1
|
Ates O, Pirlepesov F, Uh J, Hua CH, Merchant TE, Boria A, Davidoff AM, Graetz DE, Krasin MJ. Evaluating the Impact of Bowel Gas Variations for Wilms' Tumor in Pediatric Proton Therapy. Cancers (Basel) 2024; 16:642. [PMID: 38339393 PMCID: PMC10854738 DOI: 10.3390/cancers16030642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 01/27/2024] [Accepted: 01/31/2024] [Indexed: 02/12/2024] Open
Abstract
(1) Background: Proton therapy, a precise form of radiation treatment, can be significantly affected by variations in bowel content. The purpose was to identify the most beneficial gantry angles that minimize deviations from the treatment plan quality, thus enhancing the safety and efficacy of proton therapy for Wilms' tumor patients. (2) Methods: Thirteen patients with Wilms' tumor, enrolled in the SJWT21 clinical trial, underwent proton therapy. The variations in bowel gas were systematically monitored using daily Cone Beam Computed Tomography (CBCT) imaging. Air cavities identified in daily CBCT images were analyzed to construct daily verification plans and measure water equivalent path length (WEPL) changes. A worst-case scenario simulation was conducted to identify the safest beam angles. (3) Results: The study revealed a maximum decrease in target dose (ΔD100%) of 8.0%, which corresponded to a WEPL variation (ΔWEPL) of 11.3 mm. The average reduction in target dose, denoted as mean ΔD100%, was found to be 2.8%, with a standard deviation (SD) of 3.2%. The mean ΔWEPL was observed as 3.3 mm, with an SD of 2.7 mm. The worst-case scenario analysis suggested that gantry beam angles oriented toward the patient's right and posterior aspects from 110° to 310° were associated with minimized WEPL discrepancies. (4) Conclusions: This study comprehensively evaluated the influence of bowel gas variability on treatment plan accuracy and proton range uncertainties in pediatric proton therapy for Wilms' tumor.
Collapse
Affiliation(s)
- Ozgur Ates
- St. Jude Children’s Research Hospital, Memphis, TN 38105, USA; (F.P.); (J.U.); (C.-h.H.); (T.E.M.); (A.B.); (A.M.D.); (D.E.G.); (M.J.K.)
| | | | | | | | | | | | | | | | | |
Collapse
|
2
|
Zhou Y, Sakai M, Li Y, Kubota Y, Okamoto M, Shiba S, Okazaki S, Matsui T, Ohno T. Robust Beam Selection Based on Water Equivalent Thickness Analysis in Passive Scattering Carbon-Ion Radiotherapy for Pancreatic Cancer. Cancers (Basel) 2023; 15:cancers15092520. [PMID: 37173985 PMCID: PMC10177227 DOI: 10.3390/cancers15092520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 04/13/2023] [Accepted: 04/20/2023] [Indexed: 05/15/2023] Open
Abstract
Carbon-ion radiotherapy (CIRT) is one of the most effective radiotherapeutic modalities. This study aimed to select robust-beam configurations (BC) by water equivalent thickness (WET) analysis in passive CIRT for pancreatic cancer. The study analyzed 110 computed tomography (CT) images and 600 dose distributions of eight patients with pancreatic cancer. The robustness in the beam range was evaluated using both planning and daily CT images, and two robust BCs for the rotating gantry and fixed port were selected. The planned, daily, and accumulated doses were calculated and compared after bone matching (BM) and tumor matching (TM). The dose-volume parameters for the target and organs at risk (OARs) were evaluated. Posterior oblique beams (120-240°) in the supine position and anteroposterior beams (0° and 180°) in the prone position were the most robust to WET changes. The mean CTV V95% reductions with TM were -3.8% and -5.2% with the BC for gantry and the BC for fixed ports, respectively. Despite ensuring robustness, the dose to the OARs increased slightly with WET-based BCs but remained below the dose constraint. The robustness of dose distribution can be improved by BCs that are robust to ΔWET. Robust BC with TM improves the accuracy of passive CIRT for pancreatic cancer.
