Mateb Al Khalifa, Tianjun Ma, Haya Aljuaid, Siyong Kim, William Y. Song
Purpose
This study describes and evaluates the acceptance procedure for a ViewRay (VR) MRIdian 0.35T MR-Linac, emphasizing key challenges, limitations, and recommendations to enhance clinical performance and accuracy.
Methods
A comprehensive acceptance test was conducted at a single institution, following the manufacturer's protocols and aligned with established acceptance guidelines. Specific tools and phantoms were used to assess three primary components: mechanical, dosimetric, and Magnetic Resonance Imaging (MRI).
Results
Overall, the test outcomes satisfied the manufacturer's specifications. However, certain issues were identified: high couch attenuation at specific gantry angles (leading to their exclusion from treatment), variations in magnetic field homogeneity at different gantry angles, and discrepancies between TPS calculations and measurements for field output factors smaller than 0.83 cm × 0.83 cm.
Conclusion
This work provides a detailed account of the acceptance testing procedure and establishes a QA baseline for 0.35T MR-Linac systems. In doing so, it also identifies key system limitations, such as couch attenuation, magnetic field inhomogeneity, and small-field output discrepancies, underscoring the need for careful gantry angle selection, field homogeneity optimization, and meticulous validation of very small fields.
目的：本研究描述并评估了ViewRay (VR) mrridian 0.35T MR-Linac的接受程序，强调了关键的挑战、限制和建议，以提高临床表现和准确性。方法：在单一机构进行全面验收测试，遵循制造商的协议，并与既定的验收指南保持一致。使用特定的工具和模型来评估三个主要组成部分：机械，剂量学和磁共振成像（MRI）。结果：总体而言，测试结果满足制造商的规格。然而，也发现了一些问题：特定龙门架角度下的高沙发衰减（导致其被排除在处理之外），不同龙门架角度下磁场均匀性的变化，以及小于0.83 cm × 0.83 cm的场输出因子的TPS计算与测量之间的差异。结论：这项工作提供了验收测试程序的详细说明，并建立了0.35T MR-Linac系统的QA基线。在此过程中，它还确定了关键的系统限制，例如couch衰减，磁场不均匀性和小场输出差异，强调需要仔细选择龙门角度，场均匀性优化以及对非常小的场进行细致的验证。
{"title":"Acceptance testing of a 0.35 T MR-Linac: procedures, QA baseline, and system limitations","authors":"Mateb Al Khalifa, Tianjun Ma, Haya Aljuaid, Siyong Kim, William Y. Song","doi":"10.1002/acm2.70488","DOIUrl":"10.1002/acm2.70488","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study describes and evaluates the acceptance procedure for a ViewRay (VR) MRIdian 0.35T MR-Linac, emphasizing key challenges, limitations, and recommendations to enhance clinical performance and accuracy.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>A comprehensive acceptance test was conducted at a single institution, following the manufacturer's protocols and aligned with established acceptance guidelines. Specific tools and phantoms were used to assess three primary components: mechanical, dosimetric, and Magnetic Resonance Imaging (MRI).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Overall, the test outcomes satisfied the manufacturer's specifications. However, certain issues were identified: high couch attenuation at specific gantry angles (leading to their exclusion from treatment), variations in magnetic field homogeneity at different gantry angles, and discrepancies between TPS calculations and measurements for field output factors smaller than 0.83 cm × 0.83 cm.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>This work provides a detailed account of the acceptance testing procedure and establishes a QA baseline for 0.35T MR-Linac systems. In doing so, it also identifies key system limitations, such as couch attenuation, magnetic field inhomogeneity, and small-field output discrepancies, underscoring the need for careful gantry angle selection, field homogeneity optimization, and meticulous validation of very small fields.</p>\u0000 </section>\u0000 </div>","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12906295/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146194577","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}
<div> <section> <h3> Purpose</h3> <p>The complexity of beam delivery and the limited availability of dedicated quality assurance (QA) devices present unique challenges for carbon ion beam therapy. Most existing systems are designed for single-parameter verification and have been adapted from photon or proton workflows, resulting in time-consuming QA procedures. This study aimed to evaluate the feasibility of using a proton QA prototype device (DQA-P) in a pencil beam scanning (PBS) carbon ion facility, with the aim of enabling fast, efficient, multiparameter QA.</p> </section> <section> <h3> Methods</h3> <p>The DQA-P integrates 25 ionization chambers at three water-equivalent depths, enabling the simultaneous measurement of multiple beam parameters, such as dose output, range, spot size, and spot position, in accordance with the recommendations of the AAPM TG-224. Over 60 measurement sessions were performed, including 47 sessions involving intentional deviations in individual beam parameters, in order to assess sensitivity. The measurements were analyzed retrospectively using custom MATLAB scripts to evaluate accuracy, reproducibility, and the impact of setup uncertainties.</p> </section> <section> <h3> Results</h3> <p>The DQA-P prototype successfully measured all QA parameters within clinically acceptable tolerances. Dose output measurements showed a standard deviation of 0.5% around the mean, with minimal systematic deviation. Spot position measurements exhibited a mean deviation of 0.16 mm, with a standard deviation of 0.32 mm. The device's sensitivity was demonstrated by its reliable detection of intentional positional offsets of <span></span><math> <semantics> <mo>±</mo> <annotation>$pm$</annotation> </semantics></math>3 mm and spot size changes of <span></span><math> <semantics> <mo>±</mo> <annotation>$pm$</annotation> </semantics></math>25%. Range validation using the proximal rise of the Bragg peak produced consistent results, albeit with lower accuracy than that achieved with standard multilayer ionization chambers. However, limitations were identified in spot size estimation due to chamber segmentation, and in range verification, as the device only captures three fixed depths.</p> </section> <section> <h3> Conclusions</h3> <p>The DQA-P prototype demonstrated feasibility for daily QA in PBS carbon ion beam therapy, offering a short overall measurement time of app
{"title":"Feasibility of proton daily QA prototype for pencil beam scanning carbon ion beam therapy","authors":"Matthias Witt, Veronika Flatten, Andreas Schönfeld, Kilian-Simon Baumann, Uli Weber, Klemens Zink","doi":"10.1002/acm2.70502","DOIUrl":"10.1002/acm2.70502","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>The complexity of beam delivery and the limited availability of dedicated quality assurance (QA) devices present unique challenges for carbon ion beam therapy. Most existing systems are designed for single-parameter verification and have been adapted from photon or proton workflows, resulting in time-consuming QA procedures. This study aimed to evaluate the feasibility of using a proton QA prototype device (DQA-P) in a pencil beam scanning (PBS) carbon ion facility, with the aim of enabling fast, efficient, multiparameter QA.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>The DQA-P integrates 25 ionization chambers at three water-equivalent depths, enabling the simultaneous measurement of multiple beam parameters, such as dose output, range, spot size, and spot position, in accordance with the recommendations of the AAPM TG-224. Over 60 measurement sessions were performed, including 47 sessions involving intentional deviations in individual beam parameters, in order to assess sensitivity. The measurements were analyzed retrospectively using custom MATLAB scripts to evaluate accuracy, reproducibility, and the impact of setup uncertainties.