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Kataria, B., Nilsson Althen, J., Smedy, Ö., Persson, A., Sökjer, H. & Sandborg, M. (2018). Assessment of image quality in abdominal CT: potential dose reduction with model-based iterative reconstruction. European Radiology
Open this publication in new window or tab >>Assessment of image quality in abdominal CT: potential dose reduction with model-based iterative reconstruction
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2018 (English)In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084Article in journal (Refereed) Epub ahead of print
Abstract [en]

Purpose To estimate potential dose reduction in abdominal CT by visually comparing images reconstructed with filtered back projection (FBP) and strengths of 3 and 5 of a specific MBIR.

Material and methods A dual-source scanner was used to obtain three data sets each for 50 recruited patients with 30, 70 and 100% tube loads (mean CTDIvol 1.9, 3.4 and 6.2 mGy). Six image criteria were assessed independently by five radiologists. Potential dose reduction was estimated with Visual Grading Regression (VGR).

Results Comparing 30 and 70% tube load, improved image quality was observed as a significant strong effect of log tube load and reconstruction method with potential dose reduction relative to FBP of 22–47% for MBIR strength 3 (p < 0.001). For MBIR strength 5 no dose reduction was possible for image criteria 1 (liver parenchyma), but dose reduction between 34 and 74% was achieved for other criteria. Interobserver reliability showed agreement of 71–76% (κw 0.201–0.286) and intra-observer reliability of 82–96% (κw 0.525–0.783).

Conclusion MBIR showed improved image quality compared to FBP with positive correlation between MBIR strength and increasing potential dose reduction for all but one image criterion.

Place, publisher, year, edition, pages
Heidelberg: Springer, 2018
Keyword
Dose Computed tomography Iterative reconstruction Abdomen FBP
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-145274 (URN)10.1007/s00330-017-5113-4 (DOI)29368163 (PubMedID)2-s2.0-85040915759 (Scopus ID)
Available from: 2018-02-20 Created: 2018-02-20 Last updated: 2018-03-09Bibliographically approved
Malusek, A., Sandborg, M. & Alm Carlsson, G. (2016). ACCURATE KAP METER CALIBRATION AS A PREREQUISITE FOR OPTIMISATION IN PROJECTION RADIOGRAPHY. Radiation Protection Dosimetry, 169(1-4), 353-359
Open this publication in new window or tab >>ACCURATE KAP METER CALIBRATION AS A PREREQUISITE FOR OPTIMISATION IN PROJECTION RADIOGRAPHY
2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 353-359Article in journal (Refereed) Published
Abstract [en]

Modern X-ray units register the air kerma–area product, PKA, with a built-in KAP meter. Some KAP meters show an energydependent bias comparable with the maximum uncertainty articulated by the IEC (25 %), adversely affecting dose-optimisation processes. To correct for the bias, a reference KAP meter calibrated at a standards laboratory and two calibration methods described here can be used to achieve an uncertainty of <7 % as recommended by IAEA. A computational model of the reference KAP meter is used to calculate beam quality correction factors for transfer of the calibration coefficient at the standards laboratory, Q0, to any beam quality, Q, in the clinic. Alternatively, beam quality corrections are measured with an energy-independent dosemeter via a reference beam quality in the clinic, Q1, to beam quality, Q. Biases up to 35 % of built-in KAP meter readings were noted. Energy-dependent calibration factors are needed for unbiased PKA. Accurate KAP meter calibration as a prerequisite for optimisation in projection radiography.

Place, publisher, year, edition, pages
Oxford University Press, 2016
National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-124662 (URN)10.1093/rpd/ncv524 (DOI)000383492100056 ()26743261 (PubMedID)
Note

Funding agencies: Swedish Radiation Safety Authority, SSM [SSM 2014-1204]

Available from: 2016-02-09 Created: 2016-02-09 Last updated: 2017-05-02Bibliographically approved
Tesselaar, E. & Sandborg, M. (2016). ASSESSING THE USEFULNESS OF THE QUASI-IDEAL OBSERVER FORQUALITY CONTROL IN FLUOROSCOPY. Radiation Protection Dosimetry, 169(1-4), 360-364
Open this publication in new window or tab >>ASSESSING THE USEFULNESS OF THE QUASI-IDEAL OBSERVER FORQUALITY CONTROL IN FLUOROSCOPY
2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 360-364Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to evaluate the reliability of the square of the signal-to-noise ratio rate, SNR2rate, as a precise measurement for quality control test in a digital fluoroscopy system. The quasi-ideal model observer was used to measure SNR2rate. The dose rate, pulse rate and field of view were varied, and their effect on dose efficiency, defined as SNR2rate=PKA;rate, was evaluated (where PKA;rate is the air kerma-area product rate). Measurements were repeated to assess reproducibility. The relative standard deviation in SNR2rate=PKA;rate over seven consecutive measurements was 5 %. No significant variation in SNR2rate=PKA;rate was observed across different pulse rates (10–30 pulses s-1). The low-dose-rate setting had a superior dose efficiency compared with the medium- and high-dose-rate settings. A smaller field of view resulted in higher dose efficiency. The results show that SNR2rate=PKA;rate measurements offer the high precision required in quality control constancy tests.

