Zeitschrift fur medizinische Physik最新文献

{"title":"Semi-automated bone tracking in dynamic CINE MRI during controlled knee motion.","authors":"A Nepal, N M Brisson, T C Wood, G N Duda, J R Reichenbach, M Krämer","doi":"10.1016/j.zemedi.2025.06.005","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.06.005","url":null,"abstract":"<p><strong>Purpose: </strong>Dynamic magnetic resonance imaging (MRI) enables in vivo imaging of bone motion during knee movement, but quantifying joint kinematics from these images remains technically challenging due to image quality trade-offs inherent in dynamic acquisition sequences. We aimed to develop a semi-automated pipeline for tracking femoral and tibial motion from sagittal plane CINE MRI during active knee flexion and extension. The performance of the method was evaluated by quantifying: (i) bone boundary alignment error, (ii) frame segmentation processing time, and (iii) consistency of derived osteokinematic parameters, with the latter two compared against manual segmentation.</p><p><strong>Methods: </strong>The presented algorithm combines Canny edge detection and connected-component labeling with frame-to-frame transformation optimization to track bone boundaries. The approach was validated in five healthy volunteers performing controlled knee flexion and extension using a dedicated MRI-compatible device. The relative bone displacements measured using the semi-automated approach were qualitatively compared to that from manual segmentation. All bone displacements were defined in the two-dimensional (2D) image coordinate system, with the centroid of the tibial segment tracked relative to the centroid of the femoral segment in the horizontal and vertical directions.</p><p><strong>Results: </strong>The semi-automated tracking method achieved an average alignment error of 0.40 ± 0.02 mm for both bones, with processing time reduced from approximately 15 minutes for manual segmentation to less than 5 minutes for semi-automated segmentation per dataset. Both approaches showed similar relative bone motion patterns, with horizontal displacement of the tibia with respect to the femur ranging between 8 and 28 mm and vertical displacement remaining relatively constant at around 57 mm through the knee motion cycle. Further analysis revealed that the semi-automated method demonstrated improved precision with smaller standard deviations (SDs) in displacement measurements compared to the manual approach, with horizontal displacements of 1.7-2.7 mm vs. 2.2-3.3 mm and vertical displacements of 0.7-1.2 mm vs. 0.9-1.7 mm.</p><p><strong>Conclusion: </strong>These results demonstrate the potential of the semi-automated method for reliable and time-efficient quantification of relative bone positions during volitional knee motion in dynamic MRI protocols. The shorter processing time and the demonstrated reliability of the semi-automated method support its utility for analyzing dynamic MRI data.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144568294","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":"Scanning mode effects on relative electron density and effective atomic number accuracy in dual-layer spectral CT: A phantom study.","authors":"Xinliang Lu, Yunfu Liu, Yongxian Zhang, Dandan Liu, Li Leng, Senlin Guo, Wentao Ma, Xiaomei Lu, Yantao Niu","doi":"10.1016/j.zemedi.2025.06.002","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.06.002","url":null,"abstract":"<p><strong>Purpose: </strong>To assess the accuracy of relative electron density (RED) and effective atomic number (EAN) measurements using dual-layer spectral CT (DLSCT) in axial and helical scanning modes.</p><p><strong>Methods: </strong>The CIRS 062M phantom was scanned with three collimation widths (16 × 0.625 mm, 32 × 0.625 mm, 64 × 0.625 mm) in axial mode and combined with two pitches (0.61 and 0.98) in helical mode. The RED and EAN were quantified using the IntelliSpace Portal, with absolute and relative errors calculated for each insert. Error metrics, including mean absolute error (MAE) and mean relative error (MRE), were subsequently derived over all the inserts. High accuracy was defined as the absolute error < 0.2. Statistical analysis was conducted using one-way ANOVA.</p><p><strong>Results: </strong>In axial mode, the MAE for RED was within 0.01 and the MRE was within 2%; for EAN, the MAE was within 0.25 and the MRE was within 3%. In helical mode, the MAE for RED was within 0.02 and the MRE was within 2.5%; for EAN, the MAE was within 0.5 and the MRE was within 6%. Lung insert showed the highest deviation, while for all other inserts, the MAE was within 0.2 and the MRE was within 2% for EAN across both scanning modes. Smaller collimation widths in axial scanning showed lower relative errors for RED and EAN compared to helical scanning for bone and most of the soft inserts.