| 1. |
- Almén, A, et al.
(författare)
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Personal Dosimetry Using Monte-Carlo Simulations For Occupational Dose Monitoring In Interventional Radiology : The Results Of A Proof Of Concept In A Clinical Setting
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:44624, s. 391-398
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Tidskriftsartikel (refereegranskat)abstract
- Exposure levels to staff in interventional radiology (IR) may be significant and appropriate assessment of radiation doses is needed. Issues regarding measurements using physical dosemeters in the clinical environment still exist. The objective of this work was to explore the prerequisites for assessing staff radiation dose, based on simulations only. Personal dose equivalent, Hp(10), was assessed using simulations based on Monte Carlo methods. The position of the operator was defined using a 3D motion tracking system. X-ray system exposure parameters were extracted from the x-ray equipment. The methodology was investigated and the simulations compared to measurements during IR procedures. The results indicate that the differences between simulated and measured staff radiation doses, in terms of the personal dose equivalent quantity Hp(10), are in the order of 30-70 %. The results are promising but some issues remain to be solved, e.g. an automated tracking of movable parts such as the ceiling-mounted protection shield.
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| 2. |
- Andersson, Martin, et al.
(författare)
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Dosimetry and Cancer Risk Estimations for Different Radiation Protection Solutions at Decommissioning a Contaminated Nuclear Power Plant Site
- 2022
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 198:19, s. 1516-1521
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Tidskriftsartikel (refereegranskat)abstract
- Contaminated sediments originating from dredging activities in a nuclear power plant site were placed in a pond, which has to be taken into consideration during the future decommissioning process. The sediments have to be handled to free release the site. The radionuclides Co-60 and Cs-137 were identified and the activity concentrations (Bq/kg) were quantified in the range of 10-6000 and 5-50 Bq kg(-1), respectively. The absorbed dose rate to individuals of various ages and sex present at the site of the dry pond area was estimated. The radiological impact in terms of lifetime attributable risk (LAR) and effective dose were calculated. For a 30-year-old male exposed during one year without any action regarding the sediments in the dried out pond, the LAR was predicted to be 0.0027, which recalculated to effective dose corresponds to 7.6 mSv year(-1). The calculations show that countermeasures will be needed for the contaminated site.
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| 3. |
- Andersson, Martin, et al.
(författare)
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IDAC-ALPHA: AN ALPHA DOSIMETRY SOFTWARE FOR NORMAL ORGANS AND TISSUES
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 327-333
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Tidskriftsartikel (refereegranskat)abstract
- Radiopharmaceuticals have been used for the treatment of various forms of cancer since the 1940s. In recent years, the advantages of alpha emitting radionuclides have emerged as a favourable treatment option. However, most alpha emitting radionuclides have long decay chains with long-lived daughter radionuclides. This leads to uncertainties in the dosimetry for normal organs and tissues, when established dosimetry models are employed. The aim of this project is to assign each progeny its own biokinetic behaviour. The novel dosimetry model was applied to Ra-223-dichloride, frequently used for the treatment of patients with metastatic bone disease from castration-resistant prostate cancer. In this dosimetry model, individual biokinetics for each daughter radionuclide was included. This resulted in a decrease in absorbed dose to bone surfaces and red marrow and increased absorbed dose to liver and kidney, when compared with dosimetry models assuming that the daughter nuclides follow the biokinetics of the parent radionuclide.
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| 4. |
- Andersson, Martin, et al.
(författare)
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Improved age and gender specific radiation risk models applied on cohorts of Swedish patients
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 334-338
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Tidskriftsartikel (refereegranskat)abstract
- AIM:The aim of this study is to implement lifetime attributable risk (LAR) predictions for radiation induced cancers for Swedish cohorts of patients of various age and sex, undergoing diagnostic investigations by nuclear medicine methods. METHODS: Calculations are performed on Swedish groups of patients with Paget's disease and with bone metastases from prostatic cancer and diagnosed with bone scintigraphy with an administration of 500 MBq 99mTc-phosphonate. RESULTS: The inclusion of patient survival rates into the calculations lowers the induced radiation cancer risk, as it takes into account that cohorts of patients have shorter predicted survival times than the general population. CONCLUSION: LAR estimations could be valuable for referring physicians, nuclear medicine physicians, nurses, medical physicists, radiologists, and oncologists and as well as ethical committees for risk estimates for specific subgroups of patients. Caution is however advised with respect to application of LAR predictions to individuals (because of individual sensitivities, circumstances, etc.).
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| 5. |
- Barufaldi, Bruno, et al.
(författare)
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Virtual Clinical Trials in Medical Imaging System Evaluation and Optimisation
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:3-4, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- Virtual clinical trials (VCTs) can be used to evaluate and optimise medical imaging systems. VCTs are based on computer simulations of human anatomy, imaging modalities and image interpretation. OpenVCT is an open-source framework for conducting VCTs of medical imaging, with a particular focus on breast imaging. The aim of this paper was to evaluate the OpenVCT framework in two tasks involving digital breast tomosynthesis (DBT). First, VCTs were used to perform a detailed comparison of virtual and clinical reading studies for the detection of lesions in digital mammography and DBT. Then, the framework was expanded to include mechanical imaging (MI) and was used to optimise the novel combination of simultaneous DBT and MI. The first experiments showed close agreement between the clinical and the virtual study, confirming that VCTs can predict changes in performance of DBT accurately. Work in simultaneous DBT and MI system has demonstrated that the system can be optimised in terms of the DBT image quality. We are currently working to expand the OpenVCT software to simulate MI acquisition more accurately and to include models of tumour growth. Based on our experience to date, we envision a future in which VCTs have an important role in medical imaging, including support for more imaging modalities, use with rare diseases and a role in training and testing artificial intelligence (AI) systems.
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| 6. |
- Begano, Dino, et al.
(författare)
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TO USE OR NOT USE PATIENT SHIELDING ON PREGNANT WOMEN UNDERGOING CT PULMONARY ANGIOGRAPHY : A PHANTOM STUDY
- 2020
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 189:4, s. 458-465
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Tidskriftsartikel (refereegranskat)abstract
- Pregnancy increases the risk of pulmonary embolism. Computed tomography pulmonary angiography (CTPA) is used for diagnosis. CT generates ionising radiation, and thus, abdominal shielding may be used. This phantom study investigated the effects of patient shielding and scan length reduction on the fetal and maternal ionising radiation dose from CTPA. The absorbed dose to the fetus was measured using thermoluminescent dosemeters. Estimated effective doses to the pregnant patient were based on the dose-length products. Shielding increased both the effective dose to the patient by 47% and the mean absorbed dose to the fetus (0.10 vs. 0.12 mGy; p < 0.001) compared with unshielded standard CTPA, as it affected the automatic exposure control. Shielded short CTPA marginally lowered only the mean fetal absorbed dose (0.03 vs. 0.02 mGy; p = 0.018). Shortening the scan reduced the fetal absorbed dose most effectively by 70% (0.10 vs. 0.03 mGy; p = 0.006), compared with the standard unshielded scan. Shielding modestly reduces fetal radiation dose but may compromise automatic exposure control, possibly increasing the maternal and fetal radiation dose. Shortening the scan is beneficial, assuming anatomical coverage is secured.