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The DQA-P prototype successfully measured all QA parameters within clinically acceptable tolerances. Dose output measurements showed a standard deviation of 0.5% around the mean, with minimal systematic deviation. Spot position measurements exhibited a mean deviation of 0.16 mm, with a standard deviation of 0.32 mm. The device's sensitivity was demonstrated by its reliable detection of intentional positional offsets of <span></span><math>\u0000 <semantics>\u0000 <mo>±</mo>\u0000 <annotation>$pm$</annotation>\u0000 </semantics></math>3 mm and spot size changes of <span></span><math>\u0000 <semantics>\u0000 <mo>±</mo>\u0000 <annotation>$pm$</annotation>\u0000 </semantics></math>25%. Range validation using the proximal rise of the Bragg peak produced consistent results, albeit with lower accuracy than that achieved with standard multilayer ionization chambers. However, limitations were identified in spot size estimation due to chamber segmentation, and in range verification, as the device only captures three fixed depths.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>The DQA-P prototype demonstrated feasibility for daily QA in PBS carbon ion beam therapy, offering a short overall measurement time of app","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12900580/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146180055","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}
<div> <section> <h3> Background</h3> <p>Accurate spinal MRI segmentation is essential for computer-aided diagnosis of spinal diseases. Existing methods have limitations in global semantic modeling and boundary delineation due to complex anatomy and imaging artifacts.</p> </section> <section> <h3> Purpose</h3> <p>Our work aimed to propose a novel Graph-Guided Frequency-Enhanced State Space Network (GF-SSNet) method to achieve more accurate 3D multi-modal spine MRI automatic segmentation, addressing the limitations of existing algorithms in global semantic modeling of high-dimensional voxel space, cross-modal information synergistic perception, and fine boundary identification of anatomically similar tissues, thereby providing technical support for intelligent diagnosis and precision medicine of spinal diseases.</p> </section> <section> <h3> Methods</h3> <p>The proposed network is based on the GF-SSNet architecture. During encoding, a dual frequency-spatial feature enhancement mechanism is employed, which adaptively fuses local frequency dynamic features and global spatial long-range dependencies through Frequency Dynamic Convolution (FDConv) and Three-Directional Mamba-based state space model (TD-Mamba). At the bottleneck, Position-Aware Attention Fusion (PAAF) and Graph Convolutional Networks (GCN) are integrated to explicitly encode topological anatomical constraints between vertebrae, enhancing the global perception capability of spinal continuity structures. During decoding, a Depth-aware Progressive Upsampling (DAPU) strategy is introduced to effectively alleviate the reconstruction loss of fine-grained spatial information. The entire framework achieves end-to-end automatic segmentation of multi-modal MR images.</p> </section> <section> <h3> Results</h3> <p>On the normal test set, GF-SSNet outperformed all baselines across all metrics. Specifically, Dice and IoU Means reached 92.04 ± 0.06% and 85.29 ± 0.10%, exceeding the best baseline results of 89.81 ± 0.61% and 81.51 ± 0.91%. HD95 and ASSD were significantly reduced to 3.06 ± 0.46 mm and 0.612 ± 0.018 mm, compared to top-tier baseline values of 4.76 ± 1.09 mm and 1.14 ± 0.01 mm, respectively. On an independent pathological test set with various spinal pathologies, GF-SSNet maintained superior performance with Dice Mean of 87.60 ± 0.10%, still outperforming all baseline methods. The 4.4 percentage point performance decline from normal cases primarily stemmed from intervertebral disc segmentation challenges in degenerative conditions, while vertebrae segmentation remained robust. Ablation stud
{"title":"Graph-guided frequency-enhanced state space network for 3D spine segmentation from MR images","authors":"Linghui Hong, Zhengchao Zhou, Wanbo Xu, Pingping Wang, Benzheng Wei","doi":"10.1002/acm2.70481","DOIUrl":"10.1002/acm2.70481","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Accurate spinal MRI segmentation is essential for computer-aided diagnosis of spinal diseases. Existing methods have limitations in global semantic modeling and boundary delineation due to complex anatomy and imaging artifacts.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>Our work aimed to propose a novel Graph-Guided Frequency-Enhanced State Space Network (GF-SSNet) method to achieve more accurate 3D multi-modal spine MRI automatic segmentation, addressing the limitations of existing algorithms in global semantic modeling of high-dimensional voxel space, cross-modal information synergistic perception, and fine boundary identification of anatomically similar tissues, thereby providing technical support for intelligent diagnosis and precision medicine of spinal diseases.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>The proposed network is based on the GF-SSNet architecture. During encoding, a dual frequency-spatial feature enhancement mechanism is employed, which adaptively fuses local frequency dynamic features and global spatial long-range dependencies through Frequency Dynamic Convolution (FDConv) and Three-Directional Mamba-based state space model (TD-Mamba). At the bottleneck, Position-Aware Attention Fusion (PAAF) and Graph Convolutional Networks (GCN) are integrated to explicitly encode topological anatomical constraints between vertebrae, enhancing the global perception capability of spinal continuity structures. During decoding, a Depth-aware Progressive Upsampling (DAPU) strategy is introduced to effectively alleviate the reconstruction loss of fine-grained spatial information. The entire framework achieves end-to-end automatic segmentation of multi-modal MR images.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>On the normal test set, GF-SSNet outperformed all baselines across all metrics. Specifically, Dice and IoU Means reached 92.04 ± 0.06% and 85.29 ± 0.10%, exceeding the best baseline results of 89.81 ± 0.61% and 81.51 ± 0.91%. HD95 and ASSD were significantly reduced to 3.06 ± 0.46 mm and 0.612 ± 0.018 mm, compared to top-tier baseline values of 4.76 ± 1.09 mm and 1.14 ± 0.01 mm, respectively. On an independent pathological test set with various spinal pathologies, GF-SSNet maintained superior performance with Dice Mean of 87.60 ± 0.10%, still outperforming all baseline methods. The 4.4 percentage point performance decline from normal cases primarily stemmed from intervertebral disc segmentation challenges in degenerative conditions, while vertebrae segmentation remained robust. Ablation stud","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12900570/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146180093","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}
This study quantifies isocenter and off-axis geometric uncertainties using MultiMet Winston–Lutz (WL) tests to optimize gross tumour volume (GTV)-to-PTV (planning target volume) margin for single isocenter multiple target (SIMT) stereotactic body radiotherapy (SBRT) across three linear accelerators.
