Physics and Imaging in Radiation Oncology最新文献

{"title":"Characterization of spatial integrity with active and passive implants in a low-field magnetic resonance linear accelerator scanner","authors":"Bertrand Pouymayou ,&nbsp;Yoel Perez-Haas ,&nbsp;Florin Allemann ,&nbsp;Ardan M. Saguner ,&nbsp;Nicolaus Andratschke ,&nbsp;Matthias Guckenberger ,&nbsp;Stephanie Tanadini-Lang ,&nbsp;Lotte Wilke","doi":"10.1016/j.phro.2024.100576","DOIUrl":"https://doi.org/10.1016/j.phro.2024.100576","url":null,"abstract":"<div><h3>Background and Purpose</h3><p>Standard imaging protocols can guarantee the spatial integrity of magnetic resonance (MR) images utilized in radiotherapy. However, the presence of metallic implants can significantly compromise this integrity. Our proposed method aims at characterizing the geometric distortions induced by both passive and active implants commonly encountered in planning images obtained from a low-field 0.35 T MR-linear accelerator (LINAC).</p></div><div><h3>Materials and Methods</h3><p>We designed a spatial integrity phantom defining 1276 control points and covering a field of view of 20x20x20 cm³. This phantom was scanned in a water tank with and without different implants used in hip and shoulder arthroplasty procedures as well as with active cardiac stimulators. The images were acquired with the clinical planning sequence (balanced steady-state free-precession, resolution 1.5x1.5x1.5 mm³). Spatial integrity was assessed by the Euclidian distance between the control point detected on the image and their theoretical locations. A first plane free of artefact (FPFA) was defined to evaluate the spatial integrity beyond the larger banding artefact.</p></div><div><h3>Results</h3><p>In the region extending up to 20 mm from the largest banding artefacts, the tested passive and active implants could cause distortions up to 2 mm and 3 mm, respectively. Beyond this region the spatial integrity was recovered and the image could be considered as unaffected by the implants.</p></div><div><h3>Conclusions</h3><p>We characterized the impact of common implants on a low field MR-LINAC planning sequence. These measurements could support the creation of extra margin while contouring organs at risk and target volumes in the vicinity of implants.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000460/pdfft?md5=10e38f5c685d8b0ecd54d8a274d223f9&pid=1-s2.0-S2405631624000460-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140605906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A deep learning based dynamic arc radiotherapy photon dose engine trained on Monte Carlo dose distributions","authors":"Marnix Witte,&nbsp;Jan-Jakob Sonke","doi":"10.1016/j.phro.2024.100575","DOIUrl":"https://doi.org/10.1016/j.phro.2024.100575","url":null,"abstract":"<div><h3>Background and purpose</h3><p>Despite hardware acceleration, state-of-the-art Monte Carlo (MC) dose engines require considerable computation time to reduce stochastic noise. We developed a deep learning (DL) based dose engine reaching high accuracy at strongly reduced computation times.</p></div><div><h3>Materials and methods</h3><p>Radiotherapy treatment plans and computed tomography scans were collected for 350 treatments in a variety of tumor sites. Dose distributions were computed using a MC dose engine for <span><math><mrow><mo>∼</mo></mrow></math></span>30,000 separate segments at 6 MV and 10 MV beam energies, both flattened and flattening filter free. For dynamic arcs these explicitly incorporated the leaf, jaw and gantry motions during dose delivery. A neural network was developed, combining two-dimensional convolution and recurrence using 64 hidden channels. Parameters were trained to minimize the mean squared log error loss between the MC computed dose and the model output. Full dose distributions were reconstructed for 100 additional treatment plans. Gamma analyses were performed to assess accuracy.</p></div><div><h3>Results</h3><p>DL dose evaluation was on average 82 times faster than MC computation at a 1 % accuracy setting. In voxels receiving at least 10 % of the maximum dose the overall global gamma pass rate using a 2 % and 2 mm criterion was 99.6 %, while mean local gamma values were accurate within 2 %. In the high dose region over 50 % of maximum the mean local gamma approached a 1 % accuracy.