Collapse
Affiliation(s)
- Yuan Zhou
- Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan
| | - Makoto Sakai
- Gunma University Heavy Ion Medical Center, Maebashi 371-8511, Japan
| | - Yang Li
- Gunma University Heavy Ion Medical Center, Maebashi 371-8511, Japan
- Department of Radiation Oncology, Harbin Medical University Cancer Hospital, Harbin 150040, China
| | - Yoshiki Kubota
- Gunma University Heavy Ion Medical Center, Maebashi 371-8511, Japan
| | - Masahiko Okamoto
- Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan
- Gunma University Heavy Ion Medical Center, Maebashi 371-8511, Japan
| | - Shintaro Shiba
- Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan
- Department of Radiation Oncology, Shonan Kamakura General Hospital, Kamakura 247-8533, Japan
| | - Shohei Okazaki
- Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan
- Gunma University Heavy Ion Medical Center, Maebashi 371-8511, Japan
| | - Toshiaki Matsui
- Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan
| | - Tatsuya Ohno
- Graduate School of Medicine, Gunma University, Maebashi 371-8511, Japan
- Gunma University Heavy Ion Medical Center, Maebashi 371-8511, Japan
| |
Collapse
|
3
|
Kaderka R, Liu KC, Liu L, VanderStraeten R, Liu TL, Lee KM, Tu YCE, MacEwan I, Simpson D, Urbanic J, Chang C. Toward automatic beam angle selection for pencil-beam scanning proton liver Treatments: A deep learning-based approach. Med Phys 2022; 49:4293-4304. [PMID: 35488864 DOI: 10.1002/mp.15676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Revised: 03/31/2022] [Accepted: 04/12/2022] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND Dose deposition characteristics of proton radiation can be advantageous over photons. Proton treatment planning however poses additional challenges for the planners. Proton therapy is usually delivered with only a small number of beam angles, and the quality of a proton treatment plan is largely determined by the beam angles employed. Finding the optimal beam angles for a proton treatment plan requires time and experience, motivating the investigation of automatic beam angle selection methods. PURPOSE A deep learning-based approach to automatic beam angle selection is proposed for proton pencil-beam scanning treatment planning of liver lesions. METHODS We cast beam-angle selection as a multi-label classification problem. To account for angular boundary discontinuity, the underlying convolution neural network is trained with the proposed Circular Earth Mover's Distance based regularization and multi-label circular-smooth label technique. Furthermore, an analytical algorithm emulating proton treatment planners' clinical practice is employed in post-processing to improve the output of the model. Forty-nine patients that received proton liver treatments between 2017 and 2020 were randomly divided into training (n = 31), validation (n = 7), and test sets (n = 11). AI-selected beam angles were compared with those angles selected by human planners, and the dosimetric outcome was investigated by creating plans using knowledge-based treatment planning. RESULTS For 7 of the 11 cases in the test set, AI-selected beam angles agreed with those chosen by human planners to within 20 degrees (median angle difference = 10°; mean = 18.6°). Moreover, out of the total 22 beam angles predicted by the model, 15 (68%) were within 10 degrees of the human-selected angles. The high correlation in beam angles resulted in comparable dosimetric statistics between proton treatment plans generated using AI- and human-selected angles. For the cases with beam angle differences exceeding 20°, the dosimetric analysis showed similar plan quality although with different emphases on organ-at-risk sparing. CONCLUSIONS This pilot study demonstrated the feasibility of a novel deep learning-based beam angle selection technique. Testing on liver cancer patients showed that the resulting plans were clinically viable with comparable dosimetric quality to those using human-selected beam angles. In tandem with auto-contouring and knowledge-based treatment planning tools, the proposed model could represent a pathway for nearly fully automated treatment planning in proton therapy. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Robert Kaderka
- Department of Radiation Medicine and Applied Sciences, University of California at San Diego, La Jolla, CA, 92121.,Department of Radiation Oncology, University of Miami, Miami, FL, 33136
| | | | - Lawrence Liu
- California Protons Cancer Therapy Center, San Diego, CA, 92121
| | | | | | | | | | - Iain MacEwan
- Department of Radiation Medicine and Applied Sciences, University of California at San Diego, La Jolla, CA, 92121.,California Protons Cancer Therapy Center, San Diego, CA, 92121