Methods and Materials
Geometric inaccuracies were quantified for Trilogy (HD-MLC, 6 MV SRS), TrueBeam (Millennium MLC), and TrueBeam STx (HD-MLC, 6-degrees-of-freedom (6DoF) couch) using a Sun Nuclear MultiMet-WL cube containing six tungsten carbide markers arranged along the superior–inferior axis. The electronic portal imaging device (EPID) images acquired at four cardinal gantry angles with varied collimator/couch rotations were analyzed using MultiMet-WL software (v2.1) to measure 3D (Δ) displacements for all the LINACs. The required GTV-to-PTV margins were calculated using a modified van Herk formula (2.5Σ+1.64σ), incorporating measured 3D displacements for isocenter and off-axis targets.
Results
The TrueBeam STx (HD-MLC/6DoF) demonstrated superior geometric accuracy, maintaining ≤0.5 mm isocenter precision and ≤0.59 mm off-axis targeting (3–7 cm). The Trilogy exceeded TG-142 tolerances (1.06 ± 0.59 to 1.09 ± 0.57 mm) at all targets, requiring 4 mm uniform margins, while the TrueBeam (MMLC) showed optimal variations (isocenter: 0.68 ± 0.34 mm; superior off-axis: 0.74 ± 0.36 mm). Both TrueBeam platforms achieved sub-millimeter accuracy but demonstrated direction dependency for off-axis targets, requiring 2–3 mm anisotropic margins. Notably, isotropic margins introduced up to 11% delineation errors for off-axis targets due to these machine-specific geometric variations, highlighting the imperative for platform-specific margin protocols in SIMT SBRT.
Conclusion
This study demonstrates that routine analysis of MultiMet WL testing is an essential tool for the spatial accuracy of the LINAC to establish machine-specific PTV margin expansion in SIMT-SBRT, particularly for targets where rotational errors dominate.
{"title":"The geometric accuracy of off-axis targets in stereotactic body radiotherapy treatments across three linear accelerators","authors":"Dinesan Chinnaiya, Gopinath Mudhana","doi":"10.1002/acm2.70383","DOIUrl":"10.1002/acm2.70383","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study quantifies isocenter and off-axis geometric uncertainties using MultiMet Winston–Lutz (WL) tests to optimize gross tumour volume (GTV)-to-PTV (planning target volume) margin for single isocenter multiple target (SIMT) stereotactic body radiotherapy (SBRT) across three linear accelerators.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods and Materials</h3>\u0000 \u0000 <p>Geometric inaccuracies were quantified for Trilogy (HD-MLC, 6 MV SRS), TrueBeam (Millennium MLC), and TrueBeam STx (HD-MLC, 6-degrees-of-freedom (6DoF) couch) using a Sun Nuclear MultiMet-WL cube containing six tungsten carbide markers arranged along the superior–inferior axis. The electronic portal imaging device (EPID) images acquired at four cardinal gantry angles with varied collimator/couch rotations were analyzed using MultiMet-WL software (v2.1) to measure 3D (Δ) displacements for all the LINACs. The required GTV-to-PTV margins were calculated using a modified van Herk formula (2.5Σ+1.64σ), incorporating measured 3D displacements for isocenter and off-axis targets.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The TrueBeam STx (HD-MLC/6DoF) demonstrated superior geometric accuracy, maintaining ≤0.5 mm isocenter precision and ≤0.59 mm off-axis targeting (3–7 cm). The Trilogy exceeded TG-142 tolerances (1.06 ± 0.59 to 1.09 ± 0.57 mm) at all targets, requiring 4 mm uniform margins, while the TrueBeam (MMLC) showed optimal variations (isocenter: 0.68 ± 0.34 mm; superior off-axis: 0.74 ± 0.36 mm). Both TrueBeam platforms achieved sub-millimeter accuracy but demonstrated direction dependency for off-axis targets, requiring 2–3 mm anisotropic margins. Notably, isotropic margins introduced up to 11% delineation errors for off-axis targets due to these machine-specific geometric variations, highlighting the imperative for platform-specific margin protocols in SIMT SBRT.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>This study demonstrates that routine analysis of MultiMet WL testing is an essential tool for the spatial accuracy of the LINAC to establish machine-specific PTV margin expansion in SIMT-SBRT, particularly for targets where rotational errors dominate.</p>\u0000 </section>\u0000 </div>","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12900569/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146180053","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}
<div> <section> <h3> Purpose</h3> <p>This study systematically quantifies the effects of five variables—respiratory cycle, tumor size, and motion amplitudes in the superior-inferior (SI), anterior-posterior (AP), and left-right (LR) directions—on the registration accuracy between four-dimensional computed tomography (4D CT) and four-dimensional cone-beam CT (4D CBCT) images, thereby providing a theoretical basis for optimizing registration strategies in image-guided radiotherapy (IGRT).</p> </section> <section> <h3> Materials and methods</h3> <p>A CIRS 008A dynamic phantom fitted with 1 and 3 cm tumor inserts was utilized to simulate various respiratory motion scenarios by manipulating respiratory cycles (<i>T</i> = 0, 2, 4, and 8 s) and three-dimensional motion amplitudes (SI, AP, and LR ranging from 0 to 15 mm, with AP and LR limited to 0, 1, and 5 mm). Corresponding four-dimensional images were acquired using a GE Discovery RT CT simulator and a Varian VitalBeam linear accelerator. Rigid registration between the 4D CT and 4D CBCT images was subsequently performed using the Varian imaging system, with registration quality quantitatively assessed via the Dice similarity coefficient (DSC). Furthermore, a Random Forest regression model was employed to determine the relative importance of each factor, and multifactor analysis of variance (ANOVA) was conducted to verify statistical significance.