Physics and Imaging in Radiation Oncology最新文献

{"title":"Treatment planning evaluation and experimental validation of the magnetic resonance-based intrafraction drift correction","authors":"Madelon van den Dobbelsteen,&nbsp;Sara L. Hackett,&nbsp;Bram van Asselen,&nbsp;Stijn Oolbekkink,&nbsp;Bas W. Raaymakers,&nbsp;Johannes C.J. de Boer","doi":"10.1016/j.phro.2024.100580","DOIUrl":"10.1016/j.phro.2024.100580","url":null,"abstract":"<div><h3>Background and purpose</h3><p>MRI-guided online adaptive treatments can account for interfractional variations, however intrafraction motion reduces treatment accuracy. Intrafraction plan adaptation methods, such as the Intrafraction Drift Correction (IDC) or sub-fractionation, are needed. IDC uses real-time automatic monitoring of the tumor position to initiate plan adaptations by repositioning segments. IDC is a fast adaptation method that occurs only when necessary and this method could enable margin reduction. This research provides a treatment planning evaluation and experimental validation of the IDC.</p></div><div><h3>Materials and methods</h3><p>An in silico treatment planning evaluation was performed for 13 prostate patients mid-treatment without and with intrafraction plan adaptation (IDC and sub-fractionation). The adaptation methods were evaluated using dose volume histogram (DVH) metrics. To experimentally verify IDC a treatment was mimicked whereby a motion phantom containing an EBT3 film moved mid-treatment, followed by repositioning of segments. In addition, the delivered treatment was irradiated on a diode array phantom for plan quality assurance purposes.</p></div><div><h3>Results</h3><p>The planning study showed benefits for using intrafraction adaptation methods relative to no adaptation, where the IDC and sub-fractionation showed consistently improved target coverage with median target coverages of 100.0%. The experimental results verified the IDC with high minimum gamma passing rates of 99.1% and small mean dose deviations of maximum 0.3%.</p></div><div><h3>Conclusion</h3><p>The straightforward and fast IDC technique showed DVH metrics consistent with the sub-fractionation method using segment weight re-optimization for prostate patients. The dosimetric and geometric accuracy was shown for a full IDC workflow using film and diode array dosimetry.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"30 ","pages":"Article 100580"},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000502/pdfft?md5=c8011bab47fdb66631d638a672a9c9a5&pid=1-s2.0-S2405631624000502-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140764359","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":"Robustness analysis of dynamic trajectory radiotherapy and volumetric modulated arc therapy plans for head and neck cancer","authors":"Hannes A. Loebner ,&nbsp;Jenny Bertholet ,&nbsp;Paul-Henry Mackeprang ,&nbsp;Werner Volken ,&nbsp;Olgun Elicin ,&nbsp;Silvan Mueller ,&nbsp;Gian Guyer ,&nbsp;Daniel M. Aebersold ,&nbsp;Marco F.M. Stampanoni ,&nbsp;Michael K. Fix ,&nbsp;Peter Manser","doi":"10.1016/j.phro.2024.100586","DOIUrl":"10.1016/j.phro.2024.100586","url":null,"abstract":"<div><h3>Background and purpose</h3><p>Dynamic trajectory radiotherapy (DTRT) has been shown to improve healthy tissue sparing compared to volumetric arc therapy (VMAT). This study aimed to assess and compare the robustness of DTRT and VMAT treatment-plans for head and neck (H&amp;N) cancer to patient-setup (PS) and machine-positioning uncertainties.</p></div><div><h3>Materials and methods</h3><p>The robustness of DTRT and VMAT plans previously created for 46 H&amp;N cases, prescribed 50–70 Gy to 95 % of the planning-target-volume, was assessed. For this purpose, dose distributions were recalculated using Monte Carlo, including uncertainties in PS (translation and rotation) and machine-positioning (gantry-, table-, collimator-rotation and multi-leaf collimator (MLC)). Plan robustness was evaluated by the uncertainties’ impact on normal tissue complication probabilities (NTCP) for xerostomia and dysphagia and on dose-volume endpoints. Differences between DTRT and VMAT plan robustness were compared using Wilcoxon matched-pair signed-rank test (<span><math><mi>α</mi></math></span> = 5 %).</p></div><div><h3>Results</h3><p>Average NTCP for moderate-to-severe xerostomia and grade ≥ II dysphagia was lower for DTRT than VMAT in the nominal scenario (0.5 %, p = 0.01; 2.1 %, p &lt; 0.01) and for all investigated uncertainties, except MLC positioning, where the difference was not significant. Average differences compared to the nominal scenario were <span><math><mo>≤</mo></math></span> 3.5 Gy for rotational PS (<span><math><mo>≤</mo></math></span> 3°) and machine-positioning (<span><math><mo>≤</mo></math></span> 2°) uncertainties, &lt;7 Gy for translational PS uncertainties (<span><math><mo>≤</mo></math></span> 5 mm) and &lt; 20 Gy for MLC-positioning uncertainties (<span><math><mo>≤</mo></math></span> 5 mm).</p></div><div><h3>Conclusions</h3><p>DTRT and VMAT plan robustness to the investigated uncertainties depended on uncertainty direction and location of the structure-of-interest to the target. NTCP remained on average lower for DTRT than VMAT even when considering uncertainties.</p></div>","PeriodicalId":36850,"journal":{"name":"Physics and Imaging in Radiation Oncology","volume":"30 ","pages":"Article 100586"},"PeriodicalIF":3.7,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2405631624000563/pdfft?md5=27937f4f3eb2aacacce30fcc8d8a8d9d&pid=1-s2.0-S2405631624000563-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141036885","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":"30 ","pages":"Article 100575"},"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":"30 ","pages":"Article 100592"},"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":"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":"30 ","pages":"Article 100593"},"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":"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":"30 ","pages":"Article 100588"},"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":"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":"30 ","pages":"Article 100590"},"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":"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":"30 ","pages":"Article 100591"},"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":"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":"30 ","pages":"Article 100579"},"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":"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":"30 ","pages":"Article 100584"},"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}