</p></div><div><h3>Conclusions</h3><p>A DL based dose engine was implemented, able to accurately reproduce MC computed dynamic arc radiotherapy dose distributions at high speed.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000459/pdfft?md5=9b69a16f8acbb3663eeeb7983084265d&pid=1-s2.0-S2405631624000459-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140551739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interobserver variation in tumor delineation of liver metastases using Magnetic Resonance Imaging","authors":"Julia E. Peltenburg ,&nbsp;Ali Hosni ,&nbsp;Rana Bahij ,&nbsp;Simon Boeke ,&nbsp;Pètra M. Braam ,&nbsp;William A. Hall ,&nbsp;Martijn P.W. Intven ,&nbsp;Luca Nicosia ,&nbsp;Jan-Jakob Sonke ,&nbsp;Marnix Witte ,&nbsp;Marlies E. Nowee ,&nbsp;Tomas Janssen","doi":"10.1016/j.phro.2024.100592","DOIUrl":"https://doi.org/10.1016/j.phro.2024.100592","url":null,"abstract":"<div><h3>Background and purpose</h3><p>Magnetic Resonance Imaging (MRI) guided stereotactic body radiotherapy (SBRT) of liver metastases is an upcoming high-precision non-invasive treatment. Interobserver variation (IOV) in tumor delineation, however, remains a relevant uncertainty for planning target volume (PTV) margins. The aims of this study were to quantify IOV in MRI-based delineation of the gross tumor volume (GTV) of liver metastases and to detect patient-specific factors influencing IOV.</p></div><div><h3>Materials and methods</h3><p>A total of 22 patients with liver metastases from three primary tumor origins were selected (colorectal(8), breast(6), lung(8)). Delineation guidelines and planning MRI-scans were provided to eight radiation oncologists who delineated all GTVs. All delineations were centrally peer reviewed to identify outliers not meeting the guidelines. Analyses were performed both in- and excluding outliers. IOV was quantified as the standard deviation (SD) of the perpendicular distance of each observer’s delineation towards the median delineation. The correlation of IOV with shape regularity, tumor origin and volume was determined.</p></div><div><h3>Results</h3><p>Including all delineations, average IOV was 1.6 mm (range 0.6–3.3 mm). From 160 delineations, in total fourteen single delineations were marked as outliers after peer review. After excluding outliers, the average IOV was 1.3 mm (range 0.6–2.3 mm). There was no significant correlation between IOV and tumor origin or volume. However, there was a significant correlation between IOV and regularity (Spearman’s ρ_s = -0.66; p = 0.002).</p></div><div><h3>Conclusion</h3><p>MRI-based IOV in tumor delineation of liver metastases was 1.3–1.6 mm, from which PTV margins for IOV can be calculated. Tumor regularity and IOV were significantly correlated, potentially allowing for patient-specific margin calculation.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000629/pdfft?md5=7858fc9860d9c4f0cacba04c519b5143&pid=1-s2.0-S2405631624000629-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141240196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A multi-institutional comparison of retrospective deformable dose accumulation for online adaptive magnetic resonance-guided radiotherapy","authors":"Martina Murr ,&nbsp;Uffe Bernchou ,&nbsp;Edyta Bubula-Rehm ,&nbsp;Mark Ruschin ,&nbsp;Parisa Sadeghi ,&nbsp;Peter Voet ,&nbsp;Jeff D Winter ,&nbsp;Jinzhong Yang ,&nbsp;Eyesha Younus ,&nbsp;Cornel Zachiu ,&nbsp;Yao Zhao ,&nbsp;Hualiang Zhong ,&nbsp;Daniela Thorwarth","doi":"10.1016/j.phro.2024.100588","DOIUrl":"10.1016/j.phro.2024.100588","url":null,"abstract":"<div><h3>Background and Purpose</h3><p>Application of different deformable dose accumulation (DDA) solutions makes institutional comparisons after online-adaptive magnetic resonance-guided radiotherapy (OA-MRgRT) challenging. The aim of this multi-institutional study was to analyze accuracy and agreement of DDA-implementations in OA-MRgRT.