Physics in medicine and biology最新文献

{"title":"Structure-guided prior-driven implicit neural representations for time-of-flight PET image reconstruction.","authors":"Yulin Zhang, Yuxuan Long, Hong Wang, Fan Rao, Hailiang Huang, Yefeng Zheng, Huafeng Liu, Wentao Zhu","doi":"10.1088/1361-6560/aea398","DOIUrl":"10.1088/1361-6560/aea398","url":null,"abstract":"<p><p><i>Objective.</i>Positron emission tomography (PET) reconstruction is an ill-posed inverse problem, particularly under low-count conditions where noise severely degrades image quality and quantitative accuracy. Although supervised learning approaches have demonstrated strong denoising capability, their performance often depends on large paired datasets and may suffer from limited generalization. This work aims to develop an unsupervised reconstruction framework for time-of-flight PET (TOF-PET) that improves image quality while maintaining quantitative reliability.<i>Approach.</i>We propose a TOF-PET reconstruction method based on implicit neural representations (INR). A differentiable forward projection model is incorporated to explicitly model TOF-PET imaging physics and enable reconstruction directly in the INR domain. To suppress noise and promote spatial smoothness, a ray-based total variation regularization is introduced. The reconstruction network combines a multi-resolution hash encoder with a prior-image encoder that injects structural image priors into the INR representation.<i>Main results.</i>The proposed framework was evaluated using simulated brain and whole-body datasets as well as clinical TOF-PET scans. Results show improved noise suppression and contrast recovery compared with conventional iterative reconstruction algorithms and representative unsupervised approaches.<i>Significance.</i>The proposed approach integrates INRs with physics-consistent modeling and prior-guided regularization, providing an effective unsupervised framework for TOF-PET reconstruction and highlighting the potential of neural field representations for tomographic imaging.</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":"148906937","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":"Study of a novel inverted collimator concept for prompt-gamma-based range verification in proton therapy using a hybrid simulation approach.","authors":"K Urban, G Borghi, M Carminati, A Forgione, M Piroddi, C Riboldi, L Santini, E S Bellotti, D Bortot, D Mazzucconi, M Pullia, C Fiorini","doi":"10.1088/1361-6560/aea7f1","DOIUrl":"10.1088/1361-6560/aea7f1","url":null,"abstract":"<p><p><i>Objective.</i>Prompt-gamma imaging is a promising technique for in-situ range verification during proton therapy, with the potential to reduce range uncertainties. Current prompt-gamma cameras typically rely on mechanical collimators, among which the knife-edge slit (KES) and multi-parallel slit (MPS) collimators are the two most widely studied concepts. In this work, we propose a novel inverted (INV) collimator concept that uses a single bar of high-density material to cast a gamma-ray shadow onto the central region of a pixelated scintillation detector. In addition to advantageous properties such as a high efficiency and a large field of view, the INV collimator also features a significantly reduced weight compared to the KES and MPS collimators.<i>Approach.</i>We optimized and compared the different collimator designs with respect to their simulated statistical range retrieval precision. To overcome the computational time limitations associated with full Monte Carlo (MC) simulations, we developed a new hybrid simulation tool based on a dedicated fixed-ray calculation of the collimator combined with precalculated MC simulations of prompt-gamma emission and detection. This approach enables rapid parameter optimization while incorporating all experimentally relevant effects, such as the detector spectral response and an empirical neutron background.<i>Main results.</i>We present optimized collimator geometries for the MPS, KES, and the novel INV collimator. The INV collimator achieves a statistical range retrieval precision (2) of 2.2 mm at a proton beam energy of 100 MeV and 2.4 mm at 150 MeV forprotons irradiating a homogeneous tissue-equivalent phantom, demonstrating performance comparable to the optimized KES design. In addition, we present a first experimental validation of the INV collimator concept at the CNAO hadron therapy facility in Pavia, Italy, demonstrating agreement between the hybrid simulation and measurements.