Medical physics最新文献

{"title":"Fast and robust T1 mapping based on a 3D dual-echo UTE sequence (PETALUTE) for superparamagnetic iron oxide nanoparticle (SPION) biodistribution assessment","authors":"Zhen Jiang, Stephen Sawiak, Alexandra Lipka, Xin Shen, Uzay Emir, Ali Özen, Mark Chiew, Justin Geise, Joseph Speth, Deng-Yuan Chang, Jessica Veenstra, Mitchell Gabalski, Luis Solorio, Gregory Tamer Jr, Matthew Scarpelli","doi":"10.1002/mp.70675","DOIUrl":"10.1002/mp.70675","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Superparamagnetic iron oxide nanoparticles (SPIONs), such as ferumoxytol, are promising theranostic agents that can be assessed with MRI. Relaxation time mapping can provide reproducible and quantitative biomarkers of SPION distribution, suitable for longitudinal and cross-individual studies. However, conventional approaches suffer from strong susceptibility artifacts, long echo times (TE), and prolonged scan times, which limit the accurate quantification of SPION biodistribution.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>To address the limitations of conventional approaches, this study aimed to develop a fast, B<sub>1</sub><sup>+</sup>-corrected <span></span><math>\u0000 <semantics>\u0000 <msub>\u0000 <mi>T</mi>\u0000 <mn>1</mn>\u0000 </msub>\u0000 <annotation>${{{mathrm{T}}}_{mathrm{1}}}$</annotation>\u0000 </semantics></math> mapping protocol based on PETALUTE (a 3D dual-echo ultrashort echo time MRI sequence with a petal-like rosette k-space trajectory) using a variable flip-angle (VFA) acquisition for T<sub>1</sub> mapping to assess ferumoxytol distribution.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>Agarose phantoms containing 0–5000 µg/mL ferumoxytol were scanned on a preclinical 7T MRI system using PETALUTE and RARE-VTR (rapid acquisition with relaxation enhancement and variable repetition time). PETALUTE T<sub>1</sub> maps were computed from two VFA acquisitions (4° and 20°). Mean R<sub>1</sub> values were correlated with ferumoxytol concentration to assess the method's reliability. For in vivo feasibility testing, mice bearing 4T1 mammary tumors and flank tumors were assigned to the control (<i>n</i> = 1) or ferumoxytol-injected group (<i>n</i> = 2; 40 mg/kg i.v.). Abdominal MRI scans were performed 24 h post-injection with both PETALUTE and RARE-VTR. Regions of interest in the thigh muscle, mammary tumors, and flank tumors were analyzed to compare the estimated T<sub>1</sub> and R<sub>1</sub> values obtained with both methods.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In the phantom study, PETALUTE preserved positive contrast for ferumoxytol at all concentrations, whereas the conventional RARE-VTR sequence exhibited signal loss and hypointensity. For PETALUTE, there was a significant linear correlation between R<sub>1</sub> and ferumoxytol concentration (<i>R</i> = 0.975, <i>p</i> < 0.01), while RARE-VTR showed no significant correlation (<i>R</i> = 0.672, <i>p","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 10","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mp.70675","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149043179","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":"A novel integrated circular radiography (ICRAD) phantom for evaluating non-uniform image quality metrics in radiography","authors":"Che-Lun Hsu,&nbsp;Ming-Chung Chou","doi":"10.1002/mp.70680","DOIUrl":"https://doi.org/10.1002/mp.70680","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Anode heel effects have been shown to cause a non-uniform distribution of X-ray photon fluence, and anode angle could cause focal spot size variations across field. However, no previous study has investigated their effects on image quality metrics in radiography.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>The present study aimed to propose an integrated circular radiography (ICRAD) phantom for assessing non-uniform image quality metrics in digital radiography.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>The phantom was fabricated using multi-layer circular acrylic plates with various sized details and an outer ring of tungsten. It was exposed ten times at different tube voltage and current-time product settings using a digital radiographic system. The visible ratio (VR), normalized mutual information (nMI), and modulation transfer function at 10% (MTF_10%) and 50% contrast (MTF_50%) were calculated from different orientations to evaluate the non-uniform image quality in radiography. For comparison, a conventional contrast-detail radiography (CDRAD) phantom was also exposed ten times at the same tube voltage and tube current-time product, and rotated at angles of 0, 90, 180, and 270 degrees to understand the effect of anode angle on image quality evaluation using the inverse image quality figure (IQF_inv). Statistical comparisons and correlation analysis were performed and the results were considered significant if <i>P</i> &lt; 0.05.