</p></div><div><h3>Material and Methods</h3><p>One gold standard (GS) case deformed with a biomechanical-model and five clinical cases consisting of prostate (2x), cervix, liver, and lymph node cancer, treated with OA-MRgRT, were analyzed. Six centers conducted DDA using institutional implementations. Deformable image registration (DIR) and DDA results were compared using the contour metrics Dice Similarity Coefficient (DSC), surface-DSC, Hausdorff-distance (HD95%), and accumulated dose-volume histograms (DVHs) analyzed via intraclass correlation coefficient (ICC) and clinical dosimetric criteria (CDC).</p></div><div><h3>Results</h3><p>For the GS, median DDA errors ranged from 0.0 to 2.8 Gy across contours and implementations. DIR of clinical cases resulted in DSC &gt; 0.8 for up to 81.3% of contours and a variability of surface-DSC values depending on the implementation. Maximum HD95%=73.3 mm was found for duodenum in the liver case. Although DVH ICC &gt; 0.90 was found after DDA for all but two contours, relevant absolute CDC differences were observed in clinical cases: Prostate I/II showed maximum differences in bladder V28Gy (10.2/7.6%), while for cervix, liver, and lymph node the highest differences were found for rectum D2cm³ (2.8 Gy), duodenum Dmax (7.1 Gy), and rectum D0.5cm³ (4.6 Gy).</p></div><div><h3>Conclusion</h3><p>Overall, high agreement was found between the different DIR and DDA implementations. Case- and algorithm-dependent differences were observed, leading to potentially clinically relevant results. Larger studies are needed to define future DDA-guidelines.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000587/pdfft?md5=4e084b551f085805fb1f4386347fa500&pid=1-s2.0-S2405631624000587-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141028662","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dose-volume metric-based prediction of radiotherapy-induced lymphocyte loss in patients with non-small-cell lung cancer treated with modern radiotherapy techniques","authors":"Zuzanna Nowicka ,&nbsp;Kasper Kuna ,&nbsp;Mateusz Łaszczych ,&nbsp;Małgorzata Łazar-Poniatowska ,&nbsp;Bartosz Kamil Sobocki ,&nbsp;Konrad Stawiski ,&nbsp;Michał Dąbrowski ,&nbsp;Konrad Bruski ,&nbsp;Adam Zięba ,&nbsp;Mateusz Pajdziński ,&nbsp;Emilia Staniewska ,&nbsp;Marcin Miszczyk ,&nbsp;Harald Paganetti ,&nbsp;Wojciech Fendler ,&nbsp;Bartłomiej Tomasik","doi":"10.1016/j.phro.2024.100593","DOIUrl":"https://doi.org/10.1016/j.phro.2024.100593","url":null,"abstract":"<div><h3>Background and Purpose</h3><p>Radiation-induced lymphopenia (RIL) is a common side effect of radiotherapy (RT) that may negatively impact survival. We aimed to identify RIL predictors in patients with non-small-cell lung cancer (NSCLC) treated intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT).</p></div><div><h3>Materials and Methods</h3><p>We retrospectively analysed data of 306 patients who underwent radical RT for NSCLC. Absolute lymphocyte count (ALC) loss was evaluated for each patient by fitting an exponential decay curve to data from first 45 days since treatment start, and percentage ALC loss relative to baseline was calculated based on area under the decay curve and baseline ALC. We compared IMRT and VMAT treatment plans and used linear regression to predict ALC loss.</p></div><div><h3>Results</h3><p>ALC decreased during RT in the whole patient group, while neutrophil counts remained stable and decreased only in those treated with concurrent chemoradiotherapy (CRT). Percentage ALC loss ranged between 11 and 78 % and was more strongly than lymphocyte nadir correlated with dose-volume metrics for relevant normal structures. We found evidence for the association of high radiation dose to the lungs, heart and body with percentage ALC loss, with lung volume exposed to 20–30 Gy being most important predictors in patients treated with IMRT. A multivariable model based on CRT use, baseline ALC and first principal component (PC1) of the dose-volume predictors showed good predictive performance (bias-corrected R² of 0.40).</p></div><div><h3>Conclusion</h3><p>Percentage lymphocyte loss is a robust measure of RIL that is predicted by baseline ALC, CRT use and dose-volume parameters to the lungs, heart and body.