National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-123020 (URN)10.1093/rpd/ncv434 (DOI)000383492100057 ()26493947 (PubMedID)
Note

Funding agencies: ALF (Avtal om Lakarutbildning och Forskning) grants from Region Ostergotland [LIO-357651]

Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-12-01Bibliographically approved
Kardell, M., Magnusson, M., Sandborg, M., Alm Carlsson, G., Jeuthe, J. & Malusek, A. (2016). AUTOMATIC SEGMENTATION OF PELVIS FOR BRACHYTHERAPYOF PROSTATE. Radiation Protection Dosimetry, 169(1-4), 398-404
Open this publication in new window or tab >>AUTOMATIC SEGMENTATION OF PELVIS FOR BRACHYTHERAPYOF PROSTATE
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2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 398-404Article in journal (Refereed) Published
Abstract [en]

Advanced model-based iterative reconstruction algorithms in quantitative computed tomography (CT) perform automatic segmentation of tissues to estimate material properties of the imaged object. Compared with conventional methods, these algorithms may improve quality of reconstructed images and accuracy of radiation treatment planning. Automatic segmentation of tissues is, however, a difficult task. The aim of this work was to develop and evaluate an algorithm that automatically segments tissues in CT images of the male pelvis. The newly developed algorithm (MK2014) combines histogram matching, thresholding, region growing, deformable model and atlas-based registration techniques for the segmentation of bones, adipose tissue, prostate and muscles in CT images. Visual inspection of segmented images showed that the algorithm performed well for the five analysed images. The tissues were identified and outlined with accuracy sufficient for the dual-energy iterative reconstruction algorithm whose aim is to improve the accuracy of radiation treatment planning in brachytherapy of the prostate.

National Category
Medical Image Processing
Identifiers
urn:nbn:se:liu:diva-122978 (URN)10.1093/rpd/ncv461 (DOI)000383492100063 ()26567322 (PubMedID)
Funder
Swedish Cancer Society, CAN 2012/764Swedish Cancer Society, CAN 2014/691
Note

Funding agencies: Swedish Cancer Foundation [CAN 2012/764, CAN 2014/691]; Medical Faculty, Linkoping University; ALF Grants, Region Ostergotland [LiO-438731]

Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2017-12-01
Tesselaar, E., Dahlström, N. & Sandborg, M. (2016). CLINICAL AUDIT OF IMAGE QUALITY IN RADIOLOGY USING VISUAL GRADING CHARACTERISTICS ANALYSIS. Radiation Protection Dosimetry, 169(1-4), 340-346
Open this publication in new window or tab >>CLINICAL AUDIT OF IMAGE QUALITY IN RADIOLOGY USING VISUAL GRADING CHARACTERISTICS ANALYSIS
2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 340-346Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to assess whether an audit of clinical image quality could be efficiently implemented within a limited time frame using visual grading characteristics (VGC) analysis. Lumbar spine radiography, bedside chest radiography and abdominal CT were selected. For each examination, images were acquired or reconstructed in two ways. Twenty images per examination were assessed by 40 radiology residents using visual grading of image criteria. The results were analysed using VGC. Inter-observer reliability was assessed. The results of the visual grading analysis were consistent with expected outcomes. The inter-observer reliability was moderate to good and correlated with perceived image quality (r2 5 0.47). The median observation time per image or image series was within 2 min. These results suggest that the use of visual grading of image criteria to assess the quality of radiographs provides a rapid method for performing an image quality audit in a clinical environment.

National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-123019 (URN)10.1093/rpd/ncv411 (DOI)000383492100054 ()26410763 (PubMedID)
Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-05-03
Simard, T., Hibbert, B., Natarjan, M., Mercuri, M., Hetherington, S., Wright, R., . . . So, D. (2016). Impact of Center Experience on Patient Radiation Exposure During Transradial Coronary Angiography and Percutaneous Intervention: A Patient-Level, International, Collaborative, Multi-Center Analysis. Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease, 5(6)
Open this publication in new window or tab >>Impact of Center Experience on Patient Radiation Exposure During Transradial Coronary Angiography and Percutaneous Intervention: A Patient-Level, International, Collaborative, Multi-Center Analysis
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2016 (English)In: Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease, ISSN 2047-9980, E-ISSN 2047-9980, Vol. 5, no 6Article in journal (Refereed) Published
Abstract [en]