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>The results demonstrated that the VR, nMI, MTF_50%, and IQF_inv increased with tube voltage and tube current-time product, and all metrics were significantly correlated with each other. The VR, nMI, and MTF_50% metrics were significantly higher in the cathode direction than in the anode direction, while the IQF_inv metric was significantly greater when small details were placed toward the cathode direction compared to the anode direction. Moreover, the MTF_10% metric was significantly lower in the cathode direction than in the anode direction.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusion</h3>\u0000 \u0000 <p>The proposed ICRAD phantom is a suitable tool for assessing non-uniform image quality and spatial resolution caused by the anode heel effect in digital radiography.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 10","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mp.70680","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994365","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":"AAPM task group 324 report 91.b: The management of respiratory motion in radiation oncology","authors":"Paul J. Keall,&nbsp;Lakshmi Santanam,&nbsp;Laurence E. Court,&nbsp;Rojano Kashani,&nbsp;Daniel A. Low,&nbsp;Abilio Pacheco,&nbsp;Per Rugaard Poulsen,&nbsp;Suresh Senan,&nbsp;Chun-Chien Shieh,&nbsp;James Tanyi,&nbsp;Marcel van Herk,&nbsp;Ellen D. Yorke","doi":"10.1002/mp.70677","DOIUrl":"https://doi.org/10.1002/mp.70677","url":null,"abstract":"<p>The Task Group charge was to provide a concise, updated report of American Association of Physicists in Medicine Task Group 76: The Management of Respiratory Motion in Radiation Oncology to describe new technology, new knowledge, and practice changes since the original 2006 publication. The updated report includes a revised literature review, new respiratory motion management technologies that have emerged and are clinically practiced, and revised recommendations of clinical processes and quality assurance. To have broad applicability and to not overlap with existing task group reports, the current report scope focuses on technologies available to most clinics: four-dimensional computed tomography, treatment planning systems, and linear accelerators with gantry-mounted X-ray guidance. The deliverables from the current report include an explanation of respiratory motion management; terms and definitions relevant to respiratory motion management; the clinical benefit of, clinical experience with, and clinical implementation guidelines for respiratory motion management; quality assurance guidelines; a clinical decision pathway; future outlook; and overall recommendations.</p>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 10","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mp.70677","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994336","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":"Measurement-anchored Monte Carlo prediction of diagnostic x-ray air kerma using HVL-matched spectra and per-electron normalization","authors":"Yusuke Obara,&nbsp;Michiharu Sekimoto,&nbsp;Toyohiro Kato","doi":"10.1002/mp.70679","DOIUrl":"https://doi.org/10.1002/mp.70679","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;Quantitative Monte Carlo (MC) prediction of diagnostic x-ray air kerma is limited by mismatch between theoretical spectra and measured beam quality and by the lack of a reproducible normalization from source-photon tallies to mAs-based exposures.&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 test whether HVL-matched spectra combined with measurement-anchored per-electron normalization can predict free-in-air and transmitted air kerma under selected radiographic exposure settings and to evaluate the framework in PHITS and EGS5.&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;Birch-Marshall spectra at 50, 80, and 120 kV were adjusted by tuning the Al-equivalent filtration parameter so that the theoretical HVL agreed with the measured HVL. The matched spectra were used as common input for PHITS and EGS5. Free-in-air air kerma was measured for 102 exposure conditions, and transmitted air kerma was measured after 2.0-cm PMMA or 0.5-cm Al for seven conditions at each tube voltage. From measured air kerma and MC air-kerma tallies expressed per source photon, we defined the normalization constant &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Y&lt;/mi&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;I&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;t&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$Y( {V,I,t} )$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, the