-β, 3.6±1.1 mM, (P<0.05) compared with the control group (10.0±4.2 mM and 4.2±0.3 mM, respectively). The concentrations of phosphomonoesters (PME) were higher in the patient group, although this was not significant. Constructing an anabolic charge (AC) based on absolute concentrations, [PME]/([PME] + [PDE]), the patients had a significantly larger AC than the control subjects, 0.29 vs. 0.16 (P<0.005). Absolute concentration measurements of phosphorus metabolites in the liver are feasible using a slice selective sequence, and the technique demonstrates significant differences between patients and healthy subjects.

  • 118.
    Norén, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Morales, Olallo
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Renhet och kontrastbeslag - jämförelse mellan två tarmrengöringsmetoder vid colonröntgen2001In: Medicinska Riksstämman i Stockholm/Älvsjö,2001, 2001, p. 254-254Conference paper (Refereed)
  • 119.
    Norén, Bengt
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Ressner, Marcus
    Linköping University, The Institute of Technology. Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Lundberg, Peter
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Quantification of liver metabolites with phosphorus-31 Magnetic Resonance Spectroscopy2002In: European Congress of Radiology March 1-5, 2002,2002, 2002, p. 353-353Conference paper (Refereed)
  • 120. Nyström, Ingela
    et al.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    A New presentation method for magnetic resonance angiography images based on skeletonization2000In: Proceedings of SPIE jfr 1998-2000 SPIE proceedings ISSN 1017-2653, ISSN 1605-7422, Vol. 3976, p. 515-522Article in journal (Refereed)
  • 121. Nyström, Ingela
    et al.
    Smedby, Örjan
    Linköping University, Department of Medicine and Care, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Analysis of magnetic resonance angiography images using skeletonization and distance tranforms.2000In: Discrete mathematics and theoretical computer science (Online), ISSN 1462-7264, E-ISSN 1365-8050, Vol. 55, p. 75-89Article in journal (Refereed)
  • 122.
    Nyström, Ingela
    et al.
    Uppsala University, Sweden.
    Smedby, Örjan
    Linköping University, Department of Medicine and Care, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Analysis of magnetic resonance angiography images using skeletonization and distance transforms2000In: Discrete Mathematical Problems with Medical Applications / [ed] Ding-Zhu Du, Panos M. Pardalos and Jie Wang, American Mathematical Society (AMS), 2000, p. 75-89Conference paper (Refereed)
    Abstract [en]

    Magnetic resonance angiography (MRA) is increasingly performed as a non-invasive method of evaluating patients with suspected vascular disease. In this study we have used images of the arteries of the pelvis obtained after intravenous injection of paramagnetic contrast material, i.e., gadolinium chelates, for arterial enhancement. These images are fairly easy to segment. When interpreting and analysing MRA images, the 3D tree structure and the thickness of the blood vessels are of interest. This shape information may be easier to obtain from the "skeleton" of the blood vessels.

    The following image processing steps were performed in the analysis of the blood vessels: resampling the image to cubic voxels, segmentation of the blood vessels from the background through grey-level thresholding and morphological smoothing operations, distance transformation, skeletonization, skeleton pruning (and straightening of zig-zag parts), and finally quantitative (and qualitative) skeleton analysis.

    Skeletonization of digital volume objects is either a reduction to a 2D structure consisting of 3D surfaces and curves, or a reduction to a 1D structure consisting of 3D curves only. Thin elongated objects, e.g., blood vessels, are well suited for reduction to curve skeletons. Our skeletonization method first reduces the object to a surface skeleton from which the original object can be recovered. Secondly, the surface skeleton is reduced to a curve skeleton. The topology (i.e., number of components, tunnels, and cavities) and the shape of the object are preserved. The skeletonization is based on a small number of simple local neighbourhood operations, which makes it fairly time efficient. The skeletal voxels are labelled with their (D6) distance to the original background, which in this case conveys information about the local width of the object. Positions for possible artery stenoses may be identified by locating local distance minima in our curve skeletons, which will be investigated further.

    Future work will also be directed towards achieving more rotation and noise independent skeletons. We will also develop more "intelligent" and shape preserving pruning methods.

