Physics in medicine and biology最新文献

{"title":"Role of modeled high-grade glioma cell invasion and survival on the prediction of tumor progression after radiotherapy.","authors":"Wille Häger, Iuliana Toma-Dașu, Mehdi Astaraki, Marta Lazzeroni","doi":"10.1088/1361-6560/adbcf4","DOIUrl":"10.1088/1361-6560/adbcf4","url":null,"abstract":"<p><p><i>Objective.</i>Glioblastoma (GBM) prognosis remains poor despite progress in radiotherapy and imaging techniques. Tumor recurrence has been attributed to the widespread tumor invasion of normal tissue. Since the complete extension of invasion is undetectable on imaging, it is not deliberately treated. To improve the treatment outcome, models have been developed to predict tumor invasion based standard imaging data. This study aimed to investigate whether a tumor invasion model, together with the predicted number of surviving cells after radiotherapy, could predict tumor progression post-treatment.<i>Approach.</i>A tumor invasion model was applied to 56 cases of GBMs treated with radiotherapy. The invasion was quantified as the volume encompassed by the 100 cells mm^-3isocontour (<i>V</i>₁₀₀). A new metric, cell-volume-product, was defined as the product of the volume with cell density greater than a threshold value (in cells mm^-3), and the number of surviving cells within that volume, post-treatment. Tumor progression was assessed at 20 ± 10 d and 90 ± 20 d after treatment. Correlations between the disease progression and the gross tumor volume (GTV),<i>V</i>₁₀₀, and cell-volume-product, were determined using receiver operating characteristic curves.<i>Main results.</i>For the early follow-up time, the correlation between GTV and tumor progression was not statistically significant (<i>p</i>= 0.684). However, statistically significant correlations with progression were found between<i>V</i>₁₀₀and cell-volume-product with a cell threshold of 10^-6cells mm^-3with areas-under-the-curve of 0.69 (<i>p</i>= 0.023) and 0.66 (<i>p</i>= 0.045), respectively. No significant correlations were found for the late follow-up time.<i>Significance.</i>Modeling tumor spread otherwise undetectable on conventional imaging, as well as radiobiological model predictions of cell survival after treatment, may provide useful information regarding the likelihood of tumor progression at an early follow-up time point, which could potentially lead to improved treatment decisions for patients with GBMs.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143567956","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":"Model observers and detectability index in x-ray imaging: historical review, applications and future trends.","authors":"Elsa Bifano Pimenta, Paulo Roberto R Costa","doi":"10.1088/1361-6560/adc070","DOIUrl":"https://doi.org/10.1088/1361-6560/adc070","url":null,"abstract":"<p><p>The detectability index, originally developed in psychophysics, has been applied in medical imaging to integrate objective metrics with subjective assessments. This index accounts for both image processing properties and the limitations of the human visual system, thus enhancing the clinical efficacy of imaging technologies. By providing a single metric that captures multiple aspects of image quality, the detectability index offers a comprehensive evaluation of clinical images. Numerous applications of this index across various areas of medical imaging are documented in the literature, along with recommendations for its use in periodic performance evaluations of imaging devices. However, since different modalities of images may require different detectability indices, it is crucial to assess the adequacy of the properties of the image being analyzed and those from the adopted index. A thorough understanding of this metric, including its statistical nature and complex relationship with model observers, is essential to ensure its proper application and interpretation, and to prevent misuse. Medical physicists face the challenge of a lack of organized guidance on the detectability index, necessitating a comprehensive review of its merits and drawbacks. This paper aims to trace the origins, concepts, and clinical applications of the detectability index, offering insight into its strengths, limitations, and future potential. To achieve this, an extensive literature review was conducted, covering the evolution of the index from its early use in radar interpretation to its current applications in modern imaging techniques and future trends. The paper includes supplementary materials such as a compendium of fundamental concepts, ancillary information, and mathematical deductions to help readers less experienced in the subject.