per-electron correction factor &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;X&lt;/mi&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;I&lt;/mi&gt;\u0000 &lt;mo&gt;,&lt;/mo&gt;\u0000 &lt;mi&gt;t&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$X( {V,I,t} )$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and the tube-voltage-averaged coefficient &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;X&lt;/mi&gt;\u0000 &lt;mo&gt;′&lt;/mo&gt;\u0000 &lt;/msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 ","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 10","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994366","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":"Comment on “Resilience-depletion hypothesis: Unifying BED from conventional to ablative radiotherapy”","authors":"Ehsan Khodamoradi","doi":"10.1002/mp.70678","DOIUrl":"https://doi.org/10.1002/mp.70678","url":null,"abstract":"","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 10","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148994432","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":"AAPM Task Group 66U1 report 83.B: Quality assurance for computed-tomography simulators in radiation oncology","authors":"Jochen Cammin,&nbsp;Mihaela Rosu-Bubulac,&nbsp;Sarah Castillo,&nbsp;Jessica R. Miller,&nbsp;Bernice Hoppel,&nbsp;Hao Zhang,&nbsp;Hao Dang,&nbsp;Indra J. Das,&nbsp;Qihui Lyu,&nbsp;Jainil Shah,&nbsp;Kenneth J. Ruchala,&nbsp;Shuai Leng,&nbsp;Douglas E. Prah,&nbsp;M. Saiful Huq,&nbsp;Heng Li","doi":"10.1002/mp.70659","DOIUrl":"https://doi.org/10.1002/mp.70659","url":null,"abstract":"<p>This Task Group (TG) report provides updated guidance from American Association of Physicists in Medicine TG 66, published in 2003, on quality assurance (QA) of computed tomography (CT) simulators used for radiation therapy (RT) treatment planning. In addition to updates and expansions of the original recommendations, this report provides recommendations for QA on various techniques that are now commonly used in radiation oncology but were not covered by TG 66, including respiratory-correlated four-dimensional CT (4D-CT), extended Hounsfield Unit scales, metal-artifact reduction, extended field-of-view, and multi-energy CT. The report provides recommendations for the scanning of material-density calibration phantoms and for the maintenance and management of CT scan protocols. A risk-based analysis of the CT simulation process is presented, using an example of the 4D-CT process for lung stereotactic body RT simulation. A comprehensive summary of recommendations from both the original and the updated report is included for reference in the appendix.</p>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 10","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/mp.70659","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148974869","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":"Context-informed personalized segmentation from radiology reports: A fully automated framework for long-term liver tumor follow-up","authors":"Jaehee Chun,&nbsp;McKell Woodland,&nbsp;Austin Castelo,&nbsp;Caleb O'Connor,&nbsp;Mais Altaie,&nbsp;Aashish Gupta,&nbsp;Shanli Ding,&nbsp;Allyson Nguyen,&nbsp;Eugene J Koay,&nbsp;Kristy K Brock","doi":"10.1002/mp.70624","DOIUrl":"10.1002/mp.70624","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Purpose&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Personalized segmentation has been shown to improve performance over generalized models in follow-up imaging; however, its robustness across large temporal gaps remains unclear. We propose a fully automated, context-informed personalization framework that integrates radiology report-derived clinical context with imaging features to improve longitudinal liver tumor segmentation.&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;This retrospective study included 171 patients for generalized model training and 41 longitudinal patients with follow-up CT scans acquired 3–15 months after baseline for personalization and evaluation. We developed a U-Net-based vision-language segmentation framework that automatically summarizes free-text radiology reports, encodes them into language embeddings, and integrates them into intermediate image features to provide clinical context. A generalized model was trained using paired CT-report data. For each longitudinal patient, personalization was performed at the 3-month follow-up using either image-only input (vision-only personalization) or paired image–report input (context-informed personalization). Models were then evaluated on subsequent 6–15-month follow-up scans without further adaptation. Patients were stratified into Stable and Dynamic cohorts based on relative GTV volume variability. Performance was assessed using the Dice similarity coefficient (DSC) and LogPenalty Score (LPS), with additional ablation studies examining language models and report components.