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| 7. |
- Borota, Ljubisa, et al.
(författare)
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Spot Region of Interest Imaging : A Novel Functionality Aimed at X-Ray Dose Reduction in Neurointerventional Procedures
- 2020
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 188:3, s. 322-331
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Tidskriftsartikel (refereegranskat)abstract
- AIM OF THE STUDY: The aim of this study was to describe a new functionality aimed at X-ray dose reduction, referred to as spot region of interest (Spot ROI) and to compare it with existing dose-saving functionalities, spot fluoroscopy (Spot F), and conventional collimation (CC).MATERIAL AND METHODS: Dose area product, air kerma, and peak skin dose were measured for Spot ROI, Spot F, and CC in three different fields of view (FOVs) 20 × 20 cm, 15 × 15 cm, and 11 × 11 cm using an anthropomorphic head phantom RS-230T. The exposure sequence was 5 min of pulsed fluoroscopy (7.5 pulses per s) followed by 7× digital subtraction angiography (DSA) runs with 30 frames per DSA acquisition (3 fps × 10 s). The collimation in Spot F and CC was adjusted such that the size of the anatomical area exposed was as large as the Spot ROI area in each FOV.RESULTS: The results for all FOVs were the following: for the fluoroscopy, all measured parameters for Spot ROI and Spot F were lower than corresponding values for CC. For DSA and DSA plus fluoroscopy, all measured parameters for Spot ROI were lower than corresponding parameters for Spot F and CC.CONCLUSION: Spot ROI is a promising dose-saving technology that can be applied in fluoroscopy and acquisition. The biggest benefit of Spot ROI is its ability to keep the entire FOV information always visible.
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| 8. |
- Båth, Magnus, et al.
(författare)
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OPTIMISATION in X-RAY and MOLECULAR IMAGING 2020
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 133-133
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Chipiga, Larisa, et al.
(författare)
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Comparison of organ absorbed doses in whole-body computed tomography scans of paediatric and adult patient models estimated by different methods
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 246-256
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to identify the uncertainty in estimations of organ absorbed dose using dedicated software by comparing with corresponding doses measured in physical phantoms. The comparison was performed for whole-body computed tomography (CT) obtained as part of positron emission tomography. Whole-body CT scans provide an advantage in terms of comparison because all organs are in the primary beam of the irradiated area. Organ doses estimated by the different software programs (CT-Expo, VirtualDose and NCICT) were compared by thermoluminescent detector measurements in anthropomorphic phantoms in 1-y-old, 5-y-old and adult patients. Differences were within ~15% in 12 major organs. However, differences of ~30% were observed in organs located at slightly different positions in the computational models compared to the physical phantoms. All investigated programs were deemed suitable for accurate estimation of organ absorbed dose.
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| 10. |
- Elgström, Henrik, et al.
(författare)
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Signal-To-Noise Ratio Rate Measurement in Fluoroscopy For Quality Control and Teaching Good Radiological Imaging Technique
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 407-415
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Tidskriftsartikel (refereegranskat)abstract
- Visibility of low-contrast details in fluoroscopy and interventional radiology is important. Assessing detail visibility with human observers typically suffers from large observer variances. Objective, quantitative measurement of low-contrast detail visibility using a model observer, such as the square of the signal-to-noise ratio rate (SNR2rate), was implemented in MATLAB™ and evaluated. The expected linear response of SNR2rate based on predictions by the so-called Rose model and frame statistics was verified. The uncertainty in the measurement of SNR2rate for a fixed imaging geometry was 6% based on 16 repeated measurements. The results show that, as expected, reduced object thickness and x-ray field size substantially improved SNR2rate/PKA,rate with PKA,rate being the air kerma area product rate. The measurement precision in SNR2rate/PKA,rate (8–9%) is sufficient to detect small but important improvements, may guide the selection of better imaging settings and provides a tool for teaching good radiological imaging techniques to clinical staff.
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| 11. |
- Hansson, Jonny, et al.
(författare)
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EVALUATION OF VGC ANALYZER BY COMPARISON WITH GOLD STANDARD ROC SOFTWARE AND ANALYSIS OF SIMULATED VISUAL GRADING DATA
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 378-390
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present work was to evaluate the use of resampling statistical methods for analysis of visual grading data-implemented in the software VGC Analyzer-by comparing the reanalyzed results from previously performed visual grading studies with the results calculated by gold standard receiver operating characteristic (ROC) methodology, Obuchowski-Rockette (OR)-Dorfman-Berbaum-Metz (DBM) multiple-readers and multiple-case (MRMC) and by analysis of simulated visual grading data where the true distribution was presumed to be known. The reanalysis was performed on two multiple-reader studies with non-paired data and paired data, respectively. The simulation study was performed by simulating a large number of visual grading characteristics (VGC) studies and by analyzing the statistical distribution of null hypothesis (H-0) rejection rate. The comparison with OR-DBM MRMC showed good agreement when analyzing non-paired data for both fixed-reader and random-reader settings for the calculated area under the curve values and the confidence intervals (CIs). For paired data analysis, VGC Analyzer showed significantly lower CIs compared with the ROC software. This effect was also illustrated by the simulation study, where the VGC Analyzer, in general, showed good accuracy for simulated studies with stable statistical basis. For simulated studies with unstable statistics, the accuracy in the H-0 rejection rate decreased. The present study has shown that resampling methodology can be used to accurately perform the statistical analysis of a VGC study, although the resampling technique used makes the method sensitive to small data sets.
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| 12. |
- Hettinger, E, et al.
(författare)
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Evaluation of Model-Based Iterative Reconstruction in Abdominal Computed Tomography Imaging at Two Different Dose Levels
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:44624, s. 205-211
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to qualitatively evaluate recently introduced Model-based iterative reconstruction method (IMR) and routinely used iterative reconstruction algorithm iDose4 to investigate future dose reduction possibilities for abdominal CT exams. The study contained data from 34 patients who underwent abdominal CT in SkåneUniversityHospital Lund, Sweden. A low-dose scan (CTDIvol3.4 mGy) reconstructed with both iDose4 and IMR and a standard-dose scan (CTDIvol 5.3 mG) reconstructed with iDose4 alone were visually graded in ViewDEX v2.0 by four radiologists using modified EU image criteria. The visual grading characteristics analysis for the evaluation comparing iDose4 standard dose with IMR low dose did not show any statistically significant difference in five of six criteria. In one of the criteria, iDose4 was superior to IMR. The result show promising possibilities are introduced for substantial radiation dose reduction (35%) in abdominal CT imaging when replacing iDose4 with IMR. Still, care should be taken when considering the reproduction of adrenal glands.
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| 13. |
- Hultenmo, M., et al.