  • 123.
    Nyström, Ingela
    et al.
    Uppsala.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Skeletonization of volumetric vascular images - distance information utilized for visualization2001In: Journal of combinatorial optimization, ISSN 1382-6905, E-ISSN 1573-2886, Vol. 5, p. 27-41Article in journal (Refereed)
  • 124.
    Persson, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Brismar, Torkel
    Karolinska Institutet, CLINTEC, Röntgenavdelningen, Karolinska Universitetssjukhuset Huddinge.
    Lundström, Claes
    Linköping University, Department of Science and Technology, Visual Information Technology and Applications (VITA). Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Othberg, Fredrik
    Linköping University, Department of Biomedical Engineering, Center for Medical Image Science and Visualization. Linköping University, Faculty of Health Sciences.
    Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta2006In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 47, no 2, p. 172-178Article in journal (Refereed)
    Abstract [en]

    Purpose: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets.

    Material and Methods: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA.

    Results: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA).

    Conclusion: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.

  • 125.
    Persson, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Department of Radiology, Hudiksvall Hospital, Sweden.
    Engellau, Lena
    Department of Radiology, Lund University, Malmö University Hospital.
    Larsson, Elna-Marie
    Department of Radiology, Lund University Hospital.
    Brismar, Torkel B.
    Center for Surgical Sciences, Division of Radiology, Karolinska Institutet, Stockholm.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Volume rendering compared with maximum intensity projection for magnetic resonance angiography measurements of the abdominal aorta2004In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 45, no 4, p. 453-459Article in journal (Refereed)
    Abstract [en]

    Purpose: To compare the volume rendering technique (VRT) with maximum intensity projection (MIP) for aortic diameter measurements in MR angiography (MRA) data sets.

    Material and Methods: Existing contrast-enhanced 3-dimensional MRA and digital subtraction angiography (DSA) data sets from 20 patients were analyzed. In each MRA data set, two aortic diameters were measured using MIP and VRT. Agreement with DSA measurements, dependence on rendering parameters, and interobserver agreement were assessed.

    Results: Diameters measured on MIP with fixed parameters showed no significant difference compared with DSA and with freely selected parameters a slight overestimation relative to DSA. Diameters measured on VRT were larger than on DSA. For both MIP and VRT, the measurements depended on the chosen parameters. The error relative to DSA was larger for VRT than for MIP with fixed parameters but not with freely chosen parameters. Interobserver agreement did not differ significantly.

    Conclusions: VRT is not suitable for diameter measurements of the abdominal aorta with fixed parameter settings but may be useful with user-selected settings.

  • 126.
    Persson, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping. Linköping University, Department of Medicine and Care, Medical Radiology.
    Dahlström, Nils
    Department of Radiology, Hudiksvall Hospital, Sweden .
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Brismar, T. B.
    Division of Radiology, Karolinska Institutet, Sweden .
    Three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective analysis of feasibility and adverse reaction to contrast material2006In: BMC Medical Imaging, ISSN 1471-2342, E-ISSN 1471-2342, Vol. 6, no 1Article in journal (Refereed)
    Abstract [en]

    Background

    Computed Tomography Cholangiography (CTC) is a fast and widely available alternative technique to visualise hepatobiliary disease in patients with an inconclusive ultrasound when MRI cannot be performed. The method has previously been relatively unknown and sparsely used, due to concerns about adverse reactions and about image quality in patients with impaired hepatic function and thus reduced contrast excretion. In this retrospective study, the feasibility and the frequency of adverse reactions of CTC when using a drip infusion scheme based on bilirubin levels were evaluated.

    Methods

    The medical records of patients who had undergone upper abdominal spiral CT with subsequent three-dimensional rendering of the biliary tract by means of CTC during seven years were retrospectively reviewed regarding serum bilirubin concentration, adverse reaction and presence of visible contrast media in the bile ducts at CT examination. In total, 153 consecutive examinations in 142 patients were reviewed.

