Physics in medicine and biology最新文献

{"title":"Physicochemical indication of the FLASH effect from shoot-through proton pencil beam scanning parameters delivered under ultra-high dose rates.","authors":"Andrew M Friberg, Hai Siong Tan, Eric S Diffenderfer, Ioannis Verginadis, Michele M Kim, Keith Cengel, Rodney Wiersma, Lei Dong, Costas Koumenis, Boon-Keng K Teo, Wei Zou","doi":"10.1088/1361-6560/adf58e","DOIUrl":"10.1088/1361-6560/adf58e","url":null,"abstract":"<p><p><i>Objective.</i>Ultra-high dose rate (UHDR) proton pencil beam scanning (PBS) delivery results in irregular temporal-varying dose accumulation. It is difficult to establish a dose rate standard for the indication of proton PBS FLASH effect. In this work, we adopted a published physicochemical approach and investigated the impact of proton PBS UHDR parameters on the formation and downstream reactions of reactive oxygen species (ROS).<i>Approach.</i>From the ROS physicochemical model, the dose-rate dependent alkyl hydroperoxide (ROOH) formation was validated against published lipid peroxide absorbance data and correlated with mice skin damage data. For proton PBS delivery with specified beam current, voxelized temporal dose and ROS accumulation was calculated at the plateau region to simulate a shoot-through FLASH delivery. The ROS were obtained mimicking the irradiation of hypoxic skin. We examine the ROS-volume histogram in relation to the proton PBS delivery parameters.<i>Main results.</i>ROOH production clearly indicates sparing effects under UHDR. For PBS deliveries of 10 Gy to a 100 × 100 mm²field at 8 mm depth, the ROOH yield at 500 nA FLASH beam current is equivalent to a 8.78 Gy delivery at 1nA CONV delivery. The yield of ROOH depends strongly on the dose and beam current but has minimal dependency on the field size and spot spacing. Introducing inter-beam intervals of two minutes reduces the FLASH reduction in ROOH, consistent with reduced FLASH effect in murine experiment.<i>Significance.</i>The volumetric statistics of the ROOH yield showed consistent indication of FLASH effects in preclinical observations and correlated with the lipid peroxidation damage in tissue. Using simulated ROOH production metrics can potentially indicate the FLASH sparing effect under various PBS delivery parameters. Our simulations indicate that the shoot-through PBS FLASH effect depends mainly on the total dose and the pencil beam current, and is relatively independent of field sizes and spot spacings.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12362236/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144744196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Beam intensity and stability control on a modified clinical linear accelerator for FLASH irradiation.","authors":"Yuewen Tan, Naresh T Deoli, Andrew D Harken, David J Brenner, Guy Garty","doi":"10.1088/1361-6560/adf8ac","DOIUrl":"10.1088/1361-6560/adf8ac","url":null,"abstract":"<p><p><i>Objective.</i>The FLASH effect has gained significant attention in radiobiology and radiation oncology due to its potential to improve therapeutic outcomes by delivering ultra-high dose-rate (UHDR) irradiations. Understanding UHDR biological mechanisms can also contribute to the development of biodosimetry and radiological medical countermeasures. However, achieving stable and reproducible high-current UHDR electron beams has been reported to be challenging with modified clinical linear accelerator (Linac) systems, and has not been systematically studied.<i>Approach.</i>We investigated how key standing-wave linear accelerator parameters, including electron gun current, pulse-forming network voltage, and auto-frequency control, affect the stability of electron beam intensity on a modified Varian Clinac 2100 C. We also developed a parameter-tuning method to adjust beam intensity and improve beam stability.<i>Main results.</i>This approach enabled (1) fine-tuning of dose-per-pulse without modifying the physical setup and (2) reduction of beam fluctuations, particularly during cold starts. These improvements enhanced both pulse-by-pulse stability and trial-by-trial reproducibility. The resulting stability was validated through multiple biological experiments.<i>Significance.</i>This work offers practical guidance for improving UHDR beam stability and reproducibility, as well as enabling intensity tuning in modified clinical linear accelerators. It can support the development of more reliable preclinical FLASH irradiators, thereby contributing to the advancement of FLASH research.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12351235/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144795011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radiation damage evaluation of materials for radiotherapy quality assurance devices under high dose and ultra-high dose rate electron and proton beams.","authors":"M Orts, Y C Gedik, A Bourgouin, R P Kapsch, C Koumeir, T Sounalet, S Rossomme, K Souris, E Sterpin","doi":"10.1088/1361-6560/adf796","DOIUrl":"10.1088/1361-6560/adf796","url":null,"abstract":"<p><p><i>Objective.