(författare)
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DOSE EVALUATION AND PROPOSAL OF LOCAL DIAGNOSTIC REFERENCE LEVELS FOR PAEDIATRIC CARDIAC CATHETERIZATIONS PERFORMED ON A HIGH-SENSITIVITY ANGIOGRAPHIC SYSTEM ALLOWING LOW-DOSE IMAGING
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 279-288
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Tidskriftsartikel (refereegranskat)abstract
- Radiation doses from paediatric cardiac catheterizations were analysed based on procedure type and patient weight, and local diagnostic reference levels (LDRLs) were proposed. The procedures were performed on a Siemens Artis Q.zen biplane system with high-sensitivity detectors allowing low-dose imaging. Good radiological practice, e.g. adapting dose level and frame rate continuously and minimizing the x-ray field with collimators, was routine during procedures. The median total dose-area-product (DAP) value was 58 mu Gym(2) for diagnostic catheterizations, 48 mu Gym(2) for interventional catheterizations and 33 mu Gym(2) for myocardial biopsies. The median DAP per body weight was 4.0 mu Gym(2) kg(-1). The median total fluoroscopy time varied from 6.0 min for myocardial biopsies, to 9.7 and 10.5 min, respectively, for diagnostic and interventional catheterizations. The third quartile of the DAP values in each weight group was proposed as LDRL. LDRLs for fluoroscopy time were determined solely based on procedure type, due to the absence of weight dependence.
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| 14. |
- Ivarsson, Jonas, 1976, et al.
(författare)
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Aligning Video-And Structured Data for Imaging Optimisation.
- 2021
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:3-4, s. 134-138
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Tidskriftsartikel (refereegranskat)abstract
- Imaging optimisation can benefit from combining structured data with qualitative data in the form of audio and video recordings. Since video is complex to work with, there is a need to find a workable solution that minimises the additional time investment. The purpose of the paper is to outline a general workflow that can begin to address this issue. What is described is a data management process comprising the three steps of collection, mining and contextualisation. This process offers a way to work systematically and at a large scale without succumbing to the context loss of statistical methods. The proposed workflow effectively combines the video and structured data to enable a new level of insights in the optimisation process.
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| 15. |
- Jeuthe, Julius, et al.
(författare)
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Semi-Automated 3D Segmentation of Pelvic Region Bones in CT Volumes for the Annotation of Machine Learning Datasets
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 172-176
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Tidskriftsartikel (refereegranskat)abstract
- Automatic segmentation of bones in computed tomography (CT) images is used for instance in beam hardening correction algorithms where it improves the accuracy of resulting CT numbers. Of special interest are pelvic bones, which—because of their strong attenuation—affect the accuracy of brachytherapy in this region. This work evaluated the performance of the JJ2016 algorithm with the performance of MK2014v2 and JS2018 algorithms; all these algorithms were developed by authors. Visual comparison, and, in the latter case, also Dice similarity coefficients derived from the ground truth were used. It was found that the 3D-based JJ2016 performed better than the 2D-based MK2014v2, mainly because of the more accurate hole filling that benefitted from information in adjacent slices. The neural network-based JS2018 outperformed both traditional algorithms. It was, however, limited to the resolution of 1283 owing to the limited amount of memory in the graphical processing unit (GPU).
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| 16. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(författare)
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Extracolonic Findings-Identification at Low-Dose CTC.
- 2021
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:3-4, s. 188-197
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to optical colonoscopy, computed tomography colonography (CTC) has the ability to reveal pathology outside of the colon. While identification of colorectal lesions at CTC requires only limited radiation dose, the detection of abnormalities in extracolonic soft tissue requires more radiation. The purpose of this study was to investigate the influence of ultra-low-dose (ULD) CTC on the detection and characterisation of extracolonic findings. In a prospective study 49 patients with colorectal symptoms were examined with CTC adding a ULD series (mean effective dose 0.9±0.4mSv) to the normal unenhanced standard dose (SD) series (mean effective dose 3.6±1.2mSv). Five radiologists individually and blindly evaluated the ULD, followed by evaluation of the SD after ≥9weeks (median 35weeks). A ViewDEX-based examination protocol was used, including a confidence scale and a graded assessment of need for follow-up according to the CTC Reporting and Data System (C-RADS E0-E4). The reference findings comprised the combined information from CTC (ULD, SD and contrast-enhanced CTC series) and a 4-year radiological and clinical follow-up. For the overall detection of reference findings (E2-E4) we found a statistically significant difference in favour of SD. This, however, was not the case when looking at classification of possibly important/important reference findings (E3-E4). Our results suggest that CTC with ULD (0.9mSv) is comparable to SD (3.6mSv) for identification of clinically relevant extracolonic pathology, but there is a large inter-observer variability.
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| 17. |
- Kataria, Bharti, 1955-, et al.
(författare)
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Image Quality and Potential Dose Reduction Using Advanced Modeled Iterative Reconstruction (Admire) in Abdominal Ct : A Review
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 177-187
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Forskningsöversikt (refereegranskat)abstract
- Traditional filtered back projection (FBP) reconstruction methods have served the computed tomography (CT) community wellfor over 40 years. With the increased use of CT during the last decades, efforts to minimise patient exposure, while maintainingsufficient or improved image quality, have led to the development of model-based iterative reconstruction (MBIR) algorithms fromseveral vendors. The usefulness of the advanced modeled iterative reconstruction (ADMIRE) (Siemens Healthineers) MBIR inabdominal CT is reviewed and its noise suppression and/or dose reduction possibilities explored. Quantitative and qualitativemethods with phantom and human subjects were used. Assessment of the quality of phantom images will not always correlatepositively with those of patient images, particularly at the higher strength of the ADMIRE algorithm. With few exceptions,ADMIRE Strength 3 typically allows for substantial noise reduction compared to FBP and hence to significant (≈30%) patientdose reductions. The size of the dose reductions depends on the diagnostic task.
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| 18. |
- Kataria, Bharti, 1955-, et al.
(författare)
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Image quality in CT thorax: effect of altering reconstruction algorithm and tube load : Image quality in CT thorax
- 2024
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 200:5, s. 504-514
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Tidskriftsartikel (refereegranskat)abstract
- Non-linear properties of iterative reconstruction (IR) algorithms can alter image texture. We evaluated the effect of a model-basedIR algorithm (advanced modelled iterative reconstruction; ADMIRE) and dose on computed tomography thorax image quality.Dual-source scanner data were acquired at 20, 45 and 65 reference mAs in 20 patients. Images reconstructed with filteredback projection (FBP) and ADMIRE Strengths 3–5 were assessed independently by six radiologists and analysed using an ordinallogistic regression model. For all image criteria studied, the effects of tube load 20 mAs and all ADMIRE strengths were significant(p < 0.001) when compared to reference categories 65 mAs and FBP. Increase in tube load from 45 to 65 mAs showed imagequality improvement in three of six criteria. Replacing FBP with ADMIRE significantly improves perceived image quality for allcriteria studied, potentially permitting a dose reduction of almost 70% without loss in image quality
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| 19. |
- Khan, Jehangir, 1985, et al.