| | - Daniel Simpson
- Department of Radiation Medicine and Applied Sciences, University of California at San Diego, La Jolla, CA, 92121
| | - James Urbanic
- Department of Radiation Medicine and Applied Sciences, University of California at San Diego, La Jolla, CA, 92121.,California Protons Cancer Therapy Center, San Diego, CA, 92121
| | - Chang Chang
- Department of Radiation Medicine and Applied Sciences, University of California at San Diego, La Jolla, CA, 92121.,California Protons Cancer Therapy Center, San Diego, CA, 92121
| |
Collapse
|
4
|
Schreuder N, Ding X, Li Z. Fixed beamlines can replace gantries for particle therapy. Med Phys 2022; 49:2097-2100. [PMID: 35147222 DOI: 10.1002/mp.15531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 01/06/2022] [Accepted: 01/27/2022] [Indexed: 11/12/2022] Open
Affiliation(s)
- Niek Schreuder
- Leo Cancer Care, 12611 Lovelace Rd, Knoxville, TN, 37832
| | - Xuanfeng Ding
- Radiation Oncology Department, William Beaumont Hospital, 3601 W 13 Mile Rd, Royal Oak, MI, 48073
| | - Zuofeng Li
- Radiation Oncology Department, Guangzhou Concord Cancer Center, #9 CIJI Road, Sino-Singapore Knowledge City, Huangpu District, Guangzhou, Guangdong, China
| |
Collapse
|
5
|
Paganetti H, Botas P, Sharp GC, Winey B. Adaptive proton therapy. Phys Med Biol 2021; 66:10.1088/1361-6560/ac344f. [PMID: 34710858 PMCID: PMC8628198 DOI: 10.1088/1361-6560/ac344f] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/28/2021] [Indexed: 12/25/2022]
Abstract
Radiation therapy treatments are typically planned based on a single image set, assuming that the patient's anatomy and its position relative to the delivery system remains constant during the course of treatment. Similarly, the prescription dose assumes constant biological dose-response over the treatment course. However, variations can and do occur on multiple time scales. For treatment sites with significant intra-fractional motion, geometric changes happen over seconds or minutes, while biological considerations change over days or weeks. At an intermediate timescale, geometric changes occur between daily treatment fractions. Adaptive radiation therapy is applied to consider changes in patient anatomy during the course of fractionated treatment delivery. While traditionally adaptation has been done off-line with replanning based on new CT images, online treatment adaptation based on on-board imaging has gained momentum in recent years due to advanced imaging techniques combined with treatment delivery systems. Adaptation is particularly important in proton therapy where small changes in patient anatomy can lead to significant dose perturbations due to the dose conformality and finite range of proton beams. This review summarizes the current state-of-the-art of on-line adaptive proton therapy and identifies areas requiring further research.
Collapse
Affiliation(s)
- Harald Paganetti
- Department of Radiation Oncology, Physics Division, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
| | - Pablo Botas
- Department of Radiation Oncology, Physics Division, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
- Foundation 29 of February, Pozuelo de Alarcón, Madrid, Spain
| | - Gregory C Sharp
- Department of Radiation Oncology, Physics Division, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
| | - Brian Winey
- Department of Radiation Oncology, Physics Division, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
| |
Collapse
|
6
|
Zhou Y, Li Y, Kubota Y, Sakai M, Ohno T. Robust Angle Selection in Particle Therapy. Front Oncol 2021; 11:715025. [PMID: 34621672 PMCID: PMC8490826 DOI: 10.3389/fonc.2021.715025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 08/19/2021] [Indexed: 11/13/2022] Open
Abstract
The popularity of particle radiotherapy has grown exponentially over recent years owing to the marked advantage of the depth–dose curve and its unique biological property. However, particle therapy is sensitive to changes in anatomical structure, and the dose distribution may deteriorate. In particle therapy, robust beam angle selection plays a crucial role in mitigating inter- and intrafractional variation, including daily patient setup uncertainties and tumor motion. With the development of a rotating gantry, angle optimization has gained increasing attention. Currently, several studies use the variation in the water equivalent thickness to quantify anatomical changes during treatment. This method seems helpful in determining better beam angles and improving the robustness of planning. Therefore, this review will discuss and summarize the robust beam angles at different tumor sites in particle radiotherapy.
