Zeitschrift fur Medizinische Physik最新文献

{"title":"The Medical Device Regulation and its impact on device development and research in Germany","authors":"Mark E. Ladd","doi":"10.1016/j.zemedi.2023.09.002","DOIUrl":"10.1016/j.zemedi.2023.09.002","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 459-461"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923001149/pdfft?md5=2ec676734624e9c1443edac357f21c0f&pid=1-s2.0-S0939388923001149-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49687314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Validating a double Gaussian source model for small proton fields in a commercial Monte-Carlo dose calculation engine","authors":"Fabian Kugel , Jörg Wulff , Christian Bäumer , Martin Janson , Jana Kretschmer , Leonie Brodbek , Carina Behrends , Nico Verbeek , Hui Khee Looe , Björn Poppe , Beate Timmermann","doi":"10.1016/j.zemedi.2022.11.011","DOIUrl":"10.1016/j.zemedi.2022.11.011","url":null,"abstract":"<div><h3>Purpose</h3><p>The primary fluence of a proton pencil beam exiting the accelerator is enveloped by a region of secondaries, commonly called “spray”. Although small in magnitude, this spray may affect dose distributions in pencil beam scanning mode e.g., in the calculation of the small field output, if not modelled properly in a treatment planning system (TPS). The purpose of this study was to dosimetrically benchmark the Monte Carlo (MC) dose engine of the RayStation TPS (v.10A) in small proton fields and systematically compare single Gaussian (SG) and double Gaussian (DG) modeling of initial proton fluence providing a more accurate representation of the nozzle spray.</p></div><div><h3>Methods</h3><p>The initial proton fluence distribution for SG/DG beam modeling was deduced from two-dimensional measurements in air with a scintillation screen with electronic readout. The DG model was either based on direct fits of the two Gaussians to the measured profiles, or by an iterative optimization procedure, which uses the measured profiles to mimic in-air scan-field factor (SF) measurements. To validate the DG beam models SFs, i.e. relative doses to a 10 × 10 cm<sup>2</sup> field, were measured in water for three different initial proton energies (<span><math><mrow><mn>100</mn><mspace></mspace><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></mrow></math></span>, <span><math><mrow><mn>160</mn><mspace></mspace><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></mrow></math></span>, <span><math><mrow><mn>226.7</mn><mspace></mspace><mspace></mspace><mi>M</mi><mi>e</mi><mi>V</mi></mrow></math></span>) and square field sizes from <span><math><mrow><mn>1</mn><mspace></mspace><mo>×</mo><mn>1</mn><mspace></mspace><mspace></mspace><msup><mrow><mi>c</mi><mi>m</mi></mrow><mn>2</mn></msup></mrow></math></span> to <span><math><mrow><mn>10</mn><mspace></mspace><mo>×</mo><mn>10</mn><mspace></mspace><mspace></mspace><msup><mrow><mi>c</mi><mi>m</mi></mrow><mn>2</mn></msup></mrow></math></span> using a small field ionization chamber (IBA CC01) and an IBA ProteusPlus system (universal nozzle). Furthermore, the dose to the center of spherical target volumes (diameters: <span><math><mrow><mn>1</mn><mspace></mspace><mspace></mspace><mi>c</mi><mi>m</mi></mrow></math></span> to <span><math><mrow><mn>10</mn><mspace></mspace><mspace></mspace><mi>c</mi><mi>m</mi></mrow></math></span>) was determined using the same small volume ionization chamber (IC). A comprehensive uncertainty analysis was performed, including estimates of influence factors typical for small field dosimetry deduced from a simple two-dimensional analytical model of the relative fluence distribution. Measurements were compared to the predictions of the RayStation TPS.</p></div><div><h3>Results</h3><p>SFs deviated by more than <span><math><mrow><mn>2</mn><mspace></mspace><mo>%</mo></mrow></math></span> from TPS predictions in all fields <span><math><mrow><mo><</mo><mn>4</mn><mspace></mspace><mo>×</mo><mn>4<","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 529-541"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001325/pdfft?md5=acc41f4e71e3b623bcf07aca85ececd9&pid=1-s2.0-S0939388922001325-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10447935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"BFRnet: A deep learning-based MR background field removal method for QSM of the brain containing significant pathological susceptibility sources","authors":"Xuanyu Zhu,&nbsp;Yang Gao,&nbsp;Feng Liu,&nbsp;Stuart Crozier,&nbsp;Hongfu Sun","doi":"10.1016/j.zemedi.2022.08.001","DOIUrl":"10.1016/j.zemedi.2022.08.001","url":null,"abstract":"<div><h3>Introduction</h3><p>Background field removal (BFR) is a critical step required for successful quantitative susceptibility mapping (QSM). However, eliminating the background field in brains containing significant susceptibility sources, such as intracranial hemorrhages, is challenging due to the relatively large scale of the field induced by these pathological susceptibility sources.