Medical physics最新文献

{"title":"Possibility of increasing linear energy transfer in multi-ion radiotherapy for bone and soft tissue sarcomas","authors":"Hideyuki Takei, Reiko Imai, Takamitsu Masuda, Katsumi Aoki, Taku Nakaji, Yusuke Nomura, Asami Inomata, Yui Suzuki, Taku Inaniwa","doi":"10.1002/mp.18097","DOIUrl":"10.1002/mp.18097","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Multi-ion radiotherapy using carbon, oxygen, and neon ions aims to improve local control by increasing dose-averaged linear energy transfer (LET<sub>d</sub>) in the target. However, there has been limited understanding of how to utilize variables for multi-ion treatment planning such as the selection and arrangement of ion species.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>An in silico study was conducted to explore the feasibility of increasing a minimum LET<sub>d</sub>, and the optimal selection and arrangement of ion species in multi-ion therapy for increasing LET<sub>d</sub> in tumors of varying sizes mimicking bone and soft tissue sarcomas (BSTS). Additionally, the robustness of multi-ion therapy against setup and range errors was evaluated.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Spherical targets of 500, 1000, and 1500-mL volumes were placed at the center or 80 mm horizontally displaced from the center of a numerical phantom to simulate BSTS treatments. Treatment plans were made for these targets with two orthogonal fields of carbon-only, oxygen+carbon, and neon+carbon ions with a total dose of 70.4 Gy (RBE). The treatment parameters were optimized to increase the LET<sub>d</sub> in the targets while ensuring adequate target dose coverage and dose homogeneity. The plans were evaluated based on the dose covering 95% of the target (<i>D</i><sub>95%</sub>), skin dose (<i>D</i><sub>skin</sub>), and the minimum LET<sub>d</sub> excluding the 1 mL volume with the lowest LET<sub>d</sub> (<i>L</i><sub>1mL</sub>). Multi-ion radiotherapy treatment plans were also developed for 12 patients with BSTS who had previously received carbon-ion radiotherapy. <i>D</i><sub>95%</sub> and <i>L</i><sub>1m</sub> of the target, and the dose to organs at risk (OARs) such as the rectum, intestine, and spinal cord were assessed. The robustness of the plans created in the phantom against setup and range errors was evaluated under 2 mm shifts in six directions combined with 2.5% variation of the stopping power ratio, resulting in 12 scenarios. Differences in the target <i>D</i><sub>95%</sub> and <i>L</i><sub>1mL</sub>, and <i>D</i><sub>skin</sub> in each scenario from those in the nominal plan were evaluated.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The target dose coverage was comparable for any ion species combinations regardless of target size and position. The <i>L</i><sub>1mL</sub> in the target increased by 7–9 and 15–20 keV/µm with the oxygen+carbon and neon+carbon plans, respectively, compared to the carbon-only plans, while maintaining homogeneity index values below 0.10. Additionally, the s","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A thermochromic tissue-mimicking phantom for catheter-based radiofrequency ablation of heterogenous lesions","authors":"Ruizhe Hou,&nbsp;Quanshu Han,&nbsp;Jincheng Zou,&nbsp;Shiqing Zhao,&nbsp;Aili Zhang","doi":"10.1002/mp.18112","DOIUrl":"10.1002/mp.18112","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>In catheter-based radiofrequency ablation (RFA), energy is delivered to heterogeneous thin-walled tissues to induce therapeutic heating. Variations in electrical and mechanical properties of tissue contents have a great effect on outcomes.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>The objective of this study is to develop models that replicate tissue heterogeneity and visualize ablation zones for effective evaluation and optimization.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>A tunable thermochromic phantom formulation was developed, consisting of deionized water, acrylamide aqueous solution (Acr/Bis), thermochromic microcapsule powder, Tris-HCl buffer, ammonium persulfate solution, and <i>N</i>,<i>N</i>,<i>N</i>',<i>N</i>'-tetramethylethylenediamine. The color-change temperature threshold, electrical conductivity, and elastic modulus were characterized with different formulation compositions. A dual-parameter inverse design method based on concentration-property regression models was proposed to match the electrical and mechanical properties of tissues simultaneously, which was validated through RFA experiments on phantoms.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The phantoms exhibited an immediate and irreversible color change from indigo to deep pink at 60°C, clearly delineating ablation margins. Electrical conductivity ranged from 0.1892 to 0.5958 S/m and elastic modulus from 6.70 to 138 kPa, effectively encompassing the characteristic properties of diverse lesion tissues. RFA experiments on phantoms mimicking porcine myocardium and chicken breast demonstrated strong agreement with ex vivo results. Ablation of heterogeneous phantoms mimicking atherosclerotic structures revealed significant differences compared to homogeneous models.