| 1. |
- Polymeri, Erini, et al.
(författare)
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Artificial Intelligence-Based Organ Delineation for Radiation Treatment Planning of Prostate Cancer on Computed Tomography
- 2024
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Ingår i: Advances in Radiation Oncology. - 2452-1094. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Meticulous manual delineations of the prostate and the surrounding organs at risk are necessary for prostate cancer radiation therapy to avoid side effects to the latter. This process is time consuming and hampered by inter- and intraobserver variability, all of which could be alleviated by artificial intelligence (AI). This study aimed to evaluate the performance of AI compared with manual organ delineations on computed tomography (CT) scans for radiation treatment planning. Methods and Materials: Manual delineations of the prostate, urinary bladder, and rectum of 1530 patients with prostate cancer who received curative radiation therapy from 2006 to 2018 were included. Approximately 50% of those CT scans were used as a training set, 25% as a validation set, and 25% as a test set. Patients with hip prostheses were excluded because of metal artifacts. After training and fine-tuning with the validation set, automated delineations of the prostate and organs at risk were obtained for the test set. Sørensen-Dice similarity coefficient, mean surface distance, and Hausdorff distance were used to evaluate the agreement between the manual and automated delineations. Results: The median Sørensen-Dice similarity coefficient between the manual and AI delineations was 0.82, 0.95, and 0.88 for the prostate, urinary bladder, and rectum, respectively. The median mean surface distance and Hausdorff distance were 1.7 and 9.2 mm for the prostate, 0.7 and 6.7 mm for the urinary bladder, and 1.1 and 13.5 mm for the rectum, respectively. Conclusions: Automated CT-based organ delineation for prostate cancer radiation treatment planning is feasible and shows good agreement with manually performed contouring.
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| 2. |
- Fujio, Kazuki, et al.
(författare)
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TALYS calculations of prompt fission observables and independent fission product yields for the neutron-induced fission of 235U
- 2023
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Ingår i: European Physical Journal A. - : Springer. - 1434-6001 .- 1434-601X. ; 59
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Tidskriftsartikel (refereegranskat)abstract
- The TALYS nuclear reaction code’s Hauser-Feshbach statistical decay model has been adapted in order to calculate prompt fission neutron and γ-ray observables by iterating over deexciting fission fragments. Several fission fragment generators such as GEF, HF3D, and SPY were employed to provide TALYS with databases. These databases contain standardized tables with fission fragment yields, mean excitation energies and their widths, and average total kinetic energy, as a function of charge and mass number of primary fission fragments. The resulting calculations, including prompt particle multiplicities, spectra, average energies, and independent fission product yields, were compared with experimental and evaluated data. This work first outlines the new methodology implemented in TALYS and examines the effects of three important parameters on the final evaporation data. Furthermore, the neutron-induced fission of 235U is investigated in detail as a function of incident energy. The results from TALYS, with input from GEF and HF3D, were compared with available experimental data and the results of the stand-alone GEF code. The proposed methodology contributes to an improved capability to model the fission process.
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| 3. |
- Terzidis, Emmanouil, 1994, et al.
(författare)
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Different aspects of plan complexity in prostate VMAT plans
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- In this work we evaluated VMAT plan complexity by using different methods and approaches: complexity related to the aperture shape, the nature of the dynamic delivery, the impact of delivery variations as well as complexity analyses based on measurements. Prostate cancer treatment plans with different levels of complexity were created for three different patient cases. The plans intended to be most complex were also scored to be the most complex according to the evaluation methods used. The results for the other plans were more diverse. The methods that included 3D spatial information on complexity gave additional information important for the analysis of clinical relevance. In order to use specific complexity estimation methods for taking clinical decisions it is essential to understand how different aspects of complexity are incorporated in each method.
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| 4. |
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| 5. |
- Terzidis, Emmanouil, 1994, et al.
