Zeitschrift fur medizinische Physik最新文献

{"title":"Deformable image registration (DIR) in Swiss radiotherapy: Usage patterns survey and multi-institutional deformable dose accumulation comparison.","authors":"Florian Amstutz, Björn Zobrist, Peter Manser, Michael K Fix","doi":"10.1016/j.zemedi.2025.05.001","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.05.001","url":null,"abstract":"<p><strong>Background and purpose: </strong>Deformable image registration (DIR) enables advanced applications for image-guided and adaptive radiotherapy. However, DIR has not yet been widely adopted in clinical settings. This study addresses two challenges: (1) evaluating DIR practices and identifying barriers through a survey of Swiss radiotherapy institutes, providing Swiss-specific insights, and (2) assessing multi-institutional deformable-based dose accumulation (DDA) uncertainties by analyzing dose discrepancies on the accumulated dose. These findings aim to inform consensus guidelines, quantify DDA uncertainties, and support standardized future DIR integration into routine RT.</p><p><strong>Material and methods: </strong>All Swiss radiotherapy institutes with available contact details were invited to participate in the study's two parts: a survey and a multi-institutional DDA evaluation. The survey consisted of 25 questions and was conducted from August 23 to October 31, 2024. Survey results were compared to surveys from other countries. For the DDA evaluation, participants used shared datasets, including a lung cancer case with two dose distributions, one conventional VMAT dose and one artificially created cuboid dose, to perform DIR and accumulate doses. The cuboid dose was used to have a standardized dose with a \"perfect\" dose gradient. The level of inter-institutional dose discrepancies was assessed visually and by calculating dose differences on a voxel level.</p><p><strong>Results: </strong>Eighteen out of 26 institutes (69%) completed the survey. All 18 institutes use rigid image registration (RIR) clinically, 11 (61.1%) use DIR. Five of those institutes use DIR in research projects. RIR is primarily applied for image fusion (100% of the institutes), patient positioning (88.9%), and as a preliminary step to DIR or adaptive RT (55.6%). DIR use cases include image fusion, dose accumulation, and adaptive workflows. Barriers to DIR adoption in clinical routine include software limitations and a lack of quality management methods. Standardized quality management of DIRs is largely missing in Swiss radiotherapy institutes so far. Six institutes participated in the dose accumulation part, submitting dose accumulation results for a VMAT and a cuboid dose distribution. Visual inspection revealed inter-institutional differences, particularly in steep dose gradient areas. Quantitative analysis showed average voxel-wise absolute differences of 0.01-0.03 Gy (VMAT), corresponding to 0.1%-0.3%, and 0.18-0.45 Gy (cuboid), corresponding to 1.8%-4.5%, for a total dose of 10 Gy. Differences were more pronounced in steep dose gradients and, consequently, in proximity to the PTV. The voxel-wise maximum-minimum analysis highlighted variability in gradient regions, even for the same algorithms used by different institutes, emphasizing the impact of software, software usage, and workflow choices on dose accumulation outcomes. The cuboid dose showed increase","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144145176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Time course of transimpedances is affected by cochlea implant surgical technique.","authors":"Luise Wagner, Stefan K Plontke, Torsten Rahne, Anna C Kopsch","doi":"10.1016/j.zemedi.2025.04.006","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.04.006","url":null,"abstract":"<p><strong>Background: </strong>For cochlear implant (CI) users after subtotal cochlectomy for removal of intracochlear schwannomas, significantly different intracochlear potentials can be observed compared with cochleae of CI patients after round window electrode insertion. The time course of this difference after surgery is so far unknown.</p><p><strong>Purpose: </strong>The change of intracochlear potentials over time and differences between surgical approaches are investigated.</p><p><strong>Methods: </strong>In a retrospective study of cochlear implant recipients, the electrode transimpedances were measured and compared between 19 patients after subtotal cochlectomy and 20 patients after round window insertion. Transimpedances were measured with pulse widths of 37 µs and current units of 100 CL to 110 CL using a monopolar stimulation and recording mode (MP2). For each patient, at least three time points over a period of up to four years were used for time course analysis.</p><p><strong>Results: </strong>The transimpedances of patients after subtotal cochlectomy were significantly smaller than those of the round window group. The largest transimpedance changes over time were observed for basal electrode contacts in patients after round window insertion.</p><p><strong>Conclusions: </strong>For the interpretation of transimpedances, it is relevant to consider the time since surgery and the CI insertion technique. The width of the electric field may be related to loss of intracochlear conductive fluid due to surgical trauma and fibrotic processes.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144003198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a TLD-100 based set up for in vivo dosimetry in Intraoperative Electron Beam Radiation Therapy (IOERT): an experimental and clinical evaluation.","authors":"Charoula Iliaskou, Mark Gainey, Benedikt Thomann, Michael Kollefrath, Rainer Saum, Eleni Gkika, Uwe A Wittel, Dietrich A Ruess, Anca-Ligia Grosu, Dimos Baltas","doi":"10.1016/j.zemedi.2025.04.007","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.04.007","url":null,"abstract":"<p><strong>Purpose: </strong>This study presents an in-house developed set-up enabling the placement of multiple TLDs over the target region, for in vivo dosimetry in intraoperative electron beam radiotherapy (IOERT).