</p><p><strong>Conclusions: </strong>DLSCT accurately estimates RED and EAN in both scanning modes, suitable for clinical quantitative tissue analysis, with the exception of lung tissue. Smaller collimation widths in axial scanning are recommended for enhanced measurement accuracy and stability.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144562536","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":"Microdosimetry of a clinical carbon-ion pencil beam at MedAustron - Part 1: experimental characterization.","authors":"Cynthia Meouchi, Sandra Barna, Anatoly Rozenfeld, Linh T Tran, Hugo Palmans, Giulio Magrin","doi":"10.1016/j.zemedi.2025.06.003","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.06.003","url":null,"abstract":"<p><strong>Objective: </strong>This paper characterizes the microdosimetric spectra of a single-energy carbon-ion pencil beam with a nominal energy of 284.7 MeV/u at MedAustron using a miniature solid-state silicon microdosimeter to estimate the impact on the profile of the microdosimetric spectra when moving at different lateral distances from the beam axis.</p><p><strong>Approach: </strong>The microdosimeter was fixed at one depth and then laterally moved away from the central beam axis in steps of approximately 2 mm. The measurements were taken in both horizontal and vertical directions due to the fact that the pencil beams are not radially symmetric. These measurements were performed in a water phantom at different depths. At a position on the distal dose fall-off beyond the Bragg peak, the frequency-mean and the dose-mean lineal energies,y¯_F and y¯_D, were derived using either the entire range of y-values, or a sub-range of y values, presumably corresponding mainly to contributions from primary particles and secondary fragments.</p><p><strong>Main results: </strong>The measured microdosimetric spectra did not exhibit a significant change up to 4 mm away from the beam central axis. For lateral positions greater than 4 mm away from the central axis, the relative contribution of the lower lineal-energy part of the spectrum increases with lateral distance due to the increased partial dose from secondary fragments. The average values y¯_F and y¯_D were almost constant for each partial contribution. However, when all particles were considered together, the average value of y¯_F and y¯_D varied with distance from the axis due to the changing dose fractions of these two components varying by 30 % and 10 %, respectively, up to the most off-axis vertical position. Characteristic features in the microdosimetric spectra providing strong indications of the presence of helium and boron fragments were observed downstream of the distal part of the Bragg peak.</p><p><strong>Significance: </strong>The radiation quality was investigated as function of off-axis position. These measurements emphasized variation of the radiation quality within the beam and this has implications in terms of relative biological effectiveness.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144546714","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":"Novel approach for determining beam latency using the center of mass of the radiation field measured with a diode detector array.","authors":"Mathias Dierl, Ndimofor Chofor, Arnd Röser, Christoph Bert, Andreas A Schönfeld","doi":"10.1016/j.zemedi.2025.06.001","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.06.001","url":null,"abstract":"<p><strong>Purpose: </strong>This study presents a novel approach to measure beam-on/off latency of a surface-guided radiotherapy (SGRT) system by employing a setup with a commercial diode detector array to simultaneously capture motion profiles and monitor real-time radiation delivery on a single timestamp, without the need to synchronize different measurements devices.</p><p><strong>Methods: </strong>Beam-on/off latencies were assessed for an AlignRT SGRT system integrated with an Elekta Versa HD and a Varian TrueBeam linear accelerator (linac). The SGRT system triggered the beam by tracking a commercial modular phantom setup comprising of an anthropomorphic head add-on surrogate and a centrally located diode detector array, with the setup mounted on a Dynamic Motion Platform (DMP). Leveraging the diode array's high sampling frequency of 50 ms, motion was simultaneously tracked by mapping the dose distribution's center of mass (CoM) to the radiation delivery timeline during the delivery of a 2×2 cm2 static field. The region of interest (ROI) for CoM calculation was confined to dose levels exceeding a 10% threshold. Latencies were evaluated for 6 MV flattened (FF) and flattening filter-free (FFF) beams at various dose rates (DR) using three DMP motion patterns (sinusoidal, sharkfin, and sawtooth). Amplitude-based gating was implemented at the SGRT system with a 5 mm position tolerance.