| 1. |
- Andersson, Peter, 1975, et al.
(författare)
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Cylindrical ionization chamber response in static and dynamic 6 and 15 MV photon beams
- 2023
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Ingår i: Biomedical Engineering & Physics Express. - : Institute of Physics. - 2057-1976. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. To investigate the response of the CC13 ionization chamber under non-reference photon beam conditions, focusing on penumbra and build-up regions of static fields and on dynamic intensity-modulated beams. Methods. Measurements were performed in 6 MV 100 × 100, 20 × 100, and 20 × 20 mm2 static fields. Monte Carlo calculations were performed for the static fields and for 6 and 15 MV dynamic beam sequences using a Varian multi-leaf collimator. The chamber was modelled using EGSnrc egs_chamber software. Conversion factors were calculated by relating the absorbed dose to air in the chamber air cavity to the absorbed dose to water. Correction and point-dose correction factors were calculated to quantify the conversion factor variations. Results. The correction factors for positions on the beam central axis and at the penumbra centre were 0.98-1.02 for all static fields and depths investigated. The largest corrections were obtained for chamber positions beyond penumbra centre in the off-axis direction. Point-dose correction factors were 0.54-0.71 at 100 mm depth and their magnitude increased with decreasing field size and measurement depth. Factors of 0.99-1.03 were obtained inside and near the integrated penumbra of the dynamic field at 100 mm depth, and of 0.92-0.94 beyond the integrated penumbra centre. The variations in the ionization chamber response across the integrated dynamic penumbra qualitatively followed the behaviour across penumbra of static fields. Conclusions. Without corrections, the CC13 chamber was of limited usefulness for profile measurements in 20-mm-wide fields. However, measurements in dynamic small irregular beam openings resembling the conditions of pre-treatment patient quality assurance were feasible. Uncorrected ionization chamber response could be applied for dose verification at 100 mm depth inside and close to large gradients of dynamically accumulating high- and low-dose regions assuming 3% tolerance between measured and calculated doses. © 2023 The Author(s).
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| 2. |
- Dobbins, James T, et al.
(författare)
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Multi-Institutional Evaluation of Digital Tomosynthesis, Dual-Energy Radiography, and Conventional Chest Radiography for the Detection and Management of Pulmonary Nodules.
- 2017
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Ingår i: Radiology. - : Radiological Society of North America (RSNA). - 1527-1315 .- 0033-8419. ; 282:1
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Tidskriftsartikel (refereegranskat)abstract
- Purpose To conduct a multi-institutional, multireader study to compare the performance of digital tomosynthesis, dual-energy (DE) imaging, and conventional chest radiography for pulmonary nodule detection and management. Materials and Methods In this binational, institutional review board-approved, HIPAA-compliant prospective study, 158 subjects (43 subjects with normal findings) were enrolled at four institutions. Informed consent was obtained prior to enrollment. Subjects underwent chest computed tomography (CT) and imaging with conventional chest radiography (posteroanterior and lateral), DE imaging, and tomosynthesis with a flat-panel imaging device. Three experienced thoracic radiologists identified true locations of nodules (n = 516, 3-20-mm diameters) with CT and recommended case management by using Fleischner Society guidelines. Five other radiologists marked nodules and indicated case management by using images from conventional chest radiography, conventional chest radiography plus DE imaging, tomosynthesis, and tomosynthesis plus DE imaging. Sensitivity, specificity, and overall accuracy were measured by using the free-response receiver operating characteristic method and the receiver operating characteristic method for nodule detection and case management, respectively. Results were further analyzed according to nodule diameter categories (3-4 mm, >4 mm to 6 mm, >6 mm to 8 mm, and >8 mm to 20 mm). Results Maximum lesion localization fraction was higher for tomosynthesis than for conventional chest radiography in all nodule size categories (3.55-fold for all nodules, P < .001; 95% confidence interval [CI]: 2.96, 4.15). Case-level sensitivity was higher with tomosynthesis than with conventional chest radiography for all nodules (1.49-fold, P < .001; 95% CI: 1.25, 1.73). Case management decisions showed better overall accuracy with tomosynthesis than with conventional chest radiography, as given by the area under the receiver operating characteristic curve (1.23-fold, P < .001; 95% CI: 1.15, 1.32). There were no differences in any specificity measures. DE imaging did not significantly affect nodule detection when paired with either conventional chest radiography or tomosynthesis. Conclusion Tomosynthesis outperformed conventional chest radiography for lung nodule detection and determination of case management; DE imaging did not show significant differences over conventional chest radiography or tomosynthesis alone. These findings indicate performance likely achievable with a range of reader expertise. (©) RSNA, 2016 Online supplemental material is available for this article.
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| 3. |
- Katsarelias, Dimitrios, et al.
(författare)
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Leakage through the bone-marrow during isolated limb perfusion in the lower extremity.