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>A tunable thermochromic phantom formulation was developed, exhibiting a precise color change at 60°C while replicating the electrical and mechanical properties of heterogeneous tissues, enabling direct visualization of ablation boundaries. The phantom offers a robust platform for evaluating catheter-based RFA in clinically relevant complex tissues, supporting the development of personalized and optimized treatment strategies.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Lightweight hybrid Mamba2 for unsupervised medical image registration","authors":"Aobo Xu,&nbsp;Shaofei Shen,&nbsp;Wenkang Chen,&nbsp;Xuejun Zhang","doi":"10.1002/mp.18104","DOIUrl":"10.1002/mp.18104","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Background&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Deformable medical image registration is a critical task in medical imaging-assisted diagnosis and treatment. In recent years, medical image registration methods based on deep learning have made significant success by leveraging prior knowledge, and the registration accuracy and computational efficiency have been greatly improved. Models based on Transformers have achieved better performance than convolutional neural network methods (ConvNet) in image registration. However, their secondary computational complexity leads to significant computational overhead, posing substantial challenges for deployment in resource-constrained medical environments. Recently, Mamba-2 introduced the structured state-space Duality (SSD) framework to address the high computational cost of Transformer, achieving state-of-the-art performance across multiple domains. Mamba-2 may be a more powerful competitor than Transformer in the field of image registration. The design of its global receptive field and linear computational complexity enable it to show substantial advantages and efficiency in accurately understanding the nonlinear spatial relationships between the moving images and fixed images.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;To address the challenges of deployment in resource-constrained medical environments and further improve the efficiency and accuracy of medical image registration, we propose HybridMorph, a lightweight hybrid Mamba2 model for medical image registration. In this study, we also introduce three versions of HybridMorph with different parameter numbers.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;We propose a Residual Hybrid Module (RHM) that reconstructs a feature extraction module for medical image registration tasks based on convolution and Mamba-2, along with a novel lightweight method called the parallel channel feature aggregator (PCFA), which extracts richer feature representations with lower computational overhead.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;The proposed model was evaluated by comparing it with various existing baseline registration methods. The results show that HybridMorph achieves significant performance improvements over the baseline methods, achieving the highest average Dice scores of 0.780 and 0.824 in atlas-to-patient and inter-patient brain Magnetic Resonance Imaging (MRI) registration, respectively. Notably, compared to the renowned TransMorph, HybridMorph achieves superior registration performance while reducing the number of parameters and computational cost by 10.1 and 5.8 times, respectively.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;se","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simultaneous optimization of multiple plans within one treatment course with dosimetric pathfinding for temporally feathered radiation therapy","authors":"Julius Arnold,&nbsp;Chengchen Zhu,&nbsp;Gian Guyer,&nbsp;Silvan Mueller,&nbsp;Barbara Knäusl,&nbsp;Olgun Elicin,&nbsp;Marco FM Stampanoni,&nbsp;Peter Manser,&nbsp;Michael K Fix,&nbsp;Jenny Bertholet","doi":"10.1002/mp.18123","DOIUrl":"10.1002/mp.18123","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Background&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Radiotherapy workflows conventionally deliver one treatment plan multiple times throughout the treatment course. Non-coplanar techniques with beam angle optimization or dosimetrically optimized pathfinding (DOP) exploit additional degrees of freedom to improve spatial conformality of the dose distribution compared to widely used techniques like volumetric-modulated arc therapy (VMAT). The temporal dimension of dose delivery can be exploited using multiple plans (sub-plans) within one treatment course. For instance, temporally feathered radiation therapy (TFRT) uses iso-curative sub-plans to deliver an alternance of higher and lower doses compared to a single plan to selected organs-at-risk (OARs), facilitating the dynamic recovery process of healthy tissues.