<i>Significance.</i>These results suggest that the INV collimator is a promising concept for future prompt-gamma cameras, offering competitive performance and facilitating clinical implementation due to its reduced device weight.</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":"148977581","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":"Toward quantitative reconstruction of delivered dose in a 3D digital water phantom for electron FLASH-RT via annular-array electron-induced acoustic imaging.","authors":"Xulin Hu, Hongyu Liu, Yaozu Wang, Qin Yang, Deqi Cheng, Yi Zhang, Xiaoqin Nie, Junling Wang, Liuyuan Zhou, Dai Wu","doi":"10.1088/1361-6560/aeabec","DOIUrl":"10.1088/1361-6560/aeabec","url":null,"abstract":"<p><p><i>Objective</i>. Electron FLASH radiotherapy (FLASH-RT) represents a disruptive radiotherapy modality. It enables high-dose radiation to tumor lesions over an extremely short duration, ensuring therapeutic efficacy while markedly mitigating damage to normal tissues. However, the accurate dosimetry of FLASH-RT is severely challenged under ultra-high-dose-rate (UHDR) and ultra-short-pulse conditions, where conventional ionization chambers suffer from dose saturation and spatial-averaging artifacts that fundamentally undermine their ability to resolve the delivered volumetric dose distribution. This study aims to evaluate the feasibility of quantitatively reconstructing dose distributions in electron-based FLASH-RT from multi-angle electron-induced acoustic (EA) signals in a three-dimensional (3D) digital water phantom, systematically assessing the effects of transducer configuration, the efficacy of deconvolution for signal restoration, and the depth dependence of reconstruction accuracy.<i>Approach.</i>We propose and validate an electron-induced acoustic imaging (EAI) reconstruction framework that synergistically integrates adaptive denoising preprocessing (via bandpass filtering and Savitzky-Golay smoothing), Wiener deconvolution for signal restoration, and time-reversal imaging for spatial mapping, to enable quantitative characterization of the delivered dose in electron-based FLASH-RT. An annular array transducer is employed to acquire time-variant acoustic matrix signals induced by UHDR pulsed electron-beam irradiation in a 3D digital water phantom; these signals serve as the input data for reconstructing the dose distribution and profiles. Comparative simulations are conducted to evaluate the influence of array transducer parameters on dose reconstruction performance, accounting for the transducer's frequency response and the dosimetry system's independent response characteristics.<i>Main results.</i>The results demonstrate that, for acoustic array signals acquired by a 128-element annular array transducer, the gamma passing rate of the dose distribution reconstructed by the proposed method was above 95% under the 5%/5 mm and 3%/3 mm criteria, and remained above 89% even under the most stringent 3%/2 mm criterion. Also, the central-profile dose curve was in good agreement with the reference dose curve, with an average dose difference of less than 6.35%.<i>Significance.</i>The results demonstrate the potential of this EAI-based dosimetry method for quantitative dose assessment and beam parameter characterization in electron-based FLASH-RT.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149031181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A deep learning framework for radiotherapy dose prediction: from MLC motion to patient-specific dose perturbation.","authors":"Liyuan Chen, Hairui Yang, Peng Jin, Dong Yang, Huanli Luo, Liang Tan, Bin Feng, Xin Yang, Zhaoyang Feng, Rui Xu, Zhihui Wang, Fu Jin","doi":"10.1088/1361-6560/ae95d3","DOIUrl":"10.1088/1361-6560/ae95d3","url":null,"abstract":"<p><p><i>Objective.</i>The precision of modern radiotherapy hinges on the dynamic sculpting of dose by multi leaf collimators (MLCs). This study introduces a physics informed, interpretable framework that models MLC related delivery uncertainties and predicts their dosimetric impact, shifting patient-specific quality assurance (PSQA) from passive verification to proactive intervention.<i>Approach.