(författare)
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Uppskattning av dosimetriska osäkerheter baserat på andel dos från penumbraregionen för VMAT-planer av olika komplexitet
- 2023
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Ingår i: Nationellt möte om sjukhusfysik 2023.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Absorbed dose delivered to the patient from a penumbra region have higher uncertainties compared to the dose delivered from the center of the treatment field. The magnitude of these uncertainties could be important input when evaluating absorbed dose to organs at risk (OARs) and target volumes, especially for plans of increased complexity. The aim of this work was to examine the fraction of penumbra dose in 3D for VMAT plans of different complexities. Methods and Materials: A C# software was developed in our department, able to estimate the fraction of penumbral dose in relation to the total dose, in each voxel and visualize it as a 3D distribution (uncertainty map). Twelve treatment plans of previously treated patients have been selected to represent different types of treatment geometry and different types of diagnose (prostate, head & neck, lung and gynecological cancer). The clinical plan used for the actual treatment of the patient was reoptimized in Eclipse TPS (Varian Medical Systems, Palo Alto, CA), to create one plan with reduced complexity (“simple plan”) and one of higher complexity (“complex plan”). These additional plans were generated by altering the MU constraint and the aperture shape controller (ASC) level, while retaining a similar dose distribution. The fraction of penumbra dose was calculated for both the clinical and the newly generated plans creating in total 36 uncertainty maps. Results: The generated uncertainty maps were able to highlight anatomical regions with high fraction of penumbra dose (e.g., above 50%). These regions were mostly observed outside the planning target volume (PTV). Generally, the fraction of penumbra dose, both inside and outside the PTV, was increased with increased plan complexity. For certain cases, the absorbed dose in OARs originated from penumbra regions to a considerable degree, even for the least complex version of the plan. An example is shown for the rectum in Figure 1. This observation proves the importance of evaluating dosimetric uncertainty in 3D. Conclusion: A connection was established between dose uncertainty due to fraction of penumbra dose and plan complexity. Furthermore, it is important to evaluate this uncertainty on a 3D-voxel-level.
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| 6. |
- Abel, Edvard, 1970, et al.
(författare)
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Fatigue in Patients With Head and Neck Cancer Treated With Radiation Therapy: A Prospective Study of Patient-Reported Outcomes and Their Association With Radiation Dose to the Cerebellum
- 2022
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Ingår i: Advances in Radiation Oncology. - : Elsevier BV. - 2452-1094. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Although fatigue is a known side effect in patients with head and neck cancer (HNC) receiving radiation therapy, knowledge regarding long-term fatigue and dose-response relationships to organs at risk is scarce. The aim of this prospective study was to analyze patient-reported fatigue in patients with HNC receiving radiation therapy and to explore any possible association with organ-at-risk doses. Methods and Materials: Patients with HNC referred for curative radiation therapy were eligible for inclusion in the study. To assess patient-reported fatigue, quality of life questionnaires (European Organization for Research and Treatment of Cancer QLQ-C30 and QLQ-FA12) were distributed before treatment and 1, 3, 6, 12, 24, and 60 months after the start of treatment. Mean dose (Dmean) and near maximum dose (D2%) of the cerebellum and brain stem were evaluated in relation to baseline-adjusted fatigue scores at 3 months. Results: One hundred twenty-six patients treated with intensity modulated radiation therapy between 2008 and 2010 were available for final analysis. Female sex and age <60 years were associated with higher fatigue at baseline, whereas patients also treated with chemotherapy had reduced physical and emotional fatigue at 6 months. Physical fatigue (QLQ-FA12 scale) increased from baseline up to 3 months (29 vs 59; P < .0001) but showed no difference compared with baseline from 1 to 5 years. Emotional fatigue was significantly lower at 5 years compared with baseline (14 vs 28; P < .0001). Patients with cerebellum Dmean > 3.5 Gy had higher mean physical fatigue scores at 3 months (38 vs 27; P = .036). Conclusions: Although there is a significant increase in fatigue scores for patients with HNC up to 1 year after radiation therapy, this study showed a return to baseline levels at 5 years. A possible association was found between physical fatigue and a higher mean dose to the cerebellum.
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| 7. |
- Johansson, Frida, et al.
(författare)
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Non-Invasive Evaluation of Intradiscal Deformation during Axial Loading of the Spine Using Deformation-Field Magnetic Resonance Imaging: A Potential Tool for Micro-Instability Measurements
- 2022
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Ingår i: Journal of Clinical Medicine. - : MDPI AG. - 2077-0383. ; 11:16
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Tidskriftsartikel (refereegranskat)abstract
- Degeneration alters the structural components of the disc and its mechanical behavior. Understanding this pathophysiological process is of great importance, as it may lead to back pain. However, non-invasive methods to characterize the disc mechanics in vivo are lacking. Here, a potential method for measurements of the intradiscal deformation under stress is presented. The method utilizes a standard MRI protocol, commercial loading equipment, and registration software. The lumbar spine (L1/L2-L5/S1) of 36 human subjects was imaged with and without axial loading of the spine. The resulting images were registered, and changes in the images during the registration were displayed pixel-by-pixel to visualize the internal deformation of the disc. The degeneration grade, disc height, disc angle and tilt angle were determined and correlated with the deformation using multivariate regression analysis. The largest deformation was found at the lower lumbar spine, and differences in regional behaviors between individual discs were found. Weak to moderate correlations between the deformation and different disc characteristics were found, where the degeneration grade and tilt angle were the main contributing factors. To conclude, the image-based method offers a potential tool to study the pathophysiological process of the disc.
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| 8. |
- Palmér, Emilia, 1993, et al.