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;This study presents a simultaneous optimization framework based on direct aperture optimization with or without DOP to optimize multiple coplanar or non-coplanar sub-plans within one treatment course and demonstrates its use for TFRT planning.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;The goal of the framework was to minimize an objective function consisting of weighted upper or lower dose-volume, generalized equivalent uniform dose, and normal tissue objectives set on the dose distribution of each sub-plan or the combined total plan. Reference VMAT and dynamic collimator trajectory radiotherapy (colli-DTRT) single plans were created and used to derive the objectives for TFRT planning. The TFRT high-to-low dose modulation was integrated into the objective list and systematically investigated for a digital academic phantom using three variations (“soft”, “medium”, “hard”). Additionally, a “super-soft” variation used the same objectives for all five sub-plans (i.e., no high-to-low dose modulation). Furthermore, “medium” TFRT sub-plans with colli-DTRT were created for three more complex clinically motivated head and neck cases.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;For the phantom, the sub-plans were iso-curative with target D&lt;sub&gt;98%&lt;/sub&gt; within 1.6% of the reference plans. High-to-low OAR dose modulation was achieved with median D&lt;sub&gt;mean&lt;/sub&gt; differences between high and low dose fractions of 2.7% of the prescription dose (soft), 3.3% (medium), and 4.4% (hard) for VMAT. Median OAR D&lt;sub&gt;mean&lt;/sub&gt; differences were 2.8% of the prescription dose (soft), 6.3% (medium), and 6.1% (hard) for colli-DTRT. The dose distributions of the total plans had higher homogeneity indices (HI = D&lt;sub&gt;98%&lt;/sub&gt;/D&lt;su","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://aapm.onlinelibrary.wiley.com/doi/epdf/10.1002/mp.18123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimizing dose rate to minimize delivery time in proton pencil beam dose-driven continuous scanning","authors":"Dong Han,&nbsp;Yu Yang,&nbsp;Xiaoying Liang,&nbsp;Hongcheng Liu,&nbsp;Jindong Tong,&nbsp;Sridhar Yaddanapudi,&nbsp;Chunjoo Park,&nbsp;Jun Tan,&nbsp;Keith Furutani,&nbsp;Chris Beltran,&nbsp;Bo Lu","doi":"10.1002/mp.18098","DOIUrl":"10.1002/mp.18098","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Background&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Dose-driven continuous scanning (DDCS) enhances the efficiency and precision of proton pencil beam delivery by reducing beam pauses inherent in discrete spot scanning (DSS). However, current DDCS optimization studies using traveling salesman problem (TSP) formulations often rely on fixed beam intensity and computationally expensive interpolation for move spot generation, limiting efficiency and methodological robustness.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;This study introduces a Break Spot-Guided (BSG) method, combined with two acceleration strategies—dose rate skipping and bounding—to optimize beam intensity while minimizing beam delivery time (BDT). In addition, a &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;σ&lt;/mi&gt;\u0000 &lt;annotation&gt;$sigma$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-method is proposed for efficient move spot generation, aiming to balance computational efficiency and dose calculation accuracy.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;The BSG framework simplifies the original mixed-integer nonlinear programming (MINLP) problem by transforming it into a series of TSP evaluations using break-spot dose rates. The two acceleration strategies are integrated to reduce computational complexity. The &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;σ&lt;/mi&gt;\u0000 &lt;annotation&gt;$sigma$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-method is introduced to efficiently generate move spots without compromising dose fidelity. The performance of the BSG method, with and without the acceleration strategies, and the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;σ&lt;/mi&gt;\u0000 &lt;annotation&gt;$sigma$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-method, was evaluated across multiple clinical cases.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;By jointly optimizing the scan path and dose rate, the proposed BSG-S-B method offered the most efficient delivery, achieving a 64% reduction in BDT compared to DSS and a 57% reduction compared to Liu's method in the prostate case. These gains were consistently observed across all cases. Utilizing acceleration strategies, BSG-S-B significantly reduced computation time from hours to minutes (e.g., from 10 525.7 to 108.5 s in the prostate case, and from 6202.4 to 129.8 s in the head-and-neck case). When combined with the &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mi&gt;σ&lt;/mi&gt;\u0000 &lt;annotation&gt;$sigma$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-method, it re","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Systematic