</i>We analyzed trajectory log files from 1954 volumetric modulated arc therapy (VMAT) plans deliveries across two widely used MLC designs (Varian Clinac IX and Edge). Control point level MLC and gantry deviations were modeled using motion metrics (leaf speed, speed variation) and a novel temporal latency parameter (Δ<i>t</i>_MLC) to capture system inherent uncertainties. These deviations were projected into the patient's 3D anatomy to create an MLC position deviation texture (MPDT) to capture the spatial information of the deviation caused by MLC. MPDT and planning dose served as input to a dual pathway U-Net for predicting deliverable 3D dose distributions. The model was technically trained and tested on 1250 IX/200 edge plans and clinically tested on an independent cohort of 428 IX/76 edge cases under uncertainty aware conditions by structural similarity index measure (SSIM), percentage mean absolute error (PMAE) and deviation of gamma passing rate (GPR).<i>Main results.</i>MLC deviation patterns were design specific and exhibited consistent linear or quadratic relationships (average<i>R</i>²=  0.989). The MPDT enhanced framework achieved superior dose prediction accuracy (SSIM =  0.996, PMAE =  0.39%) compared to conventional planning dose only models (SSIM =  0.932, PMAE =  2.13%), along with improved GPR consistency (|ΔGPR| =  2.40% vs. 3.92%). In clinical testing, this performance advantage persisted.<i>Significance.</i>By integrating interpretable mechanical modeling with deep learning, this work establishes a scalable paradigm for PSQA in the era of precision oncology-one that traces dose deviations to their physical origins, quantifies delivery uncertainty, and enables proactive intervention.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148679542","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":"GeoCM-Pose: geometry-aware monocular dental 2D/3D registration benchmarked against reference-assisted methods.","authors":"Zhixian Qiu, Jingang Jiang, Jie Pan, Xinrui Cheng, Qunsong Qiu, Jiawei Zhang, Jingchao Wang, Guang Yu","doi":"10.1088/1361-6560/aeaa9e","DOIUrl":"10.1088/1361-6560/aeaa9e","url":null,"abstract":"<p><p><i>Objective.</i>To develop GeoCM-Pose, a geometry-aware monocular dental 2D/3D registration method that predicts metric model-to-camera 6DoF pose from one image under weak texture, repetitive anatomy and partial visibility.<i>Approach.</i>GeoCM-Pose comprises cross-modal adaptation (CMA) and geometry-aware pose regression (GAPR). CMA uses fixed-Gaussian frequency separation and a high-frequency structure-preservation module with multi-scale edge extraction, spatial-channel gating and cross-resolution refinement. GAPR uses a ResNet-50/U-Net to predict dense object-coordinate maps; hierarchical geometric feature aggregation and geometry-aware channel refinement feed decoupled unit-quaternion and translation heads. Joint 20-point pose-matching and dense-coordinate losses train the network. The study comprised 30<i>in vitro</i>training cases, five<i>in vivo</i>validation cases, five<i>in vivo</i>internal-test cases, 10 fully held-out Teeth3DS+ dental surface models and a 200-frame benchmark generated from a single three-dimensional dental model.<i>Main Results.</i>GAPR/V0 generated pose estimates for all 200 query frames, with median reprojection, rotation and translation-vector errors of 2.156 px, 1.252° and 0.653 mm, respectively, and a <5 px pass rate of 91.5% across all attempts. It used no inference-time reference-image bank. At R01, scale-invariant feature transform and ORB generated 85/200 and 89/200 valid estimates, with <5 px all-attempt pass rates of 40.5% and 40.0%; at R20, each generated 197/200 valid estimates, with pass rates of 98.0% and 95.5%. Thus, conventional performance increased with the available reference bank, whereas GAPR/V0 provided complete query coverage from a single image without inference-time reference images. Median GAPR/V0 inference latency, including image I/O, was 11.459 ms.<i>Significance.</i>GeoCM-Pose integrates CMA, dense object-coordinate supervision and metric pose regression for monocular dental 2D/3D registration. Further case-level evaluation using intraoral endoscopic images acquired from independent patient cases and additional image domains, together with robot-integrated experiments, is required to assess generalisation and system-level performance.