Background-—The adoption of the transradial (TR) approach over the traditional transfemoral (TF) approach has been hampered by concerns of increased radiation exposure—a subject of considerable debate within the field. We performed a patient-level, multi-center analysis to definitively address the impact of TR access on radiation exposure. Methods and Results-—Overall, 10 centers were included from 6 countries—Canada (2 centers), United Kingdom (2), Germany (2), Sweden (2), Hungary (1), and The Netherlands (1). We compared the radiation exposure of TR versus TF access using measured dose-area product (DAP). To account for local variations in equipment and exposure, standardized TR:TF DAP ratios were constructed per center with procedures separated by coronary angiography (CA) and percutaneous coronary intervention (PCI). Among 57 326 procedures, we demonstrated increased radiation exposure with the TR versus TF approach, particularly in the CA cohort across all centers (weighted-average ratios: CA, 1.15; PCI, 1.05). However, this was mitigated by increasing TR experience in the PCI cohort across all centers (r=0.8; P=0.005). Over time, as a center transitioned to increasing TR experience (r=0.9; P=0.001), a concomitant decrease in radiation exposure occurred (r=0.8; P=0.006). Ultimately, when a center’s balance of TR to TF procedures approaches 50%, the resultant radiation exposure was equivalent. Conclusions-—The TR approach is associated with a modest increase in patient radiation exposure. However, this increase is  eliminated when the TR and TF approaches are used with equal frequency—a guiding principle for centers adopting the TR approach.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2016
Keyword
coronary angiography, dose-area product, percutaneous coronary intervention, radial artery catheterisation, radiation, transradial
National Category
Cardiac and Cardiovascular Systems
Identifiers
urn:nbn:se:liu:diva-129002 (URN)10.1161/JAHA.116.003333 (DOI)000386712700040 ()27247332 (PubMedID)
Note

Funding agencies: General Electric (GE) Healthcare; TeraRecon Inc.; Saul and Edna Goldfarb Research Chair in Cardiac Imaging

Available from: 2016-06-08 Created: 2016-06-08 Last updated: 2017-11-30
Kataria, B., Sandborg, M. & Nilsson Althen, J. (2016). IMPLICATIONS OF PATIENT CENTRING ON ORGAN DOSE IN COMPUTED TOMOGRAPHY. Radiation Protection Dosimetry, 169(1-4), 130-135
Open this publication in new window or tab >>IMPLICATIONS OF PATIENT CENTRING ON ORGAN DOSE IN COMPUTED TOMOGRAPHY
2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 130-135Article in journal (Refereed) Published
Abstract [en]

Automatic exposure control (AEC) in computed tomography (CT) facilitates optimisation of dose absorbed by the patient. The use of AEC requires appropriate ‘patient centring’ within the gantry, since positioning the patient off-centre may affect both image quality and absorbed dose. The aim of this experimental study was to measure the variation in organ and abdominal surface dose during CTexaminations of the head, neck/thorax and abdomen. The dose was compared at the isocenter with two off-centre positions—ventral and dorsal to the isocenter. Measurements were made with an anthropomorphic adult phantom and thermoluminescent dosemeters. Organs and surfaces for ventral regions received lesser dose (5.6–39.0 %) than the isocenter when the phantom was positioned 13 cm off-centre. Similarly, organ and surface doses for dorsal regions were reduced by 5.0–21.0 % at 25 cm off-centre. Therefore, correct vertical positioning of the patient at the gantry isocenter is important to maintain optimal imaging conditions.

Place, publisher, year, edition, pages
Oxford University Press, 2016
Keyword
computed tomography, organ dose
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-125340 (URN)10.1093/rpd/ncv527 (DOI)000383492100020 ()26743256 (PubMedID)
Available from: 2016-02-19 Created: 2016-02-19 Last updated: 2017-04-25
Örtenberg, A., Magnusson, M., Sandborg, M., Alm Carlsson, G. & Malusek, A. (2016). PARALLELISATION OF THE MODEL-BASED ITERATIVE RECONSTRUCTION ALGORITHM DIRA. Radiation Protection Dosimetry, 169(1-4), 405-409
Open this publication in new window or tab >>PARALLELISATION OF THE MODEL-BASED ITERATIVE RECONSTRUCTION ALGORITHM DIRA
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2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 405-409Article in journal (Refereed) Published
Abstract [en]

New paradigms for parallel programming have been devised to simplify software development on multi-core processors and many-core graphical processing units (GPU). Despite their obvious benefits, the parallelisation of existing computer programs is not an easy task. In this work, the use of the Open Multiprocessing (OpenMP) and Open Computing Language (OpenCL) frameworks is considered for the parallelisation of the model-based iterative reconstruction algorithm DIRA with the aim to significantly shorten the code’s execution time. Selected routines were parallelised using OpenMP and OpenCL libraries; some routines were converted from MATLAB to C and optimised. Parallelisation of the code with the OpenMP was easy and resulted in an overall speedup of 15 on a 16-core computer. Parallelisation with OpenCL was more difficult owing to differences between the central processing unit and GPU architectures. The resulting speedup was substantially lower than the theoretical peak performance of the GPU; the cause was explained.