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143625265","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":"Development and dosimetric evaluation of a modulated intraoperative radiotherapy (mIORT) system using the Zeiss intrabeam device.","authors":"Xavier Jones, Gabor Neveri, Marsha Chin, Pejman Rowshanfarzad","doi":"10.1088/1361-6560/adc06f","DOIUrl":"https://doi.org/10.1088/1361-6560/adc06f","url":null,"abstract":"<p><p>Objective&#xD;Intraoperative radiotherapy (IORT) is a specialised radiotherapy technique that delivers a precise, single high-dose fraction to the tumour bed after surgical removal of the tumour, aiming to eliminate residual cancer cells. This study investigates the incorporation of novel applicators into an existing intraoperative radiotherapy (IORT) system to enable dose modulation, performing Monte Carlo simulations, 3D printing, and experimental validation. The Zeiss Intrabeam IORT device, a low-kV IORT system capable of delivering X-rays nearly isotropically, with energies up to 50 kV, was used in this study. &#xD;Approach&#xD;Applicators were modified to alter dose distributions, incorporating features such as shielding or changes to an ellipsoid shape. The EGSnrc Monte Carlo (MC) code was employed to simulate the dose distributions of each applicator design, generating data such as dose maps, percentage depth dose (PDD) curves, percent difference maps between shielded and unshielded regions, and energy spectra to characterise each applicator. Gafchromic EBT3 film measurements were performed on select 3D printed applicators, to verify the MC simulations, with dose distribution data extracted for comparison. &#xD;Main Results&#xD;Visual comparisons of dose and percentage different maps indicate a high correlation between the MC simulations and film measurements. Most PDD points for spherical applicators showed deviations within 4%, while ellipsoid applicators had deviations of 14% for the unshielded and 5% for the shielded applicators. All RMSEs were below 0.05 for spherical and 0.18 for ellipsoid designs. Based on film data, shielded ellipsoid applicators reduced the dose by ~99%, 48%, 22%, and 8% at 0.3, 1, 2, and 3 cm, respectively, while shielded spherical applicators achieved ~83%, 35%, 14%, and 7% reductions at the same distances. Energy spectra for photons exiting shielded regions were also generated. &#xD;Significance&#xD;Results of this study may be used in the development of patient-specific IORT techniques, or the development of a treatment planning system involving mIORT. &#xD.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143625260","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":"3D<i>π</i>: three-dimensional positron imaging, a novel total-body PET scanner using xenon-doped liquid argon scintillator.","authors":"Azam Zabihi, Xinran Li, Alejandro Ramirez, Iftikhar Ahmad, Manuel D Da Rocha Rolo, Davide Franco, Federico Gabriele, Cristiano Galbiati, Michela Lai, Daniel R Marlow, Andrew Renshaw, Shawn Westerdale, Masayuki Wada","doi":"10.1088/1361-6560/adbaac","DOIUrl":"10.1088/1361-6560/adbaac","url":null,"abstract":"<p><p><i>Objective.</i>This paper introduces a novel PET imaging methodology called 3-dimensional positron imaging (3D<i>π</i>), which integrates total-body coverage, time-of-flight (TOF) technology, ultra-low dose imaging capabilities, and ultra-fast readout electronics inspired by emerging technology from the DarkSide collaboration.<i>Approach.</i>The study evaluates the performance of 3D<i>π</i>using Monte Carlo simulations based on NEMA NU 2-2018 protocols. The methodology employs a homogenous, monolithic scintillator composed of liquid argon (LAr) doped with xenon (Xe) with silicon photomultipliers (SiPMs) operating at cryogenic temperatures.<i>Main results.</i>Substantial improvements in system performance are observed, with the 3D<i>π</i>system achieving a noise equivalent count rate of 3.2 Mcps at 17.3 kBq ml^-1, continuing to increase up to 4.3 Mcps at 40 kBq ml^-1. Spatial resolution measurements show an average FWHM of 2.7 mm across both axial positions. The system exhibits superior sensitivity, with values reaching 373 kcps MBq^-1with a line source at the center of the field of view. Additionally, 3D<i>π</i>achieves a TOF resolution of 151 ps at 5.3 kBq ml^-1, highlighting its potential to produce high-quality images with reduced noise levels.<i>Significance.</i>The study underscores the potential of 3D<i>π</i>in improving PET imaging performance, offering the potential for shorter scan times and reduced radiation exposure for patients. The Xe-doped LAr offers advantages such as fast scintillation, enhanced light yield, and cost-effectiveness. Future research will focus on optimizing system geometry and further refining reconstruction algorithms to exploit the strengths of 3D<i>π</i>for clinical applications.