</p> </section> <section> <h3> Results</h3> <p>The Random Forest analysis indicated that, for the overall registration average intensity projection, the factors were ranked in order of importance as follows: tumor size (0.509), SI motion (0.315), respiratory cycle (0.094), LR motion (0.055), and AP motion (0.028). In the maximum intensity projection, tumor size (0.722) was found to have a particularly significant impact. The multifactor ANOVA further supported these findings, demonstrating that tumor size (<i>p</i> < 0.001) and SI motion (<i>p</i> < 0.001) have a highly significant influence on registration quality, whereas the respiratory cycle and AP/LR motions did not reach statistical significance (<i>p</i> > 0.05). Notably, when the tumor size was small (1 cm) and accompanied by considerable SI motion (>10 mm), registration accuracy markedly deteriorated, with the greatest variability observed under these conditions.</p> </section> <section> <h3> Conclusion</h3> <p>This study demonstrated that the registration quality between 4D CT and 4D CBCT images was significantly influenced by both tumor size and the amplitude of motion in the SI direction
{"title":"Quantifying the impact of tumor size and motion on 4DCT-4DCBCT image registration accuracy using machine learning and statistical analysis","authors":"Qiaoyan Jing, Shuyu Lin, Binyun Huang, Tingjun Luo, Xianya Li, Weiming Zhang, Shaohan Sun","doi":"10.1002/acm2.70503","DOIUrl":"10.1002/acm2.70503","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study systematically quantifies the effects of five variables—respiratory cycle, tumor size, and motion amplitudes in the superior-inferior (SI), anterior-posterior (AP), and left-right (LR) directions—on the registration accuracy between four-dimensional computed tomography (4D CT) and four-dimensional cone-beam CT (4D CBCT) images, thereby providing a theoretical basis for optimizing registration strategies in image-guided radiotherapy (IGRT).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Materials and methods</h3>\u0000 \u0000 <p>A CIRS 008A dynamic phantom fitted with 1 and 3 cm tumor inserts was utilized to simulate various respiratory motion scenarios by manipulating respiratory cycles (<i>T</i> = 0, 2, 4, and 8 s) and three-dimensional motion amplitudes (SI, AP, and LR ranging from 0 to 15 mm, with AP and LR limited to 0, 1, and 5 mm). Corresponding four-dimensional images were acquired using a GE Discovery RT CT simulator and a Varian VitalBeam linear accelerator. Rigid registration between the 4D CT and 4D CBCT images was subsequently performed using the Varian imaging system, with registration quality quantitatively assessed via the Dice similarity coefficient (DSC). Furthermore, a Random Forest regression model was employed to determine the relative importance of each factor, and multifactor analysis of variance (ANOVA) was conducted to verify statistical significance.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The Random Forest analysis indicated that, for the overall registration average intensity projection, the factors were ranked in order of importance as follows: tumor size (0.509), SI motion (0.315), respiratory cycle (0.094), LR motion (0.055), and AP motion (0.028). In the maximum intensity projection, tumor size (0.722) was found to have a particularly significant impact. The multifactor ANOVA further supported these findings, demonstrating that tumor size (<i>p</i> < 0.001) and SI motion (<i>p</i> < 0.001) have a highly significant influence on registration quality, whereas the respiratory cycle and AP/LR motions did not reach statistical significance (<i>p</i> > 0.05). Notably, when the tumor size was small (1 cm) and accompanied by considerable SI motion (>10 mm), registration accuracy markedly deteriorated, with the greatest variability observed under these conditions.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>This study demonstrated that the registration quality between 4D CT and 4D CBCT images was significantly influenced by both tumor size and the amplitude of motion in the SI direction","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12888845/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146149651","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}
Ignasi Méndez, Mateb Al Khalifa, Haya Aljuaid, Božidar Casar
<div> <section> <h3> Background</h3> <p>In the IAEA TRS-483 Code of Practice (CoP), rectangular small field sizes are approximated to equivalent square small fields using the definition proposed by Cranmer-Sargison et al. However, the CoP estimates the uncertainties associated with this formula only for rectangular fields with dimensions within the range <span></span><math> <semantics> <mrow> <mn>0.7</mn> <mo><</mo> <mi>X</mi> <mo>/</mo> <mi>Y</mi> <mo><</mo> <mn>1.4</mn> </mrow> <annotation>$0.7 < X/Y < 1.4$</annotation> </semantics></math>.</p> </section> <section> <h3> Purpose</h3> <p>The objective of the present study was to compare the accuracy of the Cranmer-Sargison definition with other formulas for equivalent square small fields in the context of measuring field output factors (FOFs) for rectangular small fields, both within and outside the range covered by the CoP.</p> </section> <section> <h3> Methods</h3> <p>Measurements were conducted using Gafchromic EBT4 radiochromic films. The models compared included Cranmer-Sargison, Sterling, Superellipse, Sterling-Partial Superellipse, Sterling-Superellipse, Vadash and Bjärngard, and Fogliata. The most accurate definition of equivalent square field size was identified as the one yielding the lowest discrepancy between measured and analytical values, with the log-likelihood of the measurements selected as the metric. Analytical values were derived using the function introduced by Sauer and Wilbert, which relates FOFs to equivalent square field sizes.