| 1. |
- Bujila, Robert, et al.
(författare)
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A validation of SpekPy: A software toolkit for modelling X-ray tube spectra
- 2020
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Ingår i: Physica medica (Testo stampato). - : Elsevier BV. - 1120-1797 .- 1724-191X. ; 75, s. 44-54
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To validate the SpekPy software toolkit that has been developed to estimate the spectra emitted fromtungsten anode X-ray tubes. The model underlying the toolkit introduces improvements upon a well-knownsemi-empirical model of X-ray emission.Materials and methods: Using the same theoretical framework as the widely-used SpekCalc software, new electronpenetration data was simulated using the Monte Carlo (MC) method, alternative bremsstrahlung crosssectionswere applied, L-line characteristic emissions were included, and improvements to numerical methodsimplemented. The SpekPy toolkit was developed with the Python programming language. The toolkit was validatedagainst other popular X-ray spectrum models (50 to 120 kVp), X-ray spectra estimated with MC (30 to150 kVp) as well as reference half value layers (HVL) associated with numerous radiation qualities from standardlaboratories (20 to 300 kVp).Results: The toolkit can be used to estimate X-ray spectra that agree with other popular X-ray spectrum modelsfor typical configurations in diagnostic radiology as well as with MC spectra over a wider range of conditions.The improvements over SpekCalc are most evident at lower incident electron energies for lightly and moderatelyfiltered radiation qualities. Using the toolkit, estimations of the HVL over a large range of standard radiationqualities closely match reference values.Conclusions: A toolkit to estimate X-ray spectra has been developed and extensively validated for central-axisspectra. This toolkit can provide those working in Medical Physics and beyond with a powerful and user-friendlyway of estimating spectra from X-ray tubes.
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| 2. |
- Merzan, D., et al.
(författare)
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Evaluating the impact of scan settings on automatic tube current modulation in CT using a novel phantom
- 2017
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Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 90:1069
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this study was to make a comprehensive evaluation of how variable scan settings can affect the performance of automatic tube current modulation (ATCM) in recent CT scanners from the four major manufacturers. Methods: A phantom was designed and manufactured for the purpose of evaluating ATCM. The phantom was scanned with four categories of systematically varied settings (scan projection radiograph, technique and reconstruction parameters and phantom miscentring). The performance of ATCM, in terms of applied tube current and noise uniformity, for the scans with varied settings was compared with a reference scan using subjective and quantitative approaches. Results: The ATCM implemented by each manufacturer is based on different principles and any affect to the performance of the ATCM, when varying scan settings, will manifest differently among the vendors. The results are summarized in four tables corresponding to the categories of varied settings. Conclusion: The developed phantom proved useful for evaluating the ATCM. It is important to understand how different implementations (vendor specific) of ATCM perform in order to make informed decisions about the selection of scan settings when designing protocols. The resulting tables can serve as a reference for understanding the different implementations of ATCM and highlight settings that should be taken into consideration when adjusting an imaging protocol. Advances in knowledge: The results from this work can serve as a reference for how changes in geometry or scan settings can affect the performance of ATCM, in terms of tube current and noise.
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| 3. |
- Nowik, P., et al.
(författare)
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The synthetic localizer radiograph – A new CT scan planning method
- 2019
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Ingår i: Physica medica (Testo stampato). - : Elsevier BV. - 1120-1797 .- 1724-191X. ; 61, s. 58-63
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate if the conventional localizer radiograph (LR)can be replaced by a synthetic LR (SLR), generated from a low-dose spiral CT scan, for CT scan planning with minimal changes to current clinical workflows. Methods: A dosimetric comparison of SLRs and LRs was made using Monte Carlo methods. Water equivalent diameters (WEDs)of a centered and mis-centered phantom were estimated from low-dose spiral CT scans and LRs acquired at different angles. Body sizes, in the form of two lengths and two diameters obtained from SLRs and LRs, were compared for 10 patients (4 men and 6 women with a mean age of 74.8 and 76.2 years respectively)undergoing CT of thorax and abdomen. The image quality of SLRs for CT scan planning relative to LRs was rated using a 5-grade scale by four radiologists and two CT radiographers. Results: An SLR can be obtained at a comparable effective dose to that of traditionally acquired LRs: 0.14 mSv. WEDs from LRs were more affected by mis-centering than WEDs calculated from low-dose spiral scans. One significant discrepancy of estimated body sizes was observed, the broadest part of the patient that on lateral localizers showed a mean deviation of 17.7 mm (range: 7.3–28.7 mm, p < 0.001). The anteroposterior/posteroanterior SLR image quality was assessed as better compared to an LR while the same could not be shown for lateral localizers. Conclusions: SLRs based on low-dose spiral scans can replace LRs for CT planning.
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| 4. |
- Omar, A., et al.
(författare)
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A framework for organ dose estimation in x-ray angiography and interventional radiology based on dose-related data in DICOM structured reports
- 2016
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Ingår i: Physics in Medicine and Biology. - Stockholm : Institute of Physics Publishing (IOPP). - 0031-9155 .- 1361-6560. ; 61:8, s. 3063-3083
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Tidskriftsartikel (refereegranskat)abstract
- Although interventional x-ray angiography (XA) procedures involve relatively high radiation doses that can lead to deterministic tissue reactions in addition to stochastic effects, convenient and accurate estimation of absorbed organ doses has traditionally been out of reach. This has mainly been due to the absence of practical means to access dose-related data that describe the physical context of the numerous exposures during an XA procedure. The present work provides a comprehensive and general framework for the determination of absorbed organ dose, based on non-proprietary access to dose-related data by utilizing widely available DICOM radiation dose structured reports. The framework comprises a straightforward calculation workflow to determine the incident kerma and reconstruction of the geometrical relation between the projected x-ray beam and the patient's anatomy. The latter is difficult in practice, as the position of the patient on the table top is unknown. A novel patient-specific approach for reconstruction of the patient position on the table is presented. The proposed approach was evaluated for 150 patients by comparing the estimated position of the primary irradiated organs (the target organs) with their position in clinical DICOM images. The approach is shown to locate the target organ position with a mean (max) deviation of 1.3 (4.3), 1.8 (3.6) and 1.4 (2.9) cm for neurovascular, adult and paediatric cardiovascular procedures, respectively. To illustrate the utility of the framework for systematic and automated organ dose estimation in routine clinical practice, a prototype implementation of the framework with Monte Carlo simulations is included.
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