Physics in medicine and biology最新文献

{"title":"Influence of a long air gap and a ratio 15:1 antiscatter grid on pediatric fluoroscopy and angiography image quality.","authors":"Kenneth A Fetterly","doi":"10.1088/1361-6560/aeb220","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb220","url":null,"abstract":"<p><p>Objective&#xD;X-ray angiography and fluoroscopy systems are used to diagnose and treat congenital heart disease in pediatric patients. Among the substantial variabilities in this clinical patient population is that patient weight ranges from <1 kg premature infants to large adolescents. The primary aim of this work was to assess whether an air gap or antiscatter grid is more efficient to mitigate the detrimental influence of scatter radiation on pediatric image quality.&#xD;Approach&#xD;The experimental approach was guided by a 2 year review of pediatric patient imaging conditions. Uniform density water-equivalent phantoms with thickness in the range 6-24 cm were used. For each phantom thickness, the X-ray technique was manually set to mimic the technique selected by automatic dose rate control. The influence of four combinations of air gap and ratio 15:1 antiscatter grid on test object SNR was measured. The air gap was varied by changing the X-ray source to detector distance from 107 to 120 cm. The analytical methods estimated pixel-specific snr2 contributions to object SNR2, thus providing for the use of iodine disks and pediatric implantable devices as test objects.&#xD;Main results&#xD;Patient weight ranged from 0.5 to 134 kg. The relationship between patient water equivalent thickness and weight was demonstrated. For all phantom thicknesses, object SNR was highest using a long air gap, non-grid technique. Decreasing the air gap between the phantom and detector and use of the anti-scatter grid both degraded SNR. These major findings were consistent between iodine disks and clinical devices as test objects.&#xD;Significance&#xD;The findings of this phantom study suggest that a long air gap, non-grid imaging technique may improve radiation dose efficiency of fluoroscopy and angiography imaging across a broad range of pediatric patient sizes.&#xD.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Learned proximal gradient flow matching for limited-angle CT reconstruction.","authors":"Genwei Ma, Dimeng Xia, Yutong He, Shusen Zhao","doi":"10.1088/1361-6560/aeb221","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb221","url":null,"abstract":"<p><strong>Objective: </strong>The primary objective of this research is to address the challenges of limited-angle computed tomography (CT) reconstruction that arises when projection data are acquired over an angular range smaller than that required for theoretically exact reconstruction. This ill-posed problem leads to severe artifacts compromising diagnostic quality. The study aims to develop a robust and efficient framework to achieve high-fidelity image reconstruction.&#xD;Approach: The proposed method, termed Learned Proximal Gradient Flow Matching (LPGFM), introduces a novel framework that synergistically combines explicit optimization principles with deep generative models. First, a pre-trained flow matching network is applied to transform the initialized solution along a learned gradient field, effectively removing artifacts while preserving anatomical details. Secondly, a proximal correction step enforces strict data consistency, enhancing robustness against deviations. This approach decouples data fidelity from prior application, preventing error propagation and ensuring stability, particularly under out-of-distribution conditions.&#xD;Main Results: The proposed LPGFM method demonstrates significant advantages in limited-angle CT reconstruction. Experiments on the medical and head datasets show that LPGFM outperforms comparative methods. Quantitative evaluations reveal that LPGFM achieves the highest PSNR and SSIM scores with the lowest RMSE. For instance, in the 150° medical data, LPGFM attains a PSNR of 30.14 dB, indicating superior artifact suppression and detail preservation. Under the more challenging 120° condition, LPGFM maintains robustness with minimal quality degradation, highlighting its generalization capability.&#xD;Significance: This work introduces a framework that combines model-based optimization with data-driven generative priors in limited-angle CT reconstruction by bridging the gap between model-based optimization and data-driven generative models. The LPGFM framework offers theoretical advantages, such as interpretability and robustness, while practical benefits include reduced reliance on large training datasets and adaptability to diverse scanning geometries. Its ability to deliver high-quality reconstructions under extreme limited-angle conditions has implications for clinical applications.