&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;In the Dynamic cohort, vision-only personalization exhibited diminishing gains at later follow-up, whereas context-informed personalization maintained statistically significant improvements in ΔLPS at 9–15 months (&lt;i&gt;p&lt;/i&gt; &lt; 0.05). In the Stable cohort, both personalization strategies showed sustained performance with comparable segmentation accuracy, indicating that incorporating report-derived clinical context did not degrade performance in cases with limited anatomical variability. Ablation studies demonstrated that domain-specific encoder-based language models (BioClinicalBERT) outperformed larger generative models and that effective context integration did not require complex architectural modifications.&lt;/p&gt;\u0000 &lt;/section&gt;\u0000 \u0000 &lt;section&gt;\u0000 \u0000 &lt;h3&gt; Conclusion&lt;/h3&gt;\u0000 \u0000 &lt;p&gt;Incorporating report-derived clinical context improves the longitudinal robustness of personalized liver tumor segmentation, particularly in patients with dynamic tumor evolution. These findings suggest that clinically","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13578125/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979036","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":"A correction to the bandwidth difference method for assessment of magnetic resonance static field homogeneity","authors":"Joseph Wishart,&nbsp;Christina L. Brunnquell,&nbsp;Daniel Vergara,&nbsp;Jason Ostenson","doi":"10.1002/mp.70673","DOIUrl":"10.1002/mp.70673","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;Published guidance offers four methods of static field inhomogeneity &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Δ&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$( {Delta {{B}_0}} )$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; measurement, including a bandwidth difference method. However, an error exists in the implementation of this method, which we demonstrate analytically and experimentally.&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 propose and validate a correction to the bandwidth difference method for quantifying &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Δ&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$Delta {{B}_0}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;.&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 outline a correction in the method for quantifying local &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;Δ&lt;/mi&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;B&lt;/mi&gt;\u0000 &lt;mn&gt;0&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$Delta {{B}_0}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; by measuring spatial translations rather than diameter measurements between MRI images with different receive bandwidths. To validate the approach, we acquired images of a cylindrical phantom containing a fixed array of fluid-filled pins. We adjusted static field shims to create approximately linear and quadratic field perturbations and acquired high- and low-bandwidth spoiled gradient echo sequences with anterior-posterior (AP) and left-right (LR) frequency-encoding. We then measured translations of centroid pin locations between low- and high-bandwidth images. Finally, we propose and validate an implementation strategy using a spherical phantom. In both cases, a vendor-provided field mapping sequence provided reference homogeneity measurements.&lt;/p&gt;\u0000 ","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13578124/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979060","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":"Contour-regulated registration framework for Liver CT perfusion images","authors":"Zhan Xu,&nbsp;Yao Zhao,&nbsp;Xinru Chen,&nbsp;Jinyong Lin,&nbsp;Roya Barati,&nbsp;Chaan S. Ng,&nbsp;Jinzhong Yang","doi":"10.1002/mp.70676","DOIUrl":"10.1002/mp.70676","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;Liver computed tomography perfusion (CTp) imaging enables quantitative assessment of vascular dynamics but is highly susceptible to motion-induced artifacts arising from breath-hold variability and involuntary patient motion. These effects cause different portions of the liver to fall within the imaging field of view across time frames and introduce in-plane deformation, creating substantial challenges for image registration. Misregistration between distinct regions of interest disrupts temporal signal consistency and perfusion estimation, underscoring the need for robust registration strategies tailored for Liver CTp.