</p> </section> <section> <h3> Results</h3> <p>The best results were achieved with the Fogliata model, followed in terms of accuracy by the Sterling-Partial Superellipse model. The Sterling-Superellipse and Vadash and Bjärngard models came next. It should be noted that the Sterling-Partial Superellipse and Sterling-Superellipse models rely solely on the geometric shape of the irradiation field size, whereas the Fogliata and Vadash and Bjärngard models incorporate a fitting parameter. The Sterling definition, while less accurate than these models, improved upon the Cranmer-Sargison definition and retained computational simplicity. Finally, the Cranmer-Sargison and Superellipse models exhibited the largest discrepancies.</p> </section> <section>
{"title":"Evaluating equivalent square field size definitions for rectangular small fields","authors":"Ignasi Méndez, Mateb Al Khalifa, Haya Aljuaid, Božidar Casar","doi":"10.1002/acm2.70500","DOIUrl":"10.1002/acm2.70500","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 <p>In the IAEA TRS-483 Code of Practice (CoP), rectangular small field sizes are approximated to equivalent square small fields using the definition proposed by Cranmer-Sargison et al. However, the CoP estimates the uncertainties associated with this formula only for rectangular fields with dimensions within the range <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>0.7</mn>\u0000 <mo><</mo>\u0000 <mi>X</mi>\u0000 <mo>/</mo>\u0000 <mi>Y</mi>\u0000 <mo><</mo>\u0000 <mn>1.4</mn>\u0000 </mrow>\u0000 <annotation>$0.7 < X/Y < 1.4$</annotation>\u0000 </semantics></math>.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 <p>The objective of the present study was to compare the accuracy of the Cranmer-Sargison definition with other formulas for equivalent square small fields in the context of measuring field output factors (FOFs) for rectangular small fields, both within and outside the range covered by the CoP.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 <p>Measurements were conducted using Gafchromic EBT4 radiochromic films. The models compared included Cranmer-Sargison, Sterling, Superellipse, Sterling-Partial Superellipse, Sterling-Superellipse, Vadash and Bjärngard, and Fogliata. The most accurate definition of equivalent square field size was identified as the one yielding the lowest discrepancy between measured and analytical values, with the log-likelihood of the measurements selected as the metric. Analytical values were derived using the function introduced by Sauer and Wilbert, which relates FOFs to equivalent square field sizes.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 <p>The best results were achieved with the Fogliata model, followed in terms of accuracy by the Sterling-Partial Superellipse model. The Sterling-Superellipse and Vadash and Bjärngard models came next. It should be noted that the Sterling-Partial Superellipse and Sterling-Superellipse models rely solely on the geometric shape of the irradiation field size, whereas the Fogliata and Vadash and Bjärngard models incorporate a fitting parameter. The Sterling definition, while less accurate than these models, improved upon the Cranmer-Sargison definition and retained computational simplicity. Finally, the Cranmer-Sargison and Superellipse models exhibited the largest discrepancies.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 ","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12887976/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146149427","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}
This study aimed to evaluate the impact of rectal gas evacuation on organ-at-risk (OAR) volumes, dose-volume histogram (DVH) parameters, and applicator displacement during cervical cancer brachytherapy.
Methods
Twenty-one cervical cancer patients who received three-dimensional brachytherapy at our center between November and December 2024 and presented with rectal gas were retrospectively included. Planning computed tomography (CT) images were acquired before and after rectal gas evacuation to evaluate changes in rectal and bladder volumes, as well as radiation dose variations to OARs (bladder, rectum, sigmoid, and small intestine). Dosimetric parameters analyzed comprised D0.1cc, D1cc, D2cc, and D5cc (minimum doses delivered to the most irradiated 0.1, 1, 2, and 5 cm3 of the OARs, respectively), as well as Dmax (maximum dose) and Dmean (mean dose). Displacements of the applicator tip and cervical stopper were quantified using a coordinate system based on pelvic bony landmarks.
Results
Rectal volume decreased by 40.1% after gas evacuation, while bladder volume increased by 18.2%. D0.1cc, D1cc, D2cc, D5cc, and Dmax in the rectum decreased significantly (P < 0.001) after gas evacuation, whereas no significant changes were observed in the DVH parameters of the other OARs. The mean displacements of the applicator tip and cervical stopper were 5.86 ± 3.64 mm and 4.23 ± 3.30 mm, respectively.
Conclusions
Rectal gas evacuation results in a statistically significant and clinically relevant reduction in rectal volume and rectal dose, underscoring its importance as a routine clinical procedure. However, as it may induce millimeter-level applicator displacement with clinically measurable dosimetric consequences, careful monitoring is warranted, with post-evacuation replanning or, if necessary, applicator adjustment.