(författare)
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ACTIVITY CONCENTRATION ESTIMATION IN AUTOMATED KIDNEY SEGMENTATION BASED ON CONVOLUTION NEURAL NETWORK METHOD FOR (LU)-L-177-SPECT/CT KIDNEY DOSIMETRY
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 164-171
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Tidskriftsartikel (refereegranskat)abstract
- For Lu-177-DOTATATE treatments, dosimetry based on manual kidney segmentation from computed tomography (CT) is accurate but time consuming and might be affected by misregistration between CT and SPECT images. This study develops a convolution neural network (CNN) for automated kidney segmentation that accurately aligns CT segmented volume of interest (VOI) to the kidneys in SPECT images. The CNN was trained with SPECT/CT images performed over the abdominal area of 137 patients treated with Lu-177-DOTATATE. Activity concentrations in automated and manual segmentations were strongly correlated for both kidneys (r > 0.96, p < 0.01) in the testing cohort (n = 20). The Bland-Altman analyses demonstrated higher accuracy for the CNN segmentation compared to the manual segmented kidneys without VOI adjustment. The CNN demonstrated a potential for accurate kidney segmentation. The CNN was a fast and robust approach for assessment of activity concentrations in SPECT images, and performed equally well as the manual segmentation method.
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| 20. |
- Larsson, Joel, 1986, et al.
(författare)
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FREQUENCY RESPONSE AND DISTORTION PROPERTIES OF RECONSTRUCTION ALGORITHMS IN COMPUTED TOMOGRAPHY
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 416-425
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Tidskriftsartikel (refereegranskat)abstract
- Denoising reconstruction techniques can introduce nonlinear properties into computed tomography (CT) systems. These nonlinear algorithms introduce distortion which affects the assessment of the resolution of the system. The purpose of the present study was to decouple and investigate amplitude modulation and waveform distortion in reconstruction algorithms in CT. The methodology developed by Wells, J. R. and Dobbins, J. T. III [Frequency response and distortion properties of nonlinear image processing algorithms and the importance of imaging context. Med. Phys. 40, 091906 (2013)] was adapted to CT reconstruction algorithms. The CT simulating program ASTRA Toolbox (c) for MATLAB (TM) was used for the reconstruction of the sinusoidal wave functions. Filtered back projection and the simultaneous iterative reconstruction technique were investigated with simple nonlinear mechanisms: a median filter and a non-negative constraint, respectively. The native reconstruction algorithms were not free from nonlinear waveform distortion, however, none of the metrics showed any dependence on the contrast-to-noise ratio (CNR). Furthermore, the algorithms including nonlinear mechanisms showed a clear and specific CNR dependence, indicating the necessity for distortion analysis in nonlinear CT reconstruction.
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| 21. |
- Lundh, Charlotta, 1977, et al.
(författare)
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A model for evaluating the use of imaging in image-guided interventional procedures-possible implications on optimisation of radiation protection.
- 2021
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:3-4, s. 139-144
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Tidskriftsartikel (refereegranskat)abstract
- The present study focuses on introducing the concept of optimisation and proposing a model, including evaluation of image quality, to be used in the clinical routines where image-guided intervention is being performed. The overall aim of the study was to develop a model for evaluating the use of imaging in X-ray-guided interventional procedures and its possible implications on optimisation of radiation protection. In the search for an adequate evaluation model, data from endovascular interventions of the aorta (EVAR procedures) were used. The procedure was schematically described in steps. Every imaging event was connected to the steps in the medical procedure and was also described with the purpose of the imaging event. Available technical, as well as procedural parameters, were studied and analysed. Data were collected from the X-ray equipment for 70 EVAR procedures and, out of these, 12 procedures were randomly selected to be recorded on video to understand the procedure better. It was possible to describe the EVAR procedures in a general way with explanations of the clinical purpose connected to each imaging event. Possible quality parameters of the procedure were identified for the imaging events (radiation dose, image quality). The model method still needs to be refined and will then be applied to clinical data and to other clinical procedures to test the validity.
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| 22. |
- Lundvall, Lise-Lott, 1959-, et al.
(författare)
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Does Radiological Protection Training or a Real-Time Staff Dosemeter Display Reduce Staff Doses During X-Ray-Guided Pulmonary Bronchoscopy?
- 2022
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Ingår i: Radiation Protection Dosimetry. - Oxford, United Kingdom : Oxford University Press. - 0144-8420 .- 1742-3406. ; :198, s. 265-273
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Tidskriftsartikel (refereegranskat)abstract
- X-ray guided interventions have increased in number and complexity. Mandatory radiological protection training includes both theoretical and practical training sessions. A recent additional training tool is real-time display dosimeters that give direct feedback to staff on their individual dose rates. Ten staff members who regularly perform pulmonary bronchoscopy wore an extra dosimeter during four two-month periods. We controlled for the patient air kerma area product and the number of procedures in each period. Between periods one and two, radiological training sessions were held and during period three, the staff used the real-time dose rate display system. Focus-group interviews with the staff were held to obtain their opinion about learning radiological protection. We hypothesised that neither training nor the additional real-time dose rate display alters the personal dose equivalent, Hp(d); d=0.07 and 10 mm. Useful experiences from radiological protection training were obtained, and median staff doses did typically decrease, however not always significantly.
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| 23. |
- Magnusson, Maria, 1961-, et al.
(författare)
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ACCURACY OF CT NUMBERS OBTAINED BY DIRA AND MONOENERGETIC PLUS ALGORITHMS IN DUAL-ENERGY COMPUTED TOMOGRAPHY
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 212-217
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Tidskriftsartikel (refereegranskat)abstract
- Dual-energy computed tomography (CT) can be used in radiotherapy treatment planning for the calculation of absorbed dose distributions. The aim of this work is to evaluate whether there is room for improvement in the accuracy of the Monoenergetic Plus algorithm by Siemens Healthineers. A Siemens SOMATOM Force scanner was used to scan a cylindrical polymethyl methacrylate phantom with four rod-inserts made of different materials. Images were reconstructed using ADMIRE and processed with Monoenergetic Plus. The resulting CT numbers were compared with tabulated values and values simulated by the proof-of-a-concept algorithm DIRA developed by the authors. Both the Monoenergetic Plus and DIRA algorithms performed well; the accuracy of attenuation coefficients was better than about ±1% at the energy of 70 keV. Compared with DIRA, the worse performance of Monoenergetic Plus was caused by its (i) two-material decomposition to iodine and water and (ii) imperfect suppression of the beam hardening artifact in ADMIRE.
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| 24. |
- Magnusson, Maria, 1961-, et al.
(författare)
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Optimal Selection of Base Materials for Accurate Dual-Energy Computed Tomography : Comparison Between the Alvarez–Macovski Method and DIRA
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 218-224
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Tidskriftsartikel (refereegranskat)abstract
- The choice of the material base to which the material decomposition is performed in dual-energy computed tomography may affect the quality of reconstructed images. The aim of this work is to investigate how the commonly used bases (water, bone), (water, iodine) and (photoelectric effect, Compton scattering) affect the reconstructed linear attenuation coefficient in the case of the Alvarez–Macovski method. The performance of this method is also compared with the performance of the Dual-energy Iterative Reconstruction Algorithm (DIRA). In both cases, the study is performed using simulations. The results show that the Alvarez–Macovski method produced artefacts when iodine was present in the phantom together with human tissues since this method can only work with one doublet. It was shown that these artefacts could be avoided with DIRA using the (water, bone) doublet for tissues and the (water, iodine) doublet for the iodine solution.
