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Alm Carlsson, GudrunORCID iD iconorcid.org/0000-0003-0209-498X
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Publications (10 of 137) Show all publications
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
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
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
Adolfsson, E., White, S., Landry, G., Lund, E., Gustafsson, H., Verhaegen, F., . . . Alm Carlsson, G. (2015). Measurement of absorbed dose to water around an electronic brachytherapy source: Comparison of two dosimetry systems: lithium formate EPR dosimeters and radiochromic EBT2 film. Physics in Medicine and Biology, 60(9), 3869-3882
Open this publication in new window or tab >>Measurement of absorbed dose to water around an electronic brachytherapy source: Comparison of two dosimetry systems: lithium formate EPR dosimeters and radiochromic EBT2 film
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2015 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 60, no 9, p. 3869-3882Article in journal (Refereed) Published
Abstract [en]

Interest in high dose rate (HDR) electronic brachytherapy operating at 50 kV is increasing. For quality assurance it is important to identify dosimetry systems that can measure the absorbed doses in absolute terms which is difficult in this energy region. In this work a comparison is made between two dosimetry systems, EPR lithium formate dosimeters and radiochromic EBT2 film.

Both types of dosimeters were irradiated simultaneously in a PMMA phantom using the Axxent EBS. Absorbed dose to water was determined at distances of 10 mm, 30 mm and 50 mm from the EBS. Results were traceable to different primary standards as regards to absorbed dose to water (EPR) and air kerma (EBT2). Monte Carlo simulations were used in absolute terms as a third estimate of absorbed dose to water.

Agreement within the estimated expanded (k = 2) uncertainties (5% (EPR), 7% (EBT2)) was found between the results at 30 mm and 50 mm from the x-ray source. The same result was obtained in 4 repetitions of irradiation, indicating high precision in the measurements with both systems. At all distances, agreement between EPR and Monte Carlo simulations was shown as was also the case for the film measurements at 30mm and 50mm. At 10mm the geometry for the film measurements caused too large uncertainty in measured values depending on the exact position (within sub-mm distances) of the EBS and the 10 mm film results were exculded from comparison.

This work has demonstrated good performance of the lithium formate EPR dosimetry system in accordance with earlier experiments at higher photon energies (192Ir HDR brachytherapy). It was also highlighted that there might be issues regarding the energy dependence and intrinsic efficiency of the EBT2 film that need to be considered for measurements using low energy sources.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
Keywords
Electronic brachytherapy, EPR, lithium formate, radiochromic film, intrinsic efficiency
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111090 (URN)10.1088/0031-9155/60/9/3869 (DOI)000354104700030 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
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
Adolfsson, E., Gustafsson, H., Lund, E., Alm Carlsson, G., Olsson, S. & Carlsson Tedgren, Å. (2014). A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry. Radiotherapy and Oncology, 113(2), 279-282
Open this publication in new window or tab >>A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry
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2014 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 113, no 2, p. 279-282Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to develop and test a remote end-to-end audit system using lithium formate EPR dosimeters. Four clinics were included in a pilot study, absorbed doses determined in the PTV agreed with TPS calculated doses within ±5% for 3D-CRT and ±7% (k=1) for IMRT/VMAT dose plans.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Dosimetry audit; remote audit; end-to-end; EPR; ESR; lithium formate
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111089 (URN)10.1016/j.radonc.2014.11.027 (DOI)000347657200021 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
Norberg, P., Persson, H. L., Schmekel, B., Alm Carlsson, G., Wahlin, K., Sandborg, M. & Gustafsson, A. (2014). Does quantitative lung SPECT detect lung abnormalities earlier than lung function tests?: Results of a pilot study. EJNMMI Research, 4(39), 1-12
Open this publication in new window or tab >>Does quantitative lung SPECT detect lung abnormalities earlier than lung function tests?: Results of a pilot study
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2014 (English)In: EJNMMI Research, ISSN 2191-219X, E-ISSN 2191-219X, Vol. 4, no 39, p. 1-12Article in journal (Refereed) Published
Abstract [en]