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Minimally invasive quantification of [¹⁸F]MC225 PET using constrained simultaneous estimation of the input function.","authors":"Laura Providência, Joost F Somsen, Chris W Van Der Weijden, Pascalle Mossel, Giordana Salvi De Souza, Rudi A Dierckx, Gert Luurtsema, Adriaan A Lammertsma, Charalampos Tsoumpas","doi":"10.1088/1361-6560/aeb222","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb222","url":null,"abstract":"<p><strong>Objective: </strong>[¹⁸F]MC225 is a PET radiotracer used to assess P-glycoprotein function at the bloodbrain barrier. [¹⁸F]MC225 PET quantification requires arterial catheterization to obtain the plasma input function, an invasive procedure. The simultaneous estimation of the input function (SIME) has been proposed as a technique for estimating the plasma input function, however, it requires at least one venous/arterial blood sample. Long axial field-of-view (LAFOV) PET scanners enable a variation of the SIME algorithm, the constrained SIME (cSIME), that incorporates information from whole-blood activity, potentially eliminating the need for blood sampling. In this study, we evaluated the feasibility of cSIME for quantifying the [¹⁸F]MC225 in the brain using a clinical dataset.</p><p><strong>Approach: </strong>Dynamic data from seven subjects scanned on a LAFOV PET system following injection of [¹⁸F]MC225 were included. The constrained SIME method was used to estimate the plasma input function of each subject. A whole-blood input function extracted from the ascending aorta was used as the initial estimate, and multiple brain regions were simultaneously fitted to estimate the parameters required to convert the whole-blood input function into a plasma input function. Volume of distribution (<i>V_T</i>) values were calculated using both the ground-truth and cSIME-estimated plasma input functions with a reversible two-tissue compartment model.</p><p><strong>Main results: </strong>Without a blood sample,<i>V_T</i>estimates using the cSIME plasma input function resulted in relative differences ranging between approximately -26% and 11% compared to the<i>V_T</i>estimates obtained with the measured plasma input function. Incorporating one blood sample as anchor at 60 minutes decrease these relative differences to 11%.</p><p><strong>Significance: </strong>The findings of this study suggest that cSIME may help reduce the invasiveness of quantitative [¹⁸F]MC225 PET studies. The clinical relevance of the observed bias will ultimately depend on its magnitude relative to disease-related differences in kinetic parameters expected in patient populations.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149138000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Narrowband isotropic magnetic particle imaging with FFL-parallel excitation.","authors":"Zhongwei Bian, Ziwei Chen, Jie He, Hui Hui, Guang Jia, Yu An, Jie Tian","doi":"10.1088/1361-6560/aea399","DOIUrl":"10.1088/1361-6560/aea399","url":null,"abstract":"<p><p><i>Objective.</i>Magnetic particle imaging (MPI) is an emerging medical imaging technique for high-sensitivity and quantitative visualization of tracer distributions. Narrowband MPI achieves high signal-to-noise ratio (SNR) by selectively detecting a few harmonics. However, in its conventional implementations,the point spread function (PSF) inevitably exhibits negative lobes, which introduce anisotropic resolution and destructive signal superposition.<i>Approach.</i>To address this, we propose a narrowband isotropic MPI system, utilizing the field-free-line (FFL)-parallel excitation (FPE) scanning strategy to eliminate negative lobes. FPE-MPI employs single-channel acquisition with coaxial excitation and receive, applies an excitation field parallel to the FFL while maintaining a constant collinear offset field, and encodes harmonic responses on the projection plane orthogonal to the FFL.<i>Main results.</i>Through simulations and phantom experiments on our in-house scanner, we demonstrate that FPE-MPI eliminates the adverse effects of negative lobes, achieves isotropic imaging, and improves image quality. Compared with conventional narrowband MPI with FFL-orthogonal excitation, FPE-MPI preserves higher SNR in the acquired signals and yields robust reconstructions at low tracer concentrations, with only a modest trade-off in spatial resolution.<i>Significance.</i>FPE-MPI facilitates robust imaging at low tracer doses and provides a feasible scanning strategy for the development of future large field-of-view (FOV) narrowband MPI systems.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148906970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-criteria proton treatment planning incorporating spot boosting for prompt gamma in-vivo range verification.","authors":"Mara Schubert, Ze Huang, Marco Pinto, Christian Thieke, Karl-Heinz Küfer, Katrin Teichert, Katia Parodi","doi":"10.1088/1361-6560/aeb223","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb223","url":null,"abstract":"<p><p><i>Objective.