| 1. |
- Arvidsson, Jonathan, 1986, et al.
(författare)
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Automated estimation of in-plane nodule shape in chest tomosynthesis images
- 2015
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Ingår i: International Federation for Medical and Biological Engineering Proceedings. - Cham : Springer International Publishing. - 1680-0737. - 9783319129679 ; 48, s. 20-23
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Konferensbidrag (refereegranskat)abstract
- The purpose of this study was to develop an automated segmentation method for lung nodules in chest tomo-synthesis images. A number of simulated nodules of different sizes and shapes were created and inserted in two different locations into clinical chest tomosynthesis projections. The tomosynthesis volumes were then reconstructed using standard cone beam filtered back projection, with 1 mm slice interval. For the in-plane segmentation, the central plane of each nodule was selected. The segmentation method was formulated as an optimization problem where the nodule boundary corresponds to the minimum of the cost function, which is found by dynamic programming. The cost function was composed of terms related to pixel intensities, edge strength, edge direction and a smoothness constraint. The segmentation results were evaluated using an overlap measure (Dice index) of nodule regions and a distance measure (Hausdorff distance) between true and segmented nodule. On clinical images, the nodule segmentation method achieved a mean Dice index of 0.96 ± 0.01, and a mean Hausdorff distance of 0.5 ± 0.2 mm for isolated nodules and for nodules close to other lung structures a mean Dice index of 0.95 ± 0.02 and a mean Hausdorff distance of 0.5 ± 0.2 mm. The method achieved an acceptable accuracy and may be useful for area estimation of lung nodules.
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| 2. |
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| 3. |
- Asplund, Sara, 1976, et al.
(författare)
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Extended analysis of the effect of learning with feedback on the detectability of pulmonary nodules in chest tomosynthesis
- 2011
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. ; 7966
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In chest tomosynthesis, low-dose projections collected over a limited angular range are used for reconstruction of section images of the chest, resulting in a reduction of disturbing anatomy at a moderate increase in radiation dose compared to chest radiography. In a previous study, we investigated the effects of learning with feedback on the detection of pulmonary nodules in chest tomosynthesis. Six observers with varying degrees of experience of chest tomosynthesis analyzed tomosynthesis cases for presence of pulmonary nodules. The cases were analyzed before and after learning with feedback. Multidetector computed tomography (MDCT) was used as reference. The differences in performance between the two readings were calculated using the jackknife alternative free-response receiver operating characteristics (JAFROC-2) as primary measure of detectability. Significant differences between the readings were found only for observers inexperienced in chest tomosynthesis. The purpose of the present study was to extend the statistical analysis of the results of the previous study, including JAFROC-1 analysis and FROC curves in the analysis. The results are consistent with the results of the previous study and, furthermore, JAFROC-1 gave lower p-values than JAFROC-2 for the observers who improved their performance after learning with feedback. © 2011 SPIE.
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| 4. |
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| 5. |
- Asplund, Sara, 1976, et al.
(författare)
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Learning aspects and potential pitfalls regarding detection of pulmonary nodules in chest tomosynthesis and proposed related quality criteria.
- 2011
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Ingår i: Acta radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 52:5, s. 503-512
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Tidskriftsartikel (refereegranskat)abstract
- Background In chest tomosynthesis, low-dose projections collected over a limited angular range are used for reconstruction of an arbitrary number of section images of the chest, resulting in a moderately increased radiation dose compared to chest radiography. Purpose To investigate the effects of learning with feedback on the detection of pulmonary nodules for observers with varying experience of chest tomosynthesis, to identify pitfalls regarding detection of pulmonary nodules, and present suggestions for how to avoid them, and to adapt the European quality criteria for chest radiography and computed tomography (CT) to chest tomosynthesis. Material and Methods Six observers analyzed tomosynthesis cases for presence of nodules in a jackknife alternative free-response receiver-operating characteristics (JAFROC) study. CT was used as reference. The same tomosynthesis cases were analyzed before and after learning with feedback, which included a collective learning session. The difference in performance between the two readings was calculated using the JAFROC figure of merit as principal measure of detectability. Results Significant improvement in performance after learning with feedback was found only for observers inexperienced in tomosynthesis. At the collective learning session, localization of pleural and subpleural nodules or structures was identified as the main difficulty in analyzing tomosynthesis images. Conclusion The results indicate that inexperienced observers can reach a high level of performance regarding nodule detection in tomosynthesis after learning with feedback and that the main problem with chest tomosynthesis is related to the limited depth resolution.
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| 6. |
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| 7. |
- Baubeta Fridh, Erik, et al.
(författare)
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Comparison of Magnetic Resonance Angiography and Digital Subtraction Angiography for the Assessment of Infrapopliteal Arterial Occlusive Lesions, Based on the TASC II Classification Criteria
- 2020
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Ingår i: Diagnostics (Basel). - : MDPI. - 2075-4418. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- This paper aimed to study the agreement and repeatability, both intra- and interobserver, of infrapopliteal lesion assessment with magnetic resonance angiography (MRA), using the TransAtlantic Inter-Society Consensus (TASC) II criteria, with perioperative digital subtraction angiography (DSA) as a reference. Sixty-eight patients with an MRA preceding an endovascular infrapopliteal revascularization were included. Preoperative MRAs and perioperative DSAs were evaluated in random order by three independent observers using the TASC II classification. The results were analyzed using visual grading characteristics (VGC) analysis and Krippendorffs alpha. No systematic difference was found between modalities: area under the VGC curve (AUC(VGC)) = 0.48 (p = 0.58) or intraobserver; AUC(VGC) for Observer 1 and 2 respectively, 0.49 (p = 0.85) and 0.53 (p = 0.52) for MRA compared with 0.54 (p = 0.30) and 0.49 (p = 0.81) for DSA. Interobserver differences were seen: AUC(VGC) of 0.63 (p < 0.01) for DSA and 0.80 (p < 0.01) for MRA. These results were confirmed using Krippendorffs alpha for the three observers showing 0.13 (95% confidence interval (CI) -0.07-0.31) for MRA and 0.39 (95% CI 0.23-0.53) for DSA. Poor interobserver agreement was also found in the choice of a target vessel on preoperative MRA: Krippendorffs alpha = 0.19 (95% CI 0.01-0.36). In conclusion, infrapopliteal lesions can be reliably determined on preoperative MRA, but interobserver variability regarding the choice of a target vessel is a major concern that appears to affect the overall TASC II grade.