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| 25. |
- Malusek, Alexandr, 1968-, et al.
(författare)
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On The Possibility To Resolve Gadolinium- And Cerium-Based Contrast Agents From Their CT Numbers In Dual-Energy Computed Tomography
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 225-231
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Tidskriftsartikel (refereegranskat)abstract
- Cerium oxide nanoparticles with integrated gadolinium have been proved to be useful as contrast agents in magnetic resonance imaging. Of question is their performance in dual-energy computed tomography. The aims of this work are to determine (1) the relation between the computed tomography number and the concentration of the I, Gd or Ce contrast agent and (2) under what conditions it is possible to resolve the type of contrast agent. Hounsfield values of iodoacetic acid, gadolinium acetate and cerium acetate dissolved in water at molar concentrations of 10, 50 and 100 mM were measured in a water phantom using the Siemens SOMATOM Definition Force scanner; gadolinium- and cerium acetate were used as substitutes for the gadolinium-integrated cerium oxide nanoparticles. The relation between the molar concentration of the I, Gd or Ce contrast agent and the Hounsfield value was linear. Concentrations had to be sufficiently high to resolve the contrast agents.
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| 26. |
- Matsitsi, S. M., et al.
(författare)
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RADIOMETRIC SURVEY OF THE TYAA RIVER SAND MINE IN KITUI, KENYA
- 2020
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 188:4, s. 405-412
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Tidskriftsartikel (refereegranskat)abstract
- Gamma spectroscopic analyses of sand and rock samples from Tyaa River report an average activity concentration of 33 +/- 1, 55 +/- 2.8 and 812 +/- 40.46 Bqkg(-1) for Ra-226, Th-232 and K-40, respectively in the sand. A similar analysis of rock samples reveals a mean of 21 +/- 2.47, 49 +/- 2.47 and 782 +/- 39.13 Bqkg(-1) for Ra-226, Th-232 and K-40, respectively. The absorbed dose rate in rocks averaged 75 +/- 3.78 nGyh(-1), while in the sand was 86.2 +/- 4.31 nGyh(-1). The ranges and mean radiological hazard indices (radium equivalent, internal and external) were within the permissible limits and the use of sand and rocks from this mine as construction material pose no health risks. Correlation analysis between the radioactivity in the sand and rocks reveals weak non-linear positive relationships suggesting that they might be from different bedrocks.
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| 27. |
- Mattsson, Sören, et al.
(författare)
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X-RAY AND MOLECULAR IMAGING DURING PREGNANCY AND BREASTFEEDING—WHEN SHOULD WE BE WORRIED?
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 339-348
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Tidskriftsartikel (refereegranskat)abstract
- Some of the ethically most sensitive issues in radiation protection arise at imaging of pregnant-and potentially pregnant-patients and of newborn. This article reviews the current literature and recommendations on imaging during pregnancy and breastfeeding. Risks related to alternative non-ionizing radiation methods are also considered. With few exceptions, exposure of the fetus through radiography, computed tomography (CT) and nuclear medicine imaging can be limited to safe levels, although studies such as abdominal-pelvic CT cannot avoid significant exposure to fetuses. Eight to 10 weeks post-conception, the fetus has a thyroid which starts to concentrate iodide having crossed the placenta barrier resulting in unacceptably high doses to the fetal thyroid after administration of 131I- and even 123I-iodide and other radiopharmaceuticals with a high content of free radioiodine. Many radiopharmaceuticals are excreted through breast milk. Breastfeeding interruption recommendations should be followed to keep the effective dose to the infant below 1 mSv.
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| 28. |
- Meher, Prabodha Kumar, et al.
(författare)
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Fluorescence in situ hybridisation for interphase chromosomal aberration-based biological dosimetry
- 2023
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Ingår i: Radiation Protection Dosimetry. - 0144-8420 .- 1742-3406. ; 199:14, s. 1501-1507
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Tidskriftsartikel (refereegranskat)abstract
- Metaphase spreads stained with Giemsa or painted with chromosome-specific probes by fluorescence in situ hybridisation (FISH) have been in use since long for retrospective dose assessment (biological dosimetry). However, in cases of accidental exposure to ionising radiation, the culturing of lymphocytes to obtain metaphase chromosomes and analysis of chromosomal aberrations is time-consuming and problematic after high radiation doses. Similarly, analysing chromosomal damage in G0/G1 cells or nondividing cells by premature chromosome condensation is laborious. Following large-scale radiological emergencies, the time required for analysis is more important than precision of dose estimate. Painting of whole chromosomes using chromosome-specific probes in interphase nuclei by the FISH technique will eliminate the time required for cell culture and allow a fast dose estimate, provided that a meaningful dose-response can be obtained by scoring the number of chromosomal domains visible in interphase nuclei. In order to test the applicability of interphase FISH for quick biological dosimetry, whole blood from a healthy donor was irradiated with 8 Gy of gamma radiation. Irradiated whole blood was kept for 2 h at 37°C to allow DNA repair and thereafter processed for FISH with probes specific for Chromosomes-1 and 2. Damaged chromosomal fragments, distinguished by extra color domains, were observed in interphase nuclei of lymphocytes irradiated with 8 Gy. These fragments were efficiently detected and quantified by the FISH technique utilising both confocal and single plane fluorescence microscopy. Furthermore, a clear dose-response curve for interphase fragments was achieved following exposure to 0, 1, 2, 4 and 8 Gy of gamma radiation. These results demonstrate interphase FISH as a promising test for biodosimetry and for studying cytogenetic effects of radiation in nondividing cells.
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| 29. |
- Meltzer, Carin, et al.
(författare)
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Quantification of Pulmonary Pathology in Cystic Fibrosis-Comparison Between Digital Chest Tomosynthesis and Computed Tomography.
- 2021
-
Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:3-4, s. 434-442
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Tidskriftsartikel (refereegranskat)abstract
- Digital tomosynthesis (DTS) is currently undergoing validation for potential clinical implications. The aim of this study was to investigate the potential for DTS as a low-dose alternative to computed tomography (CT) in imaging of pulmonary pathology in patients with cystic fibrosis (CF).DTS and CT were performed as part of the routine triannual follow-up in 31 CF patients. Extent of disease was quantified according to modality-specific scoring systems. Statistical analysis included Spearman's rank correlation coefficient (r) and Krippendorff's alpha (α).The median effective dose was 0.14 for DTS and 2.68 for CT. Intermodality correlation was very strong for total score and the subscores regarding bronchiectasis and bronchial wall-thickening (r=0.82-0.91, P<0.01). Interobserver reliability was high for total score, bronchiectasis and mucus plugging (α=0.83-0.93) in DTS.Chest tomosynthesis could be a low-dose alternative to CT in quantitative estimation of structural lung disease in CF.