</i>FLASH radiotherapy is a promising technique based on the delivery of ultra-high dose rates (UHDR) to spare healthy tissue. Robust quality assurance (QA) is required to ensure a safe delivery of the treatment. QA devices such as phantoms and ionization chambers (ICs) are typically made out of polymeric materials to ensure water equivalence. However, radiation exposure, particularly at UHDR where achieving high doses is easier, may cause irreversible changes to the structure of these materials. Such extreme conditions can, for example, induce microstructural defects that may lead to mechanical failure or alter electrical properties such as the dielectric permittivity or conductivity, potentially compromising the calibration and reliability of critical QA devices, such as ICs. This study aims to characterize radiation damage in common materials used for QA devices and identify which of them can withstand these challenging conditions.<i>Approach.</i>A variety of materials commonly used in phantoms and ICs, with diverse characteristics (transparent, opaque, conductive and non-conductive) were irradiated using 68 MeV proton and 20 MeV electron beams, reaching doses up to 1 MGy under UHDR conditions (average dose rates of 100-500 Gy s^-1). Material damage was evaluated through optical, chemical, mechanical and electrical tests to quantify change in color, structural integrity, and relevant electrical properties such as conductivity and dielectric constant that can affect detector response.<i>Main Results.</i>External appearance of some materials significantly changed after irradiation. All transparent materials exhibited change in color post-irradiation. Chemical analyses conducted after irradiation and repeated two years later indicated partial recovery in some materials. No significant difference in damage was observed between proton and electron irradiation, suggesting comparable radiation damage mechanisms. Dose rate alone did not exacerbate damage beyond total dose effects; however, extended irradiation at high dose rates resulted in thermal damage under some conditions. Mechanical testing revealed increased fragility, changes in hardness and dimensions, while some materials experienced significant changes in dielectric constant and conductivity.<i>Significance.</i>Materials such as Polymethyl Methacrylate (PMMA), PC, Polyoxymethylene (POM), and its conductive variant POM ELS, are unsuitable for prolonged irradiations at UHDR due to significant structural degradation observed. For see-through phantom construction, CPS offers a more durable alternative to PMMA. For detector construction, PEEK (for non-conductive parts) and graphite (for conductive parts) demonstrated promising durability, making them preferable choices under high dose and UHDR conditions. The higher stability of these materials can be attributed to the presence of aromatic rings in their chemical structure, which enhances radiation resistance.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144785031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Geant4-DNA physics model for electron track-structure simulations in gold nanoparticles.","authors":"Ioannis Polopetrakis, Ioanna Kyriakou, Dousatsu Sakata, Hoang N Tran, Vladimir N Ivanchenko, Pantelis Karaiskos, Susanna Guatelli, Sebastien Incerti, Dimitris Emfietzoglou","doi":"10.1088/1361-6560/adf40c","DOIUrl":"10.1088/1361-6560/adf40c","url":null,"abstract":"<p><p><i>Objective.</i>To develop a new Geant4-DNA physics model for electron track-structure simulations in gold nanoparticles (AuNPs) that overcomes important deficiencies of the current default model and is applicable over a broad energy range from 10 eV to 1 MeV.<i>Approach.</i>A model of the energy-loss-function of solid-Au with parameters optimized by optical data and self-consistency tests is presented and used to calculate inelastic cross sections using the relativistic plane wave Born approximation (RPWBA). Low-energy corrections for non-Born effects are included and a practical approximation to the Landau damping mechanism of plasmon decay is proposed that accounts for secondary electron production and facilitates its application to Monte Carlo (MC) track-structure simulations.<i>Main results.</i>Calculations of inelastic cross sections and stopping power (SP) values for the individual ionization and excitation channels of solid-Au are presented and compared against the current default model of Geant4-DNA (DNA_AU_2016), the Livermore and Penelope low-energy models of Geant4, and other published models. It is shown that the present model improves the current default model of Geant4-DNA by offering almost excellent agreement (∼2% on average) with NIST's SP data (previously at ∼6%), while eliminating the unphysical low-energy overestimation (up to 1000% or more), thus, bringing much better agreement with more elaborate physics models for solid-Au.