    Results

    Contrast media was observed in the bile ducts at 144 examinations. In 110 examinations, the infusion time had been recorded in the medical records. Among these, 42 examinations had an elevated bilirubin value (>19 umol/L). There were nine patients without contrast excretion; 3 of which had a normal bilirubin value and 6 had an elevated value (25–133 umol/L). Two of the 153 examinations were inconclusive. One subject (0.7%) experienced a minor adverse reaction – a pricking sensation in the face. No other adverse effects were noted.

    Conclusion

    We conclude that drip infusion CTC with an infusion rate of the biliary contrast agent iotroxate governed by the serum bilirubin value is a feasible and safe alternative to MRC in patients with and without impaired biliary excretion.

    In this retrospective study the feasibility and the frequency of adverse reactions when using a drip infusion scheme based on bilirubin levels has been evaluated.

  • 127.
    Persson, Anders
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Dahlström, Nils
    Linköping University, Department of Medicine and Care. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Brismar, T B
    Lundström, C
    Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Automatic parameter setting for volume rendering of MR angiography2005In: Radiological Society of North America Scientific Assembly and Annual Meeting,2005, 2005Conference paper (Other academic)
  • 128.
    Persson, Anders
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Dahlström, Nils
    Department of Radiology, Hudiksvall Hospital, Sweden.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Brismar, T.B.
    Department of Radiology, Karolinska University Hospital, Huddinge, Stockholm, Sweden .
    Volume rendering of three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective study2005In: British Journal of Radiology, ISSN 0007-1285, E-ISSN 1748-880X, Vol. 78, no 936, p. 1078-1085Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to evaluate the diagnostic potential of prolonged drip infusion CT cholangiography (DIC-CT) using meglumine iotroxate (Biliscopin®) and 3D volume rendering in patients with suspected obstructive biliary disease. From a material of 142 patients who had undergone a drip infusion CT, all cases with a verified surgical or endoscopic retrograde cholangiography (ERC) diagnosis (n=33) were selected. Age-matched controls were selected from the remaining examinations. Three radiologists reviewed all 66 examinations in retrospect, independently as well as in consensus. The image quality and the estimated diagnostic quality were rated as good or moderate in 91% of the 198 reviews. The consensus sensitivity and specificity for diagnosing biliary stones was 88% and 94%, respectively (with sensitivities ranging from 88% to 94% for individual observers, and specificities from 86% to 96%). Two out of three strictures were observed. No false positive strictures were described. The use of volume rendering technique (VRT) improved diagnostic certainty in 28/198 (14%) of the evaluations. The visualization of ductal stones was improved in 18/48 (38%). No differences in diagnostic quality between single and multislice CT were observed. We conclude that a detailed image of the biliary tree with good sensitivity and specificity can be obtained by means of bilirubin-governed infusion time DIC-CT with volume rendering reconstruction.

  • 129.
    Petersson, Helge
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Sinkvist, David
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Clinical and Experimental Medicine. Linköping University, Faculty of Health Sciences.
    Wang, Chunliang
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Web-based interactive 3D visualization as a tool for improved anatomy learning2009In: Anatomical sciences education, ISSN 1935-9772, Vol. 2, no 2, p. 61-68Article in journal (Refereed)
    Abstract [en]

    Despite a long tradition, conventional anatomy education based on dissection is declining. This study tested a new virtual reality (VR) technique for anatomy learning based on virtual contrast injection. The aim was to assess whether students value this new three-dimensional (3D) visualization method as a learning tool and what value they gain from its use in reaching their anatomical learning objectives. Several 3D vascular VR models were created using an interactive segmentation tool based on the "virtual contrast injection" method. This method allows users, with relative ease, to convert computer tomography or magnetic resonance images into vivid 3D VR movies using the OsiriX software equipped with the CMIV CTA plug-in. Once created using the segmentation tool, the image series were exported in Quick Time Virtual Reality (QTVR) format and integrated within a web framework of the Educational Virtual Anatomy (EVA) program. A total of nine QTVR movies were produced encompassing most of the major arteries of the body. These movies were supplemented with associated information, color keys, and notes. The results indicate that, in general, students' attitudes towards the EVA-program were positive when compared with anatomy textbooks, but results were not the same with dissections. Additionally, knowledge tests suggest a potentially beneficial effect on learning.