</i>Prompt gamma (PG) detection enables beam range verification and margin reduction in proton therapy, but its effectiveness is limited by counting statistics. Spot boosting has been proposed to enhance the signal-to-noise ratio by increasing the number of protons in selected spots of a pencil beam scanning treatment plan. This work integrates PG monitoring into an multi-criteria optimization (MCO) framework to investigate trade-offs between proton counts in boosted spots and dosimetric metrics.<i>Approach.</i>Intensity modulated proton therapy (IMPT) plans for a prostate-tumor and a brain-tumor patient were optimized in OpenTPS. Dose, LET weighted dose (LETxdose) and PG distributions were simulated for each pencil beam using the fast Monte Carlo (MC) engine MCSquare. For each field, ten candidate spots were selected based on three metrics quantifying the quality of PG monitoring and an even spatial distribution across the clinical target volume. Initial pencil beam weights and corresponding dose and LETxdose distributions were imported into an MCO framework for re-optimization, simultaneously considering both dosimetric goals and boosting objectives.<i>Main results.</i>Boosting up to 5 • 10⁸protons/spot maintained the plan quality without violating constraints in the prostate case. In the brain case, spot boosting required moderate deviations from the initial target dose constraints. For both cases, only minor boosting gains were obtained by relaxing dose metrics for organs at risk.<i>Significance.</i>This study is the first to visualize spot boosting trade-offs via Pareto fronts to support an informed decision, integrating verification quality aspects into the treatment planning stage. The approach enables selection of plans that preserve dose and LETxdose objectives while enhancing PG signal in targeted spots for reliable in-vivo range verification. The framework is broadly applicable and can provide a strategy for embedding verification-driven objectives into treatment optimization beyond PG monitoring.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Encoding depth heterogeneity into time: a finite-window power-series thermal response model for non-invasive tissue characterization and early tumor detection.","authors":"Hong Tang, Cong Zhang, Hai Zhang, Andreas Mandelis","doi":"10.1088/1361-6560/aea7f3","DOIUrl":"10.1088/1361-6560/aea7f3","url":null,"abstract":"<p><p><i>Objective.</i>Depth-dependent heterogeneity in perfusion and thermophysical properties remains a major obstacle to accurate non-invasive measurement of tissue thermal parameters. The objective was to develop an analytical photothermal model that encodes such spatial heterogeneity into a time-dependent effective thermal response coefficient (ETRC) for tissue characterization and early tumor detection.<i>Approach.</i>A finite-window ETRC framework was formulated using the scaling relationship between thermal diffusion depth and time. The ETRC was represented directly by a power series in time and truncated after the first-order term for experimental fitting,<i>β</i>(<i>t</i>)≈<i>β</i>₀+<i>β</i>₁<i>t</i>. The fitted ETRC was constrained to remain non-negative throughout each cooling window. An explicit analytical solution was then derived for this constrained finite-window representation through variable substitution.<i>Main results.</i>The proposed model achieved the lowest root-mean-square error in the cooling phase among the tested models. Pixel-wise fitting generated maps of the effective thermal diffusivity<i>α. In vivo, α</i>in the peritumoral vascular region decreased progressively from day 3 after inoculation and differed significantly from the pre-inoculation baseline by day 6 (<i>p</i>< 0.01), approximately 3-4 d before tumors became palpable. The area under the receiver operating characteristic curve reached 0.94 on day 12.<i>Significance.</i>An interpretable and computationally efficient approach is provided for estimating effective depth-weighted thermal diffusivity from surface-temperature decay while accounting for depth-dependent heterogeneity, without requiring pre-assumed tissue layers. The proposed method may support longitudinal non-invasive thermal imaging, early tumor detection and functional monitoring of tumor development.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148977499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Motion-guided channel resampling for grating lobe suppression in plane-wave imaging.","authors":"Doyoung Jang, Seongwoo Koo, Heechul Yoon","doi":"10.1088/1361-6560/aeb224","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb224","url":null,"abstract":"<p><strong>Objective: </strong>Plane-wave imaging (PWI) remains susceptible to grating lobe artifacts when arrays with relatively large element pitches are used. This study proposes motion-guided channel resampling for PWI (MCR-PWI) to suppress grating lobes by exploiting inter-frame motion without transducer modification or prescribed probe translation.