| 1. |
- Axelsson, Rebecca, et al.
(författare)
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Finite element model of mechanical imaging of the breast
- 2022
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Ingår i: Journal of Medical Imaging. - 2329-4302. ; 9:3, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Malignant breast lesions can be distinguished from benign lesions by their mechanical properties. This has been utilized for mechanical imaging in which the stress distribution over the breast is measured. Mechanical imaging has shown the ability to identify benign or normal cases and to reduce the number of false positives from mammography screening. Our aim was to develop a model of mechanical imaging acquisition for simulation purposes. To that end, we simulated mammographic compression of a computer model of breast anatomy and lesions. Approach: The breast compression was modeled using the finite element method. Two finite element breast models of different sizes were used and solved using linear elastic material properties in open-source virtual clinical trial (VCT) software. A spherical lesion (15 mm in diameter) was inserted into the breasts, and both the location and stiffness of the lesion were varied extensively. The average stress over the breast and the average stress at the lesion location, as well as the relative mean pressure over lesion area (RMPA), were calculated. Results: The average stress varied 6.2-6.5 kPa over the breast surface and 7.8-11.4 kPa over the lesion, for different lesion locations and stiffnesses. These stresses correspond to an RMPA of 0.80 to 1.46. The average stress was 20% to 50% higher at the lesion location compared with the average stress over the entire breast surface. Conclusions: The average stress over the breast and the lesion location corresponded well to clinical measurements. The proposed model can be used in VCTs for evaluation and optimization of mechanical imaging screening strategies.
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| 2. |
- Barufaldi, Bruno, et al.
(författare)
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Virtual Clinical Trials in Medical Imaging System Evaluation and Optimisation
- 2021
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 195:3-4, s. 363-371
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Tidskriftsartikel (refereegranskat)abstract
- Virtual clinical trials (VCTs) can be used to evaluate and optimise medical imaging systems. VCTs are based on computer simulations of human anatomy, imaging modalities and image interpretation. OpenVCT is an open-source framework for conducting VCTs of medical imaging, with a particular focus on breast imaging. The aim of this paper was to evaluate the OpenVCT framework in two tasks involving digital breast tomosynthesis (DBT). First, VCTs were used to perform a detailed comparison of virtual and clinical reading studies for the detection of lesions in digital mammography and DBT. Then, the framework was expanded to include mechanical imaging (MI) and was used to optimise the novel combination of simultaneous DBT and MI. The first experiments showed close agreement between the clinical and the virtual study, confirming that VCTs can predict changes in performance of DBT accurately. Work in simultaneous DBT and MI system has demonstrated that the system can be optimised in terms of the DBT image quality. We are currently working to expand the OpenVCT software to simulate MI acquisition more accurately and to include models of tumour growth. Based on our experience to date, we envision a future in which VCTs have an important role in medical imaging, including support for more imaging modalities, use with rare diseases and a role in training and testing artificial intelligence (AI) systems.
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| 3. |
- Bjerkén, Anna, et al.
(författare)
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Dose evaluation of simultaneous breast radiography and mechanical imaging
- 2023
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Ingår i: Medical Imaging 2023 : Physics of Medical Imaging - Physics of Medical Imaging. ; 12463
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Konferensbidrag (refereegranskat)abstract
- This study investigates the impact in terms of radiation dose when performing simultaneous digital breast tomosynthesis(DBT) and mechanical imaging (MI) – DBTMI. DBTMI has demonstrated the potential to increase specificity of cancerdetection, and reduce unnecessary biopsies, as compared to digital mammography (DM) screening. The presence of theMI sensor during simultaneous image acquisition may increase the radiation dose when automatic exposure control is used.In this project, a radiation dose study was conducted on clinically available breast imaging systems with and without theMI sensor. We have investigated three approaches to analyse the dose increase in DBTMI, using (i) the estimates of averageglandular dose (AGD) reported in DICOM headers of radiography images; (ii) AGD measured by a conventionaldosemeter; and (iii) AGD measured by optically stimulated luminescence using NaCl pellets. The relative increase in AGDestimated from DICOM headers when using the MI sensor was on average 10.7% and 12.4%, for DM and DBTmeasurements, respectively. The relative increase in AGD using the conventional dosemeter was 11.2% in DM mode and12.2% in DBT mode. The relative increase in AGD using NaCl pellets was 14.6% in DM mode. Our measurements suggestthat the use of simultaneous breast radiography and MI increases the AGD by 13% on average. The increase in dose is stillbelow the acceptable values in mammography screening recommended by the European Guidelines.