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149017802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A generalized phenomenological model of oxygen depletion for FLASH particle radiotherapy: evidence from<i>in vitro</i>data.","authors":"Kailin Fu, Jun Ken Gan, Masashi Yagi, Clifford Ghee Ann Chua, Kang Hao Lee, Kah Seng Lew, Calvin Wei Yang Koh, Kazumasa Minami, Ping Lin Yeap, Andrew Wibawa, Zubin Master, Wen Siang Lew, James Cheow Lei Lee, Shinichi Shimizu, Sung Yong Park, Hong Qi Tan","doi":"10.1088/1361-6560/aeb05e","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb05e","url":null,"abstract":"<p><strong>Objective: </strong>Ultra-high dose rate (uHDR: FLASH) radiotherapy reduces normal tissue toxicity while preserving tumour control. The oxygen depletion hypothesis posits that rapid oxygen consumption during FLASH irradiation transiently reduces radiosensitivity. However, experimental measurements suggest oxygen depletion may be limited, particularly under normoxia. This study quantitatively assesses the adequacy of this hypothesis in reproducing experimentally observed sparing effects by comparing mechanistic simulations with in vitro cell survival data across a wide range of irradiation conditions.&#xD;Approach. We developed a phenomenological framework for radiolytic oxygen depletion incorporating temporal dose delivery, dose rate, and linear energy transfer (LET). LET dependence was included through oxygen consumption efficiency and the maximum oxygen enhancement ratio. For direct comparison, simulation results were linked to clonogenic cell survival using a damage reduction factor (DRF) derived from the linear-quadratic model. Simulated DRFs were compared with experimental DRFs from six independent in vitro studies involving electrons, protons, helium ions, and carbon ions over broad ranges of LET, oxygenation, and dose rates using parity plots, residual analyses, stratified weighted statistics, and correlation analyses.&#xD;Main results. Under most irradiation conditions, simulated DRFs remained close to unity (minimum values approximately 0.96), indicating limited predicted protection from oxygen depletion. Conversely, experimental DRFs exhibited substantially larger deviations. Stratified analyses revealed systematic discrepancies between simulated and experimental DRFs across oxygenation, LET, and dose rate, with pronounced disagreement under normoxia, high LET, and ultra-high dose rates. Residual analyses demonstrated underestimation of the sparing effect by the model. Correlation analyses showed statistically insignificant associations between simulated and experimental metrics.&#xD;Significance. The oxygen depletion model considered in this work insufficiently reproduces the observed sparing effect under the in vitro conditions considered. Additional biological and physicochemical mechanisms likely play a significant role. This framework provides a quantitative basis for evaluating alternative mechanisms and integrating future experimental data toward a more complete understanding of FLASH radiotherapy.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149113690","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":"Introduce 4π dynamic spot-scanning proton arc therapy (SPArc-4π) for pancreatic cancer: a comparative planning study with IMPT.","authors":"Peng Chen, Peilin Liu, Xiaoda Cong, Yan Gao, Xian-Shu Gao, Xuanfeng Ding","doi":"10.1088/1361-6560/aeb05f","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb05f","url":null,"abstract":"<p><strong>Objective: </strong>Stereotactic body radiotherapy with a simultaneous integrated boost (SBRT-SIB) for locally advanced pancreatic cancer (LAPC) is constrained by the proximity of serial gastrointestinal organs at risk (OARs). Conventional intensity-modulated proton therapy (IMPT) relies on a limited number of fixed beam angles, which may restrict dose shaping around these critical structures. This study evaluated whether non-coplanar spot-scanning proton arc therapy (SPArc-4π) could improve OAR sparing while preserving robust target coverage.</p><p><strong>Approach: </strong>10 patients with LAPC were retrospectively selected in this study. For each patient, SBRT-SIB plans were generated using conventional IMPT and SPArc-4π. Plan robustness was assessed across 21 uncertainty scenarios. Target coverage, conformity, OAR doses, estimated delivery time, and Lyman-Kutcher-Burman normal tissue complication probability (NTCP) for four gastrointestinal endpoints were compared using the Wilcoxon signed-rank test.