<i>Significance.</i>MC track-structure codes are considered the gold standard for dose enhancement calculations in AuNP-aided radiotherapy. In particular, the Geant4-DNA toolkit offers functionalities for simulating critical cellular radiobiological effects following AuNP irradiation. Yet the accuracy of such simulations is limited by the quality of the cross sections for the individual electron-AuNP interactions. It is envisioned that the present model will allow Geant4-DNA users to perform more accurate simulations of electron transport within AuNPs and better quantify the outgoing secondary electron spectrum which is responsible for the dose enhancement effect and subsequent radiobiological damage.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144708472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calculation of DNA damage at different depths of proton SOBP based on a new method and its applications.","authors":"Xianghui Kong, Kaijin Yan, Xinjie Wang, Shenglan Wei, Jie Ni, Haiyang Li, Songbing Qin, Liang Sun","doi":"10.1088/1361-6560/adf8aa","DOIUrl":"10.1088/1361-6560/adf8aa","url":null,"abstract":"<p><p><i>Objective.</i>In examining the biological effects of proton radiation, DNA is the primary sensitive target. This study utilizes Monte Carlo simulations to efficiently calculate DNA damage yields at various proton depths to analyze the biological effects of protons and their variability on different scales.<i>Approach.</i>A new method, the 'Coefficient Method' is used to replace the complete chemical processes by adjusting parameters to obtain suitable values for simulating DNA damage yields at different spread-out Bragg peak (SOBP) depths of low-energy protons, and these parameters are then applied to high-energy proton simulations based on a mesh-type cell model. We computed two relative biological effectiveness (RBE) at two different scales:RBEmax(at 0 Gy per fraction) andRBEDSB(based on DNA damage yields).<i>Main results</i>. The results confirm the feasibility of the 'Coefficient Method,' with deviations inYDSBs(the yields of double-strand breaks (DSBs)) andYDSBc(the yields of complex DSBs) ranging from 0.60%-3.79% and 1.45%-4.1%, respectively, and a clear advantage in simulation efficiency. For high-energy protons,YSSBs(the yields of single-strand breaks) decreases with depth, whileYDSBsandYDSBcincrease. What's more, the differences in RBE across different scales are substantial. At 1 cm depth for 70_SOBP MeV protons,RBEmaxis 1.53 vsRBEDSBof 1.45; at the beam end,RBEmaxreaches 10.45 vsRBEDSBof 2.36. Mesh thickness has negligible impact onRBEmax.<i>Significance.</i>It is confirmed that using the 'Coefficient Method' to obtain DNA damage yields at different depths for high-energy protons is reliable. TheRBEDSBvalues based on this method show significant differences compared to the traditionalRBEmaxvalues. This indicates the importance of investigating the biological effects of proton radiation at the DNA scale and further emphasizes the significance of exploring the relationship between proton radiation quality and the target of interest.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144795012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unsupervised learning based perfusion maps for temporally truncated CT perfusion imaging.","authors":"Chi-Hsiang Tung, Zhong-Yi Li, Hsuan-Ming Huang","doi":"10.1088/1361-6560/adf7fd","DOIUrl":"10.1088/1361-6560/adf7fd","url":null,"abstract":"<p><p><i>Objective.</i>Computed tomography perfusion (CTP) imaging is a rapid diagnostic tool for acute stroke but is less robust when tissue time-attenuation curves are truncated.<i>Approach.</i>This study proposes an unsupervised learning method for generating perfusion maps from truncated CTP images. Real brain CTP images were artificially truncated to 15% and 30% of the original scan time. Perfusion maps of complete and truncated CTP images were calculated using the proposed method and compared with standard singular value decomposition (SVD), tensor total variation (TTV), nonlinear regression (NLR), and spatio-temporal perfusion physics-informed neural network (SPPINN).<i>Main results.