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| 4. |
- Boll, Måns, et al.
(författare)
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Evaluation of 3D printed contrast detail phantoms for mammography quality assurance
- 2022
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Ingår i: 16th International Workshop on Breast Imaging, IWBI 2022. - : SPIE. - 0277-786X .- 1996-756X. - 9781510655843 ; 12286
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Konferensbidrag (refereegranskat)abstract
- Objects created by 3D printers are increasingly used in various medical applications. Today, affordable 3D printers, using Fused Deposition Modeling are widely available. In this project, a commercially available 3D printer was used to replicate a conventional radiographic contrast detail phantom. Printing materials were selected by comparing their x-ray attenuation properties. Two replicas were printed using polylactic acid, with different filling patterns. The printed phantoms were imaged by a clinical mammography system, using automatic exposure control. Phantom images were visually and quantitively compared to images of the corresponding conventional contrast detail phantom. Visual scoring of the contrast detail elements was performed by a medical physics student. Contrast-to-noise ratio (CNR) was calculated for each phantom element. The diameter and thickness of the smallest visible phantom object were 0.44 mm and 0.09 mm, respectively, for both filling patterns. For the conventional phantom, the diameter and thickness of the smallest visible object were 0.31 mm and 0.09 mm. Visual inspection of printed phantoms revealed some linear artefacts. These artefacts were however not visible on mammographic projections. Quantitively, average CNR of printed phantom objects followed the same trend with an increase of average CNR with increasing disk height. However, there is a limitation of detail objects with disk diameters below 1.25 mm, caused by the available nozzle size. Based upon the encouraging results, future work will explore the use of different materials and smaller nozzle diameters.
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| 5. |
- Spandau, Ulrich, et al.
(författare)
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Time to consider a new treatment protocol for aggressive posterior retinopathy of prematurity?
- 2013
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Ingår i: Acta Ophthalmologica. - : Wiley. - 1755-375X .- 1755-3768. ; 91:2, s. 170-175
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To discuss treatment modalities for aggressive posterior retinopathy of prematurity (AP-ROP).Methods: The medical charts of all infants with AP-ROP at Uppsala University Hospital, Sweden, during a 2-year period (2009 and 2010) were reviewed. Eight infants (16 eyes) with a mean gestational age of 23.8 weeks and a mean birth weight of 592 g were treated with laser and/or intravitreal injections of bevacizumab (0.4 and 0.625 mg). RetCam photography was used to document the retinal appearance before and after treatment.Results: All infants (16 eyes) had AP-ROP in zone I. Mean time at initial treatment was 34 weeks postmenstrual age. Two eyes (one infant) were only treated with laser, and six eyes (three infants) were treated with laser therapy or cryopexy and, because of lack of regression, with bevacizumab as salvage therapy. Eight eyes (four infants) were treated with a first-line bevacizumab injection and four of these eyes (two infants) with additional laser ablation for continued disease progression in zone II. Macular dragging occurred in one eye of one infant primarily treated with laser.Conclusions: Given the high complication rate of the extensive laser treatment for zone I ROP, it is worth considering anti-vascular endothelial growth factor treatment as an alternative therapy. Further knowledge concerning side effects and long-term ocular and systemic outcome is warranted before this drug becomes general clinical practice.
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| 6. |
- Tomic, Hanna, et al.
(författare)
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Assessment of a tumour growth model for virtual clinical trials of breast cancer screening
- 2021
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Ingår i: Medical Imaging 2021 : Physics of Medical Imaging - Physics of Medical Imaging. - : SPIE. - 1605-7422. - 9781510640191 ; 11595
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Konferensbidrag (refereegranskat)abstract
- Image-based analysis of breast tumour growth rate may help optimize breast cancer screening and diagnosis. It may improve the identification of aggressive tumours and suggest optimal screening intervals. Virtual clinical trial (VCT) is a simulation-based method used to evaluate and optimize medical imaging systems and design clinical trials. Our work is motivated by desire to simulate multiple screening rounds with growing tumours. We have developed a model to simulate tumours with various growth rates; this study aims at evaluating the model. We used clinical data on tumour volume doubling times (TVDT) from our previous study, to fit a probability distribution ("clinical fit"). Growing tumours were inserted into 30 virtual breasts ("simulated cohort"). Based on the clinical fit we simulated two successive screening rounds for each virtual breast. TVDT from clinical and simulated images were compared. Tumour size was measured from simulated mammograms by a radiologist in three repeated sessions, to estimate TVDT ("estimated TVDT"). Reproducibility of measured sizes decreased slightly for small tumours. The mean TVDT from the clinical fit was 297±169 days, whereas the simulated cohort had 322±217 days, and the average estimated TVDT 340 ± 287 days. The median difference between the simulated and estimated TVDT was 12 days (4% of the mean clinical TVDT). Comparisons between other data sets suggest no significant difference (p>0.5). The proposed tumour growth model suggested close agreement with clinical results, supporting potential use in VCTs of temporal breast imaging.