</p><p><strong>Results: </strong>For the Versa HD, beam-on latency averaged 1650 ± 110 ms, remaining stable for DRs of 400-1200 MU/min for the 6 MV FFF beam. For the 6 MV FF beam, latency increased exponentially to approximately 2000 ms when the DR dropped from 200 to 50 MU/min. Beam-off latency averaged 230 ± 90 ms and was independent of DR for both 6 MV and 6 MV FFF beams. For the TrueBeam linac, beam-on latency averaged 280 ± 90 ms, showing no DR dependence in either beam configuration, while beam-off latency averaged 360 ± 90 ms, slightly shorter for 6 MV FFF compared to 6 MV FF.</p><p><strong>Conclusions: </strong>The CoM method has been effectively implemented to quantify beam-on/off latencies by integrating SGRT-based motion tracking with real-time radiation dose measurements from a diode detector array, all synchronized to a single timestamp. The results revealed latency variations across different linac vendors and underscored the influence of dose rate and beam energy. With this approach, beam-on/off latencies can be efficiently assessed, providing crucial guidance for defining target volume margins, enhancing both precision and safety in high-dose stereotactic radiosurgery (SRS).</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144500030","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":"Microdosimetry of a clinical carbon-ion pencil beam at MedAustron, Part 2: Monte Carlo simulation.","authors":"S Barna, C Meouchi, A F Resch, G Magrin, D Georg, Anatoly Rozenfeld, Linh T Tran, H Palmans","doi":"10.1016/j.zemedi.2025.04.005","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.04.005","url":null,"abstract":"<p><strong>Context: </strong>A first benchmark of the Monte Carlo (MC) code GATE was performed for microdosimetry in carbon ion beams. A validated MC model can, in turn, be used to calculate the radiation quality in lineal energy for any number of energies or treatment plans.</p><p><strong>Materials and methods: </strong>Measurements were performed at five depths along a carbon ion pencil beam with a nominal energy of 284.7 MeV/u, with additional offside central axis (off-CAX) measurements at four depths. The silicon-on-insulator detector used was modeled with a simplified sensitive volume geometry in the Monte Carlo (MC) toolkit GATE. The source code of GATE was modified to allow the scoring of lineal energy for slab sensitive volumes.</p><p><strong>Results: </strong>On average, the difference between the measured and simulated spectra (assuming the same keVµm^-1 cut-off value) was 15 % and 13 % for the frequency-mean and dose-mean lineal energy, respectively. By applying a shift in depth of 500µm towards the beam nozzle, the differences decreased to 10 % and 5 %, mostly affecting the positions in and the fall-off after the Bragg peak. The position in the fragmentation tail showed an edge at a different position than the expected carbon ion edge, which was determined through theoretical (stopping power tables) as well as computational (MC) means to be caused by boron ions.</p><p><strong>Conclusion: </strong>MC is a powerful tool for any potential future clinical application of microdosimetry, provided the beam model has been benchmarked with experimental data. The detector geometry can be approximated with its sensitive volume if the water equivalent thickness of the detector is well known.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144236394","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":"Safety in MR-enhanced daily adaptive SBRT Radiotherapy using a conventional C-arm linear accelerator: An FMEA approach.","authors":"Lotte Wilke, Sebastian M Christ, Riccardo Dal Bello, Elizabeth Denney, Silvia Fabiano, Hubert S Gabryś, Klara Kefer, Michael Mayinger, Ina Nilo, Sophie Perryck, Jens von der Grün, Matthias Guckenberger, Stephanie Tanadini-Lang","doi":"10.1016/j.zemedi.2025.05.002","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.05.002","url":null,"abstract":"<p><strong>Background and purpose: </strong>MR-guided adaptive Radiotherapy has the potential to compensate for interfractional changes in patient anatomy. Modern hybrid devices, which combine MR and linear accelerator technologies, have been clinically implemented but their costs may prevent broad adoption. To accelerate the adoption of MR-guided adaptive radiotherapy, we developed a workflow for MR-enhanced daily adaptive Radiotherapy on a C-arm linac using a dedicated MR simulator and a patient transfer shuttle system. A failure mode and effects analysis (FMEA) was performed to identify possible risks in this newly developed workflow.