| 31. |
- Carlander, Anna, et al.
(författare)
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The effect of radiation dose reduction on clinical image quality in chest radiography of premature neonates using a dual-side readout technique computed radiography system
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to investigate if the exposure could be reduced from the clinical setting (resulting in an effective dose of 8 microSv for a neonate of weight 0.7 kg and height 25 cm at a tube voltage of 90 kV) without negatively influencing the image quality for a dual-side readout technique computed radiography (CR) system in chest radiography of premature neonates. Chest radiographs of premature neonates were acquired with the double-side readout technique CR system. The images underwent simulated dose reduction in steps of 20 % to represent five different radiation dose levels. Four image quality criteria, related to the visibility of important anatomical structures, were used in a visual grading study where five experienced radiologists rated how well the criteria were fulfilled for all images. When reducing the radiation dose, a decrease in image quality could be observed already at the 80 % dose level for all the structures. The results indicate that a decrease in exposure from the clinically used setting affects the image quality negatively for the CR system.
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| 32. |
- Ceder, Erik, et al.
(författare)
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THORACIC SPINE IMAGING: A COMPARISON BETWEEN RADIOGRAPHY AND TOMOSYNTHESIS USING VISUAL GRADING CHARACTERISTICS
- 2016
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 169:1-4, s. 204-210
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to evaluate digital tomosynthesis (DTS) in thoracic spine imaging, comparing the reproduction of anatomical structures with that achieved using digital radiography (DR). In a prospective visual grading study, 23 patients referred in 2014 for elective radiographic examination of the thoracic spine were examined using lateral DR and DTS. The DR image and the DTS section images were read in random order by four radiologists, evaluating the ability of the modalities to present a clear reproduction of nine specific relevant structures of the thoracic vertebrae 3, 6 and 9 (T3, T6 and T9). The data were analysed using visual grading characteristics (VGC) analysis. The VGC analysis revealed a statistically significant difference in favour of DTS for all evaluated structures, except for the anterior vertebral edges and lower end plate surfaces of T6 and T9 and the cancellous bone of T9. The difference was most striking in T3 and for posterior structures. For no structure in any vertebra was the reproduction rated significantly better for DR. In conclusion, DTS of the thoracic spine appears to be a promising alternative to DR, especially in areas where the problem of overlaying anatomy is accentuated, such as posterior and upper thoracic structures.
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| 33. |
- 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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| 34. |
- Engström, Andreas, 1983, et al.
(författare)
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A case study of cost-benefit analysis in occupational radiological protection within the healthcare system of Sweden
- 2021
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Ingår i: Journal of Applied Clinical Medical Physics. - : Wiley. - 1526-9914. ; 22, s. 295-304
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to demonstrate cases of cost-benefit analysis within healthcare, of how economic factors can be considered in occupational radiological protection, in agreement with the as low as reasonably achievable principle and present Swedish legislations. In the first part of the present study, a comparison of examples within health economics used by authorities and institutes in Sweden was made. The comparison focused on value of a statistical life, quality-adjusted life year, and monetary cost assigned to a unit of collective dose for radiation protection purposes (α-value). By this comparison, an α-value was determined as an interval between $45 and $450 per man-mSv, for the Swedish society in 2021. The α-value interval can be interpreted as following:. Less than $45 per man-mSv is a good investment. From $45 to $450 per man-mSv, other factors than costs and collective dose are important to consider. More than $450 per man-mSv is too expensive. In the second part of the present study, seven cases of cost-benefit analyses in occupational radiological protection were provided. The present study focused specifically on cases where the relevant factors were costs and collective dose. The present case study shows a large variation in costs per collective dose from different types of occupational radiological protection, used at Skaraborg Hospital in Sweden.
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| 35. |
- Engström, Andreas, 1983, et al.
(författare)
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Lead aprons and thyroid collars: to be, or not to be?