Place, publisher, year, edition, pages
Oxford university press: , 2016
National Category
Computer Vision and Robotics (Autonomous Systems)
Identifiers
urn:nbn:se:liu:diva-123009 (URN)10.1093/rpd/ncv430 (DOI)000383492100064 ()26454270 (PubMedID)
Funder
Swedish Cancer Society, CAN 2012/764Swedish Cancer Society, CAN 2014/691
Note

Funding agencies: Swedish Cancer Foundation [CAN 2012/764, CAN 2014/691]

Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2018-01-10
Nilsson Althén, J. & Sandborg, M. (2016). VERIFICATION OF INDICATED SKIN ENTRANCE AIR KERMA FORCARDIAC X-RAY-GUIDED INTERVENTION USING GAFCHROMIC FILM. Radiation Protection Dosimetry, 169(1-4), 245-248
Open this publication in new window or tab >>VERIFICATION OF INDICATED SKIN ENTRANCE AIR KERMA FORCARDIAC X-RAY-GUIDED INTERVENTION USING GAFCHROMIC FILM
2016 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 169, no 1-4, p. 245-248Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to verify the indicated maximum entrance surface air kerma (ESAK) using a GE Innova IGS 520 imaging system during cardiac interventional procedures. Gafchromic XR RV3 films were used for the patient measurements to monitor the maximum ESAK. The films were scanned and calibrated to measure maximum ESAK. Thermoluminescent dosemeters were used to measure the backscatter factor from an anthropomorphic thorax phantom. The measured backscatter factor, 1.53, was in good agreement with Monte Carlo simulations but higher than the one used by the imaging system, 1.20. The median of the ratio between indicated maximum ESAK and measured maximum ESAKwas 0.68. In this work, the indicated maximum ESAK by the imaging system’s dose map model underestimates the measured maximum ESAK by 32 %. The threshold ESAK for follow-up procedures for patient with skin dose in excess of 2 Gy will be reduced to 1.4 Gy.

Place, publisher, year, edition, pages
Oxford University Press, 2016
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-122967 (URN)10.1093/rpd/ncv460 (DOI)000383492100037 ()26541185 (PubMedID)
Note

Funding agencies: County Council of Ostergotland

Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2017-12-01
Norberg, P., Olsson, A., Alm Carlsson, G., Sandborg, M. & Gustafsson, A. (2015). Optimisation of quantitative lung SPECT applied to mild COPD: a software phantom simulation study. EJNMMI research, 5(16)
Open this publication in new window or tab >>Optimisation of quantitative lung SPECT applied to mild COPD: a software phantom simulation study
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2015 (English)In: EJNMMI research, ISSN 2191-219X, Vol. 5, no 16Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: The amount of inhomogeneities in a (99m)Tc Technegas single-photon emission computed tomography (SPECT) lung image, caused by reduced ventilation in lung regions affected by chronic obstructive pulmonary disease (COPD), is correlated to disease advancement. A quantitative analysis method, the CVT method, measuring these inhomogeneities was proposed in earlier work. To detect mild COPD, which is a difficult task, optimised parameter values are needed.

METHODS: In this work, the CVT method was optimised with respect to the parameter values of acquisition, reconstruction and analysis. The ordered subset expectation maximisation (OSEM) algorithm was used for reconstructing the lung SPECT images. As a first step towards clinical application of the CVT method in detecting mild COPD, this study was based on simulated SPECT images of an advanced anthropomorphic lung software phantom including respiratory and cardiac motion, where the mild COPD lung had an overall ventilation reduction of 5%.

RESULTS: The best separation between healthy and mild COPD lung images as determined using the CVT measure of ventilation inhomogeneity and 125 MBq (99m)Tc was obtained using a low-energy high-resolution collimator (LEHR) and a power 6 Butterworth post-filter with a cutoff frequency of 0.6 to 0.7 cm(-1). Sixty-four reconstruction updates and a small kernel size should be used when the whole lung is analysed, and for the reduced lung a greater number of updates and a larger kernel size are needed.

CONCLUSIONS: A LEHR collimator and 125 (99m)Tc MBq together with an optimal combination of cutoff frequency, number of updates and kernel size, gave the best result. Suboptimal selections of either cutoff frequency, number of updates and kernel size will reduce the imaging system's ability to detect mild COPD in the lung phantom.

National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-117857 (URN)10.1186/s13550-015-0086-2 (DOI)000358130300001 ()25853022 (PubMedID)
Available from: 2015-05-12 Created: 2015-05-12 Last updated: 2016-04-24
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3352-8330

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