</p></div><div><h3>Method</h3><p>This study proposes a new deep learning-based method, BFRnet, to remove the background field in healthy and hemorrhagic subjects. The network is built with the dual-frequency octave convolutions on the U-net architecture, trained with synthetic field maps containing significant susceptibility sources. The BFRnet method is compared with three conventional BFR methods and one previous deep learning method using simulated and <em>in vivo</em> brains from 4 healthy and 2 hemorrhagic subjects. Robustness against acquisition field-of-view (FOV) orientation and brain masking are also investigated.</p></div><div><h3>Results</h3><p>For both simulation and <em>in vivo</em> experiments, BFRnet led to the best visually appealing results in the local field and QSM results with the minimum contrast loss and the most accurate hemorrhage susceptibility measurements among all five methods. In addition, BFRnet produced the most consistent local field and susceptibility maps between different sizes of brain masks, while conventional methods depend drastically on precise brain extraction and further brain edge erosions. It is also observed that BFRnet performed the best among all BFR methods for acquisition FOVs oblique to the main magnetic field.</p></div><div><h3>Conclusion</h3><p>The proposed BFRnet improved the accuracy of local field reconstruction in the hemorrhagic subjects compared with conventional BFR algorithms. The BFRnet method was effective for acquisitions of tilted orientations and retained whole brains without edge erosion as often required by traditional BFR methods.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 578-590"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000873/pdfft?md5=a43396a30e379e50097e3a5a3e24b83c&pid=1-s2.0-S0939388922000873-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40351533","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extension of the open-source TIGRE toolbox for proton imaging","authors":"Stefanie Kaser ,&nbsp;Thomas Bergauer ,&nbsp;Ander Biguri ,&nbsp;Wolfgang Birkfellner ,&nbsp;Sepideh Hatamikia ,&nbsp;Albert Hirtl ,&nbsp;Christian Irmler ,&nbsp;Benjamin Kirchmayer ,&nbsp;Felix Ulrich-Pur","doi":"10.1016/j.zemedi.2022.08.005","DOIUrl":"10.1016/j.zemedi.2022.08.005","url":null,"abstract":"<div><p>Proton irradiation is a well-established method to treat deep-seated tumors in radio oncology. Usually, an X-ray computed tomography (CT) scan is used for treatment planning. Since proton therapy is based on the precise knowledge of the stopping power describing the energy loss of protons in the patient tissues, the Hounsfield units of the planning CT have to be converted. This conversion introduces range errors in the treatment plan, which could be reduced, if the stopping power values were extracted directly from an image obtained using protons instead of X-rays. Since protons are affected by multiple Coulomb scattering, reconstruction of the 3D stopping power map results in limited image quality if the curved proton path is not considered. This work presents a substantial code extension of the open-source toolbox TIGRE for proton CT (pCT) image reconstruction based on proton radiographs including a curved proton path estimate. The code extension and the reconstruction algorithms are GPU-based, allowing to achieve reconstruction results within minutes. The performance of the pCT code extension was tested with Monte Carlo simulated data using three phantoms (Catphan® high resolution and sensitometry modules and a CIRS patient phantom). In the simulations, ideal and non-ideal conditions for a pCT setup were assumed. The obtained mean absolute percentage error was found to be below 1% and up to 8 lp/cm could be resolved using an idealized setup. These findings demonstrate that the presented code extension to the TIGRE toolbox offers the possibility for other research groups to use a fast and accurate open-source pCT reconstruction.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 552-566"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000915/pdfft?md5=46269dbaf9848d6120a6ee0827c92f50&pid=1-s2.0-S0939388922000915-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33487328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unified risk analysis in radiation therapy","authors":"Daniel Lohmann,&nbsp;Maya Shariff,&nbsp;Philipp Schubert,&nbsp;Tim Oliver Sauer,&nbsp;Rainer Fietkau,&nbsp;Christoph Bert","doi":"10.1016/j.zemedi.2022.08.006","DOIUrl":"10.1016/j.zemedi.2022.08.006","url":null,"abstract":"<div><h3>Purpose</h3><p>The increasing complexity of new treatment methods as well as the Information Technology (IT) infrastructure within radiotherapy require new methods for risk analysis. This work presents a methodology on how to model the treatment process of radiotherapy in different levels. This subdivision makes it possible to perform workflow-specific risk analysis and to assess the impact of IT risks on the overall treatment workflow.