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000630/pdfft?md5=70b73048e1aff2093b500bd187376da5&pid=1-s2.0-S2405631624000630-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141240199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative study of dynamic conformal arc therapy and volumetric modulated arc therapy for treating single brain metastases: A retrospective analysis of dosimetric and clinical outcomes","authors":"Isabelle Chambrelant ,&nbsp;Delphine Jarnet ,&nbsp;Clara Le Fèvre ,&nbsp;Laure Kuntz ,&nbsp;Julian Jacob ,&nbsp;Catherine Jenny ,&nbsp;Georges Noël","doi":"10.1016/j.phro.2024.100591","DOIUrl":"https://doi.org/10.1016/j.phro.2024.100591","url":null,"abstract":"<div><h3>Background and purpose</h3><p>Stereotactic radiation therapy (SRT) is commonly used to treat brain metastases (BMs). This retrospective study compared two SRT techniques, dynamic conformal arc therapy (DCAT) and volumetric modulated arc therapy (VMAT), for single BM treatments.</p></div><div><h3>Material and methods</h3><p>Data of patients treated between January 2010 and June 2020 were considered. Patients with multiple BMs, resected BMs, reirradiation, whole-brain radiation therapy and brainstem metastases were excluded. We focused our analysis on 97 patients who received 23.1 Gy in three fractions. Acute toxicities and follow-up outcomes were recorded. Dosimetric data were analyzed in two subgroups (PTV ≤ 10 cc and PTV &gt; 10 cc).</p></div><div><h3>Results</h3><p>DCAT and VMAT were used in 70 (72.2 %) and 27 (27.8 %) patients, respectively. Acute toxicities were not significantly different between groups (p = 0.259), and no difference was detected in the incidence rate of radionecrosis, local recurrence and cerebral recurrence (p &gt; 0.999, p &gt; 0.999 and p = 0.682, respectively). PTV coverage was better with DCAT for small volumes (PTV ≤ 10 cc). Mean conformity index (CI) was significantly higher with VMAT and mean gradient index (GI) was significantly lower with DCAT whatever volume subgroups (p &lt; 0.001). DCAT had more heterogeneous plans and VMAT required more monitor units. DCAT resulted in reduced low and intermediate doses, whereas VMAT led to decreased high doses.</p></div><div><h3>Conclusion</h3><p>DCAT and VMAT are two effective and safe SRT techniques for BMs treatment. In the era of re-irradiation, it is important to reduce the doses delivered to healthy tissues. Further prospective studies are needed to validate these findings.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000617/pdfft?md5=704f8fbf5e1a7f3a8afbc5267f284024&pid=1-s2.0-S2405631624000617-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141083733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of deep inspiration breath hold and free breathing intensity modulated proton therapy of locally advanced lung cancer","authors":"Kristine Fjellanger ,&nbsp;Ben J.M. Heijmen ,&nbsp;Sebastiaan Breedveld ,&nbsp;Inger Marie Sandvik ,&nbsp;Liv B. Hysing","doi":"10.1016/j.phro.2024.100590","DOIUrl":"10.1016/j.phro.2024.100590","url":null,"abstract":"<div><h3>Background and purpose</h3><p>For locally advanced non-small cell lung cancer (LA-NSCLC), intensity-modulated proton therapy (IMPT) can reduce organ at risk (OAR) doses compared to intensity-modulated radiotherapy (IMRT). Deep inspiration breath hold (DIBH) reduces OAR doses compared to free breathing (FB) in IMRT. In IMPT, differences in dose distributions and robustness between DIBH and FB are unclear. In this study, we compare DIBH to FB in IMPT, and IMPT to IMRT.</p></div><div><h3>Materials and methods</h3><p>Fortyone LA-NSCLC patients were prospectively included. 4D computed tomography images (4DCTs) and DIBH CTs were acquired for treatment planning and during weeks 1 and 3 of treatment. A new system for automated robust planning was developed and used to generate a FB and a DIBH IMPT plan for each patient. Plans were compared in terms of dose-volume parameters and normal tissue complication probabilities (NTCPs). Dose recalculations on repeat CTs were used to compare inter-fraction plan robustness.</p></div><div><h3>Results</h3><p>In IMPT, DIBH reduced median lungs D_mean from 9.3 Gy(RBE) to 8.0 Gy(RBE) compared to FB, and radiation pneumonitis NTCP from 10.9 % to 9.4 % (<em>p</em> &lt; 0.001). Inter-fraction plan robustness for DIBH and FB was similar. Median NTCPs for radiation pneumonitis and mortality were around 9 percentage points lower with IMPT than IMRT (<em>p</em> &lt; 0.001). These differences were much larger than between FB and DIBH within each modality.