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| 7. |
- Tomic, Hanna, et al.
(författare)
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Development and evaluation of a method for tumor growth simulation in virtual clinical trials of breast cancer screening
- 2022
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Ingår i: Journal of Medical Imaging. - 2329-4302. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Image-based analysis of breast tumor growth rate may optimize breast cancer screening and diagnosis by suggesting optimal screening intervals and guide the clinical discussion regarding personalized screening based on tumor aggressiveness. Simulation-based virtual clinical trials (VCTs) can be used to evaluate and optimize medical imaging systems and design clinical trials. This study aimed to simulate tumor growth over multiple screening rounds. Approach: This study evaluates a preliminary method for simulating tumor growth. Clinical data on tumor volume doubling time (TVDT) was used to fit a probability distribution ("clinical fit") of TVDTs. Simulated tumors with TVDTs sampled from the clinical fit were inserted into 30 virtual breasts ("simulated cohort") and used to simulate mammograms. Based on the TVDT, two successive screening rounds were simulated for each virtual breast. TVDTs from clinical and simulated mammograms were compared. Tumor sizes in the simulated mammograms were measured by a radiologist in three repeated sessions to estimate TVDT. Results: The mean TVDT was 297 days (standard deviation, SD, 169 days) in the clinical fit and 322 days (SD, 217 days) in the simulated cohort. The mean estimated TVDT was 340 days (SD, 287 days). No significant difference was found between the estimated TVDTs from simulated mammograms and clinical TVDT values (p > 0.5). No significant difference (p > 0.05) was observed in the reproducibility of the tumor size measurements between the two screening rounds. Conclusions: The proposed method for tumor growth simulation has demonstrated close agreement with clinical results, supporting potential use in VCTs of temporal breast imaging.
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| 8. |
- Tomic, Hanna, et al.
(författare)
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Simulation of breast lesions based upon fractal Perlin noise
- 2023
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Ingår i: Physica Medica. - 1120-1797. ; 114
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Steadily increasing use of computational/virtual phantoms in medical physics has motivated expanding development of new simulation methods and data representations for modelling human anatomy. This has emphasized the need for increased realism, user control, and availability. In breast cancer research, virtual phantoms have gained an important role in evaluating and optimizing imaging systems. For this paper, we have developed an algorithm to model breast abnormalities based on fractal Perlin noise. We demonstrate and characterize the extension of this approach to simulate breast lesions of various sizes, shapes, and complexity. Materials and method: Recently, we developed an algorithm for simulating the 3D arrangement of breast anatomy based on Perlin noise. In this paper, we have expanded the method to also model soft tissue breast lesions. We simulated lesions within the size range of clinically representative breast lesions (masses, 5–20 mm in size). Simulated lesions were blended into simulated breast tissue backgrounds and visualized as virtual digital mammography images. The lesions were evaluated by observers following the BI-RADS assessment criteria. Results: Observers categorized the lesions as round, oval or irregular, with circumscribed, microlobulated, indistinct or obscured margins. The majority of the simulated lesions were considered by the observers to have a realism score of moderate to well. The simulation method provides almost real-time lesion generation (average time and standard deviation: 1.4 ± 1.0 s). Conclusion: We presented a novel algorithm for computer simulation of breast lesions using Perlin noise. The algorithm enables efficient simulation of lesions, with different sizes and appearances.
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| 9. |
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| 10. |
- Tomic, Hanna, et al.