{"title":"Impact of rectal gas evacuation on dosimetry and applicator displacement in cervical cancer brachytherapy","authors":"Haiyan Wu, Chengdian he, Mei Liu, Xiujuan Zhao","doi":"10.1002/acm2.70490","DOIUrl":"10.1002/acm2.70490","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Objective</h3>\u0000 \u0000 <p>This study aimed to evaluate the impact of rectal gas evacuation on organ-at-risk (OAR) volumes, dose-volume histogram (DVH) parameters, and applicator displacement during cervical cancer brachytherapy.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Twenty-one cervical cancer patients who received three-dimensional brachytherapy at our center between November and December 2024 and presented with rectal gas were retrospectively included. Planning computed tomography (CT) images were acquired before and after rectal gas evacuation to evaluate changes in rectal and bladder volumes, as well as radiation dose variations to OARs (bladder, rectum, sigmoid, and small intestine). Dosimetric parameters analyzed comprised <i>D</i><sub>0.1cc</sub>, <i>D</i><sub>1cc</sub>, <i>D</i><sub>2cc</sub>, and <i>D</i><sub>5cc</sub> (minimum doses delivered to the most irradiated 0.1, 1, 2, and 5 cm<sup>3</sup> of the OARs, respectively), as well as <i>D</i><sub>max</sub> (maximum dose) and <i>D</i><sub>mean</sub> (mean dose). Displacements of the applicator tip and cervical stopper were quantified using a coordinate system based on pelvic bony landmarks.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Rectal volume decreased by 40.1% after gas evacuation, while bladder volume increased by 18.2%. <i>D</i><sub>0.1cc</sub>, <i>D</i><sub>1cc</sub>, <i>D</i><sub>2cc</sub>, <i>D</i><sub>5cc</sub>, and <i>D</i><sub>max</sub> in the rectum decreased significantly (<i>P</i> < 0.001) after gas evacuation, whereas no significant changes were observed in the DVH parameters of the other OARs. The mean displacements of the applicator tip and cervical stopper were 5.86 ± 3.64 mm and 4.23 ± 3.30 mm, respectively.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Rectal gas evacuation results in a statistically significant and clinically relevant reduction in rectal volume and rectal dose, underscoring its importance as a routine clinical procedure. However, as it may induce millimeter-level applicator displacement with clinically measurable dosimetric consequences, careful monitoring is warranted, with post-evacuation replanning or, if necessary, applicator adjustment.</p>\u0000 </section>\u0000 </div>","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12885748/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146149608","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}
This study evaluates the dosimetric impact of integrating thin metallic scatter foils with Cerrobend contact skin collimators to improve dose uniformity, conformality, and distal tissue sparing in small superficial electron fields.
Materials and methods
Electron beams of 8, 12, and 15 MeV from an Elekta Versa HD LINAC were delivered through a Cerrobend skin collimator with a 2.0 cm aperture at 100.0 cm SSD. Thin aluminum (Al) and lead (Pb) foils (< 2.50 mm) were placed on the collimator. Gafchromic EBT3 film in a solid-water phantom was used to measure depth-dose distributions and isodose profiles following TG-235–consistent calibration.
Results
Scatter foils produced thickness- and Z-dependent modulation of beam characteristics. At 8 MeV, the thickest Pb foil (1.07 mm) reduced the practical range (Rp) by ∼45% and shifted Dmax proximally by ∼0.5 cm, yielding substantial distal tissue sparing. Al foils caused smaller Rp reductions (15%–25%) but improved lateral dose uniformity, producing smoother and more symmetric isodose contours. The 90% isodose diameter decreased with foil thickness for both materials, with Pb showing the largest contraction (∼20%–25%, energy-dependent), enhancing field conformality. Penumbra width increased slightly for thin foils but stabilized or narrowed for larger thicknesses. These effects diminished at 15 MeV, indicating reduced sensitivity of high-energy electrons to thin-foil perturbation.
Conclusions
Thin metallic foils placed on Cerrobend skin collimators enable a controllable balance between dose uniformity (improved with Al) and conformality with distal sparing (enhanced with Pb). This simple, LINAC-independent configuration offers a cost-effective method for modulating small-field electron beam characteristics and may serve as a practical adjunct for treating superficial lesions.
{"title":"Dosimetric characterization of scatter foil-enhanced contact collimation for small superficial electron beam therapy","authors":"Abdulaziz Alhussan, Richard Crilly","doi":"10.1002/acm2.70484","DOIUrl":"10.1002/acm2.70484","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study evaluates the dosimetric impact of integrating thin metallic scatter foils with Cerrobend contact skin collimators to improve dose uniformity, conformality, and distal tissue sparing in small superficial electron fields.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Materials and methods</h3>\u0000 \u0000 <p>Electron beams of 8, 12, and 15 MeV from an Elekta Versa HD LINAC were delivered through a Cerrobend skin collimator with a 2.0 cm aperture at 100.0 cm SSD. Thin aluminum (Al) and lead (Pb) foils (< 2.50 mm) were placed on the collimator. Gafchromic EBT3 film in a solid-water phantom was used to measure depth-dose distributions and isodose profiles following TG-235–consistent calibration.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Scatter foils produced thickness- and Z-dependent modulation of beam characteristics. At 8 MeV, the thickest Pb foil (1.07 mm) reduced the practical range (<i>R</i><sub>p</sub>) by ∼45% and shifted <i>D</i><sub>m</sub><sub>a</sub><i><sub>x</sub></i> proximally by ∼0.5 cm, yielding substantial distal tissue sparing. Al foils caused smaller <i>R<sub>p</sub></i> reductions (15%–25%) but improved lateral dose uniformity, producing smoother and more symmetric isodose contours. The 90% isodose diameter decreased with foil thickness for both materials, with Pb showing the largest contraction (∼20%–25%, energy-dependent), enhancing field conformality. Penumbra width increased slightly for thin foils but stabilized or narrowed for larger thicknesses. These effects diminished at 15 MeV, indicating reduced sensitivity of high-energy electrons to thin-foil perturbation.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Thin metallic foils placed on Cerrobend skin collimators enable a controllable balance between dose uniformity (improved with Al) and conformality with distal sparing (enhanced with Pb). This simple, LINAC-independent configuration offers a cost-effective method for modulating small-field electron beam characteristics and may serve as a practical adjunct for treating superficial lesions.</p>\u0000 </section>\u0000 </div>","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12884950/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146142198","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}
Reza Reiazi, Yao Ding, Sarath Vijayan, Jinzhong Yang, Ergys Subashi, Yao Zhao, Belinda M. Lee, Hunter L. Emory, Vi T. Dinh, Greg L. Swiedom, Jie Deng, Mu-Han Lin, Peter Balter, Rajat J. Kudchadker, Elaine E. Cha, Seungtaek Choi, Yusung Kim, Eun Young Han, Surendra Prajapati
Purpose
We evaluated the feasibility of a magnetic resonance (MR)-only simulation, planning, and treatment (MROSPT) workflow for prostate cancer patients using synthetic computed tomography (sCT) generated from magnetic resonance imaging (MRI) data. By validating sCT-based dose calculations, we aimed to streamline radiotherapy workflows, eliminate the need for CT simulation, and enable reliable clinical implementation of MR-based radiotherapy for MR-linac (MRL).