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| 8. |
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| 9. |
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| 10. |
- Båth, Magnus, 1974, et al.
(författare)
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Effective dose to patients from chest examinations with tomosynthesis
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 153-158
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Tidskriftsartikel (refereegranskat)abstract
- Chest tomosynthesis, which refers to the principle of collecting low-dose projections of the chest at different angles and using these projections to reconstruct section images of the chest, is an imaging technique recently introduced to health care. The main purpose of the present work was to determine the average effective dose to patients from clinical use of chest tomosynthesis. Exposure data for two chest radiography laboratories with tomosynthesis option (Definium 8000 with VolumeRAD option, GE Healthcare, Chalfont St. Giles, UK) were registered for 20 patients with a weight between 60 and 80 kg (average weight of 70.2 kg). The recorded data were used in the Monte Carlo program PCXMC 2.0 (STUK-Radiation and Nuclear Safety Authority, Helsinki, Finland) to determine the average effective dose for each projection. The effective dose for the chest tomosynthesis examination, including a scout view and the tomosynthesis acquisition, was finally obtained by adding the effective doses from all projections. Using the weighting factors given in ICRP 103, the average effective dose for the examination was found to be 0.13 mSv, whereas the average effective dose for the conventional two-view chest radiography examination was 0.05 mSv. A conversion factor of 0.26 mSv Gy(-1) cm(-2) was found suitable for determining the effective dose from a VolumeRAD chest tomosynthesis examination from the total registered kerma-area product. In conclusion, the effective dose to a standard-sized patient (170 cm/70 kg) from a VolumeRAD chest tomosynthesis examination is ~2 % of an average chest CT and only two to three times the effective dose from the conventional two-view chest radiography examination.
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| 11. |
- 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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| 12. |
- Båth, Magnus, 1974, et al.
(författare)
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RETROSPECTIVE ESTIMATION OF PATIENT DOSE-AREA PRODUCT IN THORACIC SPINE TOMOSYNTHESIS PERFORMED USING VOLUMERAD.
- 2016
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 169:1-4, s. 281-285
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the use of a recently developed method of retrospectively estimating the patient dose-area product (DAP) of a chest tomosynthesis examination, performed using VolumeRAD, in thoracic spine tomosynthesis and to determine the necessary field-size correction factor. Digital imaging and communications in medicine (DICOM) data for the projection radiographs acquired during a thoracic spine tomosynthesis examination were retrieved directly from the modality for 17 patients. Using the previously developed method, an estimated DAP for the tomosynthesis examination was determined from DICOM data in the scout image. By comparing the estimated DAP with the actual DAP registered for the projection radiographs, a field-size correction factor was determined. The field-size correction factor for thoracic spine tomosynthesis was determined to 0.92. Applying this factor to the DAP estimated retrospectively, the maximum difference between the estimated DAP and the actual DAP was <3 %. In conclusion, the previously developed method of retrospectively estimating the DAP in chest tomosynthesis can be applied to thoracic spine tomosynthesis.
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| 13. |
- Båth, Magnus, 1974, et al.
(författare)
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Retrospective estimation of patient dose-area product in thoracic spine tomosynthesis performed using VolumeRAD
- 2015
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Ingår i: Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: For a tomosynthesis examination performed using the VolumeRAD system (GE Healthcare, Chalfont St. Giles, UK), the scout image is normally the only image stored in the picture archiving and communication system (PACS) that contains dose data in the digital imaging and communications in medicine (DICOM) header. Recently, a method of retrospectively estimating the patient dose-area product (DAP) of a chest tomosynthesis examination performed using the VolumeRAD system from DICOM data available in the scout image was presented (Båth et al, Med Phys 2014). The purpose of the present work was to evaluate the application of the method to thoracic spine tomosynthesis. Material and Methods: DICOM data for the projection radiographs acquired during the examination were retrieved directly from the modality for 17 patients undergoing thoracic spine tomosynthesis with VolumeRAD. Using information about how the exposure parameters for the tomosynthesis examination are determined by the scout image, an estimated DAP for the tomosynthesis examination was determined from DICOM data in the scout image. Based on comparing the estimated DAP with the actual DAP registered for the projection radiographs acquired during the tomosynthesis examination, a correction factor for the adjustment in field size with projection angle was determined. Results: The field-size correction factor for thoracic spine tomosynthesis was determined to 0.92. Applying this factor to the DAP estimated retrospectively from the scout image, the maximum difference between the estimated DAP and the actual DAP was smaller than 3% for all patients. Conclusions: The previously developed method of retrospectively estimating the DAP of a chest tomosynthesis examination performed using the VolumeRAD system from DICOM data in the scout image can be applied also to thoracic spine tomosynthesis. The method may thus be of value for retrospectively estimating patient dose in clinical use of thoracic spine tomosynthesis.
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| 14. |
- 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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| 15. |
- Chodorowski, Artur, 1959, et al.