Collapse
Affiliation(s)
- Yuan Zhou
- Department of Radiation Oncology, Graduate School of Medicine, Gunma University, Maebashi, Japan
| | - Yang Li
- Gunma University Heavy Ion Medical Center, Gunma University, Maebashi, Japan.,Department of Radiation Oncology, Harbin Medical University Cancer Hospital, Harbin, China
| | - Yoshiki Kubota
- Gunma University Heavy Ion Medical Center, Gunma University, Maebashi, Japan
| | - Makoto Sakai
- Gunma University Heavy Ion Medical Center, Gunma University, Maebashi, Japan
| | - Tatsuya Ohno
- Department of Radiation Oncology, Graduate School of Medicine, Gunma University, Maebashi, Japan.,Gunma University Heavy Ion Medical Center, Gunma University, Maebashi, Japan
| |
Collapse
|
7
|
Schmitz H, Rabe M, Janssens G, Bondesson D, Rit S, Parodi K, Belka C, Dinkel J, Kurz C, Kamp F, Landry G. Validation of proton dose calculation on scatter corrected 4D cone beam computed tomography using a porcine lung phantom. Phys Med Biol 2021; 66. [PMID: 34293737 DOI: 10.1088/1361-6560/ac16e9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 07/22/2021] [Indexed: 12/25/2022]
Abstract
Proton therapy treatment for lungs remains challenging as images enabling the detection of inter- and intra-fractional motion, which could be used for proton dose adaptation, are not readily available. 4D computed tomography (4DCT) provides high image quality but is rarely available in-room, while in-room 4D cone beam computed tomography (4DCBCT) suffers from image quality limitations stemming mostly from scatter detection. This study investigated the feasibility of using virtual 4D computed tomography (4DvCT) as a prior for a phase-per-phase scatter correction algorithm yielding a 4D scatter corrected cone beam computed tomography image (4DCBCTcor), which can be used for proton dose calculation. 4DCT and 4DCBCT scans of a porcine lung phantom, which generated reproducible ventilation, were acquired with matching breathing patterns. Diffeomorphic Morphons, a deformable image registration algorithm, was used to register the mid-position 4DCT to the mid-position 4DCBCT and yield a 4DvCT. The 4DCBCT was reconstructed using motion-aware reconstruction based on spatial and temporal regularization (MA-ROOSTER). Successively for each phase, digitally reconstructed radiographs of the 4DvCT, simulated without scatter, were exploited to correct scatter in the corresponding CBCT projections. The 4DCBCTcorwas then reconstructed with MA-ROOSTER using the corrected CBCT projections and the same settings and deformation vector fields as those already used for reconstructing the 4DCBCT. The 4DCBCTcorand the 4DvCT were evaluated phase-by-phase, performing proton dose calculations and comparison to those of a ground truth 4DCT by means of dose-volume-histograms (DVH) and gamma pass-rates (PR). For accumulated doses, DVH parameters deviated by at most 1.7% in the 4DvCT and 2.0% in the 4DCBCTcorcase. The gamma PR for a (2%, 2 mm) criterion with 10% threshold were at least 93.2% (4DvCT) and 94.2% (4DCBCTcor), respectively. The 4DCBCTcortechnique enabled accurate proton dose calculation, which indicates the potential for applicability to clinical 4DCBCT scans.
Collapse
Affiliation(s)
- Henning Schmitz
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany
| | - Moritz Rabe
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany
| | | | - David Bondesson
- Department of Radiology, University Hospital, LMU Munich, Munich, Germany
| | - Simon Rit
- Univ Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, F-69373, LYON, France
| | - Katia Parodi
- Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), Garching (Munich), Germany
| | - Claus Belka
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany.,German Cancer Consortium (DKTK), Partner Site Munich, Munich, Germany
| | - Julien Dinkel
- Department of Radiology, University Hospital, LMU Munich, Munich, Germany
| | - Christopher Kurz
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), Garching (Munich), Germany
| | - Florian Kamp
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany.,Department of Radiation Oncology, University Hospital Cologne, Cologne, Germany
| | - Guillaume Landry
- Department of Radiation Oncology, University Hospital, LMU Munich, Munich, Germany.,Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität München (LMU Munich), Garching (Munich), Germany
| |
Collapse
|
8
|
Hashemi Z, Tatari M, Naik H. Simulation of dose distribution and secondary particle production in proton therapy of brain tumor. Rep Pract Oncol Radiother 2020; 25:927-933. [PMID: 33088228 DOI: 10.1016/j.rpor.2020.08.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 08/01/2020] [Accepted: 08/26/2020] [Indexed: 11/18/2022] Open
Abstract
Aim The aim of this study is simulation of the proton depth-dose distribution and dose evaluation of secondary particles in proton therapy of brain tumor using the GEANT4 and FLUKA Monte Carlo codes. Background Proton therapy is a treatment method for variety of tumors such as brain tumor. The most important feature of high energy proton beams is the energy deposition as a Bragg curve and the possibility of creating the spread out Bragg peak (SOBP) for full coverage of the tumor. Materials and methods A spherical tumor with the radius of 1 cm in the brain is considered. A SNYDER head phantom has been irradiated with 30-130 MeV proton beam energy. A PMMA modulator wheel is used for covering the tumor. The simulations are performed using the GEANT4 and FLUKA codes. Results Using a modulator wheel, the Spread Out Bragg Peak longitudinally and laterally covers the tumor. Flux and absorbed dose of secondary particles produced by nuclear interactions of protons with elements in the head are considerably small compared to protons. Conclusions Using 76.85 MeV proton beam and a modulator wheel, the tumor can be treated accurately in the 3-D, so that the distribution of proton dose in the surrounding tissues is very low. The results show that more than 99% of the total dose of secondary particles and protons is absorbed in the tumor.