  • 130.
    Petersson, Joel
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Brismar, Torkel
    Department of Radiology, Karolinska University Hospital Huddinge, Sweden .
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medicine and Care. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Analysis of skeletal microstructure with clinical multislice CT2006In: Medical Image Computing and Computer-Assisted Intervention – MICCAI 2006: 9th International Conference, Copenhagen, Denmark, October 1-6, 2006. Proceedings, Part II / [ed] Rasmus Larsen, Mads Nielsen, Jon Sporring, Springer Berlin/Heidelberg, 2006, Vol. 4191, p. 880-887Conference paper (Refereed)
    Abstract [en]

    In view of the great effects of osteoporosis on public health, it would be of great value to be able to measure the three-dimensional structure of trabecular bone in vivo as a means to diagnose and quantify the disease. The aim of this work was to implement a method for quantitative characterisation of trabecular bone structure using clinical CT. Several previously described parameters have been calculated from volumes acquired with a 64-slice clinical scanner. Using automated region growing, distance transforms and three-dimensional thinning, measures describing the number, thickness and spacing of bone trabeculae was obtained. Fifteen bone biopsies were analysed. The results were evaluated using micro-CT as reference. For most parameters studied, the absolute values did not agree well with the reference method, but several parameters were closely correlated with the reference method. The shortcomings appear to be due to the low resolution and high noise level. However, the high correlation found between clinical CT and micro-CT measurements suggest that it might be possible to monitor changes in the trabecular structure in vivo.

  • 131.
    Ragnehed, Mattias
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Dahlqvist Leinhard, Olof
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Pihlsgård, Johan
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Sökjer, Hannibal
    Linköping University, Department of Computer and Information Science, MDI - Interaction and Service Design Research Group. Linköping University, The Institute of Technology.
    Fägerstam, Patrik
    Linköping University, Department of Medical and Health Sciences, Pharmacology. Linköping University, Faculty of Health Sciences.
    Jiang, Bo
    Linköping University, Department of Medical and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Visual Grading of 2D and 3D fMRI compared to image based descriptive measures2010In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 20, no 3, p. 714-724Article in journal (Refereed)
    Abstract [en]

    A prerequisite for successful clinical use of functional Magnetic Resonance Imaging (fMRI) is the selection of an appropriate imaging sequence. In this paper, 2D and 3D fMRI sequences were compared using different image quality assessment methods. Descriptive image measures, such as activation volume and temporal signal-to-noise ratio (TSNR), were compared with results from Visual Grading Characteristics (VGC) analysis of the fMRI results. It was found that significant differences in activation volume and TSNR were not directly reflected by differences in VGC scores. The results suggest that better performance on descriptive image measures is not always an indicator of improved diagnostic quality of the fMRI results. In conclusion, in addition to descriptive image measures, it is important to include measures of diagnostic quality when comparing different fMRI data acquisition methods.