review of prospective hazard analysis in radiation therapy","authors":"Jonathan Hindmarsh,&nbsp;Sonja Dieterich,&nbsp;Jeremy Booth,&nbsp;Paul Keall","doi":"10.1002/mp.18110","DOIUrl":"10.1002/mp.18110","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Introduction&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Prospective hazard analysis (PHA) was introduced to the wider medical physics community by the initiation of American association of physicists in medicine task group 100 in 2003. Since then, there has been increasing interest in the applicability of PHA to radiotherapy for the purpose of keeping patients safe and assessing the risks within the whole practice of radiotherapy. The purpose of this research was to review the PHA literature focusing on which techniques and technologies have been assessed, how they have been assessed, and what can be learnt.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;The search for English language, peer-reviewed, full-text articles was conducted across five databases and the citations of three seminal papers using a common search strategy. The collation, filtration, and analysis of articles was conducted in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement reporting standard utilizing the following PICOS approach: Population: x-ray external beam radiation therapy, Intervention: prospective hazard analysis, Comparison: none, Outcome: patient safety, Study characteristics: details of applied technique.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;689 unique studies were identified. 62 were determined to be eligible for inclusion. PHA has been applied to C-arm treatment systems (17), stereotactic radiosurgery (8), TomoTherapy (6), stereotactic body radiotherapy (5), Ethos (5), Halcyon (3), MRIdian (3), review activities (3), commissioning (2), unity (1), volumetric modulated arc therapy (1), surface guidance (1), CyberKnife (1), RefleXion (1) and other novel software and hardware systems (6). Disciplines involved in the studies were physicists (92%), physicians (75%), radiation therapists or dosimetrists (71%), external experts (38%), and facilitators (33%). Failure mode and effects analysis (FMEA) was used in 75% of studies, 10% used FMEA derived methods, 10% used system theoretic process analysis, and 5% used other methods. From the FMEA studies, 579 high-risk failure modes were extracted covering all aspects of the radiotherapy process, 50% applied to patient treatment delivery sessions and 25% applied to contouring and treatment planning. The mitigation strategies recommended by studies tended to add to the departmental workload.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Conclusions&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;62 studies were identified that used PHA in radiotherapy, within the included studies: patient journey was the most analyzed process, of the ","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://aapm.onlinelibrary.wiley.com/doi/epdf/10.1002/mp.18110","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145022273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of supine and upright postures for liver respiratory motion management in radiotherapy","authors":"Yusuke Nomura,&nbsp;Taku Inaniwa,&nbsp;Yoshitake Yamada,&nbsp;Minoru Yamada,&nbsp;Yoichi Yokoyama,&nbsp;Sodai Tanaka,&nbsp;Shunsuke Yonai,&nbsp;Hideyuki Mizuno,&nbsp;Yoshiyuki Iwata,&nbsp;Atsuya Takeda,&nbsp;Hitoshi Ishikawa,&nbsp;Masahiro Jinzaki","doi":"10.1002/mp.18111","DOIUrl":"10.1002/mp.18111","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Understanding respiratory motions of liver and its surrogate organs is crucial for precise dose delivery in liver cancer radiotherapy. Although these motions have been studied for respiratory motion management in the supine posture, few studies have quantified them and evaluated their correlations in the upright posture.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study quantified the respiratory motions of liver and surrogate organs and evaluated the correlations between the liver motions and surrogate signals for respiratory motion monitoring in both the supine and upright postures.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>4D dynamic volume computed tomography (CT) images were acquired from 13 asymptomatic volunteers in both supine and upright postures while free breathing. The 4D liver motions were calculated by performing deformable image registration. Subsequently, superior–inferior (SI) motion at the right diaphragm apex and anterior–posterior (AP) motion at the abdominal skin surface were obtained as surrogate signals from the 4D CT images. The average displacements and maximum magnitudes of liver motions and surrogate signals were compared between the postures. Moreover, the correlations between the liver motions and surrogate signals were evaluated based on correlation models.