- 2023
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Ingår i: Journal of radiological protection : official journal of the Society for Radiological Protection. - 1361-6498. ; 43:3
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Tidskriftsartikel (refereegranskat)abstract
- Wearing lead aprons and thyroid collars for long periods of time has a subjective component: to balance the effective dose reduction with the effort of carrying a heavy load. Occupational radiation exposure has decreased dramatically in the last century within the health care system. During the same period the use of lead aprons and thyroid collars has also gone up. Therefore, a question that may be raised is: how safe is safe enough? In order to promote stakeholder involvement, the aim of the present study was to investigate staff's experience of discomforts associated with wearing lead aprons and thyroid collars for long periods of time, and also to investigate staff's willingness to tolerate personal dose equivalent (expressed as radiation dose) and the corresponding increase in future cancer risk to avoid wearing these protective tools. A questionnaire was developed and given to staff working in operating or angiography rooms at Skaraborg Hospital in Sweden. The results from the 245 respondents showed that 51% experienced bothersome warmth, 36% experienced fatigue and 26% experienced ache or pain that they believed was associated with wearing lead aprons. One third of the respondents would tolerate a personal dose equivalent of 1 mSv per year to avoid wearing lead aprons, but only a fifth would tolerate the corresponding increase in future cancer risk (from 43% to 43.2%). In conclusion, discomforts associated with wearing lead aprons and thyroid collars for long periods of time are common for the staff using them. At the same time, only a minority of the staff would tolerate a small increase in future cancer risk to avoid wearing them. The present study gives an example of stakeholder involvement and points at the difficulties in making reasonable decisions about the use of these protective tools.
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| 36. |
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| 37. |
- Eriksson, Ida, et al.
(författare)
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Determination of the detective quantum efficiency of gamma camera systems: a Monte Carlo study
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 219-227
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present work was to investigate the validity of using the Monte Carlo technique for determining the detective quantum efficiency (DQE) of a gamma camera system and to use this technique in investigating the DQE behaviour of a gamma camera system and its dependency on a number of relevant parameters. The Monte Carlo-based software SIMIND, simulating a complete gamma camera system, was used in the present study. The modulation transfer function (MTF) of the system was determined from simulated images of a point source of (99m)Tc, positioned at different depths in a water phantom. Simulations were performed using different collimators and energy windows. The MTF of the system was combined with the photon yield and the sensitivity, obtained from the simulations, to form the frequency-dependent DQE of the system. As figure-of-merit (FOM), the integral of the 2D DQE was used. The simulated DQE curves agreed well with published data. As expected, there was a strong dependency of the shape and magnitude of the DQE curve on the collimator, energy window and imaging position. The highest FOM was obtained for a lower energy threshold of 127 keV for objects close to the detector and 131 keV for objects deeper in the phantom, supporting an asymmetric window setting to reduce scatter. The Monte Carlo software SIMIND can be used to determine the DQE of a gamma camera system from a simulated point source alone. The optimal DQE results in the present study were obtained for parameter settings close to the clinically used settings.
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| 38. |
- Fisichella, Valeria A, 1974, et al.
(författare)
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Computer-aided detection (CAD) as a second reader using perspective filet view at CT colonography: effect on performance of inexperienced readers.
- 2009
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Ingår i: Clinical Radiology. - : Elsevier BV. - 1365-229X .- 0009-9260. ; 64:10, s. 972-82
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Tidskriftsartikel (refereegranskat)abstract
- AIM: To evaluate whether computer-aided detection (CAD) as a second reader using perspective filet view [three-dimensional (3D) filet] improves the performance of inexperienced readers at computed tomography colonography (CTC) compared with unassisted 3D filet and unassisted two-dimensional (2D) CTC. MATERIAL AND METHODS: Fifty symptomatic patients underwent CTC and same-day colonoscopy with segmental unblinding. Two inexperienced readers read the CTC studies on 3D filet and 2D several weeks apart. Four months later, readers re-read the cases only evaluating CAD marks using 3D filet. Suspicious CAD marks not previously described on 3D filet were recorded. Jackknife free-response receiver operating characteristic (JAFROC-1) analysis was used to compare the observers' performances in detecting lesions with 3D filet, 2D and 3D filet with CAD. RESULTS: One hundred and three lesions > or =3mm were detected at colonoscopy with segmental unblinding. CAD alone had a sensitivity of 73% (75/103) at a mean false-positive rate per patient of 12.8 in supine and 11.4 in prone. For inexperienced readers sensitivities with 3D filet with CAD were 58% (60/103) and 48% (50/103) with an improvement of 14-16 percentage points (p<0.05) compared with 2D and of 10-11 percentage points (p<0.05) compared with 3D filet. For inexperienced readers, the false-positive rate was 25-41% and 71-200% higher with 3D filet with CAD compared with 3D filet and 2D, respectively. JAFROC-1 analysis showed no significant differences in per-lesion overall performance among reading modes (p=0.8). CONCLUSION: CAD applied as a second reader using 3D filet increased both sensitivity and the number of false positives by inexperienced readers compared with 3D filet and 2D, thus not improving overall performance, i.e., the ability to distinguish between lesions and non-lesions.