  • 132.
    Ragnehed, Mattias
    et al.
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Linköping University, Faculty of Health Sciences.
    Philsgård, J
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Engström, Maria
    Linköping University, Department of Medicine and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medicine and Health Sciences, Radiation Physics. Linköping University, Department of Medicine and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics UHL. Östergötlands Läns Landsting, Centre for Diagnostics, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Using Visual Grading Characteristic for the evaluation of different fMRI data acquisition methods2008Conference paper (Other academic)
  • 133. Reisenfeld, V.
    et al.
    Ahlström, H.
    Jacobsson, G.
    Elvin, A.
    Karlsson, BM.
    Lindgren, PG.
    Löfberg, AM.
    Smedby, Örjan
    Uppsala University.
    Rastad, J.
    Comparison of Angiography, Sonography and Magnetic Resonance Angiography in the Evaluation of the Portal Venous System in Pancreatic Carcinoma1995Conference paper (Other academic)
  • 134.
    Romu, Thobias
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, The Institute of Technology.
    Dahlqvist Leinhard, Olof
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Forsgren, Mikael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Almer, Sven
    Linköping University, Department of Clinical and Experimental Medicine, Gastroenterology and Hepatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Kechagias, Stergios
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Nyström, Fredrik
    Linköping University, Department of Medical and Health Sciences, Internal Medicine. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Endocrinology and Gastroenterology UHL.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Borga, Magnus
    Linköping University, Department of Biomedical Engineering, Medical Informatics. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, The Institute of Technology.
    Fat Water Classification of Symmetrically Sampled Two-Point Dixon Images Using Biased Partial Volume Effects2011In: Proceedings of the annual meeting of the International Society for Magnetic Resonance in Medicine (ISMRM 2011), 2011., 2011Conference paper (Refereed)
  • 135.
    Sandström, Per
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Surgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Surgery in Östergötland.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Dahlström, Nils
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Freij, Anna
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Kihlberg, Johan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Brismar, Torkel
    Karolinska University Hospital, Stockholm, Sweden .
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Radiology in Linköping.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Upptag i levern av kontrastmedlet Gd-EOB-DTPA påverkas kraftigt av leverfunktionen2009Conference paper (Other academic)
  • 136.
    Schaap, M.
    et al.
    Biomedical Imaging Group Rotterdam, The Netherlands.
    Metz, C.T.
    Biomedical Imaging Group Rotterdam, The Netherlands.
    van Walsum, T.
    Biomedical Imaging Group Rotterdam, The Netherlands.
    van der Giessen, A.G.
    Biomedical Imaging Group Rotterdam, The Netherlands.
    Weustink, A.C.
    Erasmus MC, Rotterdam, The Netherlands.
    Mollet, N.R.
    Erasmus MC, Rotterdam, The Netherlands.
    Bauer, C.
    Graz University of Technology, Austria.
    Bogunovic, H.
    Center for Computational Imaging and Simulation Technologies in Biomedicine (CISTIB), Barcelona, Spain.
    Castro, C.
    Universidad Politécnica de Madrid, Spain.
    Deng, X.
    Siemens Corporate Research, Princeton, NJ, USA.
    Dikici, E.
    University of Florida College of Medicine, Jacksonville, FL, USA.
    O'Donnell, T.
    Siemens Corporate Research, Princeton, NJ, USA.
    Frenay, M.
    Leiden University Medical Center, The Netherlands.
    Friman, O.
    MeVis Research, Bremen, Germany.
    Hoyos, M.H.
    Universidad de los Andes, Bogota, Colombia.
    Kitslaar, P.H.
    Leiden University Medical Center, The Netherlands.
    Krissian, K.
    University of Las Palmas of Gran Canaria, Spain.
    Kuhnel, C.
    MeVis Research, Bremen, Germany.
    Luengo-Oroz, M.A.
    Universidad Politécnica de Madrid, Spain.
    Orkisz, M.
    Université de Lyon, France.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping.
    Styner, M.
    University of North Carolina, Chapel Hill, NC, USA.
    Szymczak, A.
    Colorado School of Mines, Golden, CO, USA.
    Tek, H.
    Siemens Corporate Research, Princeton, NJ, USA.
    Wang, Chunliang
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Warfield, S.K.
    Childrens Hospital Boston, MA, USA.
    Zambal, S.
    VRVis Research Center for Virtual Reality and Visualization, Vienna, Austria.
    Zhang, Y.
    The Methodist Hospital Research Institute, Houston, TX, USA.
    Krestin, G.P.
    Erasmus MC, Rotterdam, The Netherlands.
    Niessen, W.J.
    Erasmus MC, Rotterdam, The Netherlands.
    Standardized evaluation methodology and reference database for evaluating coronary artery centerline extraction algorithms2009In: Medical Image Analysis, ISSN 1361-8415, E-ISSN 1361-8423, Vol. 13, no 5, p. 701-714Article in journal (Refereed)
    Abstract [en]

    Efficiently obtaining a reliable coronary artery centerline from computed tomography angiography data is relevant in clinical practice. Whereas numerous methods have been presented for this purpose, up to now no standardized evaluation methodology has been published to reliably evaluate and compare the performance of the existing or newly developed coronary artery centerline extraction algorithms. This paper describes a standardized evaluation methodology and reference database for the quantitative evaluation of coronary artery centerline extraction algorithms. The contribution of this work is fourfold: (1) a method is described to create a consensus centerline with multiple observers, (2) well-defined measures are presented for the evaluation of coronary artery centerline extraction algorithms, (3) a database containing 32 cardiac CTA datasets with corresponding reference standard is described and made available, and (4) 13 coronary artery centerline extraction algorithms, implemented by different research groups, are quantitatively evaluated and compared. The presented evaluation framework is made available to the medical imaging community for benchmarking existing or newly developed coronary centerline extraction algorithms.