(författare)
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Estimation and visualization of geometric fidelity using geometric offset maps for improved guidance in H&N radiation therapy
- 2022
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Ingår i: Annual Meeting ISMRM (International Society of Magnetic Resonance in Medicine).
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Konferensbidrag (refereegranskat)abstract
- n an MRI-only workflow, high geometric fidelity of the MRI data is required. Head and neck (H&N) cancer patients, however, frequently have implants, e.g., dental restorations, causing distortions of the MRI data. Geometric offset maps were computed using B0-map calculated from the Dixon-sequence included in the standard clinical protocol. Even though the implants included in this pre-study did not contribute with a significant geometric offset in the delineated target volume, visualization of the geometric offset maps as such bring additional important information when delineating structures in an MRI-only H&N workflow and could thereby become a promising tool in clinical practice.
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| 9. |
- Palmér, Emilia, 1993, et al.
(författare)
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Head and neck cancer patient positioning using synthetic CT data in MRI-only radiation therapy.
- 2022
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Ingår i: Journal of applied clinical medical physics. - : Wiley. - 1526-9914. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy and precision of patient positioning is crucial in radiotherapy; however, there are no publications available using synthetic computed tomography (sCT) that evaluate rotations in head and neck (H&N) patients positioning or the effect of translation and rotation combined. The aim of this work was to evaluate the differences between using sCT with the CT for 2D- and 3D-patient positioning in a magnetic resonance imaging (MRI)-only workflow.This study included 14 H&N cancer patients, with generated sCT data (MRI Planner v2.2) and the CT deformably registered to the MRI. Patient positioning was evaluated by comparing sCT against CT data: 3D cone beam CT (CBCT) was registered to the deformed CT (dCT) and sCT in six degrees of freedom (DoF) with a rigid auto-registration algorithm and bone threshold, and 2D deformed digital reconstructed radiographs (dDRR) and synthetic DRRs (sDRR) were manually registered to orthogonal projections in five DoF by six blinded observers. The difference in displacement in all DoF were calculated for dCT and sCT, as well as for dDRR and sDRR. The interobserver variation was evaluated by separate application of the paired dDRR and sDRR registration matrices to the original coordinates of the planning target volume (PTV) structures and calculation of the Euclidean distance between the corresponding points. The Dice similarity coefficient (DSC) was calculated between dDRR/sDRR-registered PTVs.The mean difference in patient positioning using CBCT was <0.7 mm and <0.3° and using orthogonal projections <0.4 mm and <0.2° in all directions. The maximum Euclidean distance was 5.1 mm, the corresponding mean (1SD) Euclidean distance and mean DSC were 3.5 ± 0.7 mm and 0.93, respectively.This study shows that the sCT-based patient positioning gives a comparable result with that based on CT images, allowing sCT to replace CT as reference for patient treatment positioning.
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| 10. |
- Palmér, Emilia, 1993, et al.
(författare)
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Synthetic computed tomography data allows for accurate absorbed dose calculations in a magnetic resonance imaging only workflow for head and neck radiotherapy
- 2021
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Ingår i: Physics and Imaging in Radiation Oncology. - : Elsevier BV. - 2405-6316. ; 17, s. 36-42
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Few studies on magnetic resonance imaging (MRI) only head and neck radiation treatment planning exist, and none using a generally available software. The aim of this study was to evaluate the accuracy of absorbed dose for head and neck synthetic computed tomography data (sCT) generated by a commercial convolutional neural network-based algorithm. Materials and methods: For 44 head and neck cancer patients, sCT were generated and the geometry was validated against computed tomography data (CT). The clinical CT based treatment plan was transferred to the sCT and recalculated without re-optimization, and differences in relative absorbed dose were determined for dose-volume-histogram (DVH) parameters and the 3D volume. Results: For overall body, the results of the geometric validation were (Mean ± 1sd): Mean error −5 ± 10 HU, mean absolute error 67 ± 14 HU, Dice similarity coefficient 0.98 ± 0.05, and Hausdorff distance difference 4.2 ± 1.7 mm. Water equivalent depth difference for region Th1-C7, mid mandible and mid nose were −0.3 ± 3.4, 1.1 ± 2.0 and 0.7 ± 3.8 mm respectively. The maximum mean deviation in absorbed dose for all DVH parameters was 0.30% (0.12 Gy). The absorbed doses were considered equivalent (p-value < 0.001) and the mean 3D gamma passing rate was 99.4 (range: 95.7–99.9%). Conclusions: The convolutional neural network-based algorithm generates sCT which allows for accurate absorbed dose calculations for MRI-only head and neck radiation treatment planning. The sCT allows for statistically equivalent absorbed dose calculations compared to CT based radiotherapy.
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