</p></div><div><h3>Methods</h3><p>A Unified Modeling Language (UML) activity diagram is used to model the workflows. The subdivision of the workflows into different levels is done with the help of swim lanes. The model created in this way is exported in an xml-compatible format and stored in a database with the help of a Python program.</p></div><div><h3>Results</h3><p>Based on an existing risk analysis, the workflows CT Appointment, Glioblastoma Multiforme, and Deep Inspiration Breath Hold (DIBH) were modeled in detail. Part of the analysis are automatically generated workflow-specific risk matrices including risks of medical devices incorporated into a specific workflow. In addition, SQL queries allow to quickly retrieve e.g., the details of the medical device network installed in a department.</p></div><div><h3>Conclusion</h3><p>Activity diagrams of UML can be used to model workflows in radiotherapy. Through this, a connection between the different levels of the entire workflow can be established and workflow-specific risk analysis is possible.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 479-488"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000927/pdfft?md5=ba80fcde953fca3d36d229a6788bd796&pid=1-s2.0-S0939388922000927-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33494623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Benchmark of the PenRed Monte Carlo framework for HDR brachytherapy","authors":"Sandra Oliver ,&nbsp;Vicent Giménez-Alventosa ,&nbsp;Francisco Berumen ,&nbsp;Vicente Gimenez ,&nbsp;Luc Beaulieu ,&nbsp;Facundo Ballester ,&nbsp;Javier Vijande","doi":"10.1016/j.zemedi.2022.11.002","DOIUrl":"10.1016/j.zemedi.2022.11.002","url":null,"abstract":"&lt;div&gt;&lt;h3&gt;Purpose&lt;/h3&gt;&lt;p&gt;The purpose of this study is to validate the PenRed Monte Carlo framework for clinical applications in brachytherapy. PenRed is a C++ version of Penelope Monte Carlo code with additional tallies and utilities.&lt;/p&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Methods and materials&lt;/h3&gt;&lt;p&gt;Six benchmarking scenarios are explored to validate the use of PenRed and its improved bachytherapy-oriented capabilities for HDR brachytherapy. A new tally allowing the evaluation of collisional kerma for any material using the track length kerma estimator and the possibility to obtain the seed positions, weights and directions processing directly the DICOM file are now implemented in the PenRed distribution. The four non-clinical test cases developed by the Joint AAPM-ESTRO-ABG-ABS WG-DCAB were evaluated by comparing local and global absorbed dose differences with respect to established reference datasets. A prostate and a palliative lung cases, were also studied. For them, absorbed dose ratios, global absorbed dose differences, and cumulative dose-volume histograms were obtained and discussed.&lt;/p&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Results&lt;/h3&gt;&lt;p&gt;The air-kerma strength and the dose rate constant corresponding to the two sources agree with the reference datatests within 0.3% (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;k&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and 0.1% (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;Λ&lt;/mi&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. With respect to the first three WG-DCAB test cases, more than 99.8% of the voxels present local (global) differences within &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;%&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;(&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0.1&lt;/mn&gt;&lt;mo&gt;%&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) of the reference datasets. For test Case 4 reference dataset, more than 94.9%(97.5%) of voxels show an agreement within &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;mo&gt;%&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;(&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0.1&lt;/mn&gt;&lt;mo&gt;%&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), better than similar benchmarking calculations in the literature. The track length kerma estimator scorer implemented increases the numerical efficiency of brachytherapy calculations two orders of magnitude, while the specific brachytherapy source allows the user to avoid the use of error-prone intermediate steps to translate the DICOM information into the simulation. In both clinical cases, only minor absorbed dose differences arise in the low-dose isodoses. 99.8% and 100% of the voxels have a global absorbed dose difference ratio within &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mo&gt;±&lt;/mo&gt;&lt;mn&gt;0.2&lt;/mn&gt;&lt;mo&gt;%&lt;/mo&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; for the prostate and lung cases, respectively. The role played by the different segmentation and composition material in the bone structures was discussed, obtaining negligible absorbed dose differences. Dose-volume histograms were in agreement with the reference data.