</p></div><div><h3>Conclusion</h3><p>DIBH IMPT resulted in reduced lung dose and radiation pneumonitis NTCP compared to FB IMPT. Inter-fraction robustness was comparable. OAR doses were far lower in IMPT than IMRT.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000605/pdfft?md5=28d7e0108825d4ff904eaf572aa10e9e&pid=1-s2.0-S2405631624000605-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141023249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimized raw data selection for artifact reduction of breathing controlled four-dimensional sequence scanning","authors":"Juliane Szkitsak ,&nbsp;Andre Karius ,&nbsp;Susanne Fernolendt ,&nbsp;Philipp Schubert ,&nbsp;Stefan Speer ,&nbsp;Rainer Fietkau ,&nbsp;Christoph Bert ,&nbsp;Christian Hofmann","doi":"10.1016/j.phro.2024.100584","DOIUrl":"10.1016/j.phro.2024.100584","url":null,"abstract":"<div><h3>Background and purpose</h3><p>Even with most breathing-controlled four-dimensional computed tomography (4DCT) algorithms image artifacts caused by single significant longer breathing still occur, resulting in negative consequences for radiotherapy. Our study presents first phantom examinations of a new optimized raw data selection and binning algorithm, aiming to improve image quality and geometric accuracy without additional dose exposure.</p></div><div><h3>Materials and methods</h3><p>To validate the new approach, phantom measurements were performed to assess geometric accuracy (volume fidelity, root mean square error, Dice coefficient of volume overlap) for one- and three-dimensional tumor motion trajectories with and without considering motion hysteresis effects. Scans without significantly longer breathing cycles served as references.</p></div><div><h3>Results</h3><p>Median volume deviations between optimized approach and reference of at maximum 1% were obtained considering all movements. In comparison, standard reconstruction yielded median deviations of 9%, 21% and 12% for one-dimensional, three-dimensional, and hysteresis motion, respectively. Measurements in one- and three-dimensional directions reached a median Dice coefficient of 0.970 ± 0.013 and 0.975 ± 0.012, respectively, but only 0.918 ± 0.075 for hysteresis motions averaged over all measurements for the optimized selection. However, for the standard reconstruction median Dice coefficients were 0.845 ± 0.200, 0.868 ± 0.205 and 0.915 ± 0.075 for one- and three-dimensional as well as hysteresis motions, respectively. Median root mean square errors for the optimized algorithm were 30 ± 16<!--> <!-->HU² and 120 ± 90<!--> <!-->HU² for three-dimensional and hysteresis motions, compared to 212 ± 145<!--> <!-->HU² and 130 ± 131<!--> <!-->HU² for the standard reconstruction.</p></div><div><h3>Conclusions</h3><p>The algorithm was proven to reduce 4DCT-related artifacts due to missing projection data without further dose exposure. An improvement in radiotherapy treatment planning due to better image quality can be expected.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S240563162400054X/pdfft?md5=ed2755033be696dda13b8442200c2133&pid=1-s2.0-S240563162400054X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141043749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Validation of echo planar imaging based diffusion-weighted magnetic resonance imaging on a 0.35 T MR-Linac","authors":"Philipp Wallimann ,&nbsp;Marco Piccirelli ,&nbsp;Sylwia Nowakowska ,&nbsp;Tess Armstrong ,&nbsp;Michael Mayinger ,&nbsp;Andreas Boss ,&nbsp;Andrea Bink ,&nbsp;Matthias Guckenberger ,&nbsp;Stephanie Tanadini-Lang ,&nbsp;Nicolaus Andratschke ,&nbsp;Bertrand Pouymayou","doi":"10.1016/j.phro.2024.100579","DOIUrl":"10.1016/j.phro.2024.100579","url":null,"abstract":"<div><h3>Background and Purpose</h3><p>The feasibility of acquiring diffusion-weighted imaging (DWI) images on an MR-Linac for quantitative response assessment during radiotherapy was explored. DWI data obtained with a Spin Echo Echo Planar Imaging sequence adapted for a 0.35 T MR-Linac were examined and compared with DWI data from a conventional 3 T scanner.