| 1. |
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| 2. |
- Asplund, Sara, 1976, et al.
(author)
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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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In: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. ; 7966
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Journal article (other academic/artistic)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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| 3. |
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| 4. |
- Asplund, Sara, 1976, et al.
(author)
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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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In: Acta radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 52:5, s. 503-512
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Journal article (peer-reviewed)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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| 8. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(author)
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A phantom study of nodule size evaluation with chest tomosynthesis and computed tomography.
- 2010
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In: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 140-143
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Journal article (peer-reviewed)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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| 10. |
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| 11. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(author)
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Nodule detection by chest tomosynthesis
- 2009
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In: 2nd World Congress of Thoracic Imaging and Diagnosis in Chest Disease, 30 May-2 June 2009, Valencia, Spain.
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Conference paper (other academic/artistic)
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| 12. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(author)
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Overview of two years of clinical experience of chest tomosynthesis at Sahlgrenska University Hospital.
- 2010
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In: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 139:1-3, s. 124-129
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Journal article (peer-reviewed)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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| 13. |
- Johnsson, Åse (Allansdotter), 1966, et al.
(author)
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Pulmonary nodule size evaluation with chest tomosynthesis.
- 2012
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In: Radiology. - : Radiological Society of North America (RSNA). - 1527-1315 .- 0033-8419. ; 265:1, s. 273-82
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Journal article (peer-reviewed)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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| 14. |
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| 15. |
- Pesonen, Ida, et al.
(author)
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High prevalence of interstitial lung abnormalities in middle-aged never-smokers
- 2023
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In: ERJ Open Research. - : European Respiratory Society. - 2312-0541. ; 9:5
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Journal article (peer-reviewed)abstract
- BACKGROUND: Interstitial lung abnormalities (ILA) are incidental findings on chest computed tomography (CT). These patterns can present at an early stage of fibrotic lung disease. Our aim was to estimate the prevalence of ILA in the Swedish population, in particular in never-smokers, and find out its association with demographics, comorbidities and symptoms.METHODS: Participants were recruited to the Swedish CArdioPulmonary BioImage Study (SCAPIS), a population-based survey including men and women aged 50-64 years performed at six university hospitals in Sweden. CT scan, spirometry and questionnaires were performed. ILA were defined as cysts, ground-glass opacities, reticular abnormality, bronchiectasis and honeycombing.FINDINGS: Out of 29 521 participants, 14 487 were never-smokers and 14 380 were men. In the whole population, 2870 (9.7%) had ILA of which 134 (0.5%) were fibrotic. In never-smokers, the prevalence was 7.9% of which 0.3% were fibrotic. In the whole population, age, smoking history, chronic bronchitis, cancer, coronary artery calcium score and high-sensitive C-reactive protein were associated with ILA. Both ILA and fibrotic ILA were associated with restrictive spirometric pattern and impaired diffusing capacity of the lung for carbon monoxide. However, individuals with ILA did not report more symptoms compared with individuals without ILA.INTERPRETATION: ILA are common in a middle-aged Swedish population including never-smokers. ILA may be at risk of being underdiagnosed among never-smokers since they are not a target for screening.
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| 16. |
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| 17. |
- Svalkvist, Angelica, et al.
(author)
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Evaluation of an improved method of simulating lung nodules in chest tomosynthesis
- 2012
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In: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 53:8, s. 874-884
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Journal article (peer-reviewed)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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| 18. |
- Vikgren, Jenny, 1957, et al.
(author)
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Comparison of chest tomosynthesis and chest radiography for detection of pulmonary nodules: human observer study of clinical cases.
- 2008
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In: Radiology. - : Radiological Society of North America (RSNA). - 1527-1315 .- 0033-8419. ; 249:3, s. 1034-1041
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Journal article (peer-reviewed)abstract
- PURPOSE: To compare chest tomosynthesis with chest radiography in the detection of pulmonary nodules by using multidetector computed tomography (CT) as the reference method. MATERIALS AND METHODS: The Regional Ethical Review Board approved this study, and all participants gave informed consent. Four thoracic radiologists acted as observers in a jackknife free-response receiver operating characteristic (JAFROC) study conducted in 42 patients with and 47 patients without pulmonary nodules examined with chest tomosynthesis and chest radiography. Multidetector CT served as reference method. The observers marked suspected nodules on the images by using a four-point rating scale for the confidence of presence. The JAFROC figure of merit was used as the measure of detectability. The number of lesion localizations relative to the total number of lesions (lesion localization fraction [LLF]) and the number of nonlesion localizations relative to the total number of cases (nonlesion localization fraction [NLF]) were determined. RESULTS: Performance of chest tomosynthesis was significantly better than that of chest radiography with regard to detectability (F statistic = 32.7, df = 1, 34.8, P < .0001). For tomosynthesis, the LLF for the smallest nodules (< or = 4 mm) was 0.39 and increased with an increase in size to an LLF for the largest nodules (> 8 mm) of 0.83. The LLF for radiography was small, except for the largest nodules, for which it was 0.52. In total, the LLF was three times higher for tomosynthesis. The NLF was approximately 50% higher for tomosynthesis. CONCLUSION: For the detection of pulmonary nodules, the performance of chest tomosynthesis is better, with increased sensitivity especially for nodules smaller than 9 mm, than that of chest radiography.