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| 30. |
- Nilsson, Isabelle, et al.
(författare)
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THE POTENTIAL TO USE TLD MEASUREMENTS TO VALIDATE THE OCCUPATIONAL RADIATION PROTECTION AT THE DEPARTMENT OF NUCLEAR MEDICINE
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 355-362
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Tidskriftsartikel (refereegranskat)abstract
- Diagnostic examinations in nuclear medicine increase. This can cause a higher radiation burden to the personnel. The aim of this study was to create and apply a method to validate the occupational radiation protection at the Department of Nuclear Medicine using thermoluminescence dosemeters (TLD). Occupational doses in- and outside of the department and the dose rate distribution around the positron emission tomography/computed tomography (PET/CT) were validated in terms of H-p(10) using TLD-100. Backscatter correction factors were estimated to implement the TLD measurements on different materials. After correction for backscatter, the result indicates that doses in- and outside of the department are below recommended values and dose limits. The highest and the lowest dose rate were measured beside the F-18-autoinjector and the PET/CT gantry, respectively. The method of using TLD gives a good estimate of how the occupational radiation protection performs at the Department of Nuclear Medicine and can thus help in the optimization of radiation protection.
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| 31. |
- Nocum, D. J., et al.
(författare)
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UTERINE ARTERY EMBOLISATION: CONTINUOUS QUALITY IMPROVEMENT REDUCES RADIATION DOSE WHILE MAINTAINING IMAGE QUALITY
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 196:3-4, s. 159-166
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to introduce a continuous quality improvement (CQI) program for radiation dose optimisation during uterine artery embolisation (UAE) and assess its impact on dose reduction and image quality. The CQI program investigated the effects of optimising radiation dose parameters on the kerma-area product (KAP) and image quality when comparing a 'CQI intervention' group (n = 50) and 'Control' group (n = 50). Visual grading characteristics (VGC) analysis was used to assess image quality, using the 'Control' group as a reference. A significant reduction in KAP by 17% ( P = 0.041, d = 0.2) and reference air kerma (Ka, r) by 20% (P = 0.027, d = 0.2) was shown between the two groups. The VGC analysis resulted in an area under the VGC curve (AUCVGC) of 0.54, indicating no significant difference in image quality between the two groups (P = 0.670). The implementation of the CQI program and optimisation of radiation dose parameters improved the UAE radiation dose practices at our centre. The dose reduction demonstrated no detrimental effects on image quality.
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| 32. |
- Pettersson, Erik, 1987, et al.
(författare)
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COMPARISON OF METAL ARTEFACTS FOR DIFFERENT DUAL ENERGY CT TECHNIQUES
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 232-245
-
Tidskriftsartikel (refereegranskat)abstract
- This study compares dual-energy computed tomography (DECT) images of a phantom including different material inserts and with additional lateral titanium or stainless steel inserts, simulating bilateral hip prostheses. Dual-source (DS) and fast kV-switching (FKS) DECT with/without metal artefact reduction (MAR) were compared with regards to virtually monoenergetic CT number accuracy and the depiction of different materials. Streak artefacts were observed between the metal inserts that were more severe with steel compared to titanium inserts. The artefact severity and CT number accuracy depended on the photon energy (keV) for both DECT techniques. While MAR generally increased the CT number accuracy and material depiction within the streak artefacts, it sometimes decreased the accuracy outside the streak artefacts for both DS and FKS. FKS depicted the metal inserts more accurately than DS with regards to both CT numbers and external diameter.
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| 33. |
- Rossi-Norrlund, Rauni, 1962, et al.
(författare)
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EVALUATION OF TWO CHEST TOMOSYNTHESIS CYSTIC FIBROSIS SCORING SYSTEMS USING HIGH-RESOLUTION COMPUTED TOMOGRAPHY BRODY SCORING AS REFERENCE
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 443-453
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate two chest tomosynthesis (CTS) scoring systems for cystic fibrosis (CF), one system developed by Vult von Steyern et al. (VvS) and one system based on the Brody scoring system for high-resolution computed tomography (HRCT) (modified Brody (mB)). Brody scoring of HRCT was used as reference. Methods: In conjunction with routine control HRCT at clinical follow-up, 10 consecutive adult CF patients underwent CTS for research purposes. Four radiologists scored the CTS examinations using the mB and VvS scoring systems. All scores were compared to the Brody HRCT scores. The agreement between the evaluated CTS scoring systems and the reference HRCT scoring system was determined using Spearman's rank correlation coefficient and the intraclass correlation coefficient (ICC). Major findings: Spearman's rank correlation coefficient showed strong correlations between HRCT score and both the mB and the VvS CTS total scores (median r(s) = 0.81 and 0.85, respectively). The ICC showed strong correlation between the CTS scoring systems and the reference: 0.88 for mB and 0.85 for VvS scoring. The median time for scoring was 20 and 10 minutes for the mB and VvS scoring systems, respectively. Conclusions: Both evaluated CTS scoring systems correlate well with the reference standard Brody HRCT scoring. The VvS CTS scoring system has a shorter reading time, suggesting its advantage in clinical practice.
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| 34. |
- Ryden, T., et al.
(författare)
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IMPROVEMENTS OF (IN)-I-111 SPECT IMAGES RECONSTRUCTED WITH SPARSELY ACQUIRED PROJECTIONS BY DEEP LEARNING GENERATED SYNTHETIC PROJECTIONS
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 152-157
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to improve single-photon emission computed tomography (SPECT) quality for sparsely acquired In-111 projections by adding deep learning generated synthetic intermediate projections (SIPs). Method: The recently constructed deep convolutional network for generating synthetic intermediate projections (CUSIP) was used for improving 20 sparsely acquired In-111-octreotide SPECTs. Reconstruction was performed with 120 (120P) or 30 (30P) projections, or 120 projections with 90 SIPs generated from 30 projections (30-120SIP). The SPECT reconstructions were performed with attenuation, scatter and collimator response corrections. Postfiltered 30P reconstructed SPECT was also analyzed. Image quality were quantitatively evaluated with root-mean-square error, peak signal-to-noise ratio and structural similarity index metrics. Result: The 30-120SIP reconstructed SPECT had statistically significant improved image quality parameters compared to 30P reconstructed SPECT with and without post filtering. The images visual appearance was similar to slightly filtered 120P SPECTs. Thereby, substantial acquisition time reduction with SIPs seems possible without image quality degradation.
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| 35. |
- Slavicek, Tomas, et al.
(författare)
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APPARATUS FOR LOCALIZATION AND DOSIMETRY OF WOUNDS WITH RADIOACTIVE CONTAMINATION
- 2022
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; , s. 693-697
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Disasters involving radioactive materials are one of the most dangerous accidents a living organism can be exposed to. Individuals and first responders are in risk during accidents or interventions, due to radioactive debris impact, due to the use of depleted uranium ammunition or a malevolent act against individuals. Moreover, radioactive contamination of wounds causes internal exposure in the body and standard decontamination procedures cannot be applied. In order to deal with such situations, we are developing a measurement system consisting of a robotic arm, an array of various detectors and a corresponding methodology, which allows quantifying timely the spatial distribution of contamination and the radiation dose for the adequate medical response. The aim of this publication is to the present current status of the development of the described apparatus.