&lt;/p&gt;&lt;/div&gt;&lt;div&gt;&lt;h3&gt;Conclusions&lt;/h3&gt;&lt;p&gt;PenRed incorporates new tallies and utilities and has been validated for its use for detailed and precise high-dose-rate b","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 511-528"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922001040/pdfft?md5=c747742a19f7b02d767f19528d0430ad&pid=1-s2.0-S0939388922001040-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10333707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editorial Board + Consulting Editorial Board","authors":"","doi":"10.1016/S0939-3889(23)00127-7","DOIUrl":"https://doi.org/10.1016/S0939-3889(23)00127-7","url":null,"abstract":"","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Page iii"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388923001277/pdfft?md5=a43e8d644615c977282e065a0efa2af1&pid=1-s2.0-S0939388923001277-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138570534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DNA damage by radiation as a function of electron energy and interaction at the atomic level with Monte Carlo simulation","authors":"Youssef Lamghari,&nbsp;Huizhong Lu,&nbsp;M'hamed Bentourkia","doi":"10.1016/j.zemedi.2022.07.003","DOIUrl":"10.1016/j.zemedi.2022.07.003","url":null,"abstract":"<div><p>In radiotherapy, X-ray or heavy ion beams target tumors to cause damage to their cell DNA. This damage is mainly induced by secondary low energy electrons. In this paper, we report the DNA molecular breaks at the atomic level as a function of electron energy and types of electron interactions using of Monte Carlo simulation. The number of DNA single and double strand breaks are compared to those from experimental results based on electron energies. In recent years, DNA atomistic models were introduced but still the simulations consider energy deposition in volumes of DNA or water equivalent material. We simulated a model of atomistic B-DNA in vacuum, forming 1122 base pairs of 30 nm in length. Each atom has been represented by a sphere whose radius equals the radius of van der Waals. We repeatedly simulated 10 million electrons for each energy from 4 eV to 500 eV and counted each interaction type with its position x, y, z in the volume of DNA. Based on the number and types of interactions at the atomic level, the number of DNA single and double strand breaks were calculated. We found that the dissociative electron attachment has the dominant effect on DNA strand breaks at energies below 10 eV compared to excitation and ionization. In addition, it is straightforward with our simulation to discriminate the strand and base breaks as a function of radiation interaction type and energy. In conclusion, the knowledge of DNA damage at the atomic level helps design direct internal therapeutic agents of cancer treatment.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 489-498"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S093938892200071X/pdfft?md5=6d550dd97e11543945f8d488cdc40406&pid=1-s2.0-S093938892200071X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40618592","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of Monte Carlo simulations of the electron transport in external magnetic fields using Fano cavity test","authors":"Mohamad Alissa ,&nbsp;Klemens Zink ,&nbsp;Damian Czarnecki","doi":"10.1016/j.zemedi.2022.07.002","DOIUrl":"10.1016/j.zemedi.2022.07.002","url":null,"abstract":"<div><h3>Purpose</h3><p>Monte Carlo simulations are crucial for calculating magnetic field correction factors <span><math><mrow><msub><mrow><mi>k</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow></math></span> for the dosimetry in external magnetic fields. As in Monte Carlo codes the charged particle transport is performed in straight condensed history (CH) steps, the curved trajectories of these particles in the presence of external magnetic fields can only be approximated. In this study, the charged particle transport in presence of a strong magnetic field <span><math><mrow><mover><mrow><mi>B</mi></mrow><mrow><mo>→</mo></mrow></mover></mrow></math></span> was investigated using the Fano cavity test. The test was performed in an ionization chamber and a diode detector, showing how the step size restrictions must be adjusted to perform a consistent charged particle transport within all geometrical regions.</p></div><div><h3>Methods</h3><p>Monte Carlo simulations of the charged particle transport in a magnetic field of 1.5 T were performed using the EGSnrc code system including an additional EMF-macro for the transport of charged particle in electro-magnetic fields. Detailed models of an ionization chamber and a diode detector were placed in a water phantom and irradiated with a so called Fano source, which is a monoenergetic, isotropic electron source, where the number of emitted particles is proportional to the local density.