(författare)
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An attempt to estimate out-of-plane lung nodule elongation in tomosynthesis images
- 2015
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Ingår i: Medical Imaging 2015: Physics of Medical Imaging (SPIE Proceedings). Conference on Medical Imaging - Physics of Medical Imaging. February 22-25, 2015, Orlando, Florida, USA.. - : SPIE. - 0277-786X .- 1605-7422. - 9781628415025
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Konferensbidrag (refereegranskat)abstract
- In chest tomosynthesis (TS) the most commonly used reconstruction methods are based on Filtered Back Projection (FBP) algorithms. Due to the limited angular range of x-ray projections, FBP reconstructed data is typically associated with a low spatial resolution in the out-of-plane dimension. Lung nodule measures that depend on depth information such as 3D shape and volume are therefore difficult to estimate. In this paper the relation between features from FBP reconstructed lung nodules and the true out-of-plane nodule elongation is investigated and a method for estimating the out-of-plane nodule elongation is proposed. In order to study these relations a number of steps that include simulation of spheroidal-shaped nodules, insertion into synthetic data volumes, construction of TS-projections and FBP-reconstruction were performed. In addition, the same procedure was used to simulate nodules and insert them into clinical chest TS projection data. The reconstructed nodule data was then investigated with respect to in-plane diameter, out-of-plane elongation, and attenuation coefficient. It was found that the voxel value in each nodule increased linearly with nodule elongation, for nodules with a constant attenuation coefficient. Similarly, the voxel value increased linearly with in-plane diameter. These observations indicate the possibility to predict the nodule elongation from the reconstructed voxel intensity values. Such a method would represent a quantitative approach to chest tomosynthesis that may be useful in future work on volume and growth rate estimation of lung nodules.
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| 16. |
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| 17. |
- Håkansson, Markus, et al.
(författare)
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ViewDEX 2.0: A Java-based DICOM-compatible software for observer performance studies
- 2009
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. ; 7263
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- ViewDEX (Viewer for Digital Evaluation of X-ray images) is a Java-based DICOM-compatible software tool for observer performance studies that can be used to display medical images with simultaneous registration of the observer's response. The current release, ViewDEX 2.0, is a development of ViewDEX 1.0, which was released in 2007. Both versions are designed to run in a Java environment and do not require any special installation. For example, the program can be located on a memory stick or stand alone hard drive and be run from there. ViewDEX is managed and configured by editing property files, which are plain text files where users, tasks (questions, definitions, etc.) and functionality (WW/WL, PAN, ZOOM, etc.) are defined. ViewDEX reads most common DICOM image formats and the images can be stored in any location connected to the computer. ViewDEX 2.0 is designed so that the user in a simple way can alter if the questions presented to the observers are related to localization or not, enabling e.g. free-response ROC, standard ROC and visual grading studies, as well as combinations of these, to be conducted in a fast and efficient way. The software can also be used for bench marking and for educational purposes. The results from each observer are saved in a log file, which can be exported for further analysis. The software is freely available for non-commercial purposes.
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| 18. |
- Håkansson, Markus, et al.
(författare)
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ViewDEX: an efficient and easy-to-use software for observer performance studies
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 42-51
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Tidskriftsartikel (refereegranskat)abstract
- The development of investigation techniques, image processing, workstation monitors, analysing tools etc. within the field of radiology is vast, and the need for efficient tools in the evaluation and optimisation process of image and investigation quality is important. ViewDEX (Viewer for Digital Evaluation of X-ray images) is an image viewer and task manager suitable for research and optimisation tasks in medical imaging. ViewDEX is DICOM compatible and the features of the interface (tasks, image handling and functionality) are general and flexible. The configuration of a study and output (for example, answers given) can be edited in any text editor. ViewDEX is developed in Java and can run from any disc area connected to a computer. It is free to use for non-commercial purposes and can be downloaded from http://www.vgregion.se/sas/viewdex. In the present work, an evaluation of the efficiency of ViewDEX for receiver operating characteristic (ROC) studies, free-response ROC (FROC) studies and visual grading (VG) studies was conducted. For VG studies, the total scoring rate was dependent on the number of criteria per case. A scoring rate of approximately 150 cases h(-1) can be expected for a typical VG study using single images and five anatomical criteria. For ROC and FROC studies using clinical images, the scoring rate was approximately 100 cases h(-1) using single images and approximately 25 cases h(-1) using image stacks ( approximately 50 images case(-1)). In conclusion, ViewDEX is an efficient and easy-to-use software for observer performance studies.
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(författare)
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A phantom study of nodule size evaluation with chest tomosynthesis and computed tomography.
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 140-143
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present study was to investigate nodule size measurements with chest tomosynthesis (TS) and computed tomography (CT). A 26-mm thick phantom, composed of a Polylite block with embedded spheres of different materials and sizes (4-20 mm), was scanned by both CT and TS. Six observers without prior knowledge of the true diameters of the spheres independently measured the diameter of the spheres on the CT and TS images. Four observers were allowed to change the window settings and two of the observers used predetermined fixed viewing conditions. The mean relative errors for all observers and all measured spheres compared with the known diameter of the spheres were 1.4 % (standard deviation, SD: 5.4 %) on CT images and -1.1 % (SD: 5.0 %) on TS images. With regard to the four observers where the window settings were at the discretion of the observer, the mean relative errors were 1.4 % (SD: 6.4 %) on CT images and -1.7 % (SD: 5.7 %) on TS images. Regarding the two observers using identical viewing conditions the mean relative error was 1.5 % (SD: 2.8 %) on CT images and 0.2 % (SD: 2.6 %) on TS images. In conclusion, the study suggests that nodule size measurements on chest TS might be an alternative to measurements on CT.
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| 23. |
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| 24. |
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| 25. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(författare)
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Overview of two years of clinical experience of chest tomosynthesis at Sahlgrenska University Hospital.