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143516494","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":"Regularized origin ensemble with a beam prior for range verification in particle therapy with Compton-camera data.","authors":"Jona Kasprzak, Jorge Roser, Julius Friedemann Werner, Nadja Kohlhase, Andreas Bolke, Lisa-Marie Kaufmann, Magdalena Rafecas","doi":"10.1088/1361-6560/adbfd8","DOIUrl":"https://doi.org/10.1088/1361-6560/adbfd8","url":null,"abstract":"<p><strong>Objective: </strong>In particle therapy (PT), several methods are being investigated to help reduce range margins and identify deviations from the original treatment plan, such as prompt-gamma (PG) imaging with Compton cameras (CC). To reconstruct the images, the Origin Ensemble (OE) algorithm is commonly used. In the context of PT, artifacts and strong noise often affect CC images. To improve the ability of OE to identify range shifts, and also to enhance image quality, we propose to regularize OE using beam a-priori knowledge (beam prior).&#xD;Approach: We implemented the beam prior to OE using the class of Gibbs' distribution functions. For evaluation, Monte-Carlo simulations of centered and off-center beams with therapeutic energies impinging on a PMMA target were conducted in GATE. To introduce range shifts, air layers were introduced into the target. In addition, the effect of a bone layer, closer to a realistic scenario, was investigated. OE with the beam prior (BP-OE) and conventional OE (reference) were compared using the spill-over-ratio (SOR) as well as shifts in the distal falloff in projections using cubic splines with Chebyshev nodes.&#xD;Main results: BP-OE improved the shift estimates by up to 11% compared to conventional OE for centered and up to 250% with off-centered beams. BP-OE&#xD;decreased the image noise level, improving the SOR significantly by up to 96%.&#xD;Significance: BP-OE applied to CC data can improve shift estimations compared to conventional OE. The developed Gibbs-based regularization framework also allows&#xD;further prior functions to be included into OE, for instance, smoothing or edge-preserving priors. BP-OE could be extended to PET-based range verification or multiple-beam scenarios.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143616773","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":"Ultra-high energy spectral prompt PET.","authors":"Satyajit Ghosh, Valerio Cosmi, Ruud M Ramakers, Freek J Beekman, Marlies C Goorden","doi":"10.1088/1361-6560/adbfd7","DOIUrl":"https://doi.org/10.1088/1361-6560/adbfd7","url":null,"abstract":"<p><strong>Objective: </strong>Utilizing prompt gammas in preclinical pinhole-collimated PET avoids image degradation due to positron range blurring and photon down scatter, enables multi-isotope PET and can improve counting statistics for low-abundance positron emitters. This was earlier reported for 124I, 89Zr and simultaneous 124I -18F PET using the VECTor scanner (MILabs, The Netherlands), demonstrating sub-mm resolution despite long positron ranges. The aim of the present study is to investigate if such sub-mm PET imaging is also feasible for a large variety of other isotopes including those with extremely high energy prompt gammas (>1 MeV) or with complex emission spectra of prompt gammas.</p><p><strong>Approach: </strong>We use Monte Carlo simulations to assess achievable image resolutions and uniformity across a broad range of spectrum types and emitted prompt gamma energies (603 keV - 2.2 MeV), using 52Mn, 94Tc, 89Zr, 44Sc, 86Y, 72As, 124I, 38K, and 66Ga.</p><p><strong>Main results: </strong>Our results indicate that sub-millimeter resolution imaging may be feasible for almost all isotopes investigated, with the currently used cluster pinhole collimators. At prompt gamma energies of 603 keV of 124I, an image resolution of ~0.65 mm was achieved, while for emissions at 703, 744, 834, and 909 keV of 94Tc, 52Mn, 72As, and 89Zr, respectively, ~0.7 mm resolution was obtained. Finally, at ultra-high energies of 1.2 (44Sc) and 1.4 MeV (52Mn) resolutions of ~0.75 mm and ~0.8 mm could still be achieved although ring artifacts were observed at the highest energies (1.4 MeV). For 38K (2.2 MeV), an image resolution of 1.2 mm was achieved utilizing its 2.2 MeV prompt emission.</p><p><strong>Significance: </strong>This work shows that current cluster pinhole collimators are suitable for sub-mm resolution prompt PET up till at least 1.4 MeV. This may open up new avenues to developing new tracer applications and therapies utilizing these PET isotopes.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143616775","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":"Real-time dose reconstruction in proton therapy from in-beam PET measurements.","authors":"Victor Valladolid-Onecha, Andrea Espinosa Rodriguez, Cayetano Soneira Landín, Fernando Arias-Valcayo, Sara Gaitán-Dominguez, Victor Martinez-Nouvilas, Miguel Garcia-Diez, Paula Ibáñez, Samuel Espana, Daniel Sanchez-Parcerisa, Fernando Cerron-Campoo, Juan Antonio Vera Sánchez, Alejandro Mazal, José Manuel Udías, Luis Mario Fraile","doi":"10.1088/1361-6560/adbfd9","DOIUrl":"https://doi.org/10.1088/1361-6560/adbfd9","url":null,"abstract":"<p><strong>Objective: </strong>Clinical implementation of in-beam PET monitoring in proton therapy requires the integration of an online fast and reliable