&#xD;Approach. Two consecutive coherently compounded acquisitions are combined using motion-guided channel resampling. After intra-acquisition phase compensation to reduce angle-dependent phase inconsistencies, lateral and axial inter-frame displacements are estimated from phase-compensated in-phase/quadrature data using normalized cross-correlation. These estimates guide channel-domain resampling and coherent synthesis during beamforming. Theoretical analysis predicts maximum first-grating-lobe suppression near a half-pitch lateral displacement. Performance was evaluated through numerical simulations, phantom experiments, and preliminary freehand thyroid and carotid imaging in one healthy volunteer.&#xD;Main results. At a half-pitch lateral displacement, MCR-PWI reduced simulated mean grating lobe levels by 10.72 to 20.59 dB relative to conventional PWI under lateral-only motion and by 5.98 to 14.17 dB relative to phase-compensated PWI under combined lateral-axial motion. Phantom experiments demonstrated improved cyst contrast while maintaining comparable spatial resolution. Preliminary in-vivo imaging further showed reduced clutter and improved image contrast.&#xD;Significance. MCR-PWI utilizes inter-frame motion to refine effective receive sampling and reduce grating lobe artifacts while preserving spatial resolution. The findings support its preliminary feasibility for freehand PWI. Performance depends on suitable displacement and reliable motion estimation, and further validation under broader motion conditions is required.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149137997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NL-TINR: implicit neural representation based nonlocal functional tensor decomposition for zero-shot 3D multi-contrast MRI reconstruction.","authors":"Jingran Xu, Sen Jia, Yuanbiao Yang, Yongquan Ye, Jiuping Liang, Yuanyuan Liu, Yanjie Zhu","doi":"10.1088/1361-6560/aeabed","DOIUrl":"10.1088/1361-6560/aeabed","url":null,"abstract":"<p><p><i>Objective.</i>3D quantitative magnetic resonance imaging (qMRI) enables noninvasive tissue characterization but often requires prolonged acquisition times for multi-contrast imaging, limiting its broader clinical adoption. Although deep learning has shown promise for accelerated MRI reconstruction, supervised methods rely on large-scale fully sampled 3D datasets that are difficult to obtain. Existing implicit neural representation (INR)-based self-supervised methods avoid this requirement but can exhibit spectral bias, potentially leading to over-smoothed image details.<i>Approach.</i>We propose NL-TINR, a zero-shot self-supervised reconstruction framework that integrates patch-based nonlocal self-similarity (NSS) with INR-based functional tensor decomposition. The NSS prior groups structurally similar image patches into high-dimensional tensors to explicitly exploit nonlocal redundancy and suppress aliasing artifacts while preserving fine anatomical textures. Meanwhile, INRs parameterize the tensor factor functions, providing a compact and flexible representation that captures correlations across spatial and contrast dimensions while reducing the burden of directly modeling the full 3D multi-contrast volume.<i>Main results.</i>Extensive experiments on 3D multi-echo MRI datasets demonstrate that NL-TINR consistently outperforms the compared reconstruction methods, providing improved artifact suppression and anatomical detail preservation, particularly at high acceleration factors.<i>Significance.</i>NL-TINR eliminates the dependence on fully sampled training data while effectively exploiting nonlocal structural redundancy and high-dimensional spatial-contrast correlations, providing a practical zero-shot framework for high-fidelity 3D multi-contrast qMRI reconstruction.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149031233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dosimetric validation of proton beam deflection and field shape deformation in a measured transverse magnetic field of an in-beam MR scanner using a novel dose calculation functionality in a research version of a commercial treatment planning system.","authors":"Marisa Cobanaj, Franciska Lebbink, Sergej Schneider, Louisa Schäfer, Krishna Godino Padre, Stefan Menkel, Jörg Pawelke, Jakob Ödén, Fredrik Tamm, Rasmus Nilsson, Erik Traneus, Christian Richter, Aswin Hoffmann, Felix Horst","doi":"10.1088/1361-6560/aea5d2","DOIUrl":"10.1088/1361-6560/aea5d2","url":null,"abstract":"<p><p><i>Objective.