</p></div><div><h3>Materials and Methods</h3><p>Apparent diffusion coefficient (ADC) measurements and a distortion correction technique were investigated using DWI-calibrated phantoms and in the brains of seven volunteers. All DWI utilized two phase-encoding directions for distortion correction and off-resonance field estimation. ADC maps in the brain were analyzed for automatically segmented normal tissues.</p></div><div><h3>Results</h3><p>Phantom ADC measurements on the MR-Linac were within a 3 % margin of those recorded by the 3 T scanner. The maximum distortion observed in the phantom was 2.0 mm prior to correction and 1.1 mm post-correction on the MR-Linac, compared to 6.0 mm before correction and 3.6 mm after correction at 3 T. In vivo, the average ADC values for gray and white matter exhibited variations of 14 % and 4 %, respectively, for different selections of b-values on the MR-Linac. Distortions in brain images before correction, estimated through the off-resonance field, reached 2.7 mm on the MR-Linac and 12 mm at 3 T.</p></div><div><h3>Conclusion</h3><p>Accurate ADC measurements are achievable on a 0.35 T MR-Linac, both in phantom and in vivo. The selection of b-values significantly influences ADC values in vivo. DWI on the MR-Linac demonstrated lower distortion levels, with a maximum distortion reduced to 1.1 mm after correction.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000496/pdfft?md5=f77a116ae91a1755e0d9ab302dea2363&pid=1-s2.0-S2405631624000496-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140758655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Clinical implementation of a commercial synthetic computed tomography solution for radiotherapy treatment of glioblastoma","authors":"Sevgi Emin ,&nbsp;Elia Rossi ,&nbsp;Elisabeth Myrvold Rooth ,&nbsp;Torsten Dorniok ,&nbsp;Mattias Hedman ,&nbsp;Giovanna Gagliardi ,&nbsp;Fernanda Villegas","doi":"10.1016/j.phro.2024.100589","DOIUrl":"10.1016/j.phro.2024.100589","url":null,"abstract":"<div><h3>Background and Purpose</h3><p>Magnetic resonance (MR)-only radiotherapy (RT) workflow eliminates uncertainties due to computed tomography (CT)-MR image registration, by using synthetic CT (sCT) images generated from MR. This study describes the clinical implementation process, from retrospective commissioning to prospective validation stage of a commercial artificial intelligence (AI)-based sCT product. Evaluation of the dosimetric performance of the sCT is presented, with emphasis on the impact of voxel size differences between image modalities.</p></div><div><h3>Materials and methods</h3><p>sCT performance was assessed in glioblastoma RT planning. Dose differences for 30 patients in both commissioning and validation cohorts were calculated at various dose-volume-histogram (DVH) points for target and organs-at-risk (OAR). A gamma analysis was conducted on regridded image plans. Quality assurance (QA) guidelines were established based on commissioning phase results.</p></div><div><h3>Results</h3><p>Mean dose difference to target structures was found to be within ± 0.7 % regardless of image resolution and cohort. OARs’ mean dose differences were within ± 1.3 % for plans calculated on regridded images for both cohorts, while differences were higher for plans with original voxel size, reaching up to −4.2 % for chiasma D2% in the commissioning cohort. Gamma passing rates for the brain structure using the criteria 1 %/1mm, 2 %/2mm and 3 %/3mm were 93.6 %/99.8 %/100 % and 96.6 %/99.9 %/100 % for commissioning and validation cohorts, respectively.</p></div><div><h3>Conclusions</h3><p>Dosimetric outcomes in both commissioning and validation stages confirmed sCT’s equivalence to CT. The large patient cohort in this study aided in establishing a robust QA program for the MR-only workflow, now applied in glioblastoma RT at our center.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":null,"pages":null},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000599/pdfft?md5=a8a0010d377763cc77048052e12a32c8&pid=1-s2.0-S2405631624000599-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141034422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}