</i>The NLR method yielded many perfusion values outside physiological ranges, indicating a lack of robustness. The proposed method did not improve the estimation of cerebral blood flow compared to both the SVD and TTV methods, but reduced the effect of truncation on the estimation of cerebral blood volume, with a relative difference of 15.4% in the infarcted region for 30% truncation (20.7% for SVD and 19.4% for TTV). The proposed method also showed better resistance to 30% truncation for mean transit time, with a relative difference of 16.6% in the infarcted region (25.9% for SVD and 26.2% for TTV). Compared to the SPPINN method, the proposed method had similar responses to truncation in gray and white matter, but was less sensitive to truncation in the infarcted region.<i>Significance.</i>These results demonstrate the feasibility of using unsupervised learning to generate perfusion maps from CTP images and improve robustness under truncation scenarios.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144789732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A DCT-UNet-based framework for pulmonary airway segmentation integrating label self-updating and terminal region growing.","authors":"Shuiqing Zhao, Yanan Wu, Jiaxuan Xu, Mengqi Li, Jie Feng, Shuyue Xia, Rongchang Chen, Zhenyu Liang, Wei Qian, Shouliang Qi","doi":"10.1088/1361-6560/adf486","DOIUrl":"10.1088/1361-6560/adf486","url":null,"abstract":"<p><p><i>Objective.</i>Intrathoracic airway segmentation in computed tomography is important for quantitative and qualitative analysis of various chronic respiratory diseases and bronchial surgery navigation. However, the airway tree's morphological complexity, incomplete labels resulting from annotation difficulty, and intra-class imbalance between main and terminal airways limit the segmentation performance.<i>Approach.</i>Three methodological improvements are proposed to deal with the challenges. Firstly, we design a dilated contextual transformer-UNet to collect better information on neighboring voxels and ones within a larger spatial region. Secondly, an airway label self-updating strategy is proposed to iteratively update the reference labels to conquer the problem of incomplete labels. Thirdly, a deep learning-based terminal region growing is adopted to extract terminal airways. Extensive experiments were conducted on two internal datasets and three public datasets.<i>Main Results.</i>Compared to the counterparts, the proposed method can achieve a higher branch detected, tree-length detected, branch ratio, and tree-length ratio (ISICDM2021 dataset, 95.19%, 94.89%, 166.45%, and 172.29%; binary airway segmentation dataset, 96.03%, 95.11%, 129.35%, and 137.00%). Ablation experiments show the effectiveness of three proposed solutions. Our method is applied to an in-house chronic obstructive pulmonary disease (COPD) dataset. The measures of branch count, tree length, endpoint count, airway volume, and airway surface area are significantly different between COPD severity stages.<i>Significance.</i>The proposed methods can segment more terminal bronchi and larger length of airway, even some bronchi which are real but missed in the manual annotation can be detected. Potential application significance has been presented in characterizing COPD airway lesions and severity stages.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144718322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterizing an electronic-robotic targeting platform for precise and fast brain stimulation with multi-locus transcranial magnetic stimulation.","authors":"Renan H Matsuda, Victor H Souza, Thais C Marchetti, Ana M Soto, Olli-Pekka Kahilakoski, Mikael Laine, Heikki Sinisalo, Dubravko Kicic, Pantelis Lioumis, Risto J Ilmoniemi, Oswaldo Baffa","doi":"10.1088/1361-6560/adf36e","DOIUrl":"10.1088/1361-6560/adf36e","url":null,"abstract":"<p><p><i>Background</i>. Multi-locus TMS (mTMS) enables precise electronic control of brain stimulation targeting, eliminating the need for physical coil movement. However, with a small number of coils, the stimulation area is constrained, and manual handling of the coil array is cumbersome. Combining electronic mTMS targeting with robotics enables automated, user-independent, and precise brain stimulation protocols.<i>Objective</i>. To characterize an open-source electronic-robotic mTMS platform for rapid and accurate brain stimulation targeting.<i>Methods</i>. We developed an automated robotic mTMS positioning platform. We used a 5-coil mTMS device coupled to a collaborative robot. The stimulation targeting accuracy of the system was quantified with a TMS characterizer that measures the TMS-induced electric field (<i>E</i>-field) on a model of a spherical cortex. The induced<i>E</i>-field distortion generated by robot coupling was evaluated for each coil. We compared the repositioning accuracy of robotic-electronic system to the conventional manual positioning.<i>Results</i>. Our collaborative-robot-based system offers submillimeter precision and autonomy in positioning mTMS coil sets. The electronic-robotic mTMS platform was approximately 1.8 mm and 1.0° more accurate than the conventional manual positioning. Integrating robotics and mTMS automates brain stimulation procedures, resulting in minimal reliance on user expertise and subjective analysis.