  • 137.
    Silén, Charlotte
    et al.
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Wirell, Staffan
    Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Kvist, Joanna
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Health Sciences.
    Nylander, Eva
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Fyrénius, Anna
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Clinical Physiology.
    Smedby, Örjan
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping. Linköping University, Faculty of Health Sciences.
    Advanced 3D visualization in student-centred medical education2008In: Medical teacher, ISSN 0142-159X, E-ISSN 1466-187X, Vol. 30, no 5, p. e115-e124Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Healthcare students have difficulties achieving a conceptual understanding of 3D anatomy and misconceptions about physiological phenomena are persistent and hard to address. 3D visualization has improved the possibilities of facilitating understanding of complex phenomena. A project was carried out in which high quality 3D visualizations using high-resolution CT and MR images from clinical research were developed for educational use. Instead of standard stacks of slices (original or multiplanar reformatted) volume-rendering images in the quicktime VR format that enables students to interact intuitively were included. Based on learning theories underpinning problem based learning, 3D visualizations were implemented in the existing curricula of the medical and physiotherapy programs. The images/films were used in lectures, demonstrations and tutorial sessions. Self-study material was also developed. AIMS: To support learning efficacy by developing and using 3D datasets in regular health care curricula and enhancing the knowledge about possible educational value of 3D visualizations in learning anatomy and physiology. METHOD: Questionnaires were used to investigate the medical and physiotherapy students' opinions about the different formats of visualizations and their learning experiences. RESULTS: The 3D images/films stimulated the students will to understand more and helped them to get insights about biological variations and different organs size, space extent and relation to each other. The virtual dissections gave a clearer picture than ordinary dissections and the possibility to turn structures around was instructive. CONCLUSIONS: 3D visualizations based on authentic, viable material point out a new dimension of learning material in anatomy, physiology and probably also pathophysiology. It was successful to implement 3D images in already existing themes in the educational programs. The results show that deeper knowledge is required about students' interpretation of images/films in relation to learning outcomes. There is also a need for preparations and facilitation principles connected to the use of 3D visualizations.

  • 138.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University.
    A scanning system for digital analysis of cineangiography films1992In: Computer Methods and Programs in Biomedicine, ISSN 0169-2607, E-ISSN 1872-7565, Vol. 39, no 1-2, p. 103-111Article in journal (Refereed)
    Abstract [en]

    A system for scanning and digital analysis of cinefilms is presented and its performance is compared with entirely digital radiographic equipment. Apart from the difference between logarithmic and linear gray-scale representation, a higher noise level was found in the scanning system. When its spatial resolution was assessed visually, it was comparable to that of the digital system, although lower than when the cinefilming and scanning steps were evaluated separately. Algorithms for the correction of varying exposure and geometric ("pin-cushion") distortion are also presented. It is concluded that digital analysis after scanning of cinefilms can be a useful alternative to completely digital cineradiographic studies.

  • 139.
    Smedby, Örjan
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Angiography methods for Fluid Mechanical Studies1994Conference proceedings (editor) (Refereed)
  • 140.
    smedby, Örjan
    Linköping University, Department of Medical and Health Sciences. Linköping University, Faculty of Health Sciences.
    Cineangiography and arterial flow disturbances1992Conference proceedings (editor) (Refereed)
    Abstract [en]

    Disturbances in arterial flow are believed to influence the localization and development of atherosclerotic plaques. The femoral arteries of 26 patients were studied with cineangiography, after which the films were digitized and analyzed with an image analysis computer. The image sequence was converted to a set of time-intensity curves, from which time parameters were calculated, representing the arrival time of the contrast medium at each pixel. In the resulting parametric images, zones of delayed contrast filling (ZDF) were identified by an adaptive thresholding, which identifies lighter regions within the vessel, excluding the smallest ones. The ZDF, which have been shown, in a model study, to correspond to disturbed flow, were more frequent in the inner curvature than in the outer curvature of the curved vessels. Accordingly, they were more frequent along the lateral wall than along the medial wall of the artery. Several ZDF were also found in the vicinity of bifurcations. Most of the findings tally closely with fluid mechanical theory. In future studies, flow disturbances are to be correlated with the progression of atherosclerotic lesions.