dose calculation engine. This manuscript reports on the achievement of real-time reconstruction of 3D dose and activity maps with proton range verification from experimental in-beam PET measurements. &#xD;&#xD;Approach: Several cylindrical homogeneous PMMA phantoms were irradiated with a monoenergetic 70-MeV proton beam in a clinical facility. Additionally, PMMA range-shifting foils of varying thicknesses were placed at the proximal surface of the phantom to investigate range shift prediction capabilities. PET activity was measured using a state-of-the-art in-house developed six-module PET scanner equipped with online PET reconstruction capabilities. For real-time dose estimation, we integrated this system with an in-beam dose estimation (IDE) algorithm, which combines a GPU-based 3D reconstruction algorithm with a dictionary-based software, capable of estimating deposited doses from the 3D PET activity images. The range shift prediction performance has been quantitatively studied in terms of the minimum dose to be delivered and the maximum acquisition time.&#xD;&#xD;Main results: With this framework, 3D dose maps were accurately reconstructed and displayed with a delay as short as one second. For a dose fraction of 8.4 Gy at the Bragg peak maximum, range shifts as small as 1 mm could be detected. The quantitative analysis shows that accumulating 20 seconds of statistics from the start of the irradiation, doses down to 1 Gy could be estimated online with total uncertainties smaller than 2 mm. &#xD;&#xD;Significance. The hardware and software combination employed in this work can deliver dose maps and accurately predict range shifts after short acquisition times and small doses, suggesting that real-time monitoring and dose reconstruction during proton therapy are within reach. Future work will focus on testing the methodology in more complex clinical scenarios and on upgrading the PET prototype for increased sensitivity.&#xD.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143616770","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 feasibility study of automating radiotherapy planning with large language model agents.","authors":"Qingxin Wang, Zhongqiu Wang, Minghua Li, Xinye Ni, Rong Tan, Wenwen Zhang, Maitudi Wubulaishan, Wei Wang, Zhiyong Yuan, Zhen Zhang, Cong Liu","doi":"10.1088/1361-6560/adbff1","DOIUrl":"https://doi.org/10.1088/1361-6560/adbff1","url":null,"abstract":"<p><p><b>Objective</b>: Radiotherapy planning requires significant expertise to balance tumor control and organ-at-risk (OAR) sparing. Automated planning can improve both efficiency and quality. This study introduces GPT-Plan, a novel multi-agent system powered by the GPT-4 family of large language models (LLMs), for automating the iterative radiotherapy plan optimization.<b>Approach</b>: GPT-Plan uses LLM-driven agents, mimicking the collaborative clinical workflow of a dosimetrist and physicist, to iteratively generate and evaluate text-based radiotherapy plans based on predefined criteria. Supporting tools assist the agents by leveraging historical plans, mitigating LLM hallucinations, and balancing exploration and exploitation. Performance was evaluated on 12 lung (IMRT) and 5 cervical (VMAT) cancer cases, benchmarked against the ECHO auto-planning method and manual plans. The impact of historical plan retrieval on efficiency was also assessed.<b>Results</b>: For IMRT lung cancer cases, GPT-Plan generated high-quality plans, demonstrating superior target coverage and homogeneity compared to ECHO while maintaining comparable or better OAR sparing. For VMAT cervical cancer cases, plan quality was comparable to a senior physicist and consistently superior to a junior physicist, particularly for OAR sparing. Retrieving historical plans significantly reduced the number of required optimization iterations for lung cases (p < 0.01) and yielded iteration counts comparable to those of the senior physicist for cervical cases (p=0.313). Occasional LLM hallucinations have been mitigated by self-reflection mechanisms. One limitation was the inaccuracy of vision-based LLMs in interpreting dose images.<b>Significance</b>: This pioneering study demonstrates the feasibility of automating radiotherapy planning using LLM-powered agents for complex treatment decision-making tasks. While challenges remain in addressing LLM limitations, ongoing advancements hold potential for further refining and expanding GPT-Plan's capabilities.&#xD.