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 124-129
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Tidskriftsartikel (refereegranskat)abstract
- Since December 2006, approximately 3800 clinical chest tomosynthesis examinations have been performed at our department at Sahlgrenska University Hospital. A subset of the examinations has been included in studies of the detectability of pulmonary nodules, using computed tomography (CT) as the gold standard. Visibility studies, in which chest tomosynthesis and CT have been compared side-by side, have been used to determine the depiction potential of chest tomosynthesis. Comparisons with conventional chest radiography have been made. In the clinical setting, chest tomosynthesis has mostly been used as an additional examination. The most frequent indication for chest tomosynthesis has been suspicion of a nodule or tumour. In visibility studies, tomosynthesis has depicted over 90 % of the nodules seen on the CT scan. The corresponding figure for chest radiography has been <30 %. In the detection studies, the lesion-level sensitivity has been approximately 60 % for tomosynthesis and 20 % for chest radiography. In one of the detection studies, an analysis of all false-positive nodules was performed. This analysis showed that all findings had morphological correlates on the CT examinations. The majority of the false-positive nodules were localised in the immediate subpleural region. In conclusion, chest tomosynthesis is an improved chest radiography method, which can be used to optimise the use of CT resources, thereby reducing the radiation dose to the patient population. However, there are some limitations with chest tomosynthesis. For example, patients undergoing tomosynthesis have to be able to stand still and hold their breath firmly for 10 s. Also, chest tomosynthesis has a limited depth resolution, which may explain why pathology in the subpleural region is more difficult to interpret and artefacts from medical devices may occur.
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| 26. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(författare)
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Pulmonary nodule size evaluation with chest tomosynthesis.
- 2012
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Ingår i: Radiology. - : Radiological Society of North America (RSNA). - 1527-1315 .- 0033-8419. ; 265:1, s. 273-82
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate intra- and interobserver variability, as well as agreement for nodule size measurements on chest tomosynthesis and computed tomographic (CT) images. Materials and Methods: The Regional Ethical Review Board approved this study, and all participants gave written informed consent. Thirty-six segmented nodules in 20 patients were included in the study. Eight observers measured the left-to-right, inferior-to-superior, and longest nodule diameters on chest tomosynthesis and CT images. Intra- and interobserver repeatability, as well as agreement between measurements on chest tomosynthesis and CT images, were assessed as recommended by Bland and Altman. Results: The difference between the mean manual and the segmented diameter was -2.2 and -2.3 mm for left-to-right and -2.6 and -2.2 mm for the inferior-to-superior diameter for measurements on chest tomosynthesis and CT images, respectively. Intraobserver 95% limits of agreement (LOA) for the longest diameter ranged from a lower limit of -1.1 mm and an upper limit of 1.0 mm to -1.8 and 1.8 mm for chest tomosynthesis and from -0.6 and 0.9 mm to -3.1 and 2.2 mm for axial CT. Interobserver 95% LOA ranged from -1.3 and 1.5 mm to -2.0 and 2.1 mm for chest tomosynthesis and from -1.8 and 1.1 mm to -2.2 and 3.1 mm for axial CT. The 95% LOA concerning the mean of the observers' measurements of the longest diameter at chest tomosynthesis and axial CT were ±2.1 mm (mean measurement error, 0 mm). For the different observers, the 95% LOA between the modalities ranged from -2.2 and 1.6 mm to -3.2 and 2.8 mm. Conclusion: Measurements on chest tomosynthesis and CT images are comparable, because there is no evident bias between the modalities and the repeatability is similar. The LOA between measurements for the two modalities raise concern if measurements from chest tomosynthesis and CT were to be used interchangeably. © RSNA, 2012 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12111459/-/DC1.
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| 27. |
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| 28. |
- Ludwigs, Karin, et al.
(författare)
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Poor inter-observer agreement in anatomical classifications of infrapopliteal arterial disease due to mandatory selection of only one target artery
- 2023
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 64:3, s. 1298-1306
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Tidskriftsartikel (refereegranskat)abstract
- Background Established anatomical classifications of infrapopliteal arterial lesion severity are based on assessment of only one target artery, not including all infrapopliteal arteries although multivessel revascularization is common. Purpose To investigate the reproducibility of one of these classifications and a new aggregated score. Material and Methods A total of 68 patients undergoing endovascular infrapopliteal revascularization at Sahlgrenska University Hospital during 2008-2016 were included. Preoperative magnetic resonance angiographies (MRA) and digital subtraction angiographies (DSA) were evaluated by three blinded observers in random order, using the infrapopliteal TransAtlantic Inter-Society Consensus (TASC) II classification. An aggregated score, the Infrapopliteal Total Atherosclerotic Burden (I-TAB) score, including all infrapopliteal arteries, was constructed and used for comparison. Results Inter-observer agreement on lesion severity for each evaluated artery was good; Krippendorff's alpha for MRA 0.64-0.79 and DSA 0.66-0.84. Inter-observer agreement on TASC II grade, based on the selected target artery as stipulated, was poor; Krippendorff's alpha 0.14 (95% confidence interval [CI]=-0.05 to 0.30) for MRA and 0.48 (95% CI=0.33-0.61) for DSA. Inter-observer agreement for the new I-TAB score was good; Krippendorff's alpha 0.76 (95% CI=0.70-0.81) for MRA and 0.79 (95% CI=0.74-0.84) for DSA. Conclusion Reproducible assessment of infrapopliteal lesion severity can be achieved for separate arteries with both MRA and DSA using the TASC II definitions. However, poor inter-observer agreement in selecting the target artery results in low reproducibility of the overall infrapopliteal TASC II grade. An aggregated score, such as I-TAB, results in less variability and may provide a more robust evaluation tool of atherosclerotic disease severity.
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| 29. |
- Mirzai, Maral, et al.
