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Andersson, Mats
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Cros, O., Knutsson, H., Andersson, M., Pawels, E., Borga, M. & Gaihede, M. (2016). Determination of the mastoid surface area and volume based on micro-CT scanning of human temporal bone: Geometrical parameters dependence on scanning resolutions. Hearing Research, 340, 127-134
Öppna denna publikation i ny flik eller fönster >>Determination of the mastoid surface area and volume based on micro-CT scanning of human temporal bone: Geometrical parameters dependence on scanning resolutions
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2016 (Engelska)Ingår i: Hearing Research, ISSN 0378-5955, E-ISSN 1878-5891, Vol. 340, s. 127-134Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The mastoid air cell system (MACS) with its large complex of interconnected air cells reflects an enhanced surface area (SA) relative to its volume (V), which may indicate that the MACS is adapted to gas exchange and has a potential role in middle ear pressure regulation. Thus, these geometric parameters of the MACS have been studied by high resolution clinical CT scanning. However, the resolution of these scans is limited to a voxel size of around 0.6 mm in all dimensions, and so, the geometrical parameters are also limited. Small air cells may appear below the resolution and cannot be detected. Such air cells may contribute to a much higher SA than the V, and thus, also the SA/V ratio. More accurate parameters are important for analysis of the function of the MACS including physiological modeling.

Our aim was to determine the SA, V, and SA/V ratio in MACS in human temporal bones at highest resolution by using micro-CT-scanning. Further, the influence of the resolution on these parameters was investigated by downsampling the data. Eight normally aerated temporal bones were scanned at the highest possible resolution (30-60 μm). The SA was determined using a triangular mesh fitted onto the segmented MACS. The V was determined by summing all the voxels containing air. Downsampling of the original data was applied four times by a factor of 2.

The mean SA was 194 cm2, the mean V was 9 cm3, and the mean SA/V amounted to 22 cm-1. Decreasing the resolution resulted in a non-linear decrement of SA and SA/V, whereas V was mainly independent of the resolution.

The current study found significantly higher SA and SA/V compared with previous studies using clinical CT scanning at lower resolutions. These findings indicate a separate role of the MACS compared with the tympanum, and the results are important for a more accurate modeling of the middle ear physiology.

Nyckelord
Mastoid air cells; medical imaging; micro-CT; surface area; volume
Nationell ämneskategori
Radiologi och bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-122176 (URN)10.1016/j.heares.2015.12.005 (DOI)000386417900016 ()
Tillgänglig från: 2015-10-23 Skapad: 2015-10-23 Senast uppdaterad: 2019-12-02Bibliografiskt granskad
Diczfalusy, E., Andersson, M. & Wårdell, K. (2015). A diffusion tensor-based finite element model of microdialysis in the deep brain. Computer Methods in Biomechanics and Biomedical Engineering, 18(2), 201-212
Öppna denna publikation i ny flik eller fönster >>A diffusion tensor-based finite element model of microdialysis in the deep brain
2015 (Engelska)Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, Vol. 18, nr 2, s. 201-212Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Microdialysis of the basal ganglia was recently used to study neurotransmitter levels in relation to deep brain stimulation. In order to estimate the anatomical origin of the obtained data, the maximum tissue volume of influence (TVImax) for a microdialysis catheter was simulated using the finite element method. This study investigates the impact of brain heterogeneity and anisotropy on the TVImax using diffusion tensor imaging (DTI) to create a second-order tensor model of the basal ganglia. Descriptive statistics showed that the maximum migration distance for neurotransmitters varied by up to 55% (n = 98,444) for DTI-based simulations compared with an isotropic reference model, and the anisotropy differed between different targets in accordance with theory. The size of the TVImax was relevant in relation to the size of the anatomical structures of interest, and local tissue properties should be accounted for when relating microdialysis data to their anatomical targets.

Ort, förlag, år, upplaga, sidor
Taylor & Francis, 2015
Nationell ämneskategori
Annan medicinteknik
Identifikatorer
urn:nbn:se:liu:diva-91886 (URN)10.1080/10255842.2013.789103 (DOI)000343606800011 ()23627319 (PubMedID)
Tillgänglig från: 2013-05-03 Skapad: 2013-05-03 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Wårdell, K., Kefalopoulou, Z., Diczfalusy, E., Andersson, M., Åström, M., Limousin, P., . . . Hariz, M. (2015). Deep Brain Stimulation of the Pallidum Internum for Gilles de la Tourette Syndrome: A Patient-Specific Model-Based Simulation Study of the Electric Field. Neuromodulation (Malden, Mass.) (2), 90-96
Öppna denna publikation i ny flik eller fönster >>Deep Brain Stimulation of the Pallidum Internum for Gilles de la Tourette Syndrome: A Patient-Specific Model-Based Simulation Study of the Electric Field
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2015 (Engelska)Ingår i: Neuromodulation (Malden, Mass.), ISSN 1094-7159, E-ISSN 1525-1403, nr 2, s. 90-96Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Objectives

The aim of this study was to investigate the deep brain stimulation (DBS) electric field distribution in proton-density MRI scans visualizing the globus pallidus internus (GPi) of patients with Gilles de la Tourette syndrome (GTS), along with its relation to the anatomy.