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| 19. |
- Vikgren, Jenny, 1957, et al.
(author)
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Detection of mild emphysema by computed tomography density measurements
- 2005
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In: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 46:3, s. 237-245
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Journal article (peer-reviewed)abstract
- Purpose: To assess the ability of a conventional density mask method to detect mild emphysema by high- resolution computed tomography ( HRCT), to analyze factors influencing quantification of mild emphysema, and to validate a new algorithm for detection of mild emphysema. Material and Methods: Fifty- five healthy male smokers and 34 never- smokers, 61 - 62 years of age, were examined. Emphysema was evaluated visually, by the conventional density mask method, and by a new algorithm compensating for the effects of gravity and artifacts due to motion and the reconstruction algorithm. Effects of the reconstruction algorithm, slice thickness, and various threshold levels on the outcome of the density mask area were evaluated. Results: Forty- nine percent of the smokers had mild emphysema. The density mask area was higher the thinner the slice irrespective of the reconstruction algorithm and threshold level. The sharp algorithm resulted in increased density mask area. The new reconstruction algorithm could discriminate between smokers with and those without mild emphysema, whereas the density mask method could not. The diagnostic ability of the new algorithm was dependent on lung level. At about 90% specificity, sensitivity was 65 - 100% in the apical levels, but low in the rest of the lung. Conclusion: The conventional density mask method is inadequate for detecting mild emphysema, while the new algorithm improves the diagnostic ability but is nevertheless still imperfect.
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| 20. |
- Vikgren, Jenny, 1957, et al.
(author)
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High-resolution computed tomography in healthy smokers and never-smokers: a 6-year follow-up study of men born in 1933
- 2004
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In: Acta Radiol. ; 45:1
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Journal article (peer-reviewed)abstract
- PURPOSE: To elucidate whether emphysematous lesions and other high-resolution computed tomography (HRCT) findings considered associated with smoking are part of a progressive process, and to measure the extent to which similar changes are found in never-smokers. MATERIAL AND METHODS: Healthy smokers and never-smokers were recruited from a randomized epidemiological study and investigated with a 6-year interval. Emphysema, parenchymal and subpleural nodules, ground-glass opacities, bronchial alterations, and septal lines were evaluated in 66 subjects (40 smokers, 11 of whom had stopped smoking in the interval, and 26 never-smokers). Lung function was tested. RESULTS: All except emphysematous lesions were present to some extent in never-smokers. Emphysema, parenchymal nodules, and septal lines occurred significantly more in current smokers, and a progression in extent of emphysema, ground-glass opacities, bronchial alterations and septal lines was seen. There was no significant change among those who stopped and never-smokers except for bronchial alterations, which progressed in never-smokers. CONCLUSION: In healthy, elderly never-smokers a low extent of various HRCT findings has to be considered normal. Emphysema, parenchymal nodules, and ground-glass opacities are indicative of smoking-induced disease. Further progress may cease if smoking is stopped.
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| 21. |
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| 22. |
- Vikgren, Jenny, 1957, et al.