(författare)
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The Effect of Dose Reduction on Overall Image Quality in Clinical Chest Tomosynthesis
- 2021
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Ingår i: Academic Radiology. - : Elsevier BV. - 1076-6332. ; 28:10, s. 289-296
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Tidskriftsartikel (refereegranskat)abstract
- Rationale and Objectives: To evaluate the effect of reduction in effective dose on the reproduction of anatomical structures in chest tomosynthesis (CTS). Materials and Methods: Twenty-four CTS examinations acquired at exposure settings resulting in an effective dose of 0.12 mSv for an average sized patient were included in the study. The examinations underwent simulated dose reduction to dose levels corresponding to 32%, 50%, and 70% of the original dose using a previously described and validated method. The image quality was evaluated by five thoracic radiologists who rated the fulfillment of specified image quality criteria in a visual grading study. The ratings for each image quality criterion in the dose-reduced images were compared to the corresponding ratings for the full-dose examinations using visual grading characteristics (VGC) analysis. The area under the resulting VGC curve (AUCVGC) provides a measure of the difference between the ratings, where an AUCVGC of 0.5 indicates no difference. Results: The dose reductions resulted in inferior reproduction of structures compared to the original dose level (AUCVGC <0.5). Structures in the central region of the lung obtained the lowest AUCVGC for each dose level whereas the reproduction of structures in the parenchyma was least affected by the dose reduction. Conclusion: Although previous studies have shown that dose reduction in CTS is possible without affecting the performance of certain clinical tasks, the reproduction of normal anatomical structures is significantly degraded even at small reductions. It is therefore important to consider the clinical purpose of the CTS examinations before deciding on a permanent dose reduction. © 2020 The Association of University Radiologists
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| 30. |
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| 31. |
- Svalkvist, Angelica, et al.
(författare)
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Comparison of different approaches of estimating effective dose from reported exposure data in 3D imaging with interventional fluoroscopy systems
- 2014
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Ingår i: SPIE Medical Imaging 2014, 15-20 February 2014, San Diego, California, USA. Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. ; 9033
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Three-dimensional (3D) imaging with interventional fluoroscopy systems is today a common examination. The examination includes acquisition of two-dimensional projection images, used to reconstruct section images of the patient. The aim of the present study was to investigate the difference in resulting effective dose obtained using different levels of complexity in calculations of effective doses from these examinations. In the study the Siemens Artis Zeego interventional fluoroscopy system (Siemens Medical Solutions, Erlangen, Germany) was used. Images of anthropomorphic chest and pelvis phantoms were acquired. The exposure values obtained were used to calculate the resulting effective doses from the examinations, using the computer software PCXMC (STUK, Helsinki, Finland). The dose calculations were performed using three different methods: 1. using individual exposure values for each projection image, 2. using the mean tube voltage and the total DAP value, evenly distributed over the projection images, and 3. using the mean kV and the total DAP value, evenly distributed over smaller selection of projection images. The results revealed that the difference in resulting effective dose between the first two methods was smaller than 5%. When only a selection of projection images were used in the dose calculations the difference increased to over 10%. Given the uncertainties associated with the effective dose concept, the results indicate that dose calculations based on average exposure values distributed over a smaller selection of projection angles can provide reasonably accurate estimations of the radiation doses from 3D imaging using interventional fluoroscopy systems. © 2014 SPIE.
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| 32. |
- Svalkvist, Angelica, et al.
(författare)
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Comparison of different approaches of estimating the effective dose from CBCT examinations performed using interventional fluoroscopy systems
- 2013
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Ingår i: Nationellt möte om sjukhusfysik 2013, 13-14 november 2013, Varberg.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Three-dimensional (3D) imaging with interventional fluoroscopy systems is today a common examination. The examination includes the collection of a large number of twodimensional projection images of the patient. The projection images are then used to reconstruct CT like images of the patient. The technique is often referred to as cone-beam CT (CBCT). The resulting patient radiation doses from CBCT examinations have previously been reported to be comparable to the radiation doses from conventional CT examinations. However, determining the radiation doses from CBCT examinations is not a straight-forward task. Especially as detailed exposure parameters from the examinations are not provided by the system commercially available. Hence, variations in exposure parameters between the different projection images included in the examination can not always be accounted for. The aim of this study was therefore to evaluate the errors connected to using different methods for calculating the radiation doses from CBCT examinations performed using interventional fluoroscopy systems. In the study the Siemens Artis Zee interventional fluoroscopy system (Siemens Medical Solutions, Erlangen, Germany) was used. An eight-second DynaCT digital radiography protocol was used to collect images of the anthropomorphic pelvis phantom. The exposure values obtained from the examination was used to perform Monte Carlo based calculations of the effective doses resulting from the examination, using the computer software PCXMC (STUK, Helsinki, Finland). Both individual exposure values (kV and mAs) for each projection image included in the examination and constant mean values (kV/mAs and DAP) for all projections were used as input for the dose calculations. In addition, the effects of not including all the projection images in the dose calculations were investigated. Preliminary results show that the effective dose from a pelvis examination using this system is approximately 6 mSv. Only very small variations in resulting effective doses were found between the different methods used for dose calculations (variations smaller than 4%). The results thereby indicate that simplified dose calculations, e.g. using mean exposure values and/or not accounting for each projection image included in the examination, can be used to estimate the radiation doses from CBCT examinations performed using interventional fluoroscopy systems with reasonable accuracy
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| 33. |
- Svalkvist, Angelica
(författare)
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Development of methods for evaluation and optimization of chest tomosynthesis