Methods

Patient-specific brain tissue models (n = 7) with bilateral DBS electrodes in the GPi were set up using the finite element method in five patients who had undergone stereotactic proton-density MRI-guided surgery and showed variable improvement with DBS. Simulations (n = 27) of the electric field were performed and the results visualized on the respective preoperative stereotactic MRI scans. The mean electric field volumes (n = 81) within the 0.1, 0.15, and 0.2 V/mm isosurfaces were calculated and compared with the anatomy.

Results

Visualization of the simulated electric field confirmed that the anteromedial limbic GPi was the main stimulated target for four of the patients and the posteromedial sensorimotor GPi for one. Larger volumes extended asymmetrically, with parts of fields stretching into the lamina between GPi and globus pallidus externus and into the internal capsule. There was a high correlation (r = 0.994, n = 54) between volumes and brain sides, but with a systematic shift toward the right side, especially for the larger volumes. Simulations with homogeneous tissue models showed no differences.

Conclusions

Patient-specific DBS electric field simulations in the GPi as visualized on proton-density MR scans can be implemented in patients with GTS. Visualization of electric fields together with stereotactic thin-slice MRI can provide further support when predicting anatomical structures possibly influenced by DBS in this complex disorder.

Ort, förlag, år, upplaga, sidor
John Wiley & Sons, 2015
Nyckelord
Deep brain stimulation, electric field simulation, globus pallidus internus, modeling and simulation, Tourette syndrome
Nationell ämneskategori
Medicinsk bioteknologi Medicinsk biovetenskap
Identifikatorer
urn:nbn:se:liu:diva-113589 (URN)10.1111/ner.12248 (DOI)000350461600004 ()25284508 (PubMedID)
Tillgänglig från: 2015-01-23 Skapad: 2015-01-23 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
Eklund, A., Nichols, T., Andersson, M. & Knutsson, H. (2015). Empirically Investigating the Statistical Validity of SPM, FSL and AFNI for Single Subject fMRI Analysis. In: 2015 IEEE 12th International Symposium on Biomedical Imaging (ISBI): . Paper presented at IEEE 12th International Symposium on Biomedical Imaging (pp. 1376-1380). IEEE conference proceedings
Öppna denna publikation i ny flik eller fönster >>Empirically Investigating the Statistical Validity of SPM, FSL and AFNI for Single Subject fMRI Analysis
2015 (Engelska)Ingår i: 2015 IEEE 12th International Symposium on Biomedical Imaging (ISBI), IEEE conference proceedings, 2015, s. 1376-1380Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

The software packages SPM, FSL and AFNI are the most widely used packages for the analysis of functional magnetic resonance imaging (fMRI) data. Despite this fact, the validity of the statistical methods has only been tested using simulated data. By analyzing resting state fMRI data (which should not contain specific forms of brain activity) from 396 healthy con- trols, we here show that all three software packages give in- flated false positive rates (4%-96% compared to the expected 5%). We isolate the sources of these problems and find that SPM mainly suffers from a too simple noise model, while FSL underestimates the spatial smoothness. These results highlight the need of validating the statistical methods being used for fMRI. 