- 2019
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Ingår i: Journal of surgical case reports. - : Oxford University Press (OUP). - 2042-8812. ; 2019:4
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Tidskriftsartikel (refereegranskat)abstract
- Isolated limb perfusion (ILP) is used for melanoma in-transit metastases of the extremities. The use of Melphalan and TNF-alpha, necessitates monitoring of possible systemic leakage throughout the perfusion. It has been suspected that leakage through bone marrow is possible. We present the case of a patient with in-transit melanoma metastases in the lower extremity, who underwent minimally invasive ILP, according to our new protocol through percutaneous insertion of the catheters under fluoroscopy. Following cannulation of the vessels a high leakage rate was recorded. The procedure was converted to open with clamping of the artery and vein, however the leakage was not possible to control, and venography showed that this was due to bone marrow veins. To the best of our knowledge this is the first case of a verified leakage during ILP through bone marrow veins. We believe that some minor leakages registered under ILP could be attributed to this leakage route.
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| 4. |
- Leonhardt, Henrik, 1963, et al.
(författare)
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Imaging evaluation of uterine arteries in potential living donors for uterus transplantation: a comparative study of MRA, CTA, and DSA.
- 2022
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Ingår i: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 32, s. 2360-2371
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To evaluate uterine arteries (UA) of potential living donors for uterus transplantation (UTx) by comparison of CT angiography (CTA), digital subtraction angiography (DSA), and MR angiography (MRA) with care taken to minimize radiation doses. M&M: Prospective donors for a clinical UTx trial were included. CTA, DSA, and MRA measurements in three predefined segments of the UAs were evaluated. Radiation doses were estimated and 1-year graft survival was recorded. Results: Twelve potential donors (age 37-62years) were investigated. There was no difference in visualized average UA lumen diameter when comparing CTA (mean 2.0mm, SD 0.4), DSA (mean 2.1mm, SD 0.6), and MRA (mean 2.0mm, SD 0.3). MRA was not able to fully evaluate 10 (43%) out of 23 UA that proved to be patent on DSA. One UA was not identified by any of the modalities, and three MRA-absent UAs were identified by both CTA and DSA. The estimated mean effective dose was lower for DSA (5.1mSv, SD 2.8) than CTA (7.1mSv, SD 2.0), but not significantly (p value=0.06). Three potential donors were excluded due to UA pathology and one due to adenomyosis. Eight donors underwent hysterectomy, with 1-year graft survival in six women. Conclution: MRI including MRA should be the initial modality to examine potential UTx donors to acquire valuable details of uterine anatomy, and if UAs are fully visualized, there is no need for further angiographic methods with radiation. If UAs are not visualized by MRA, CTA may be performed and in selective cases with addition of the invasive modality DSA. Key points: • For uterine transplantation, pelvic MRI with MRA provides information of the uterine structure and of the diameters of uterine arteries in living donors. • Failure of MRA to demonstrate uterine arteries could be followed by CTA which will visualize the uterine arteries in a majority of cases. If MRA and additional CTA provide inconclusive results, the uterine arteries should be further evaluated by DSA. • Information of CTA can be used in the angio-system for DSA settings to minimize the radiation and contrast media doses.
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| 5. |
- Meltzer, Carin, et al.
(författare)
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Surveillance of small, solid pulmonary nodules at digital chest tomosynthesis: data from a cohort of the pilot Swedish CArdioPulmonary bioImage Study (SCAPIS)
- 2021
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 62:3, s. 348-359
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Tidskriftsartikel (refereegranskat)abstract
- Background Digital tomosynthesis (DTS) might be a low-dose/low-cost alternative to computed tomography (CT). Purpose To investigate DTS relative to CT for surveillance of incidental, solid pulmonary nodules. Material and Methods Recruited from a population study, 106 participants with indeterminate solid pulmonary nodules on CT underwent surveillance with concurrently performed CT and DTS. Nodule size on DTS was assessed by manual diameter measurements and semi-automatic nodule segmentations were independently performed on CT. Measurement agreement was analyzed according to Bland-Altman with 95% limits of agreement (LoA). Detection of nodule volume change > 25% by DTS in comparison to CT was evaluated with receiver operating characteristics (ROC). Results A total of 81 nodules (76%) were assessed as measurable on DTS by two independent observers. Inter- and intra-observer LoA regarding change in average diameter were +/- 2 mm. Calculation of relative volume change on DTS resulted in wide inter- and intra-observer LoA in the order of +/- 100% and +/- 50%. Comparing relative volume change between DTS and CT resulted in LoA of -58% to 67%. The area under the ROC curve regarding the ability of DTS to detect volumetric changes > 25% on CT was 0.58 (95% confidence interval [CI] = 0.40-0.76) and 0.50 (95% CI = 0.35-0.66) for the two observers. Conclusion The results of the present study show that measurement variability limits the agreement between DTS and CT regarding nodule size change for small solid nodules.
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