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143616768","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":"IPEM code of practice for proton therapy dosimetry based on the NPL primary standard proton calorimeter calibration service.","authors":"Stuart Green, Ana Lourenço, Hugo Palmans, Nigel Lee, Richard A Amos, Derek D' Souza, Francesca Fiorini, Frank Van Den Heuvel, Andrzej Kacperek, Ranald Mackay, John Pettingell, Russell Thomas","doi":"10.1088/1361-6560/adad2e","DOIUrl":"10.1088/1361-6560/adad2e","url":null,"abstract":"<p><p>Internationally, reference dosimetry for clinical proton beams largely follows the guidelines published by the International Atomic Energy Agency (IAEA TRS-398 Rev. 1 (2024). This approach yields a relative standard uncertainty of 1.7% (<i>k</i>= 1) on the absorbed dose to water determined under reference conditions. The new IPEM code of practice presented here, enables the relative standard uncertainty on the absorbed dose to water measured under reference conditions to be reduced to 1.0% (<i>k</i>= 1). This improvement is based on the absorbed dose to water calibration service for proton beams provided by the National Physical Laboratory (NPL), the UK's primary standards laboratory. This significantly reduced uncertainty is achieved through the use of a primary standard level graphite calorimeter to derive absorbed dose to water directly in the clinical department's beam. This eliminates the need for beam quality correction factors (kQ,Q0) as required by the IAEA TRS-398 approach. The portable primary standard level graphite calorimeter, developed over a number of years at the NPL, is sufficiently robust to be useable in the proton beams of clinical facilities both in the UK and overseas. The new code of practice involves performing reference dosimetry measurements directly traceable to the primary standard level graphite calorimeter in a clinical proton beam. Calibration of an ionisation chamber is performed in the centre of a standard test volume (STV) of dose, defined here to be a 10 × 10 × 10 cm volume in water, centred at a depth of 15 cm. Further STVs at reduced and increased depths are also utilised. The designated ionisation chambers are Roos-type plane-parallel chambers. This article provides all the necessary background material, formalism, and specifications of reference conditions required to implement reference dosimetry according to this new code of practice. The Annexes provide a detailed review of ion recombination and how this should be assessed (Annex A1) and detailed work instructions for creating and delivering the STVs (Annex A2).</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143023993","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-institution investigations of online daily adaptive proton strategies for head and neck cancer patients.","authors":"Evangelia Choulilitsa, Mislav Bobić, Brian Winey, Harald Paganetti, Antony J Lomax, Francesca Albertini","doi":"10.1088/1361-6560/adbb51","DOIUrl":"10.1088/1361-6560/adbb51","url":null,"abstract":"<p><p><i>Objective.</i>Fast computation of daily reoptimization is key for an efficient online adaptive proton therapy workflow. Various approaches aim to expedite this process, often compromising daily dose. This study compares Massachusetts General Hospital's (MGH's) online dose reoptimization approach, Paul Scherrer Institute's (PSI's) online replanning workflow and a full reoptimization adaptive workflow for head and neck cancer (H&N) patients.<i>Approach.</i>Ten H&N patients (PSI:5, MGH:5) with daily cone beam computed tomographys (CBCTs) were included. Synthetic CTs were created by deforming the planning CT to each CBCT. Targets and organs at risk (OARs) were deformed on daily images. Three adaptive approaches were investigated: (i) an online dose reoptimization approach modifying the fluence of a subset of beamlets, (ii) full reoptimization adaptive workflow modifying the fluence of all beamlets, and (iii) a full online replanning approach, allowing the optimizer to modify both fluence and position of all beamlets. Two non-adapted (NA) scenarios were simulated by recalculating the original plan on the daily image using: Monte Carlo for NA_MGHand raycasting algorithm for NA_PSI.<i>Main results.</i>All adaptive scenarios from both institutions achieved the prescribed daily target dose, with further improvements from online replanning. For all patients, low-dose CTV D_98%shows mean daily deviations of -2.2%, -1.1%, and 0.4% for workflows (i), (ii), and (iii), respectively. For the online adaptive scenarios, plan optimization averages 2.2 min for (iii) and 2.4 for (i) while the full dose reoptimization requires 72 min. The OA_MGH20%dose reoptimization approach produced results comparable to online replanning for most patients and fractions. However, for one patient, differences up to 11% in low-dose CTV D_98%occurred.<i>Significance.</i>Despite significant anatomical changes, all three adaptive approaches ensure target coverage without compromising OAR sparing. Our data suggests 20% dose reoptimization suffices, for most cases, yielding comparable results to online replanning with a marginal time increase due to Monte Carlo. For optimal daily adaptation, a rapid online replanning is preferable.</p>","PeriodicalId":20185,"journal":{"name":"Physics in medicine and biology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143524138","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}