</p></div><div><h3>Results</h3><p>The results of the Fano cavity test strongly depend on the energy of charged particles and the density within the given geometry. By adjusting the maximal length of the charged particle steps, it was possible to calculate the deposited dose in the investigated regions with high accuracy (<span><math><mrow><mo>&lt;</mo><mn>0.1</mn></mrow></math></span>%). The Fano cavity test was performed in all regions of the detailed detector models. Using the default value for the step size in the external magnetic field, the maximal deviation between Monte Carlo based and analytical dose value in the sensitive volume of the ion chamber and diode detector was 8% and 0.1%, respectively.</p></div><div><h3>Conclusions</h3><p>The Fano cavity test is a crucial validation method for the modeled detectors and the transport algorithms when performing Monte Carlo simulations in a strong external magnetic field. Special care should be given, when calculating dose in volumes of low density. This study has shown that the Fano cavity test is a useful method to adapt particle transport parameters for a given simulation geometry.</p></div>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":"33 4","pages":"Pages 499-510"},"PeriodicalIF":2.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0939388922000708/pdfft?md5=f9914e535afc2afbde7509d0bf9ffbe9&pid=1-s2.0-S0939388922000708-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"40644115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Generation, validation, and benchmarking of a commercial independent Monte Carlo calculation beam model for multi-target SRS.","authors":"Justus Adamson,&nbsp;Brett G Erickson,&nbsp;Chunhao Wang,&nbsp;Yunfeng Cui,&nbsp;Markus Alber,&nbsp;John Kirkpatrick,&nbsp;Fang-Fang Yin","doi":"10.1016/j.zemedi.2023.08.004","DOIUrl":"https://doi.org/10.1016/j.zemedi.2023.08.004","url":null,"abstract":"<p><strong>Background: </strong>Dosimetric validation of single isocenter multi-target radiosurgery plans is difficult due to conditions of electronic disequilibrium and the simultaneous irradiation of multiple off-axis lesions dispersed throughout the volume. Here we report the benchmarking of a customizable Monte Carlo secondary dose calculation algorithm specific for multi-target radiosurgery which future users may use to guide their commissioning and clinical implementation.</p><p><strong>Purpose: </strong>To report the generation, validation, and clinical benchmarking of a volumetric Monte Carlo (MC) dose calculation beam model for single isocenter radiosurgery of intracranial multi-focal disease.</p><p><strong>Methods: </strong>The beam model was prepared within SciMoCa (ScientificRT, Munich Germany), a commercial independent dose calculation software, with the aim of broad availability via the commercial software for use with single isocenter radiosurgery. The process included (1) definition & acquisition of measurement data required for beam modeling, (2) tuning model parameters to match measurements, (3) validation of the beam model via independent measurements and end-to-end testing, and finally, (4) clinical benchmarking and validation of beam model utility in a patient specific QA setting. We utilized a 6X Flattening-Filter-Free photon beam from a TrueBeam STX linear accelerator (Siemens Healthineers, Munich Germany).</p><p><strong>Results: </strong>In addition to the measured data required for standard IMRT/VMAT (depth dose, central axis profiles & output factors, leaf gap), beam modeling and validation for single-isocenter SRS required central axis and off axis (5 cm & 9 cm) small field output factors and comparison between measurement and simulation of backscatter with aperture for jaw much greater than MLCs. Validation end-to-end measurements included SRS MapCHECK in StereoPHAN geometry (2%/1 mm Gamma = 99.2% ± 2.2%), and OSL & scintillator measurements in anthropomorphic STEEV phantom (6 targets, volume = 0.1-4.1cc, distance from isocenter = 1.2-7.9 cm) for which mean difference was -1.9% ± 2.2%. For 10 patient cases, MC for individual PTVs was -0.8% ± 1.5%, -1.3% ± 1.7%, and -0.5% ± 1.8% for mean dose, D_95%, and D_1%, respectively. This corresponded to custom passing rates action limits per AAPM TG-218 guidelines of ±5.2%, ±6.4%, and ±6.3%, respectively.</p><p><strong>Conclusions: </strong>The beam modeling, validation, and clinical action criteria outlined here serves as a benchmark for future users of the customized beam model within SciMoCa for single isocenter radiosurgery of multi-focal disease.</p>","PeriodicalId":54397,"journal":{"name":"Zeitschrift fur Medizinische Physik","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10192034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}