Methods
We developed a comprehensive workflow encompassing the entire process from initial consultation to treatment delivery. After developing the workflow, a retrospective dosimetric validation study was performed on nine men with prostate cancer. They underwent CT and MRI simulations, and sCTs were generated from the MRI data. Contours and intensity-modulated radiation therapy treatment plans were created on the reference simulation CT (rCT) and transferred to sCTs for dose-calculation comparisons. Dosimetric accuracy was evaluated using gamma analysis (dose/distance; 2%/2mm). Bulk density sCTs (bCTs) were created by overriding organ density values with their mean (bulk) sCT-determined densities. bCT based on sCT allows treatment planning directly on MRI for MRL workflow efficiency.
Results
Minimal non-bone Hounsfield units (HU)-value differences between rCT and sCT (5.5 ± 2.9 HU for prostate) demonstrated the reliability of the sCT generation process. Dosimetric comparisons between treatment plans (rCT vs. sCT, rCT vs. bCT) showed agreement within ± 2% in gamma analysis, confirming robust accuracy. The gamma index pass rate for rCT versus sCT and rCT versus bCT were consistently > 95% using 2%/2 mm criteria. A dry run of the entire simulation-to-treatment workflow was successfully completed.
Conclusion
The MROSPT workflow using sCT is clinically feasible and dosimetrically accurate for prostate cancer patients. Dose calculations based on sCT demonstrated high dosimetric agreement with simulation CT, with no statistically significant differences across all evaluated metrics. These findings support the adoption of sCT‑based planning for prostate cancer radiotherapy and suggest its potential applicability in other anatomical regions especially in the pelvis. Integration of robust quality‑assurance processes and treatment‑delivery flexibility will further enhance its clinical utility.
{"title":"Development and implementation of an MRI-only simulation, planning, and treatment workflow for prostate radiotherapy using synthetic CT on MR-linac","authors":"Reza Reiazi, Yao Ding, Sarath Vijayan, Jinzhong Yang, Ergys Subashi, Yao Zhao, Belinda M. Lee, Hunter L. Emory, Vi T. Dinh, Greg L. Swiedom, Jie Deng, Mu-Han Lin, Peter Balter, Rajat J. Kudchadker, Elaine E. Cha, Seungtaek Choi, Yusung Kim, Eun Young Han, Surendra Prajapati","doi":"10.1002/acm2.70499","DOIUrl":"10.1002/acm2.70499","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>We evaluated the feasibility of a magnetic resonance (MR)-only simulation, planning, and treatment (MROSPT) workflow for prostate cancer patients using synthetic computed tomography (sCT) generated from magnetic resonance imaging (MRI) data. By validating sCT-based dose calculations, we aimed to streamline radiotherapy workflows, eliminate the need for CT simulation, and enable reliable clinical implementation of MR-based radiotherapy for MR-linac (MRL).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>We developed a comprehensive workflow encompassing the entire process from initial consultation to treatment delivery. After developing the workflow, a retrospective dosimetric validation study was performed on nine men with prostate cancer. They underwent CT and MRI simulations, and sCTs were generated from the MRI data. Contours and intensity-modulated radiation therapy treatment plans were created on the reference simulation CT (rCT) and transferred to sCTs for dose-calculation comparisons. Dosimetric accuracy was evaluated using gamma analysis (dose/distance; 2%/2mm). Bulk density sCTs (bCTs) were created by overriding organ density values with their mean (bulk) sCT-determined densities. bCT based on sCT allows treatment planning directly on MRI for MRL workflow efficiency.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Minimal non-bone Hounsfield units (HU)-value differences between rCT and sCT (5.5 ± 2.9 HU for prostate) demonstrated the reliability of the sCT generation process. Dosimetric comparisons between treatment plans (rCT vs. sCT, rCT vs. bCT) showed agreement within ± 2% in gamma analysis, confirming robust accuracy. The gamma index pass rate for rCT versus sCT and rCT versus bCT were consistently > 95% using 2%/2 mm criteria. A dry run of the entire simulation-to-treatment workflow was successfully completed.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>The MROSPT workflow using sCT is clinically feasible and dosimetrically accurate for prostate cancer patients. Dose calculations based on sCT demonstrated high dosimetric agreement with simulation CT, with no statistically significant differences across all evaluated metrics. These findings support the adoption of sCT‑based planning for prostate cancer radiotherapy and suggest its potential applicability in other anatomical regions especially in the pelvis. Integration of robust quality‑assurance processes and treatment‑delivery flexibility will further enhance its clinical utility.</p>\u0000 </section>\u0000 </div>","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12885750/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146149493","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}