</p><p><strong>Methods and materials: </strong>TLD-100 (LiF:MgTi) rods were calibrated at 10 Gy and their response was determined for the nominal electron energies of the Mobetron LINAC within the dose range from 4 Gy to 20 Gy. Irradiation of various set-ups was performed using the ionisation chambers (IC) ROOS parallel plate 34001 (PTW, Freiburg) and 3D Semiflex 31021 (PTW, Freiburg), a microdiamond detector 60019 (PTW, Freiburg) and EBT3 films (Ashland™) to investigate beam perturbations that may result due to the structure of the set up. EGSnrc Monte Carlo (MC) simulations evaluated the response of the TLDs in clinical beams of the available electron energies, the influence of the catheter to the TLD dose scoring and the depth dependence of the TLD dose assessment. TLD measurements in-phantoms and in patient in vivo were realised and compared to the expected doses estimated using data of water phantom measurements and 3D MC electron dose calculations of a dedicated IOERT treatment planning system (Radiance TPS- GmV, Tres Cantos, Madrid).</p><p><strong>Results: </strong>MC and measurements verified that no energy correction is needed for the used electron beams. Correction factors for the dose non-linear response were evaluated. High resolution dose measurements showed local hot spots beneath the flap. However, there are no significant perturbations of the electron beam or on the dose delivery to the targeted volume. MC simulations demonstrated no signal attenuation due to the catheter and 1 % effect of the depth of TLD measurement relative to the depth of calibration was noted. TLD measurements in phantom set-ups agreed with expected doses with less than 2.6 % in phantoms and by 1 % in patient in vivo.</p><p><strong>Conclusions: </strong>Our results demonstrate the suitability of using the implemented TLD-based workflow for in vivo dosimetry purposes in the operation room (OR) environment.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144060322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative analysis of open-source against commercial AI-based segmentation models for online adaptive MR-guided radiotherapy.","authors":"Dominik Langner, Marcel Nachbar, Monica Lo Russo, Simon Boeke, Cihan Gani, Maximilian Niyazi, Daniela Thorwarth","doi":"10.1016/j.zemedi.2025.04.008","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.04.008","url":null,"abstract":"<p><strong>Background and purpose: </strong>Online adaptive magnetic resonance-guided radiotherapy (MRgRT) has emerged as a state-of-the-art treatment option for multiple tumour entities, accounting for daily anatomical and tumour volume changes, thus allowing sparing of relevant organs at risk (OARs). However, the annotation of treatment-relevant anatomical structures in context of online plan adaptation remains challenging, often relying on commercial segmentation solutions due to limited availability of clinically validated alternatives. The aim of this study was to investigate whether an open-source artificial intelligence (AI) segmentation network can compete with the annotation accuracy of a commercial solution, both trained on the identical dataset, questioning the need for commercial models in clinical practice.</p><p><strong>Materials and methods: </strong>For 47 pelvic patients, T2w MR imaging data acquired on a 1.5 T MR-Linac were manually contoured, identifying prostate, seminal vesicles, rectum, anal canal, bladder, penile bulb, and bony structures. These training data were used for the generation of an in-house AI segmentation model, a nnU-Net with residual encoder architecture featuring a streamlined single image inference pipeline, and re-training of a commercial solution. For quantitative evaluation, 20 MR images were contoured by a radiation oncologist, considered as ground truth contours (GTC) and compared with the in-house/commercial AI-based contours (iAIC/cAIC) using Dice Similarity Coefficient (DSC), 95% Hausdorff distances (HD95), and surface DSC (sDSC). For qualitative evaluation, four radiation oncologists assessed the usability of OAR/target iAIC within an online adaptive workflow using a four-point Likert scale: (1) acceptable without modification, (2) requiring minor adjustments, (3) requiring major adjustments, and (4) not usable.</p><p><strong>Results: </strong>Patient-individual annotations were generated in a median [range] time of 23 [16-34] s for iAIC and 152 [121-198] s for cAIC, respectively. OARs showed a maximum median DSC of 0.97/0.97 (iAIC/cAIC) for bladder and minimum median DSC of 0.78/0.79 (iAIC/cAIC) for anal canal/penile bulb. Maximal respectively minimal median HD95 were detected for rectum with 17.3/20.6 mm (iAIC/cAIC) and for bladder with 5.6/6.0 mm (iAIC/cAIC). Overall, the average median DSC/HD95 values were 0.87/11.8mm (iAIC) and 0.83/10.2mm (cAIC) for OAR/targets and 0.90/11.9mm (iAIC) and 0.91/16.5mm (cAIC) for bony structures. For a tolerance of 3 mm, the highest and lowest sDSC were determined for bladder (iAIC:1.00, cAIC:0.99) and prostate in iAIC (0.89) and anal canal in cAIC (0.80), respectively. Qualitatively, 84.8% of analysed contours were considered as clinically acceptable for iAIC, while 12.9% required minor and 2.3% major adjustments or were classed as unusable. Contour-specific analysis showed that iAIC achieved the highest mean scores with 1.00 for the anal canal and the lowest w","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144056741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}