(författare)
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Tumor growth rate estimations in a breast cancer screening population
- 2022
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Ingår i: 16th International Workshop on Breast Imaging, IWBI 2022. - : SPIE. - 0277-786X .- 1996-756X. - 9781510655843 ; 12286
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Konferensbidrag (refereegranskat)abstract
- Tumor growth rate estimations can provide useful information about tumor progression and aggressiveness. Understanding the breast cancer progression and aggressiveness could aid with personalized screening/follow-up, treatment options, and prognosis. This paper reports a preliminary estimation of the tumor volume doubling time (TVDT) for cancers detected during the Malmö Breast Tomosynthesis Screening Trial (MBTST). The trial included 14 848 women in whom 139 cancers were detected. Out of those, 101 spiculated or circumscribed masses, had prior images available, making them suitable for tumor growth evaluation. In the preliminary analysis of images from 30 women, tumor size was measured in mammograms from MBTST and prior images. The analyzed cases were selected among women with visible tumors in two consecutive screening exams. The tumor size was measured in two orthogonal directions. The average of the two measurements was used in the analysis. The mean time and the corresponding standard deviation (SD) between the two consecutive mammograms were 744 ± 73 days. The mean TVDT and SD were 637 ± 428 days (range 159-2373 days). Future work will include the analysis of a larger number of women and a stratification of TVDT related to screening intervals.
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| 11. |
- Tomic, Hanna, et al.
(författare)
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Using simulated breast lesions based on Perlin noise for evaluation of lesion segmentation
- 2024
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Ingår i: Medical Imaging 2024 : Physics of Medical Imaging - Physics of Medical Imaging. - : SPIE-Intl Soc Optical Eng. - 1605-7422. - 9781510671546 ; 12925
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Konferensbidrag (refereegranskat)abstract
- Segmentation of diagnostic radiography images using deep learning is progressively expanding, which sets demands on the accessibility, availability, and accuracy of the software tools used. This study aimed at evaluating the performance of a segmentation model for digital breast tomosynthesis (DBT), with the use of computer-simulated breast anatomy. We have simulated breast anatomy and soft tissue breast lesions, by utilizing a model approach based on the Perlin noise algorithm. The obtained breast phantoms were projected and reconstructed into DBT slices using a publicly available open-source reconstruction method. Each lesion was then segmented using two approaches: 1. the Segment Anything Model (SAM), a publicly available AI-based method for image segmentation and 2. manually by three human observers. The lesion area in each slice was compared to the ground truth area, derived from the binary mask of the lesion model. We found similar performance between SAM and manual segmentation. Both SAM and the observers performed comparably in the central slice (mean absolute relative error compared to the ground truth and standard deviation SAM: 4 ± 3 %, observers: 3 ± 3 %). Similarly, both SAM and the observers overestimated the lesion area in the peripheral reconstructed slices (mean absolute relative error and standard deviation SAM: 277 ± 190 %, observers: 295 ± 182 %). We showed that 3D voxel phantoms can be used for evaluating different segmentation methods. In preliminary comparison, tumor segmentation in simulated DBT images using SAM open-source method showed a similar performance as manual tumor segmentation.
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| 12. |
- Tomic, Hanna, et al.
(författare)
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Virtual clinical trial of simultaneous digital breast tomosynthesis and mechanical imaging: : model calibration and the effect of tumor depth
- 2022
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Ingår i: Medical Imaging 2022: : Physics of Medical Imaging - Physics of Medical Imaging. - : SPIE. ; 12031
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Konferensbidrag (refereegranskat)abstract
- Simultaneous Digital Breast Tomosynthesis (DBT) and mechanical imaging (MI), called DBTMI, is a novel breast imaging method aimed at improving sensitivity and specificity of breast cancer screening. DBTMI combines improved cancer detection by three-dimensional DBT imaging, with the analysis of local stress over the compressed breast by MI, which can reduce false positive findings. The MI signal is affected by various factors, e.g., breast size, composition, tumor depth, etc. Assessing the individual effect of those factors using clinical data is difficult, due to their interdependence. These open clinical questions can be addressed by virtual clinical trials. Our current work is focused on the effects of tumor depth on the DBTMI signal. We simulated the breast anatomy by a matrix of adipose and glandular tissue compartments. Spherical tumors were inserted at various depths. The MI sensor is modeled by a compound material of PMMA and Ag. We calculated the local stress on the compressed breast surface at the tumor location and simulated the MI sensor output. We also simulated the corresponding DBT images and calculated the signal-difference-to-noise ratio (SDNR) with and without pre-processing to analyze the reduction in artifacts. Our preliminary analysis of 24 simulated tumors has shown 16% reduction in the local stress, when increasing tumor depth by 15 mm (10-25 mm from the breast surface). The SDNR improvement was highest for tumors near the sensor and the effect of pre-processing decreased with increasing tumor depth.
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