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tomosynthesis is a low-dose technique that has attracted increasing interest from the medical imaging community during the past decade. Tomosynthesis refers to the technique of acquiring a number of projection radiographs using extremely low exposure over a limited angular range, and using these radiographs to reconstruct slices of the imaged object. These reconstructed slices contain much less overlaying anatomical structures than conventional radiographs, which improves the possibility of obtaining relevant diagnostic information from the examination. The work described in this thesis concerns the development of methods for the evaluation and optimization of tomosynthesis for chest imaging. Conversion factors between exposure and the resulting effective dose to the patient are available for established X-ray procedures. In the present work, corresponding conversion factors were determined for different chest tomosynthesis system configurations and patient sizes using the Monte Carlo technique. Using these conversion factors, the resulting effective dose from a tomosynthesis examination can be estimated using only information on the total exposure resulting from the examination. According to the ALARA (as low as reasonably achievable) principle, all medical imaging should be performed using the lowest possible exposure of the patients to produce images of satisfactory diagnostic quality. To determine the lowest reasonably achievable exposure it is necessary to evaluate images acquired using various amounts of exposure. A method of simulating dose reduction in tomosynthesis was developed in this work. The method is based on the creation of a noise image that can be added to an image to simulate acquisition of the image at a lower dose. By using information about the noise power spectrum (NPS) of the system at different detector dose levels, and by establishing the relationship between pixel value and pixel variance as a function of dose, the noise image can be filtered with a frequency filter to obtain the correct NPS and pixel values. In this way, possible variations in detective quantum efficiency can be accounted for in the dose simulation process. Results from an evaluation of the method indicate that the method is appropriate for simulating dose reduction of tomo¬synthesis projection radiographs. In order to thoroughly evaluate the performance of chest tomosynthesis in nodule detection, images containing nodules of different sizes and densities, located in different regions of the lung parenchyma, are needed. A method of simulating lung nodules in chest tomosynthesis was developed and evaluated. The method is based on the creation of three-dimensional artificial nodules that are inserted into the tomosynthesis projection images before reconstruction of the section images. The signal spread in the detector, the scattered radiation and patient motion were accounted for in the simulation process. The sensitivity for the simulated nodules was shown to be similar to that for real nodules, and experienced radiologists had difficulty in visually differentiating between real and simulated nodules. The nodule simulation method can be used to investigate the limitations in detection of lung nodules in chest tomosynthesis, without introducing any substantial bias compared to the use of clinical images.
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| 34. |
- Svalkvist, Angelica, et al.
(författare)
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EFFECTIVE DOSE TO PATIENTS FROM THORACIC SPINE EXAMINATIONS WITH TOMOSYNTHESIS.
- 2016
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 169:1-4, s. 274-280
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Tidskriftsartikel (refereegranskat)abstract
- The purposes of the present work were to calculate the average effective dose to patients from lateral tomosynthesis examinations of the thoracic spine, compare the results with the corresponding conventional examination and to determine a conversion factor between dose-area product (DAP) and effective dose for the tomosynthesis examination. Thoracic spine examinations from 17 patients were included in the study. The registered DAP and information about the field size for each projection radiograph were, together with patient height and mass, used to calculate the effective dose for each projection radiograph. The total effective doses for the tomosynthesis examinations were obtained by adding the effective doses from the 60 projection radiographs included in the examination. The mean effective dose was 0.47 mSv (range 0.24-0.81 mSv) for the tomosynthesis examinations and 0.20 mSv (range 0.07-0.29 mSv) for the corresponding conventional examinations (anteroposterior + left lateral projection). For the tomosynthesis examinations, a conversion factor between total DAP and effective dose of 0.092 mSv Gycm(-2) was obtained.
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| 35. |
- Svalkvist, Angelica, et al.
(författare)
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Effective dose to patients from thoracic spine examinations with tomosynthesis
- 2015
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Ingår i: Optimisation in X-ray and Molecular Imaging 2015 - the Fourth Malmö Conference on Medical Imaging, Gothenburg, Sweden, 28-30 May 2015.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Tomosynthesis, which refers to the principle of collecting low-dose projections of the patient at different angles and using these projections to reconstruct section images of the patient, is an imaging technique recently introduced to healthcare. Phantom evaluations have indicated that the effective dose of a thoracic spine examination using tomosynthesis is about twice the dose from a conventional radiological thoracic spine examination (including four projections), but no detailed description of actual patient doses has been published. The aims of the present work were to calculate the average effective dose to patients from clinical use of tomosynthesis for lateral thoracic spine examinations and to determine a conversion factor between kerma-area product (KAP) and effective dose for the examination. The GE Discovery XR656 system with VolumeRAD option (GE Healthcare, Chalfont St. Giles, UK) was used to perform thoracic spine tomosynthesis examinations on 17 patients. The examinations included both patients standing up and patients laying down. The recorded dose data consisted of the registered KAP for each of the 60 projection radiographs collected in a tomosynthesis examination and by examining the image data, the field size for each projection radiograph was obtained. These data, together with information of the patient height and weight, were used in the Monte Carlo program PCXMC 2.0 (STUK – Radiation and Nuclear Safety Authority, Helsinki, Finland) to calculate the effective dose for each projection radiograph, using the conversion factors given in ICRP 103. The total effective dose for the tomosynthesis examinations were finally obtained by adding the effective doses from the 60 projection radiographs included in each examination. Based on a comparison between the total registered KAP of the tomosynthesis examination and the calculated effective dose, a conversion factor between total KAP and effective dose was determined. The results revealed that the mean effective dose for the thoracic spine examinations was 0.47 mSv (range, 0.24-0.81 mSv). Using the mean total KAP of the examinations and the mean calculated effective dose a conversion factor of 0.092 mSv/Gycm2 was obtained. The obtained conversion factor agrees well with the conversion factor of 0.091 mSv/Gycm2 previously reported for conventional radiological lateral thoracic spine examinations (Wall et al., Report HPA-CRCE-028, Health Protection Agency, UK, 2011).
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| 36. |
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| 37. |
- Svalkvist, Angelica, et al.