</p><p><strong>Materials and methods: </strong>A workflow for MR-enhanced daily adaptive SBRT (MEDAS) on a Varian Truebeam linac was developed using a stand-alone 1.5T MR-simulator and patient transfer using a shuttle system. The different process steps were conceptualized in a multidisciplinary team and an FMEA of the different process steps was performed as well as measures for mitigation of possible risks were discussed.</p><p><strong>Results: </strong>The FMEA identified 23 failure modes across eight process steps, with the majority occurring during base plan preparation and adaptive planning. Seventeen (74%) failure modes were classified as low risk, while six (26%) were assessed as medium risk. No high-risk failure modes were identified. Risk mitigation measures, including workflow automation and checklist enhancements, successfully reduced all failure modes to low risk while not introducing new risks CONCLUSION: We developed a workflow for MEDAS on a conventional C-Arm linac. In this process, an FMEA was performed in a multidisciplinary team. The FMEA identified and addressed six medium-risk failure modes within the MEDAS workflow. Through further automation and adaption of existing checklists, the occurrence- and discover probability was successfully reduced, such that these failure modes are decreased to a low risk.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144218098","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":"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":"&lt;p&gt;&lt;strong&gt;Background and purpose: &lt;/strong&gt;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.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Material and methods: &lt;/strong&gt;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.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;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":"Advancing risk management in nuclear medicine diagnostic and therapy through incident-driven risk management tools.","authors":"Lidia Strigari, David Menichelli, Elisa Lodi Rizzini, Arber Golemi, Gian Mauro Sacchetti, Lucia Leva, Cristina Nanni, Paolo Castelucci, Stefano Fanti, Alessio Giuseppe Morganti, Roberta Matheoud","doi":"10.1016/j.zemedi.2025.03.004","DOIUrl":"https://doi.org/10.1016/j.zemedi.2025.03.004","url":null,"abstract":"<p><p>Accidental or unintended exposures in nuclear medicine present significant risks, demanding proactive and systematic risk management strategies. This study explores the development and implementation of a novel software tool that integrates Failure Modes and Effects Analysis (FMEA) and Fault Tree Analysis (FTA) into a unified platform tailored for nuclear medicine. The tool addresses the complexities of risk assessment across diagnostic and therapeutic workflows, offering customizable templates and a streamlined process for identifying, prioritizing, and mitigating failure modes. A multicenter study involving nuclear medicine departments of various sizes demonstrated the tool's efficacy in standardizing risk analysis and enhancing interdisciplinary collaboration. Key scenarios, such as errors in radiopharmaceutical preparation and administration, were assessed, with rankings assigned based on a refined Risk Priority Number (RPN) system. The results underscore the transformative potential of combining FMEA and FTA in nuclear medicine, addressing the limitations of standalone methodologies. This approach improves workflow efficiency and ensures a robust framework for patient safety. Future directions include expanding the tool's applications, refining templates, and fostering a proactive culture of risk assessment. These advancements pave the way for safer, more efficient practices in nuclear medicine, benefiting patients and professionals alike.</p>","PeriodicalId":101315,"journal":{"name":"Zeitschrift fur medizinische Physik","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144121900","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":"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":"&lt;p&gt;&lt;strong&gt;Background and purpose: &lt;/strong&gt;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.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Materials and methods: &lt;/strong&gt;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.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;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}