Background: Heterogeneous ventilation in lungs of allergic individuals, cigarette smokers, asthmatics and chronic obstructive pulmonary disease (COPD) patients has been demonstrated using imaging modalities such as PET, MR and SPECT. These individuals suffer from narrow and/or closed airways to various extents. By calculating regional heterogeneity in lung ventilation SPECT images as the coefficient of variation (CV) in small elements of the lung, heterogeneity maps and CV-frequency curves can be generated and used to quantitatively measure heterogeneity. This work explores the potential to use such measurements to detect mild ventilation heterogeneities in lung healthy subjects.

Method: Fourteen healthy subjects without documented lung disease or respiratory symptoms, and two patients with documented airway disease, inhaled on average approximately 90 MBq 99mTc-Technegas immediately prior to the 20 min SPECT acquisition. Variation in activity uptake between subjects was compensated for in resulting CV values. The area under the compensated CV frequency curve (AUC), for CV values greater than a threshold value CVT, AUC(CV> CVT), was used as the measure of ventilation heterogeneity.

Results: Patients with lung function abnormalities, according to lung function tests, generated higher AUC(CV>20%) values compared to healthy subjects (p=0.006). Strong linear correlations with the AUC(CV>20%) values were found for age (p=0.006) and height (p=0.001). These demonstrated that ventilation heterogeneities increased with age and that they depend on lung size. Strong linear correlations were found for the lung function value related to indices of airway closure/air trapping, RV/TLC (p=0.009), and DLCOc (p=0.009), a value partly related to supposed ventilation/perfusion mismatch. These findings support the association between conventional lung function tests and the AUC(CV>20%) value.

Conclusions: Among the healthy subjects there is a group with increased AUC(CV>20%) values, but with normal lung function tests, which implies that it might be possible to differentiate ventilation heterogeneities earlier in a disease process than by lung function tests.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2014
Keywords
Quantitative lung SPECT, ventilation heterogeneities, lung function tests
National Category
Clinical Medicine Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-106666 (URN)10.1186/s13550-014-0039-1 (DOI)000358049300001 ()26055938 (PubMedID)2-s2.0-84905881037 (Scopus ID)
Note

On the date of the defence date of the Ph.D. Thesis the status of this article was Manuscript.

Available from: 2014-05-19 Created: 2014-05-19 Last updated: 2017-12-05Bibliographically approved
Malusek, A., Helmrot, E., Sandborg, M., Grindborg, J.-E. & Alm Carlsson, G. (2014). In-situ calibration of clinical built-in KAP meters with traceability to a primary standard using a reference KAP meter. Physics in Medicine and Biology, 59(23), 7195-7210
Open this publication in new window or tab >>In-situ calibration of clinical built-in KAP meters with traceability to a primary standard using a reference KAP meter
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2014 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 59, no 23, p. 7195-7210Article in journal (Refereed) Published
Abstract [en]

The air kerma-area product (KAP) is used for settings of diagnostic reference levels. The International Atomic Energy Agency (IAEA) recommends that doses in diagnostic radiology (including the KAP values) be estimated with an accuracy of at least +/- 7% (k = 2). Industry standards defined by the International Electrotechnical Commission (IEC) specify that the uncertainty of KAP meter measurements should be less than +/- 25% (k = 2). Medical physicists willing to comply with the IAEAs recommendation need to apply correction factors to KAP values reported by x-ray units. The aim of this work is to present and evaluate a calibration method for built-in KAP meters on clinical x-ray units. The method is based on (i) a tandem calibration method, which uses a reference KAP meter calibrated to measure the incident radiation, (ii) measurements using an energy-independent ionization chamber to correct for the energy dependence of the reference KAP meter, and (iii) Monte Carlo simulations of the beam quality correction factors that correct for differences between beam qualities at a standard laboratory and the clinic. The method was applied to the KAP meter in a Siemens Aristos FX plus unit. It was found that values reported by the built-in KAP meter differed from the more accurate values measured by the reference KAP meter by more than 25% for high tube voltages (more than 140 kV) and heavily filtered beams (0.3 mm Cu). Associated uncertainties were too high to claim that the IECs limit of 25% was exceeded. Nevertheless the differences were high enough to justify the need for a more accurate calibration of built-in KAP meters.