<div> <section> <h3> Background</h3> <p>Computed tomography (CT) examinations of the head, paranasal sinus (PNS), and cervical spine (C-spine) are frequently performed in emergency settings, raising concerns about radiation exposure to the radiosensitive eye lens. Overexposure can cause radiation-induced ocular damage. To address this concern, organ dose modulation (ODM) has emerged as a promising technique for reducing eye lens dose in CT examinations.</p> </section> <section> <h3> Purpose</h3> <p>This study aimed to evaluate radiation exposure to the eye lens and objective image quality metrics for head, PNS, and C-spine CT examinations using fixed tube current, automatic tube current modulation (ATCM), and ODM techniques.</p> </section> <section> <h3> Methods</h3> <p>Eye lens doses were measured using nanoDot optically stimulated luminescence dosimeters (OSLDs) placed bilaterally to the eye lens of a whole-body anthropomorphic phantom (PBU-60). CT scans were performed using a Revolution EX CT scanner with three scanning techniques: fixed tube current, ATCM, and ODM. The phantom was scanned twice for each examination type (head, PNS, and C-spine) with all three techniques. Eye lens dose reductions with the ODM technique were quantified relative to fixed tube current and ATCM techniques. Image quality was quantitatively evaluated in terms of image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR).</p> </section> <section> <h3> Results</h3> <p>Mean eye lens doses ± standard deviation (SD) using the ODM technique were 38.44 ± 1.37, 17.92 ± 1.01, and 9.77 ± 0.38 mGy for head, PNS, and C-spine, respectively. These eye lens doses were reduced by 4.28%, 21.33%, and 47.97% compared to the fixed tube current techniques and by 19.40%, 24.70%, and 13.69% compared to the ATCM techniques, for head, PNS, and C-spine, respectively. These dose reductions were achieved while maintaining image quality metrics (image noise, SNR, and CNR) with no statistically significant differences (<i>p</i> > 0.05) compared to fixed tube current and ATCM techniques.</p> </section> <section> <h3> Conclusion</h3> <p>Implementation of the ODM technique resulted in significant eye lens dose reduction (4.28%–47.97%) across head, PNS, and C-spine CT examinations with no significant differences in image noise, SNR, and CNR compared to both fixed tube current and ATCM techniques. ODM demonstrates potential as a practical dose optimization strategy for routine emerg
背景：头部、副鼻窦（PNS）和颈椎（C-spine）的计算机断层扫描（CT）检查经常在紧急情况下进行，这引起了对辐射敏感眼晶状体辐射暴露的担忧。过度暴露会引起辐射引起的眼部损伤。为了解决这一问题，器官剂量调节（ODM）已经成为一种很有前途的技术，用于减少CT检查中的晶状体剂量。目的：本研究旨在评估使用固定管电流、自动管电流调制（ATCM）和ODM技术进行头部、PNS和颈椎CT检查时，眼晶状体的辐射暴露和客观图像质量指标。方法：采用纳米点光刺激发光剂量计（osld）测量眼晶状体剂量，该剂量计放置在全身拟人幻影（PBU-60）的眼晶状体两侧。CT扫描使用Revolution EX CT扫描仪，采用三种扫描技术：固定管电流、ATCM和ODM。采用所有三种技术对每个检查类型（头部、PNS和颈椎）的幻肢进行两次扫描。相对于固定管电流和ATCM技术，对ODM技术的眼晶状体剂量减少量进行了量化。通过图像噪声、信噪比（SNR）和噪声对比比（CNR）对图像质量进行定量评价。结果：使用ODM技术，头部、PNS和颈椎的平均晶状体剂量±标准差（SD）分别为38.44±1.37、17.92±1.01和9.77±0.38 mGy。与固定管电流技术相比，这些眼球晶状体剂量分别减少4.28%、21.33%和47.97%，与ATCM技术相比，头部、PNS和颈椎的晶状体剂量分别减少19.40%、24.70%和13.69%。与固定管电流和ATCM技术相比，在保持图像质量指标（图像噪声、信噪比和CNR）的同时实现了这些剂量的降低，没有统计学上的显著差异（p > 0.05）。结论：与固定管电流和ATCM技术相比，ODM技术的实施使头部、PNS和颈椎CT检查的晶体剂量显著降低（4.28%-47.97%），图像噪声、信噪比和CNR无显著差异。ODM显示了作为常规急诊头颈部CT成像的实用剂量优化策略的潜力。建议进一步研究主观图像质量评估，以评估医院设置的临床诊断可接受性。
{"title":"Reduction of radiation dose to the eye lens during common CT examinations of the head, paranasal sinus, and cervical spine in emergency settings: A phantom study","authors":"Sowitchaya Huakham, Wirachad Sripoori, Raksumon Suksi, Thawatchai Thaikan, Thanyawee Pengpan","doi":"10.1002/acm2.70486","DOIUrl":"10.1002/acm2.70486","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Computed tomography (CT) examinations of the head, paranasal sinus (PNS), and cervical spine (C-spine) are frequently performed in emergency settings, raising concerns about radiation exposure to the radiosensitive eye lens. Overexposure can cause radiation-induced ocular damage. To address this concern, organ dose modulation (ODM) has emerged as a promising technique for reducing eye lens dose in CT examinations.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study aimed to evaluate radiation exposure to the eye lens and objective image quality metrics for head, PNS, and C-spine CT examinations using fixed tube current, automatic tube current modulation (ATCM), and ODM techniques.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Eye lens doses were measured using nanoDot optically stimulated luminescence dosimeters (OSLDs) placed bilaterally to the eye lens of a whole-body anthropomorphic phantom (PBU-60). CT scans were performed using a Revolution EX CT scanner with three scanning techniques: fixed tube current, ATCM, and ODM. The phantom was scanned twice for each examination type (head, PNS, and C-spine) with all three techniques. Eye lens dose reductions with the ODM technique were quantified relative to fixed tube current and ATCM techniques. Image quality was quantitatively evaluated in terms of image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR).</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>Mean eye lens doses ± standard deviation (SD) using the ODM technique were 38.44 ± 1.37, 17.92 ± 1.01, and 9.77 ± 0.38 mGy for head, PNS, and C-spine, respectively. These eye lens doses were reduced by 4.28%, 21.33%, and 47.97% compared to the fixed tube current techniques and by 19.40%, 24.70%, and 13.69% compared to the ATCM techniques, for head, PNS, and C-spine, respectively. These dose reductions were achieved while maintaining image quality metrics (image noise, SNR, and CNR) with no statistically significant differences (<i>p</i> > 0.05) compared to fixed tube current and ATCM techniques.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>Implementation of the ODM technique resulted in significant eye lens dose reduction (4.28%–47.97%) across head, PNS, and C-spine CT examinations with no significant differences in image noise, SNR, and CNR compared to both fixed tube current and ATCM techniques. ODM demonstrates potential as a practical dose optimization strategy for routine emerg","PeriodicalId":14989,"journal":{"name":"Journal of Applied Clinical Medical Physics","volume":"27 2","pages":""},"PeriodicalIF":2.2,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12885872/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146149661","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号