  • 141.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University, Sweden.
    Do plaques grow upstream or downstream?: an angiographic study in the femoral artery.1997In: Arteriosclerosis, Thrombosis and Vascular Biology, ISSN 1079-5642, E-ISSN 1524-4636, Vol. 17, no 5, p. 912-918Article in journal (Refereed)
    Abstract [en]

    Although the distribution of atherosclerosis has been described, little is known about the direction of growth of plaques. In this study, 237 patients with slight or moderate atherosclerosis underwent femoral angiography twice at a 3-year interval, and the films were studied with computerized image analysis. First, atherosclerosis was measured as edge roughness, and the change in roughness of each 1-cm segment over the 3-year period was related to the edge roughness of the segments immediately upstream and downstream. On the medial side of the artery, the change in edge roughness was found to be more strongly related to the roughness values upstream than to those downstream of the segment studied. This suggests that growth in the downstream direction is more common than growth in the upstream direction. On the lateral side, more equivocal results were obtained. Atherosclerosis was also assessed by study of the cross-sectional area of the artery as a function of distance along the vessel. A mathematical model of plaque growth was formulated as a nonlinear filtering of this curve. Growth in the downstream direction was significantly (P<.001) more frequent than growth in the upstream direction. The findings are compatible with an atherogenic effect of fluid mechanical disturbances, such as flow separation, that may occur downstream of a stenosis.

  • 142.
    Smedby, Örjan
    Uppsala University.
    Fluid Mechanical Analysis by Radiological Methods1995In: Proceedings of the 4th International Conference on Physiological Fluid Dynamics / [ed] M Singh & VP Saxena, New Delhi: Narosa Publishing House, 1995, p. 101-108Conference paper (Refereed)
  • 143.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University, Sweden.
    Fluid Mechanical Factors in Atherogenesis1994In: Proceedings : 18th International Congress of Radiology: proceedings / [ed] Lenny Tan, Edwin Siew, Continental Press , 1994Conference paper (Refereed)
    Abstract [en]

    The purpose of this thesis is to investigate the feasibility of using angiographic methods to study, in vivo, fluid mechanical phenomena believed to influence the development and localization of atherosclerotic lesions, in particular, separated flow. This involved developing a method to recognize separated flow by digital analysis of cineangiography films, testing this method both with model measurements and in a clinical material, and a detailed analysis of certain methodological problems. In addition, methods have been developed to measure the tortuosity of arteries, a phenomenon which may, according to fluid mechanical theory, promote the occurrence of separated flow. In a glass model of an arterial bifurcation, a pump generated a pulsatile flow resembling that in large arteries. Using LDV (laser Doppler velocimetry) as a reference method, three velocity profiles in the symmetry plane of the model were recorded. During diastole, extensive separated flow was demonstrated in the larger branch of the bifurcation. The flow was then cineradiographed during injection of contrast medium, and the image sequence was transferred to an image analysis workstation. Treating the image sequence as a set of time-intensity curves, time parameters representing the arrival time of the contrast agent were computed. In the resulting parametric images, zones of delayed filling were identified and found to correspond to the separated flow. Viscosity was measured for seven radiographic contrast media and, as expected, the highest values were found for the largest molecules. For iohexol and ioxaglate, which were studied in detail, a linear relation to temperature and a quadratic relation to concentration were found. Whole-blood viscosity was measured for 5 healthy volunteers at high and low shear rates, before and after mixing with contrast agents in varying proportions. At low shear, viscosity decreased, while at high shear, it increased with increasing contrast concentration. The conclusion was that modern contrast media, despite their higher viscosity, seem to affect blood rheology less than older agents. In a study of the imaging characteristics of the digitization equipment for cinefilms, the resolution proved comparable to that of an entirely digital system, while the noise level was higher. Algorithms for the correction of variations in exposure and geometric distortion are also presented. The method for analysis of cinefilms, tried in the model study, was applied, with slight modifications, to a material of 26 patients with hyperlipidemia and slight or moderate atherosclerosis.(ABSTRACT TRUNCATED AT 400 WORDS)