Place, publisher, year, edition, pages
IOP Publishing: Hybrid Open Access, 2014
Keywords
KAP-meter; kerma-area product; calibration
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-112993 (URN)10.1088/0031-9155/59/23/7195 (DOI)000345254000010 ()25369212 (PubMedID)
Note

Funding Agencies|Swedish Radiation Safety Authority

Available from: 2015-01-12 Created: 2015-01-08 Last updated: 2017-12-05
Adolfsson, E., Carlsson Tedgren, Å., Alm Carlsson, G., Gustafsson, H. & Lund, E. (2014). Optimisation of an EPR dosimetry system for robust and high precision dosimetry. Radiation Measurements, 70, 21-28
Open this publication in new window or tab >>Optimisation of an EPR dosimetry system for robust and high precision dosimetry
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2014 (English)In: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 70, p. 21-28Article in journal (Refereed) Published
Abstract [en]

Clinical applications of electron paramagnetic resonance (EPR) dosimetry systems demand high accuracy causing time consuming analysis. The need for high spatial resolution dose measurements in regions with steep dose gradients demands small sized dosimeters. An optimization of the analysis was therefore needed to limit the time consumption. The aim of this work was to introduce a new smaller lithium formate dosimeter model (diameter reduced from standard diameter 4.5 mm to 3 mm and height from 4.8 mm to 3 mm). To compensate for reduced homogeneity in a batch of the smaller dosimeters, a method for individual sensitivity correction suitable for EPR dosimetry was tested. Sensitivity and repeatability was also tested for a standard EPR resonator and a super high Q (SHQE) one. The aim was also to optimize the performance of the dosimetry system for better efficiency regarding measurement time and precision. A systematic investigation of the relationship between measurement uncertainty and number of readouts per dosimeter was performed. The conclusions drawn from this work were that it is possible to decrease the dosimeter size with maintained measurement precision by using the SHQE resonator and introducing individual calibration factors for dosimeter batches. It was also shown that it is possible reduce the number of readouts per dosimeter without significantly decreasing the accuracy in measurements.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
EPR; ESR; Lithium formate; High precision dosimetry; High spatial resolution dosimetry
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111088 (URN)10.1016/j.radmeas.2014.08.013 (DOI)000345110700005 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
Norberg, P., Olsson, A., Alm Carlsson, G., Sandborg, M. & Gustafsson, A. (2014). Optimisation of quantitative lung SPECT applied to mild COPD: a Monte Carlo-based analysis.
Open this publication in new window or tab >>Optimisation of quantitative lung SPECT applied to mild COPD: a Monte Carlo-based analysis
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2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

The amount of inhomogeneities in a 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 (Norberg et al., 2013). To detect mild COPD, which is a difficult task, optimized parameter values are needed. In this work, the CVT-method was optimized with respect to the parameter values of acquisition, reconstruction and analysis. The ordered subset expectation maximization (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 phantom including respiratory and cardiac motion, where the mild COPD lung had an overall ventilation reduction of 5%. The largest separation between healthy and mild COPD lung images as determined using the CVT-measure of ventilation inhomogeneity and 125 MBq 99mTc was obtained using a low-energy high-resolution collimator and a Butterworth postfilter with a cut-off frequency of 0.6-0.7 cm-1. Sixty-four reconstruction updates should be used when the whole lung is analysed and for the reduced lung a greater number of updates is needed.

National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-106665 (URN)
Available from: 2014-05-19 Created: 2014-05-19 Last updated: 2015-03-31Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0209-498X

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