Ort, förlag, år, upplaga, sidor
IEEE conference proceedings, 2015
Serie
IEEE International Symposium on Biomedical Imaging, ISSN 1945-7928
Nyckelord
fMRI, statistics, neuroimaging, random field theory
Nationell ämneskategori
Datavetenskap (datalogi) Sannolikhetsteori och statistik Signalbehandling
Identifikatorer
urn:nbn:se:liu:diva-119755 (URN)10.1109/ISBI.2015.7164132 (DOI)000380546000331 ()978-1-4799-2374-8 (ISBN)
Konferens
IEEE 12th International Symposium on Biomedical Imaging
Tillgänglig från: 2015-06-25 Skapad: 2015-06-25 Senast uppdaterad: 2018-01-11Bibliografiskt granskad
Sjölund, J., Forsberg, D., Andersson, M. & Knutsson, H. (2015). Generating patient specific pseudo-CT of the head from MR using atlas-based regression. Physics in Medicine and Biology, 60(2), 825-839
Öppna denna publikation i ny flik eller fönster >>Generating patient specific pseudo-CT of the head from MR using atlas-based regression
2015 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 60, nr 2, s. 825-839Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Radiotherapy planning and attenuation correction of PET images require simulation of radiation transport. The necessary physical properties are typically derived from computed tomography (CT) images, but in some cases, including stereotactic neurosurgery and combined PET/MR imaging, only magnetic resonance (MR) images are available. With these applications in mind, we describe how a realistic, patient-specific, pseudo-CT of the head can be derived from anatomical MR images. We refer to the method as atlas-based regression, because of its similarity to atlas-based segmentation. Given a target MR and an atlas database comprising MR and CT pairs, atlas-based regression works by registering each atlas MR to the target MR, applying the resulting displacement fields to the corresponding atlas CTs and, finally, fusing the deformed atlas CTs into a single pseudo-CT. We use a deformable registration algorithm known as the Morphon and augment it with a certainty mask that allows a tailoring of the influence certain regions are allowed to have on the registration. Moreover, we propose a novel method of fusion, wherein the collection of deformed CTs is iteratively registered to their joint mean and find that the resulting mean CT becomes more similar to the target CT. However, the voxelwise median provided even better results; at least as good as earlier work that required special MR imaging techniques. This makes atlas-based regression a good candidate for clinical use.

Nationell ämneskategori
Medicinsk bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-113297 (URN)10.1088/0031-9155/60/2/825 (DOI)000347675100023 ()25565133 (PubMedID)
Tillgänglig från: 2015-01-15 Skapad: 2015-01-15 Senast uppdaterad: 2018-01-16Bibliografiskt granskad
Johansson, G., Andersson, M. & Knutsson, H. (2015). Motion Field Regularization for Sliding Objects using Global Linear Optimization. In: : . Paper presented at The 4th International Conference on Pattern Recognition Applications and Methods, Januari 10-12, Lisbon, Portugal.
Öppna denna publikation i ny flik eller fönster >>Motion Field Regularization for Sliding Objects using Global Linear Optimization
2015 (Engelska)Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
Abstract [en]

In image registration it is often necessary to employ  regularization in one form or another to be able to find a plausible  displacement field. In medical applications, it is useful to define  different constraints for different areas of the data. For instance  to measure if organs have moved as expected after a finished  treatment. One common problem is how to find plausible motion  vectors far away from known motion. This paper introduces a new  method to build and solve a Global Linear Optimizations (GLO)  problem with a novel set of terms which enable specification of  border areas to allow a sliding motion. The GLO approach is  important especially because it allows simultaneous incorporation of  several different constraints using information from medical atlases  such as localization and properties of organs. The power and  validity of the method is demonstrated using two simple, but  relevant 2D test images. Conceptual comparisons with previous  methods are also made to highlight the contributions made in this  paper. The discussion explains important future work and experiments  as well as exciting future improvements to the GLO framework.

Nyckelord
Image Registration, Missing Data, Medical Image Processing, Global Linear Optimization
Nationell ämneskategori
Radiologi och bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-112210 (URN)
Konferens
The 4th International Conference on Pattern Recognition Applications and Methods, Januari 10-12, Lisbon, Portugal
Projekt
Dynamic Context Atlases for Image Denoising and Patient SafetyGlobal Linear Optimization
Forskningsfinansiär
Vetenskapsrådet, 2011-5176Linnaeus research environment CADICS
Tillgänglig från: 2014-11-18 Skapad: 2014-11-18 Senast uppdaterad: 2015-04-17Bibliografiskt granskad
Andersson, M., Burdakov, O., Knutsson, H. & Zikrin, S. (2015). Sparsity Optimization in Design of Multidimensional Filter Networks. Optimization and Engineering, 16(2), 259-277
Öppna denna publikation i ny flik eller fönster >>Sparsity Optimization in Design of Multidimensional Filter Networks
2015 (Engelska)Ingår i: Optimization and Engineering, ISSN 1389-4420, E-ISSN 1573-2924, Vol. 16, nr 2, s. 259-277Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Filter networks are used as a powerful tool used for reducing the image processing time and maintaining high image quality.They are composed of sparse sub-filters whose high sparsity ensures fast image processing.The filter network design is related to solvinga sparse optimization problem where a cardinality constraint bounds above the sparsity level.In the case of sequentially connected sub-filters, which is the simplest network structure of those considered in this paper, a cardinality-constrained multilinear least-squares (MLLS) problem is to be solved. Even when disregarding the cardinality constraint, the MLLS is typically a large-scale problem characterized by a large number of local minimizers, each of which is singular and non-isolated.The cardinality constraint makes the problem even more difficult to solve.