</p><p><strong>Main results: </strong>SPArc-4π maintained target coverage comparable to IMPT, with similar clinical target volume (CTV) and boost-volume coverage, while CTV conformity improved with SPArc-4π (conformity index: 0.50 vs. 0.56; p = 0.02). SPArc-4π significantly reduced maximum dose (Gy(RBE)) to the stomach (30.01 to 24.53), duodenum (35.14 to 33.14), bowel (32.60 to 28.91), and spinal cord (15.38 to 5.58; all p ≤ 0.01). Predicted toxicity decreased across all four gastrointestinal endpoints: gastric bleed risk decreased from 8.19% to 6.15%, grade ≥3 gastrointestinal toxicity from 3.91% to 3.81%, ulceration/perforation from 0.03% to 0.01%, and diarrhea from 24.14% to 22.34% (all p ≤ 0.005). All plans met robustness criteria. The main trade-off was delivery efficiency, with SPArc-4π requiring approximately 2-3 minutes longer delivery time than IMPT.</p><p><strong>Significance: </strong>SPArc-4π provides a promising proton planning strategy for pancreatic SBRT-SIB by preserving robust target coverage while improving gastrointestinal organ sparing and reducing predicted toxicity. These findings support further investigation of SPArc-4π for safer dose escalation in LAPC.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149113803","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":"Biodistribution and dosimetry of free¹¹⁸Te, an<i>in vivo</i>generator of the positron emitter¹¹⁸Sb for long-term positron emission tomography.","authors":"Jaewoong Jang, Sotaro Miyao, Xindi Qiu, Toson Hamza, Yousuke Kanayama, Atsuko Nakanishi Ozeki, Yuki Mitsuya, Masako Kawabata, Izumi O Umeda, Toshimitsu Momose, Youichiro Wada, Hiromitsu Haba, Hiroyuki Takahashi, Nobuyoshi Akimitsu","doi":"10.1088/1361-6560/aeb089","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb089","url":null,"abstract":"<p><p><i>Objective</i>. Tellurium-118 (¹¹⁸Te;<i>t</i>_1/2= 6.00 ± 0.02 d) can act as an<i>in vivo</i>generator of the positron emitter antimony-118 (¹¹⁸Sb;<i>t</i>_1/2= 3.6 ± 0.3 min), enabling positron emission tomography (PET) over a week or longer. This work assessed absorbed doses associated with free¹¹⁸Te to establish a dosimetric safety basis for¹¹⁸Te radiopharmaceuticals.<i>Approach</i>. Injection solutions of free¹¹⁸Te were prepared by alpha-particle irradiation of an enriched tin-116 target followed by radiochemical isolation.<i>Ex vivo</i>biodistribution in healthy female Slc:ICR mice was acquired at seven time points from 2 h to 29 d postinjection (<i>n</i>= 6 per time point). Time-integrated activity coefficients were computed from the biodistribution profiles and extrapolated to a human model using relative mass scaling. Absorbed dose coefficients (ADCs) were calculated following the Medical Internal Radiation Dose formalism with computational phantoms implemented in the dosimetry software OLINDA. Dosimetric contributions from¹¹⁸Te and its coproduced radioisotopic impurity^119mTe (<i>t</i>_1/2= 4.69 ± 0.04 d), along with their equilibrium daughters¹¹⁸Sb and¹¹⁹Sb, were individually assessed.<i>Main results</i>. The kidneys exhibited the highest ADC in both mouse (2666.0 mGy MBq^-1) and human (2.639 mGy MBq^-1) models. Bone received the second-highest ADC in the mouse model, 1855.5 mGy MBq^-1. Antimony-118 dominated absorbed doses across all organs examined, accounting for more than 82% of ADCs in both models. Contributions from¹¹⁸Te,^119mTe, and¹¹⁹Sb were minor by comparison.<i>Significance</i>. The kidneys and bone were identified as the primary dosimetric targets of free¹¹⁸Te, with its daughter¹¹⁸Sb being the principal dose contributor. The limited dosimetric impact from¹¹⁸Te provides justification for its use as an<i>in vivo</i>generator of¹¹⁸Sb for long-term PET. The ADCs reported here offer a quantitative basis for assessing the dosimetric safety of¹¹⁸Te radiopharmaceuticals.