(författare)
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Evaluation of an improved method of simulating lung nodules in chest tomosynthesis
- 2012
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 53:8, s. 874-884
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Tidskriftsartikel (refereegranskat)abstract
- Background: Simulated pathology is a valuable complement to clinical images in studies aiming at evaluating an imaging technique. In order for a study using simulated pathology to be valid, it is important that the simulated pathology in a realistic way reflect the characteristics of real pathology. Purpose: To perform a thorough evaluation of a nodule simulation method for chest tomosynthesis, comparing the detection rate and appearance of the artificial nodules with those of real nodules in an observer performance experiment. Material and Methods: A cohort consisting of 64 patients, 38 patients with a total of 129 identified pulmonary nodules and 26 patients without identified pulmonary nodules, was used in the study. Simulated nodules, matching the real clinically found pulmonary nodules by size, attenuation, and location, were created and randomly inserted into the tomosynthesis section images of the patients. Three thoracic radiologists and one radiology resident reviewed the images in an observer performance study divided into two parts. The first part included nodule detection and the second part included rating of the visual appearance of the nodules. The results were evaluated using a modified receiver-operating characteristic (ROC) analysis. Results: The sensitivities for real and simulated nodules were comparable, as the area under the modified ROC curve (AUC) was close to 0.5 for all observers (range, 0.43-0.55). Even though the ratings of visual appearance for real and simulated nodules overlapped considerably, the statistical analysis revealed that the observers to were able to separate simulated nodules from real nodules (AUC values range 0.70-0.74). Conclusion: The simulation method can be used to create artificial lung nodules that have similar detectability as real nodules in chest tomosynthesis, although experienced thoracic radiologists may be able to distinguish them from real nodules.
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| 38. |
- Svalkvist, Angelica, et al.
(författare)
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Evaluation of deep-learning image reconstruction for chest CT examinations at two different dose levels.
- 2023
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Ingår i: Journal of applied clinical medical physics. - : Wiley. - 1526-9914. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- The aims of the present study were to, for both a full-dose protocol and an ultra-low dose (ULD) protocol, compare the image quality of chest CT examinations reconstructed using TrueFidelity (Standard kernel) with corresponding examinations reconstructed using ASIR-V (Lung kernel) and to evaluate if post-processing using an edge-enhancement filter affects the noise level, spatial resolution and subjective image quality of clinical images reconstructed using TrueFidelity.A total of 25 patients were examined with both a full-dose protocol and an ULD protocol using a GE Revolution APEX CT system (GE Healthcare, Milwaukee, USA). Three different reconstructions were included in the study: ASIR-V 40%, DLIR-H, and DLIR-H with additional post-processing using an edge-enhancement filter (DLIR-H + E2). Five observers assessed image quality in two separate visual grading characteristics (VGC) studies. The results from the studies were statistically analyzed using VGC Analyzer. Quantitative evaluations were based on determination of two-dimensional power spectrum (PS), contrast-to-noise ratio (CNR), and spatial resolution in the reconstructed patient images.For both protocols, examinations reconstructed using TrueFidelity were statistically rated equal to or significantly higher than examinations reconstructed using ASIR-V 40%, but the ULD protocol benefitted more from TrueFidelity. In general, no differences in observer ratings were found between DLIR-H and DLIR-H + E2. For the three investigated image reconstruction methods, ASIR-V 40% showed highest noise and spatial resolution and DLIR-H the lowest, while the CNR was highest in DLIR-H and lowest in ASIR-V 40%.The use of TrueFidelity for image reconstruction resulted in higher ratings on subjective image quality than ASIR-V 40%. The benefit of using TrueFidelity was larger for the ULD protocol than for the full-dose protocol. Post-processing of the TrueFidelity images using an edge-enhancement filter resulted in higher image noise and spatial resolution but did not affect the subjective image quality.
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| 39. |
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| 40. |
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| 41. |
- Svalkvist, Angelica, et al.
(författare)
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Investigation of the dosimetry of chest tomosynthesis
- 2009
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Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. ; 7258
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Chest tomosynthesis has recently been introduced to healthcare as a low-dose alternative to CT or as a tool for improved diagnostics in chest radiography with only a modest increase in radiation dose to the patient. However, no detailed description of the dosimetry for this type of examination has been presented. The aim of this work was therefore to investigate the dosimetry of chest tomosynthesis. The chest tomosynthesis examination was assumed to be performed using a stationary detector and a vertically moving x-ray tube, exposing the patient from different angles. The Monte Carlo-based computer software PCXMC was used to determine the effective dose delivered to a standard-sized patient from various angles using different assumptions of the distribution of the effective dose over the different projections. The obtained relationships between input dose measures and effective dose for chest tomosynthesis for different angular intervals were then compared with the osteroanterior (PA) projection. The results indicate that the error is small when using the assumption that all effective dose in the case of chest tomosynthesis is delivered in PA projection for estimating the total effective dose for chest tomosynthesis for normally sized patients. This is especially true if the relationship between the kerma-area product (KAP) and effective dose is used. © 2009 SPIE.
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| 42. |
- Svalkvist, Angelica, et al.
(författare)
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Investigation of the effect of varying scatter-to-primary ratios on nodule contrast in chest tomosynthesis
- 2011
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Ingår i: Medical Imaging 2011. - : SPIE - International Society for Optical Engineering. - 9780819485038 ; 7961
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The primary aim of the present work was to analyze the effects of varying scatter-to-primary ratios on the appearance of simulated nodules in chest tomosynthesis section images. Monte Carlo simulations of the chest tomosynthesis system GE Definium 8000 VolumeRAD (GE Healthcare, Chalfont St. Giles, UK) were used to investigate the variation of scatter-to-primary ratios between different angular projections. The simulations were based on a voxel phantom created from CT images of an anthropomorphic chest phantom. An artificial nodule was inserted at 80 different positions in the simulated phantom images, using five different approaches for the scatter-to-primary ratios in the insertion process. One approach included individual determination of the scatter-to primary-ratio for each projection image and nodule location, while the other four approaches were using mean value, median value and zero degree projection value of the scatter-to-primary ratios at each nodule position as well as using a constant scatter-to-primary ratio of 0.5 for all nodule positions. The results indicate that the scatter-to-primary ratios vary up to a factor of 10 between the different angular tomosynthesis projections (±15°). However, the error in the resulting nodule contrast introduced by not taking all variations into account is in general smaller than 10 %.