&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 develop and evaluate a contour-regulated automated registration framework for correcting motion artifacts and aligning time-resolved images in Liver CTp series.&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;Forty-six CTp datasets from 23 patients were analyzed; each dataset consisted of a pre-contrast static scan, a post-contrast high temporal resolution cine scan (59–79 time frames), and a post-contrast low temporal resolution helical scan (8–10 time frames). A 2D liver auto-segmentation nnU-Net model was trained on 23 whole liver contours that had been manually delineated on pre-contrast static images and applied to all 46 cine and helical series. The auto-segmented contours were used to regulate a two-stage registration pipeline consisting of affine registration followed by TransMorph-based deformable registration. The models with different parameters were trained by using intensity-corrected images on 36 randomly selected cases and tested on the remaining 10 cases. Performance of multiple registration model variants were evaluated against the unregistered series by using mean surface distance (MSD) and 95th percentile Hausdorff distance (HD95) on simplified 3D surfaces reconstructed from manually placed anchor points.&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;Liver auto-segmentation achieved mean Dice similarity coefficients of 0.92 for helical scans and 0.89 for cine scans. Structure alignment was improved significantly compared with raw data after registration. The best-performing model had an auto-determined contour regularization weighting factor (&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mrow&gt;\u0000 ","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13578123/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979089","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":"Quantitative SPECT imaging of 225Ac and its daughters in mice in vivo","authors":"Shixian Du,&nbsp;Kondapa Naidu Bobba,&nbsp;Robin Peter,&nbsp;Grant T. Gullberg,&nbsp;Robert R. Flavell,&nbsp;Javier Caravaca,&nbsp;Youngho Seo","doi":"10.1002/mp.70674","DOIUrl":"10.1002/mp.70674","url":null,"abstract":"<div>\u0000 \u0000 \u0000 <section>\u0000 \u0000 <h3> Background</h3>\u0000 \u0000 <p>Targeted alpha therapy (TAT) using actinium-225 (²²⁵Ac) holds great promise for cancer treatment, and to advance ²²⁵Ac therapy it is required to develop accurate dosimetry method. ²²⁵Ac daughters, especially ²¹³Bi, may redistribute and cause renal toxicity. Currently, direct imaging of ²²⁵Ac-emitted photons at low injected activity levels remains a technical challenge for image-based ²²⁵Ac dosimetry.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Purpose</h3>\u0000 \u0000 <p>This study aims to assess the feasibility and accuracy of quantitative in vivo SPECT/CT imaging for ²²⁵Ac and its decay daughters at activity levels similar to those in small animal studies.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Methods</h3>\u0000 \u0000 <p>A state-of-the-art commercial preclinical SPECT/CT scanner was used to image healthy nude mice in vivo and ex vivo after injection of unlabeled ²²⁵Ac from the United States Department of Energy isotope program, at activities below 48.8 kBq. Each in-vivo imaging was 1.5 h and ex-vivo imaging was 12 h, at approximately 2 h after injection of ²²⁵Ac, and all SPECT images were reconstructed at multi-energy windows (82, 218, and 440 keV). Mouse-like phantom imaging for 1 h at 0.078 MBq and 12 h at 0.496 MBq were also performed to validate quantitative accuracy.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Results</h3>\u0000 \u0000 <p>In vivo SPECT/CT images clearly showed abundant liver uptake, and significant kidney uptake was also observed in 440 keV images for ²¹³Bi, consistent with known renal toxicity from daughter redistribution. However, quantitative analysis of in vivo, ex vivo, and low-activity phantom images revealed suboptimal quantitative accuracy, with high background recovery coefficients and variations in measured activity across the energy windows.</p>\u0000 </section>\u0000 \u0000 <section>\u0000 \u0000 <h3> Conclusions</h3>\u0000 \u0000 <p>We demonstrated the ability to image ²²⁵Ac and its daughters in vivo at low activity levels. However, the quantitative results confirmed that, even with the state-of-the-art preclinical SPECT/CT system, current methods and reconstruction algorithms may not provide sufficient accuracy for accurate dosimetry at typical activity used in small animal studies.</p>\u0000 </section>\u0000 </div>","PeriodicalId":18384,"journal":{"name":"Medical physics","volume":"53 9","pages":""},"PeriodicalIF":3.2,"publicationDate":"2026-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13575294/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148972800","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}