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The average liver displacements from the end-exhalation along the SI, AP, and left-right directions were −6.1, 2.1, and −0.4 mm in the supine posture and −4.6, 2.5, and 0.1 mm in the upright posture, respectively. The maximum motion range along the SI direction significantly decreased from 16.3 ± 6.6 mm in the supine posture to 11.0 ± 2.7 mm in the upright posture. Similar to the supine posture, the correlation models also reproduced the liver motions with high fitting accuracy in the upright posture.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>Compared to the conventional supine posture, the liver SI motion became smaller in the upright posture while keeping evident correlations with the surrogate signals, which suggests the upright posture will allow precise dose delivery with reduced internal target margins.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145022274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High spatiotemporal-resolution abdominal 4D-MRI through respiratory-synchronized frame collaborative reconstruction","authors":"Yinghui Wang,&nbsp;Lu Wang,&nbsp;Yidan Feng,&nbsp;Zhi Chen,&nbsp;Jing Qin,&nbsp;Tian Li,&nbsp;Jing Cai","doi":"10.1002/mp.18101","DOIUrl":"10.1002/mp.18101","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Background&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Four-dimensional magnetic resonance imaging (4D-MRI) holds great promise for precise abdominal radiotherapy guidance. However, current 4D-MRI methods are limited by an inherent trade-off between spatial and temporal resolutions, resulting in compromised image quality characterized by low spatial resolution and significant motion artifacts, hindering clinical implementation. Despite recent advancements, existing methods inadequately exploit redundant frame information and struggle to restore structural details from highly undersampled acquisitions.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;This study aims to develop a technique that leverages information across multiple frames to mitigate spatial undersampling, thereby enabling superior spatiotemporal resolution in abdominal 4D-MRI.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;We introduce a novel reconstruction approach for 4D-MRI that leverages respiratory-synchronized frames to reconstruct target frames with enhanced image quality. Specifically, we introduce a multi-frame collaborative reconstruction network (MCR-Net) that capitalizes on inter-frame correlations and complementary information for faithful reconstruction. MCR-Net integrates two key mechanisms: the Inter-frame mutual-attention mechanism (IMM) and the structure-aware consolidation module (SaCM). IMM enhances feature extraction by exploiting correlations among neighboring respiratory-synchronized frames, thereby reinforcing shared anatomical features while suppressing random artifacts and noise. SaCM consolidates structural information across frames by leveraging context-aware residual learning, enhancing high-frequency details, and filtering irrelevant data during multi-frame fusion, thus significantly improving the clarity and anatomical integrity.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Experimental evaluations on clinical patient datasets (training: &lt;i&gt;n&lt;/i&gt; = 20; validation: &lt;i&gt;n&lt;/i&gt; = 6) demonstrate that our method significantly outperforms nine state-of-the-art reconstruction approaches in both visual quality and quantitative accuracy. MCR-Net achieves superior performance in MAE, SSIM, and PSNR, outperforming the next-best methods by 3.77%, 1.03%, and 6.74%, respectively. Furthermore, our experiments validate that MCR-Net enhances registration accuracy compared to original low-quality 4D-MRI by 10.66%, 3.60%, and 1.94% in MAE, SSIM, and NCC metrics. Additionally, simulations demonstrate that MCR-Net effectively maintains high image quality even under significantly increased undersampling ratios.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 ","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145022297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-resolution dual-ended readout PET detectors based on 0.5 mm pitch LYSO arrays with various reflectors","authors":"Jiahao Xie,&nbsp;Haibo Wang,&nbsp;Junwei Du","doi":"10.1002/mp.18103","DOIUrl":"10.1002/mp.18103","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Background&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;High-resolution and high-sensitivity small-animal positron emission tomography (PET) scanners are essential non-invasive functional imaging tools in preclinical research. To develop small-animal PET scanners with uniform and high spatial resolution across the field-of-view, PET detectors capable of providing good depth-of-interaction (DOI) information are critical. Dual-ended readout detectors based on lutetium–yttrium oxyorthosilicate (LYSO) arrays with fine pitch represent a promising approach, wherein the choice of inter-crystal reflector significantly impacts the detector performance. Toray E60, with a 50 µm thickness, has been used for over two decades as an inter-crystal reflector for fabricating LYSO arrays used in dual-ended readout detectors. However, the Toray E60 has recently been discontinued.