<i>Conclusion</i>. Our open-source platform combining rapid mTMS targeting with robotic precision enhances the safety and reproducibility of TMS, enabling more efficient and reliable outcomes than previous techniques.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144699224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical positron range model for PET with cross-code Monte Carlo benchmarking.","authors":"Robert J Paneque-Yunta, Nerea Encina-Baranda, Lukas M Carter, Pablo Galve, Paula Ibáñez, Khaled M Abushab, José M Udías, Joaquín L Herraiz","doi":"10.1088/1361-6560/adf591","DOIUrl":"10.1088/1361-6560/adf591","url":null,"abstract":"<p><p><i>Introduction.</i>The positron range (PR) effect is a significant factor limiting spatial resolution in positron emission tomography (PET), particularly for high-resolution systems and non-standard isotopes.<i>Objective.</i>This study introduces a novel analytical model to accurately and rapidly describe PR distributions (PRd) for various PET radioisotopes to better include its effect in PET reconstruction algorithms.<i>Approach.</i>The proposed model explicitly incorporates the Coulomb repulsion effect, the multi-branch nature of certainβ+emitters, and the scaling of PR with electronic density. To minimise bias, we used a histogram-free statistical method to derive the cumulative PRd from Monte Carlo (MC) simulated annihilation datasets, avoiding arbitrary histogram binning. A comparative analysis of PR estimates was conducted across three major MC radiation transport algorithm packages: PENELOPE (via PenEasy/PeneloPET), GEANT4 (via GATE), and EGS5 (via PHITS), revealing notable discrepancies between codes, versions, and input configurations, especially at short distances from the source.<i>Main results.</i>The new analytical model demonstrated an excellent reproduction of the simulated data for isotopes including11C,13N,15O,18F,64Cu,68Ga,82Rband124I, achieving in general coefficients of determination (<i>R</i>²) greater than 0.995 and mean absolute percentage errors≲20%. Compared to previous methods, our model provides a more accurate description of PRd at low distances and offers improved<i>R</i>²values.<i>Significance.</i>This work provides a robust framework for generating accurate annihilation point spread function kernels, facilitating improved PR correction in quantitative Nuclear Medical Imaging and supporting research with diverse radioisotopes.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144744172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Expansion of applicability of multiple scan average dose measurements for CT dosimetry.","authors":"Ákos Sudár, Tamás Pócza, Richárd Elek, Tibor Major, Ádám Domonkos Tárnoki, Dávid László Tárnoki, Csilla Pesznyák","doi":"10.1088/1361-6560/adf40d","DOIUrl":"10.1088/1361-6560/adf40d","url":null,"abstract":"<p><p><i>Objective.</i>The CT dose index (CTDI) can be directly measured only for axial scan protocols; however, these days, helical protocols are applied in most cases, and sometimes axial protocols are not even available. The multiple scan average dose (MSAD) method can address this issue, but it is not widely adopted. This article aims to support the appropriateness of the MSAD method first by showing that it is measurable with the CTDI tools, and second by presenting a simple rule for scan pitch to avoid the main uncertainty of the measurement.<i>Approach.</i>Monte Carlo simulation was combined with its analytical postprocessing to accurately calculate scattering and speed up calculations to investigate several imaging and beam parameter combinations. The calculations were validated by measurements, and the model was used to examine the uncertainty of MSAD caused by an uncontrolled parameter.<i>Main results.</i>The widespread 150 mm long CTDI phantom and the 100 mm long ionization chamber are applicable for the MSAD method and reach80.8±0.2% efficiency in the estimation of CTDI_vol, in contrast to78.0±0.3% efficiency of the CTDI₁₀₀method. By utilizing the periodicity of the MSAD measurement, the uncertainty can be reduced to1.38±0.02% in contrast to26.85±0.16% in the worst case.<i>Significance.</i>The MSAD measurement with the CTDI setup is slightly more efficient than the CTDI₁₀₀measurement protocol, so there is no need for a long phantom or farmer chamber to use MSAD in quality assurance (QA) measurements. The MSAD applies to both helical and axial scans; therefore, we recommend using direct MSAD measurement for QA in the clinical environment.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.4,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144708470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}