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| 39. |
- Fisichella, Valeria A, 1974, et al.
(författare)
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Evaluation of image quality and lesion perception by human readers on 3D CT colonography: comparison of standard and low radiation dose
- 2010
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Ingår i: European Radiology. - 1432-1084. ; 20:3, s. 630-9
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: We compared the prevalence of noise-related artefacts and lesion perception on three-dimensional (3D) CT colonography (CTC) at standard and low radiation doses. METHODS: Forty-eight patients underwent CTC (64 x 0.625 mm collimation; tube rotation time 0.5 s; automatic tube current modulation: standard dose 40-160 mA, low dose 10-50 mA). Low- and standard-dose acquisitions were performed in the supine position, one after the other. The presence of artefacts (cobblestone and snow artefacts, irregularly delineated folds) and the presence of polyps were evaluated by five radiologists on 3D images at standard dose, the original low dose and a modified low dose, i.e. after manipulation of opacity on 3D. RESULTS: The mean effective dose was 3.9 +/- 1.3 mSv at standard dose and 1.03 +/- 0.4 mSv at low dose. The number of images showing cobblestone artefacts and irregularly delineated folds at original and modified low doses was significantly higher than at standard dose (P < 0.0001). Most of the artefacts on modified low-dose images were mild. No significant difference in sensitivity between the dose levels was found for polyps >/=6 mm. CONCLUSIONS: Reduction of the effective dose to 1 mSv significantly affects image quality on 3D CTC, but the perception of >/=6 mm lesions is not significantly impaired.
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| 40. |
- Hansson, Jonny, et al.
(författare)
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A practical approach to prioritise among optimisation tasks in X-ray imaging: introducing the 4-bit concept
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 393-399
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Tidskriftsartikel (refereegranskat)abstract
- According to European and national legislation, as well as international recommendations, X-ray examinations shall be optimised. However, with limited resources and hundreds of different types of X-ray examinations, it may be difficult to prioritise among the optimisation tasks at a radiology department. This work is focused on describing a method that can be used to determine the order of which the examinations should be optimised. In the Medical Exposure Directive from 1997, the European Commission prescribes the content of an optimisation process in relation to medical exposure. A reasonable interpretation of the directive is that the assurance of medical purpose for a justified examination is superior to the need of decreased radiation dose. This was used as a basis for developing a method for prioritisation among optimisation tasks. For each examination type, the following four yes/no questions are raised: (i) Is the present image quality unacceptable? (ii) Is the examination of particular importance? (iii) Is the radiation dose suspiciously high? (iv) Are there special dose level concerns, e.g. diagnostic reference levels? Arguing that a positive response to any of the four questions results in the examination being higher prioritised than otherwise and that the questions are labelled in order of decreasing relevance, it can be shown that the resulting flow chart, determining the order of which the examinations should be optimised, can be described by a 4-bit binary scale. In this way, each examination type is given a number from 0 to 15, a higher number corresponding to the examination being prioritised higher in the optimisation work. The method was applied to a general radiology department and resulted in a well-discriminated distribution of examinations prioritised for optimisation tasks. In conclusion, taking into account both medical outcome and potential risk, the proposed method can be used to determine the order in which examinations at a radiology department should be optimised.
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