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| 43. |
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| 44. |
- Svalkvist, Angelica, et al.
(författare)
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Monte Carlo simulations of the dosimetry of chest tomosynthesis
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 144-152
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Tidskriftsartikel (refereegranskat)abstract
- The aims of this work were to explore the dosimetry of chest tomosynthesis and to determine conversion factors between air kerma-area product (KAP) and the effective dose for different system configurations and patient sizes. Tomosynthesis systems were modelled with different angular intervals and tube voltages for the collection of the projection images as well as different distributions of the total exposure over the projections. The Monte Carlo-based computer software PCXMC developed by STUK (Radiation and Nuclear Safety Authority in Finland) was used to calculate the effective doses for each modelled tomosynthesis system for various patient sizes. The conversion factor between KAP and effective dose was obtained both for the zero-degree projection alone and for the entire tomosynthesis examination for each system configuration and patient size. The results reveal that the conversion factor for the zero-degree projection can be used to estimate the total effective dose from a tomosynthesis examination with acceptable accuracy, leading to an error smaller than 10 % irrespective of the system configuration and patient size. For higher accuracy, conversion factors between the total KAP and the total effective dose that take the angular interval and exposure configuration into account are presented for each system.
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| 45. |
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| 46. |
- Svalkvist, Angelica, et al.
(författare)
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Simulation of dose reduction in tomosynthesis.
- 2010
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Ingår i: Medical physics. - : Wiley. - 0094-2405. ; 37:1, s. 258-69
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Methods for simulating dose reduction are valuable tools in the work of optimizing radiographic examinations. Using such methods, clinical images can be simulated to have been collected at other, lower, dose levels without the need of additional patient exposure. A recent technology introduced to healthcare that needs optimization is tomosynthesis, where a number of low-dose projection images collected at different angles is used to reconstruct section images of an imaged object. The aim of the present work was to develop a method of simulating dose reduction for digital radiographic systems, suitable for tomosynthesis. METHODS: The developed method uses information about the noise power spectrum (NPS) at the original dose level and the simulated dose level to create a noise image that is added to the original image to produce an image that has the same noise properties as an image actually collected at the simulated dose level. As the detective quantum efficiency (DQE) of digital detectors operating at the low dose levels used for tomosynthesis may show a strong dependency on the dose level, it is important that a method for simulating dose reduction for tomosynthesis takes this dependency into account. By applying an experimentally determined relationship between pixel mean and pixel variance, variations in both dose and DQE in relevant dose ranges are taken into account. RESULTS: The developed method was tested on a chest tomosynthesis system and was shown to produce NPS of simulated dose-reduced projection images that agreed well with the NPS of images actually collected at the simulated dose level. The simulated dose reduction method was also applied to tomosynthesis examinations of an anthropomorphic chest phantom, and the obtained noise in the reconstructed section images was very similar to that of an examination actually performed at the simulated dose level. CONCLUSIONS: In conclusion, the present article describes a method for simulating dose reduction suitable for tomosynthesis. However, the method applies equally well to any digital radiographic system, although the benefits of correcting for DQE variations may be smaller.
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| 47. |
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| 48. |
- Svalkvist, Angelica, et al.
(författare)
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Simulation of lung nodules in chest tomosynthesis
- 2010
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Ingår i: RADIATION PROTECTION DOSIMETRY. - : Oxford University Press. - 0144-8420 .- 1742-3406. ; 139:1-3, s. 130-139
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present work was to develop an adequate method for simulating lung nodules in clinical chest tomosynthesis images. Based on the visual appearance of real nodules, artificial, three-dimensional nodules with irregular shape and surface structure were created using an approach of combining spheres of different sizes and central points. The nodules were virtually positioned at the desired locations inside the patient and by using the known geometry of the tomosynthesis acquisition, the radiation emitted from the focal spot, passing through the nodule and reaching the detector could be simulated. The created nodules were thereby projected into raw-data tomosynthesis projection images before reconstruction of the tomosynthesis section images. The focal spot size, signal spread in the detector, scattered radiation, patient motion and existing anatomy at the location of the nodule were taken into account in the simulations. It was found that the blurring caused by the modulation transfer function and the patient motion overshadows the effects of a finite focal spot and aliasing and also obscures the surface structure of the nodules, which provides an opportunity to simplify the simulations and decrease the simulation times. Also, the limited in-depth resolution of the reconstructed tomosynthesis section images reduces the necessity to take details of the anatomical structures at the location of the inserted nodule into account.
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| 49. |
- Svalkvist, Angelica, et al.
(författare)
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The benefit of accounting for DQE variations in simulated dose reduction of digital radiographic systems
- 2010
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 57-61
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Tidskriftsartikel (refereegranskat)abstract
- Adding noise to clinical radiographs to simulate dose reduction can be used to investigate the relationship between dose level and clinical image quality without exposing patients to additional radiation. The purpose of the present paper was to examine the benefits of using a method that accounts for detective quantum efficiency (DQE) variations that may occur in different dose ranges in the simulated dose reduction process. A method initially intended for simulated dose reduction in tomosynthesis was applied to extremely low-dose posterioanterior radiographs of an anthropomorphic chest phantom, selected from a group of projection images included in a tomosynthesis examination and compared with a previous method that do not account for DQE variations. A comparison of images simulated to be collected at a lower dose level (73 % of the original dose level) and images actually collected at this lower dose level revealed that the error in the integrated normalised noise power spectrum was smaller than 4 % for the method that accounts for DQE variations in the simulated dose reduction, whereas the error was larger than 20 % for the previous method. This indicates that an increased validity in dose reduction simulation of digital radiographic systems is obtained with a method accounting for DQE variations.
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| 50. |
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