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;This study aims to identify an optimal alternative to the Toray E60 reflector, facilitating the continued development of dual-ended readout detectors for high-resolution and high-sensitivity small-animal PET scanners.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Methods&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Five dual-ended readout detectors based on 10 × 10 LYSO arrays were constructed and evaluated. These LYSO arrays employed different reflectors: Toray E60 with 50 µm thickness, Barium sulfate (BaSO&lt;sub&gt;4&lt;/sub&gt;) with 80 µm thickness, and Toray E20 with thicknesses of 40, 52, and 76 µm. All LYSO arrays featured the same pitch of 0.5 mm and thickness of 20 mm. Two linearly-graded silicon photomultipliers (LG-SiPMs) served as photodetectors. The performance of the five detectors in terms of crystal identification ability, energy resolution, coincidence timing resolution (CTR), and DOI resolution was comprehensively compared.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Results&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Among the five reflectors, the detector based on the LYSO array with the 52 µm thick Toray E20 reflector exhibited the best crystal identification ability and achieved an energy resolution of 20.2 ± 3.8%, a DOI resolution of 2.07 ± 0.48 mm, and a CTR of 882 ± 38 ps. Conversely, the detector based on the LYSO array with the 50 µm thick Toray E60 reflector showed an energy resolution of 22.0 ± 3.3%, a DOI resolution of 1.88 ± 0.25 mm, and a CTR of 833 ± 32 ps.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Conclusions&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;The Toray E20 reflector with a thickness of 52 µm represents a viable alternative to the discontinued Toray E60 with a 50 µm thickness. It is suitable for fabricating finely pitched and thick LYSO arrays used in dual-ended readout detectors to","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145022272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel direct-indirect dual-layer flat-panel detector for contrast-enhanced breast imaging: Experimental assessment","authors":"Xiaoyu Duan,&nbsp;Hailiang Huang,&nbsp;Salman M. Arnab,&nbsp;Yves Chevalier,&nbsp;Luc Laperrière,&nbsp;Adrian Howansky,&nbsp;Wei Zhao","doi":"10.1002/mp.18108","DOIUrl":"10.1002/mp.18108","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>In contrast-enhanced digital mammography (CEDM) and contrast-enhanced digital breast tomosynthesis (CEDBT), low-energy (LE) and high-energy (HE) images are acquired after injection of iodine contrast agent. Weighted subtraction is then applied to generate dual-energy (DE) images, where normal breast tissues are suppressed, leaving iodinated objects enhanced. Currently, clinical systems employ a dual-shot (DS) method, where LE and HE images are acquired with two separate exposures. However, patient motion between these exposures can cause residual breast tissue structure to appear in the recombined DE images, reducing the visibility of iodinated lesions. To address this issue, we propose a direct-indirect dual-layer flat-panel detector (DI-DLFPD), which eliminates patient motion artifact by acquiring LE and HE images simultaneously.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study aims to: (1) experimentally validate CEDM and CEDBT imaging using a first-generation prototype DI-DLFPD, (2) compare lesion conspicuity with images obtained using the DS method, (3) optimize the k-edge filter for the DI-DLFPD based on breast thickness.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>CEDM and CEDBT images were acquired using both the prototype DI-DLFPD and a conventional DS single-layer detector at comparable dose levels to evaluate image quality and iodine target conspicuity. The figure of merit (FOM) was defined as the square of signal difference to noise ratio (SDNR) divided by the mean glandular dose. The selection of k-edge filter for DI-DLFPD was assessed based on varying breast thickness.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>By eliminating patient motion artifacts, DI-DLFPD images exhibit a significant improvement (∼233%) in iodine object FOM compared to DS images affected by patient motion. Iodine quantification accuracy was also improved. The results suggest using a sliver filter for average breast thickness (4 cm) and a Tin filter for thicker breasts (8 cm) to achieve optimal iodine SDNR for DI-DLFPD.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>This study presents experimental results from the first-generation prototype DI-DLFPD for CEDM and CEDBT. A practical strategy was recommended, where the x-ray filter for DI-DLFPD was optimized based on the compressed breast thickness.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"52 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145022303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}