  • 144.
    smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences.
    Fluid mechanices factores in atherogenesis1994Conference proceedings (editor) (Refereed)
  • 145.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University.
    Geometric risk factors for atherosclerosis in the aortic bifurcation: a digitized angiography study.1996In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 24, no 4, p. 481-488Article in journal (Refereed)
    Abstract [en]

    To clarify the relationship between arterial geometry and atherosclerosis at the aortic bifurcation, angiograms of 84 patients with slight or moderate atherosclerosis were studied by computerized image analysis. The degree of atherosclerosis involvement was assessed as angiographic edge roughness. The branching angles were found to be related to edge roughness of the left outer wall and the right side of the aorta. The position of the flow divider was related to edge roughness of the medial wall of the right common iliac and the right side of the aorta. For these two locations, there were also significant relationships to the area ratio, i.e., the ratio between cross-sectional areas distal and proximal to the bifurcations. On the basis of these findings, the concept of "geometric risk factors" for atherosclerosis and the potential influence of blood flow on atherogenesis are discussed.

  • 146.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University.
    Geometrical risk factors for atherosclerosis in the femoral artery: a longitudinal angiographic study.1998In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686, Vol. 26, no 3, p. 391-397Article in journal (Refereed)
    Abstract [en]

    In order to study the evolution of atherosclerosis in the superficial femoral artery in relation to local factors of vascular geometry, image processing of digitized angiograms was carried out in 237 hyperlipidemic patients before and after a three-year period of lipid-lowering treatment. The degree of atherosclerosis was measured as edge roughness, which was calculated separately for inner curves, outer curves, and straight segments and, in a subgroup of 110 patients, for segments with and without branches on either side of the artery. Initially, inner curves had significantly higher roughness values than outer curves, and outer curves higher than straight segments. After three years, there was an increase of borderline significance in the outer curves, and the difference between inner and outer curves was no longer significant. In several subpopulations, the increase in outer curve roughness was clearly significant. When branched and nonbranched segments were compared, the only significant difference was at the second examination where segments with a lateral branch had higher roughness of the medial edge than those without such a branch. It is concluded that curves are more likely than bifurcations to constitute a geometric risk factor for atherosclerosis, but it remains to explain the causal mechanism for this factor.

  • 147.
    Smedby, Örjan
    Uppsala Universitet.
    MR-angiografi1994Conference paper (Other academic)
  • 148.
    Smedby, Örjan
    Uppsala University.
    MR-angiografiteknik1996Conference paper (Other academic)
  • 149.
    Smedby, Örjan
    Uppsala University.
    Quantitation of atherosclerosis with MRI and image processing1996Conference paper (Other academic)
  • 150.
    Smedby, Örjan
    Department of Diagnostic Radiology, Uppsala University Hospital.
    Viscosity of some contemporary contrast media before and after mixing with whole blood.1992In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 33, no 6, p. 600-605Article in journal (Refereed)
    Abstract [en]

    The viscosity of 7 contrast media was measured using a rotational viscometer. When solutions with similar iodine concentrations were compared, the highest viscosities were found for the nonionic dimers iodixanol and iotrolan, the lowest for diatrizoate, iopamidol, and iopromide, and intermediate values for iohexol and ioxaglate. The viscosity of iohexol and ioxaglate was found to vary linearly with temperature and quadratically with concentration. Whole-blood viscosity was measured for 5 subjects at high and low shear rates before and after mixing with contrast media in various proportions. Low-shear viscosity was found to decrease and high-shear viscosity to increase with contrast medium concentration. It is concluded that the contrast media currently used may affect blood rheology less than previous agents, despite their higher viscosity.

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