An approach for approximately solving the cardinality-constrained MLLS problem is presented.It is then applied to solving a bi-criteria optimization problem in which both thetime and quality of image processing are optimized. The developed approach is extended to designing filter networks of a more general structure. Its efficiency is demonstrated by designing certain 2D and 3D filter networks. It is also compared with the existing approaches.

Ort, förlag, år, upplaga, sidor
Springer, 2015
Nyckelord
Sparse optimization; Cardinality Constraint; Multicriteria Optimization; Multilinear Least-Squares Problem; Filter networks; Medical imaging
Nationell ämneskategori
Beräkningsmatematik
Identifikatorer
urn:nbn:se:liu:diva-115788 (URN)10.1007/s11081-015-9280-3 (DOI)000358253700001 ()
Tillgänglig från: 2015-03-19 Skapad: 2015-03-19 Senast uppdaterad: 2017-12-04Bibliografiskt granskad
Cros, O., Gaihede, M., Andersson, M. & Knutsson, H. (2015). Structural Analysis of Micro-channels in Human Temporal Bone. In: IEEE 12th International Symposium on Biomedical Imaging (ISBI), 2015 IEEE 12th International Symposium on: . Paper presented at IEEE 12th International Symposium on Biomedical Imaging (ISBI), 2015 IEEE 12th International Symposium on, 16-19 April, New York, USA (pp. 9-12). Institute of Electrical and Electronics Engineers (IEEE)
Öppna denna publikation i ny flik eller fönster >>Structural Analysis of Micro-channels in Human Temporal Bone
2015 (Engelska)Ingår i: IEEE 12th International Symposium on Biomedical Imaging (ISBI), 2015 IEEE 12th International Symposium on, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 9-12Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

Recently, numerous micro-channels have been discovered in the human temporal bone by micro-CT-scanning. Preliminary structure of these channels has suggested they contain a new separate blood supply for the mucosa of the mastoid air cells, which may have important functional implications. This paper proposes a structural analysis of the microchannels to corroborate this role. A local structure tensor is first estimated. The eigenvalues obtained from the estimated local structure tensor were then used to build probability maps representing planar, tubular, and isotropic tensor types. Each tensor type was assigned a respective RGB color and the full structure tensor was rendered along with the original data. Such structural analysis provides new and relevant information about the micro-channels but also their connections to mastoid air cells. Before carrying a future statistical analysis, a more accurate representation of the micro-channels in terms of local structure tensor analysis using adaptive filtering is needed.

Ort, förlag, år, upplaga, sidor
Institute of Electrical and Electronics Engineers (IEEE), 2015
Serie
IEEE International Symposium on Biomedical Imaging, ISSN 1945-7928
Nyckelord
Human temporal bone, mastoid, microchannels, quadrature filters, structure tensor, visualization
Nationell ämneskategori
Radiologi och bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-122177 (URN)10.1109/ISBI.2015.7163804 (DOI)000380546000003 ()978-1-4799-2374-8 (ISBN)
Konferens
IEEE 12th International Symposium on Biomedical Imaging (ISBI), 2015 IEEE 12th International Symposium on, 16-19 April, New York, USA
Tillgänglig från: 2015-10-23 Skapad: 2015-10-23 Senast uppdaterad: 2017-05-10Bibliografiskt granskad
Forsberg, D., Lundström, C., Andersson, M. & Knutsson, H. (2014). Eigenspine: Eigenvector Analysis of Spinal Deformities in Idiopathic Scoliosis. In: Jianhua Yao, Tobias Kinder and Shuo Li Shuo (Ed.), Jianhua Yao,Tobias Klinder, Shuo Li (Ed.), Computational Methods and Clinical Applications for Spine Imaging: Proceedings of the Workshop held at the 16th International Conference on Medical Image Computing and Computer Assisted Intervention, September 22-26, 2013, Nagoya, Japan. Paper presented at 16th International Conference on Medical Image Computing and Computer Assisted Intervention, September 22-26, 2013, Nagoya, Japan (pp. 123-134). Springer, 17
Öppna denna publikation i ny flik eller fönster >>Eigenspine: Eigenvector Analysis of Spinal Deformities in Idiopathic Scoliosis
2014 (Engelska)Ingår i: Computational Methods and Clinical Applications for Spine Imaging: Proceedings of the Workshop held at the 16th International Conference on Medical Image Computing and Computer Assisted Intervention, September 22-26, 2013, Nagoya, Japan / [ed] Jianhua Yao,Tobias Klinder, Shuo Li, Springer, 2014, Vol. 17, s. 123-134Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