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| 36. |
- Strandberg, Louise, et al.
(författare)
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EVALUATION OF RADIATION DOSES USING CONE BEAM COMPUTED TOMOGRAPHY IN ENDOVASCULAR AORTIC REPAIR AND SCOLIOSIS PROCEDURES
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 306-313
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this project was to evaluate the radiation dose to patients for cone beam computed tomography (CBCT) in endovascular aortic repair (EVAR) and scoliosis procedures and to compare radiation doses between CBCT and computed tomography (CT). An anthropomorphic phantom and Siemens and General Electric X-ray equipment were used. Default protocol settings were used for comparison of protocols and modalities. The ratio between the highest and lowest CBCT effective dose, for each equipment, had a maximum of 13 (Artis Pheno) for EVAR and 1.8 (Artis Zeego) for scoliosis. It is difficult to predict which modality gives the highest effective dose, e.g. for the CT protocol 'Aorta before EVAR' the ratio between effective doses varied from 0.12 to 1.8, between CBCT and CT. For CBCT EVAR, the effective dose and dose area product decreased using collimation or zoom.
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| 37. |
- Sund, Patrik
(författare)
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IMPROVING IMAGE QUALITY BY INCREASING THE AMOUNT OF LIGHT IN THE READING ROOM
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 426-433
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Tidskriftsartikel (refereegranskat)abstract
- Many standards and guidelines related to the use of medical displays require viewers to be in dark rooms. The purpose of this theoretical study was to examine the validity of some commonly used requirements in terms of image contrast and contrast stability in rooms with fluctuating illuminance. By using the grayscale standard display function (Dicom part 14), contrast was calculated for several combinations of display minimum and maximum luminance as well as the possible range of illuminance fluctuations that will not exceed given contrast tolerance levels. The results show that some requirements are only valid in dark viewing rooms, which are also usually recommended or enforced. However, image contrast, contrast stability, ergonomics and fatigue would improve by using brighter displays in brighter rooms. With a better set of requirements, it would also be possible for displays in brighter rooms, like dentist departments and operating rooms, to conform to the requirements.
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| 38. |
- Svahn, Tony M, et al.
(författare)
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Comparison of photon-counting and flat-panel digital mammmography for the purpose of 3D imaging using a novel image processing method
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 454-461
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present work was to compare the quality of low-dose projections from a photon-counting with a flat-panel system, and to evaluate a novel image processing method. Images were acquired of phantoms in both systems at average glandular doses ranging from similar to 0.15 to 1.4 mGy. Automated detection of low-contrast features and modulation transfer functions were evaluated in phantom images. The novel image processing method was compared with standard processing in a series of clinical cases. At low-doses (similar to 0.15) the photon-counting system out-performed the flat-panel system with a much higher detectability of low-contrast features. The novel algorithm was superior to both manufacturers' processing in terms of conspicuity of soft-tissue lesions (p > 0.05), whereas it was not significantly different in calcification conspicuity. Photon-counting should allow more low-dose projections to be acquired at the same total dose. The novel image enhancer can help to further increase the image quality.
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| 39. |
- Svahn, Tony M, et al.
(författare)
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Comparison of Pulmonary Nodule Detection, Reading Times and Patient Doses of Ultra-Low Dose CT, Standard Dose CT and Digital Radiography
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 196:3-4, s. 234-240
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present work was to evaluate performance in pulmonary nodule detection, reading times and patient doses for ultra-low dose computed tomography (ULD-CT), standard dose chest CT (SD-CT), and digital radiography (DR). Pulmonary nodules were simulated in an anthropomorphic lung phantom. Thirty cases, 18 with lesions (45 total lesions of 3-12 mm) and 12 without lesions were acquired for each imaging modality. Three radiologists interpreted the cases in a free-response study. Performance was assessed using the JAFROC figure-of-merit (FOM). Performance was not significantly different between ULD- CT and SD-CT (FOMs: 0.787 vs 0.814; Delta FOM: 0.03), but both CT techniques were superior to DR (FOM: 0.541; Delta FOM: 0.31 and 0.28). Overall, the CT modalities took longer time to interpret than DR. ULD chest CT may serve as an alternative to both SD-CT and conventional radiography, considerably reducing dose in the first case and improving diagnostic accuracy in the second.
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| 40. |
- Svahn, Tony M, et al.
(författare)
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Effective dose and effect of dose modulation for localizer radiographs using applied and alternative settings on Toshiba/Canon CT systems
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 198-204
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to estimate the effective dose of Toshiba/Canon thorax localizer radiographs for available parameter settings, and to test their dose modulation ability. Localizer radiographs were acquired of anthropomorphic chest phantoms (body mass indices 29 and 23) using various settings (120-80 kV, 100-10 mA). The milliamperes values were compared from resulting helical scan data. Effective dose was computed for two computed tomography (CT) scanners (Aquilion Prime and One Genesis) using a Monte Carlo-based software. For the smaller phantom, all curves were superimposed. For the larger phantom, most curves were also superimposed, except for the one generated from the lowest parameters. The Aquilion Prime system yielded an effective dose of 0.40/0.56 mSv (male/female) using the default parameters. The localizer radiograph dose could be reduced by >90% without affecting the dose modulation. The dose was further reduced by 30-50% in the One Genesis CT system due to improved beam filtration.
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| 41. |
- Svalkvist, Angelica, et al.
(författare)
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VIEWDEX 3.0-RECENT DEVELOPMENT OF A SOFTWARE APPLICATION FACILITATING ASSESSMENT OF IMAGE QUALITY AND OBSERVER PERFORMANCE
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 372-377
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Tidskriftsartikel (refereegranskat)abstract
- ViewDEX (Viewer for Digital Evaluation of X-ray Images) is an image viewer compatible with Digital Imaging and Communications in Medicine (DICOM) that has been especially designed to facilitate image perception and observer performance studies within medical imaging. The software was first released in 2004 and since then a continuous development has been ongoing. One of the major drawbacks of previous versions of ViewDEX has been that they have lacked functionality enabling the possibility to evaluate multiple images and/or image stacks simultaneously. This functionality is especially requested by researchers working with modalities, where an image acquisition can result in multiple image stacks (e.g. axial, coronal and sagittal reformations in computed tomography). In ViewDEX 3.0 this functionality has been added and it is now possible to perform image evaluations of multiple images and/or image stacks simultaneously, by using multiple monitors and/or multiple image canvases in monitors. Additionally, some of the previously available functionality has been updated and improved. This paper describes the recent developments of ViewDEX 3.0.
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| 42. |
- Tesselaar, Erik, 1977-, et al.