</i>Integrating in-beam magnetic resonance imaging (MRI) with proton therapy (PT) introduces magnetic fields (MFs) that affect proton beam transport and therefore require accurate incorporation into the treatment planning system (TPS) for magnetic resonance (MR)-integrated PT (MRiPT). This study experimentally validates Monte Carlo-based proton dose calculation in the presence of the MF in a research version of the commercial TPS RayStation for MRiPT, using a measured three-dimensional (3D) magnetic vector field map of a 0.32 T in-beam MR scanner combined with a horizontal proton pencil beam scanning beam line.<i>Approach.</i>An MR-compatible mapping framework was used to acquire a high-resolution 3D magnetic vector field map, subsequently implemented into the TPS following coordinate transformations. Proton spot patterns and square radiation fields at 100, 150, and 220 MeV were delivered with and without the MF present. Dose distributions in air were measured using a 2D ionisation chamber array at multiple positions and compared with TPS dose calculations by analysing lateral beam shifts and field shape deformations with local-analysis. Clinically relevant patient treatment fields were evaluated at different water-equivalent depths (WEDs) in a phantom.<i>Main results.</i>Implementation of the measured magnetic vector field map preserved field vector magnitude, orientation and spatial alignment within the TPS. Dose measurements showed energy- and position-dependent MF-induced effects, which were accurately reproduced by the TPS. Agreement in lateral beam shifts was within 1-3 mm, and-pass rates exceeded 97% for a 3%/3 mm local criterion (10% dose threshold). Similar agreement was observed for patient treatment fields throughout all WEDs.<i>Significance.</i>This work validates the TPS capability to accurately model MF-induced proton beam transport in air as well as in a water-equivalent phantom. The present workflow establishes a foundation for proton treatment planning in the presence of MFs and thereby contributes to the clinical implementation of MRiPT.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148930226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hierarchical 4π Monte Carlo-based proton beam angle pre-screening framework: a proof-of-concept.","authors":"Ozgur Ates, Thomas E Merchant, Chia-Ho Hua","doi":"10.1088/1361-6560/aeb16b","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb16b","url":null,"abstract":"<p><strong>Objective: </strong>Current proton beam-angle optimization methods are constrained by limited angular candidate sets and the high computational cost of Monte Carlo (MC)-based dose evaluation, hindering practical implementation of full-sphere (4π) optimization. We propose a 4π beam angle optimization framework that integrates beam's-eye-view (BEV) target projection filtering, water-equivalent path-length (WEPL)-based range assessment, and linear energy transfer (LET) pre-screening to reduce the angular search space prior to full MC simulation.&#xD;&#xD;Approach: The proposed 4π beam angle optimization framework consists of two phases: (1) a fast hierarchical pre-screening stage that uses raytracing to combine target visibility, WEPL, and analytical dose-weighted LET (dLET) evaluation, and (2) MC dose simulation applied to the reduced set of non-coplanar beams. A Geant4-based conceptual toy model with a centrally located soft-tissue target, six organ-at-risk (OAR) structures with varied material compositions arranged along orthogonal axes, and an adjacent toroidal blood OAR was used to evaluate 684 candidate beams generated by uniform full sphere angular sampling using 10° increments in polar (couch) and azimuthal (gantry) angles. A graphical user interface was implemented to visualize candidate beam angles, apply pre-screening thresholds, and transfer the filtered beam set to the MC simulation stage.&#xD;&#xD;Main Results: From the initial 684 candidate beams, 72 met the ≥95% target-visibility criterion following BEV-based OAR filtering. Two-tier WEPL filtering identified en-face beam paths based on target proximity and width (distal minus proximal edge), reducing the set to 52 beams and further refining it to 48 beams through analytical dLET filtering. Pre-screening was completed in <5 min. The subsequent MC simulation, implemented within a standalone in-house optimization algorithm, required 71 min. on a 64-bit, 32 GB RAM, 12-core CPU system and demonstrated feasibility of dose calculation in the conceptual phantom, achieving prescription-level target coverage with target D95% = 54 Gy, D98% = 52.9 Gy, and D2% = 62.7 Gy for Rx = 54 Gy, and toroidal OAR D50% = 40.6 Gy with Dmax = 54.2 Gy.&#xD;&#xD;Significance: A hierarchical 4π proton beam angle optimization framework combining pre-screening with MC-based simulation was shown to be computationally feasible while effectively leveraging non-coplanar beam configurations.&#xD.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149128412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}