In this paper, we propose the concept of eigenspine, a data analysis schemeuseful for quantifying the linear correlation between different measures relevant fordescribing spinal deformities associated with spinal diseases, such as idiopathic scoliosis.The proposed concept builds upon the use of principal component analysis(PCA) and canonical correlation analysis (CCA), where PCA is used to reduce thenumber of dimensions in the measurement space, thereby providing a regularizationof the measurements, and where CCA is used to determine the linear dependence betweenpair-wise combinations of the different measures. To demonstrate the usefulnessof the eigenspine concept, the measures describing position and rotation of thelumbar and the thoracic vertebrae of 22 patients suffering from idiopathic scoliosiswere analyzed. The analysis showed that the strongest linear relationship is foundbetween the anterior-posterior displacement and the sagittal rotation of the vertebrae,and that a somewhat weaker but still strong correlation is found between thelateral displacement and the frontal rotation of the vertebrae. These results are wellin-line with the general understanding of idiopathic scoliosis. Noteworthy though isthat the obtained results from the analysis further proposes axial vertebral rotationas a differentiating measure when characterizing idiopathic scoliosis. Apart fromanalyzing pair-wise linear correlations between different measures, the method isbelieved to be suitable for finding a maximally descriptive low-dimensional combinationof measures describing spinal deformities in idiopathic scoliosis.

Ort, förlag, år, upplaga, sidor
Springer, 2014
Serie
Lecture Notes in Computational Vision and Biomechanics, ISSN 2212-9391 ; 17
Nationell ämneskategori
Medicinsk bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-108975 (URN)10.1007/978-3-319-07269-2_11 (DOI)978-3-319-07268-5 (ISBN)978-3-319-07269-2 (ISBN)
Konferens
16th International Conference on Medical Image Computing and Computer Assisted Intervention, September 22-26, 2013, Nagoya, Japan
Forskningsfinansiär
Vetenskapsrådet, 2007-4786Stiftelsen för strategisk forskning (SSF), SM10-0022
Tillgänglig från: 2014-07-16 Skapad: 2014-07-16 Senast uppdaterad: 2015-06-04Bibliografiskt granskad
Forsberg, D., Lundström, C., Andersson, M. & Knutsson, H. (2014). Model-based registration for assessment of spinal deformities in idiopathic scoliosis. Physics in Medicine and Biology, 59(2), 311-326
Öppna denna publikation i ny flik eller fönster >>Model-based registration for assessment of spinal deformities in idiopathic scoliosis
2014 (Engelska)Ingår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 59, nr 2, s. 311-326Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Detailed analysis of spinal deformity is important within orthopaedic healthcare, in particular for assessment of idiopathic scoliosis. This paper addresses this challenge by proposing an image analysis method, capable of providing a full three-dimensional spine characterization. The proposed method is based on the registration of a highly detailed spine model to image data from computed tomography. The registration process provides an accurate segmentation of each individual vertebra and the ability to derive various measures describing the spinal deformity. The derived measures are estimated from landmarks attached to the spine model and transferred to the patient data according to the registration result. Evaluation of the method provides an average point-to-surface error of 0.9 mm ± 0.9 (comparing segmentations), and an average target registration error of 2.3 mm ± 1.7 (comparing landmarks). Comparing automatic and manual measurements of axial vertebral rotation provides a mean absolute difference of 2.5° ± 1.8, which is on a par with other computerized methods for assessing axial vertebral rotation. A significant advantage of our method, compared to other computerized methods for rotational measurements, is that it does not rely on vertebral symmetry for computing the rotational measures. The proposed method is fully automatic and computationally efficient, only requiring three to four minutes to process an entire image volume covering vertebrae L5 to T1. Given the use of landmarks, the method can be readily adapted to estimate other measures describing a spinal deformity by changing the set of employed landmarks. In addition, the method has the potential to be utilized for accurate segmentations of the vertebrae in routine computed tomography examinations, given the relatively low point-to-surface error.

Ort, förlag, år, upplaga, sidor
Institute of Physics and Engineering in Medicine, 2014
Nationell ämneskategori
Medicinsk bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-91233 (URN)10.1088/0031-9155/59/2/311 (DOI)000332842000005 ()
Forskningsfinansiär
Vetenskapsrådet, 2007-4786Stiftelsen för strategisk forskning (SSF), SM10-0022
Tillgänglig från: 2013-04-17 Skapad: 2013-04-17 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
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