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149113705","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":"AnF-DiffPET: anatomy- and frequency-guided diffusion for simulated low-dose PET/CT denoising.","authors":"Xuepeng Liu, Ruili Li, Zetong Liu, Renyiming Li, Yan Li, Yin Dai, Chao Li, Yueyang Teng","doi":"10.1088/1361-6560/aeb061","DOIUrl":"https://doi.org/10.1088/1361-6560/aeb061","url":null,"abstract":"<p><strong>Objective: </strong>Positron emission tomography (PET) provides essential functional information for disease assessment. However, reducing injected activity or acquisition time produces low-dose (LD) PET with stronger count-dependent noise and less reliable uptake quantification. Diffusion models offer a promising solution for PET denoising by progressively recovering high-dose (HD) PET images from LD inputs. However, LD-to-HD PET denoising remains challenging because of limited anatomical guidance, unstable multi-scale feature propagation, and inaccurate recovery of uptake patterns in the frequency domain.&#xD;&#xD;Approach: We propose AnF-DiffPET, an anatomy- and frequency-guided diffusion framework for computed tomography (CT)-conditioned LD PET denoising. The framework integrates Anatomical-Frequency Guidance (AFG), Multi-Scale Cross-Transformer Reconstruction (MSCTR), and Frequency-Contrastive Hard Mining (FCHM) to enhance anatomy-aware feature modulation and frequency-domain consistency during denoising.&#xD;&#xD;Main results: Experimental results across four simulated low-dose PET/CT datasets show that the proposed method improves image fidelity, anatomical consistency, and quantitative fidelity over representative CNN-based, GAN-based, Transformer-based, Mamba-based, and diffusion-based methods.&#xD;Significance: AnF-DiffPET provides a PET/CT-specific diffusion restoration framework that combines anatomical guidance, multi-scale feature reconstruction, and frequency-domain regularization for LD PET denoising. The code and trained models will be publicly released upon acceptance.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149113710","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":"Humidity effects in GafChromic^TMEBT4 films for postal audits: characterization, reversibility and exploration of correction methods.","authors":"Leon Armand de Prez","doi":"10.1088/1361-6560/aeafa7","DOIUrl":"https://doi.org/10.1088/1361-6560/aeafa7","url":null,"abstract":"<p><strong>Objective: </strong>No harmonized methodology exists that enables traceable reference dosimetry with EBT4-film. The influence of humidity on EBT4 films is often overlooked and currently under-documented. This study quantified humidity effects for postal-audit reference dosimetry and explored the feasibility of empirical correction methods.&#xD;Approach. EBT4 films mounted in slide-frames were stored in humidity-controlled environments between 0 %RH and 100 %RH and scanned using a slide-scanner. Optical density (OD) was evaluated as a function of dose and humidity. Humidity darkening, changes in dose response and post irradiation growth were quantified. A humidity response factor, HOD, was introduced to describe the humidity dependent changes in dose-response. Two film intrinsic proxies were evaluated as possible proxies for the film humidity state.&#xD;Main results. Humidity was shown to affect OD and the humidity response factor, HOD. If not accounted for, this can lead to significant dosimetric errors. Between 12 %RH and 68 %RH, HOD exhibited linear behaviour as did the two film intrinsic proxies. Both humidity darkening and HOD showed to be reversible within the experimental uncertainty after re-acclimatization at 56 %RH. Exposure to 0 %RH and 100 %RH resulted in behaviour outside the practical operating range. The use of 0-Gy control films substantially reduced humidity-dependent offsets. The film-intrinsic humidity proxies showed relationships with HOD within the present single-sheet experiment, but their practical use requires further validation across film-lots and scanners.&#xD;Significance. This study demonstrates that humidity is a relevant influence quantity for EBT4-based reference dosimetry and should be controlled during film transport and storage. For the VSL postal audit service, humidity is regulated using BOVEDA-49 packages and monitored during transport as a practical mitigation strategy. The proposed correction formalism provides a method to investigate humidity-response behaviour for a specific film-sheet and scanner combination but does not yet constitute a generally validated correction method.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.1,"publicationDate":"2026-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149113768","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}