Collapse
Affiliation(s)
- Zahra Hashemi
- Physics Department, Faculty of Science, Yazd University, Yazd 89195-741, Iran
| | - Mansoureh Tatari
- Physics Department, Faculty of Science, Yazd University, Yazd 89195-741, Iran
| | - Haladhara Naik
- Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| |
Collapse
|
9
|
Andersen AG, Park YK, Elstrøm UV, Petersen JBB, Sharp GC, Winey B, Dong L, Muren LP. Evaluation of an a priori scatter correction algorithm for cone-beam computed tomography based range and dose calculations in proton therapy. Phys Imaging Radiat Oncol 2020; 16:89-94. [PMID: 33458349 PMCID: PMC7807858 DOI: 10.1016/j.phro.2020.09.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 09/22/2020] [Accepted: 09/30/2020] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND AND PURPOSE Scatter correction of cone-beam computed tomography (CBCT) projections may enable accurate online dose-delivery estimations in photon and proton-based radiotherapy. This study aimed to evaluate the impact of scatter correction in CBCT-based proton range/dose calculations, in scans acquired in both proton and photon gantries. MATERIAL AND METHODS CBCT projections of a Catphan and an Alderson phantom were acquired on both a proton and a photon gantry. The scatter corrected CBCTs (corrCBCTs) and the clinical reconstructions (stdCBCTs) were compared against CTs rigidly registered to the CBCTs (rigidCTs). The CBCTs of the Catphan phantom were segmented by materials for CT number analysis. Water equivalent path length (WEPL) maps were calculated through the Alderson phantom while proton plans optimized on the rigidCT and recalculated on all CBCTs were compared in a gamma analysis. RESULTS In medium and high-density materials, the corrCBCT CT numbers were much closer to those of the rigidCT than the stdCBCTs. E.g. in the 50% bone segmentations the differences were reduced from above 300 HU (with stdCBCT) to around 60-70 HU (with corrCBCT). Differences in WEPL from the rigidCT were typically well below 5 mm for the corrCBCTs, compared to well above 10 mm for the stdCBCTs with the largest deviations in the head and thorax regions. Gamma pass rates (2%/2mm) when comparing CBCT-based dose re-calculations to rigidCT calculations were improved from around 80% (with stdCBCT) to mostly above 90% (with corrCBCT). CONCLUSION Scatter correction leads to substantial artefact reductions, improving accuracy of CBCT-based proton range/dose calculations.
Collapse
Affiliation(s)
| | | | - Ulrik Vindelev Elstrøm
- Danish Centre for Particle Therapy, Aarhus University Hospital/Aarhus University, Aarhus, Denmark
| | | | - Gregory C. Sharp
- Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA
| | - Brian Winey
- Massachusetts General Hospital/Harvard Medical School, Boston, MA, USA
| | - Lei Dong
- University of Pennsylvania, Philadelphia, PA, USA
| | - Ludvig Paul Muren
- Danish Centre for Particle Therapy, Aarhus University Hospital/Aarhus University, Aarhus, Denmark
| |
Collapse
|