(författare)
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MEASUREMENT OF SKIN DOSE AND RADIATION-INDUCED CHANGES IN SKIN MICROCIRCULATION IN CHRONIC TOTAL OCCLUSION PERCUTANEOUS CARDIAC INTERVENTIONS (CTO-PCI)
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 195:3-4, s. 257-263
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Tidskriftsartikel (refereegranskat)abstract
- Skin injuries may occur when radiation doses to the skin exceed 2 Gy. This study aimed to measure changes in skin microcirculation in patients undergoing chronic total occlusion percutaneous coronary interventions (CTO-PCI). In 14 patients, peak skin dose (PSD) was estimated with radiographic films and skin microcirculation was assessed with laser speckle contrast imaging (LSCI), before, 1 day after the intervention, and 4–6 weeks later. The mean PSD was 1.8 ± 0.9 Gy. Peak skin microcirculation increased by 12% from 45 ± 6 PU before to 50 ± 9 PU 1 day after the intervention (p = 0.01), and returned to 46 ± 8 PU after 4–6 weeks (p = 0.15). There was no significant correlation between PSD and the change in perfusion, neither 1 day (r = −0.13, p = 0.69) nor 4–6 weeks after the intervention (r = 0.33, p = 0.35). These results suggest that there are no radiation-induced microvascular changes in the skin after CTO-PCI at skin doses below 2 Gy.
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| 43. |
- Thomas, Rimon, et al.
(författare)
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Analysis of radioactivity in commercially available products aiming to improve health and wellness
- 2023
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Ingår i: Radiation Protection Dosimetry. - 0144-8420 .- 1742-3406. ; 199:13, s. 1392-1400
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Tidskriftsartikel (refereegranskat)abstract
- There are products available on the online market that claim to contain unique ‘energies’ that can improve health and wellness by eliminating toxins and pains and energising food and drinking water. We investigated these products by alpha and gamma spectrometry, and the analysis showed that they contained a few to hundreds of kilobecquerels per kilogram of naturally occurring radionuclides from the 232Th and 238U series. The committed effective dose for an adult drinking water that had been in contact with these products just once was estimated to 12 nSv. Considering a worst-case scenario for the workers inhaling the radioactive substance, 1 d of work would result in an effective dose of 0.39 mSv. The product descriptions do not mention the radionuclide content, and concerns are raised for the consumers and workers exposed to these products with no knowledge of the radioactive content.
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| 44. |
- Visanuyanont, T., et al.
(författare)
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AUTOMATED QC FOR INTERVENTIONAL SYSTEMS AND MAMMOGRAPHY SYSTEMS
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 399-406
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Tidskriftsartikel (refereegranskat)abstract
- Quality control (QC) of X-ray equipment is an important task for patient safety. Periodic QC should not take long to perform, especially in a stressful clinical environment where downtime should be minimised. DOSESTAT-QC (R) is a new quick QC software with automatic image analysis that has been developed into a quality-assured and user-friendly tool for daily use. Trained X-ray personnel can easily perform the QC with selected image phantoms and immediately approve the results onsite before the equipment is used clinically. Image analysis includes visibility of contrast detail groups, homogeneity, signal-to-noise ratio and contrast-to-noise ratio. In the event of unapproved QC, a message is automatically sent to medical physicists and/or medical engineers. The results are stored over time and are available for trend analysis. The present paper describes the DOSESTAT-QC (R) software and its application in QC of interventional X-ray systems and mammography systems.
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| 45. |
- Vodovatov, Aleksandr, et al.
(författare)
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Estimation of the effective doses from typical fluoroscopic examinations with barium contrast
- 2021
-
Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 264-272
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Tidskriftsartikel (refereegranskat)abstract
- The current study aimed to estimate the effective doses and conversion coefficients (CCs) for typical barium swallow (BS), barium meal (BM) and barium enema (BE) protocols and to evaluate the impact of different examination parameters on the resulting CCs. Data were collected in surgical and therapy departments in St. Petersburg Urban Mariinsky Hospital. Computational models were developed using PCXMC 2.0 software. CCs (μSv × μGy-1 × m-2) were estimated, as follows, for over couch and under couch exposure geometries, respectively: 2.3 and 1.7 for BS (surgical department); 2.4 and 2.0 for BM (surgical department); 2.6 and 2.1 for BE (surgical department) 2.5 and 3.8 for BM (therapy department). The effective doses and CCs are mainly influenced by the combination of different fluoroscopic series and X-ray images taken in different projections, the irradiation field size and the energy characteristics of the X-ray beam.
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| 46. |
- Wikberg, Emma, et al.
(författare)
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EVALUATION OF THE SPATIAL RESOLUTION IN MONTE CARLO-BASED SPECT/CT RECONSTRUCTION OF (IN)-I-111-OCTREOTIDE IMAGES
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 195:3-4, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to evaluate the spatial resolution in In-111-octreotide single-photom emission computed tomography (SPECT)/computed tomography (CT) imaging following reconstructions with three different ordered subset expectation maximizations (OSEM) reconstruction algorithms; attenuation corrected (AC) OSEM, AC OSEM with resolution recovery (ACRR OSEM) and Monte Carlo-based OSEM reconstruction (MC OSEM). SPECT/CT imaging of a triple line phantom containing In-111 in air and water was performed. The spatial resolution, represented by the full width at half maximum (FWHM) of a line profile, was determined for each line, for X and Y direction and for all reconstructions. The mean FWHM was 12.2 mm (+/- standard deviation [SD] 3.7 mm) for AC OSEM, 9.3 mm (+/- SD 2.5 mm) for ACRR OSEM and 8.2 mm (+/- SD 2.0 mm) for MC OSEM. MC-based SPECT/CT reconstruction clearly improves the spatial resolution in In-111-octreotide imaging and since MC simulations can be performed for all photon energies MC OSEM has the potential to improve SPECT/CT imaging overall.
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| 47. |
- Ramzaev, Valery, et al.
(författare)
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Ambient dose equivalent rates of gamma radiation from natural radionuclides and 137Cs at grasslands and forests in the area of the Belarusian NPP in the pre-commissioning period (2019)
- 2024
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Ingår i: Radiation Protection Dosimetry. - 0144-8420. ; 200:5, s. 496-503
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Tidskriftsartikel (refereegranskat)abstract
- In situ gamma-spectrometric measurements were performed at grasslands (45 plots) and forests (6 plots) in the vicinity of the Belarusian nuclear power plant in September–October 2019. The aim of the study was to evaluate the baseline level of ambient dose equivalent rates of gamma radiation from natural radionuclides and 137Cs in the period preceding the commissioning of the NPP. The study revealed more than a 2-fold variability in values of the total ambient dose equivalent rate: from 29 to 72 nSv/h. This spread can be explained by variability in the content of natural radionuclides in the environment and, accordingly, ambient dose equivalent rate. At forest sites, compared to grassland sites, the values of ambient dose equivalent rates of gamma radiation from natural radionuclides were statistically significantly lower. The contribution of gamma radiation from 137Cs to the total ambient dose equivalent rate was insignificant and averaged 3% for grasslands and 6% for forests.
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