(author)
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Visual and Quantitative Evaluation of Emphysema: A Case-Control Study of 1111 Participants in the Pilot Swedish CArdioPulmonary BioImage Study (SCAPIS)
- 2020
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In: Academic Radiology. - : Elsevier BV. - 1076-6332 .- 1878-4046. ; 27:5, s. 636-643
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Journal article (peer-reviewed)abstract
- Rationale and Objectives: Emphysema is a hallmark of chronic obstructive pulmonary disease. The primary aim of this study was to investigate inter- and intraobserver agreement of visual assessment of mild emphysema in low-dose multidetector computed tomography of subjects in the pilot SCAPIS in order to certify consistent detection of mild emphysema. The secondary aim was to investigate the performance of quantitative densitometric measurements in the cohort. Materials and Methods: Participants with emphysema (n = 100, 56 males and 44 females) reported in the electronic case report form of pilot SCAPIS and 100 matched controls (gender, age, height, and weight) without emphysema were included. To assess interobserver variability the randomized examinations were evaluated by two thoracic radiologists. For intraobserver variability three radiologists re-evaluated randomized examinations which they originally evaluated. The results were evaluated statistically by Krippendorff's α. The dataset was also assessed quantitively for % lung attenuation value −950 HU (LAV950), mean lung density and total lung volume by commercially available software. Results: Emphysema was visually scored as mild and Krippendorff's α was ≥0.8 for both the inter- and intraobserver agreement regarding presence of emphysema and approaching 0.8 regarding presence and extent of emphysema by location in the upper lobes. Mean LAV950 was not different between the emphysematous and the nonemphysematous participants; 8.3% and 8.4%, respectively. Conclusion: The inter- and intraobserver agreement for visual detection of mild emphysema in low-dose multidetector computed tomography was good. Surprisingly, quantitative analysis could not reliably identify participants with mild emphysema, which hampers the use of automatic evaluation. © 2019 The Association of University Radiologists
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| 23. |
- Zachrisson, Sara, et al.
(author)
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Effect of clinical experience of chest tomosynthesis on detection of pulmonary nodules.
- 2009
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In: Acta radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 50:8, s. 884-891
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Journal article (peer-reviewed)abstract
- BACKGROUND: The new technique chest tomosynthesis 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 at a radiation dose comparable to that of chest radiography. PURPOSE: To investigate if, for experienced thoracic radiologists, the detectability of pulmonary nodules obtained after only a short initial learning period of chest tomosynthesis improves with additional clinical experience of the new technique. MATERIAL AND METHODS: Two readings of the same clinical chest tomosynthesis cases, the first performed after 6 months of clinical experience and the second after an additional period of 1 year, were conducted. Three senior thoracic radiologists, with more than 20 years of experience of chest radiography, acted as observers, with the task of detecting pulmonary nodules in a jackknife free-response receiver operating characteristics (JAFROC1) study. The image material consisted of 42 patients with and 47 patients without pulmonary nodules examined with chest tomosynthesis. Multidetector computed tomography (MDCT) was used as a reference. The total number of nodules was 131. The JAFROC1 figure of merit (FOM) was used as the principal measure of detectability. RESULTS: The difference in the observer-averaged JAFROC1 FOM of the two readings was 0.004 (95% confidence interval: -0.11, 0.12; F-statistic: 0.01 on 1 and 2.65 df; P=0.91). Thus, no significant improvement in detectability was found after the additional clinical experience of tomosynthesis. CONCLUSION: The study indicates that experienced thoracic radiologists already within the first months of clinical use of chest tomosynthesis are able to take advantage of the new technique in the task of detecting pulmonary nodules.
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| 24. |
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| 25. |
- Zachrisson, Sara, et al.
(author)
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Evaluation of chest tomosynthesis for the detection of pulmonary nodules: Effect of clinical experience and comparison with chest radiography
- 2009
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In: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1605-7422. ; 7263
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Journal article (other academic/artistic)abstract
- Chest tomosynthesis refers to the technique of collecting low-dose projections of the chest at different angles and using these projections to reconstruct section images of the chest. In this study, a comparison of chest tomosynthesis and chest radiography in the detection of pulmonary nodules was performed and the effect of clinical experience of chest tomosynthesis was evaluated. Three senior thoracic radiologists, with more than ten years of experience of chest radiology and 6 months of clinical experience of chest tomosynthesis, acted as observers in a jackknife free-response receiver operating characteristics (JAFROC-1) study, performed on 42 patients with and 47 patients without pulmonary nodules examined with both chest tomosynthesis and chest radiography. Multidetector computed tomography (MDCT) was used as reference and the total number of nodules found using MDCT was 131. In order to investigate the effect of additional clinical experience of chest tomosynthesis, a second reading session of the tomosynthesis images was performed one year after the initial one. The JAFROC-1 figure of merit (FOM) was used as the principal measure of detectability. In comparison with chest radiography, chest tomosynthesis performed significantly better with regard to detectability. The observer-averaged JAFROC-1 FOM was 0.61 for tomosynthesis and 0.40 for radiography, giving a statistically significant difference between the techniques of 0.21 (p<0.0001). The observer-averaged JAFROC-1 FOM of the second reading of the tomosynthesis cases was not significantly higher than that of the first reading, indicating no improvement in detectability from the additional clinical experience of tomosynthesis.
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