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Stengl C, Muñoz ID, Arbes E, Rauth E, Christensen JB, Vedelago J, Runz A, Jäkel O, Seco J. Dosimetric study for breathing-induced motion effects in an abdominal pancreas phantom for carbon ion mini-beam radiotherapy. Med Phys 2024; 51:5618-5631. [PMID: 38631000 DOI: 10.1002/mp.17077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 03/14/2024] [Accepted: 04/02/2024] [Indexed: 04/19/2024] Open
Abstract
BACKGROUND Particle mini-beam therapy exhibits promise in sparing healthy tissue through spatial fractionation, particularly notable for heavy ions, further enhancing the already favorable differential biological effectiveness at both target and entrance regions. However, breathing-induced organ motion affects particle mini-beam irradiation schemes since the organ displacements exceed the mini-beam structure dimensions, decreasing the advantages of spatial fractionation. PURPOSE In this study, the impact of breathing-induced organ motion on the dose distribution was examined at the target and organs at risk(OARs) during carbon ion mini-beam irradiation for pancreatic cancer. METHODS As a first step, the carbon ion mini-beam pattern was characterized with Monte Carlo simulations. To analyze the impact of breathing-induced organ motion on the dose distribution of a virtual pancreas tumor as target and related OARs, the anthropomorphic Pancreas Phantom for Ion beam Therapy (PPIeT) was irradiated with carbon ions. A mini-beam collimator was used to deliver a spatially fractionated dose distribution. During irradiation, varying breathing motion amplitudes were induced, ranging from 5 to 15 mm. Post-irradiation, the 2D dose pattern was analyzed, focusing on the full width at half maximum (FWHM), center-to-center distance (ctc), and the peak-to-valley dose ratio (PVDR). RESULTS The mini-beam pattern was visible within OARs, while in the virtual pancreas tumor a more homogeneous dose distribution was achieved. Applied motion affected the mini-beam pattern within the kidney, one of the OARs, reducing the PVDR from 3.78 ± $\pm$ 0.12 to 1.478 ± $\pm$ 0.070 for the 15 mm motion amplitude. In the immobile OARs including the spine and the skin at the back, the PVDR did not change within 3.4% comparing reference and motion conditions. CONCLUSIONS This study provides an initial understanding of how breathing-induced organ motion affects spatial fractionation during carbon ion irradiation, using an anthropomorphic phantom. A decrease in the PVDR was observed in the right kidney when breathing-induced motion was applied, potentially increasing the risk of damage to OARs. Therefore, further studies are needed to explore the clinical viability of mini-beam radiotherapy with carbon ions when irradiating abdominal regions.
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Affiliation(s)
- Christina Stengl
- Medical Faculty Heidelberg, Heidelberg University, Heidelberg, Germany
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Iván D Muñoz
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Department for Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Eric Arbes
- Department for Physics and Astronomy, Heidelberg University, Heidelberg, Germany
- Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Evelyn Rauth
- Department for Physics and Astronomy, Heidelberg University, Heidelberg, Germany
- Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Jeppe B Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institute (PSI), Villigen, Switzerland
| | - José Vedelago
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Heidelberg, Germany
| | - Armin Runz
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Oliver Jäkel
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Heidelberg Ion Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Heidelberg, Germany
| | - Joao Seco
- Department for Physics and Astronomy, Heidelberg University, Heidelberg, Germany
- Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
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Stengl C, Panow K, Arbes E, Muñoz ID, Christensen JB, Neelsen C, Dinkel F, Weidner A, Runz A, Johnen W, Liermann J, Echner G, Vedelago J, Jäkel O. A phantom to simulate organ motion and its effect on dose distribution in carbon ion therapy for pancreatic cancer. Phys Med Biol 2023; 68:245013. [PMID: 37918022 DOI: 10.1088/1361-6560/ad0902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 11/02/2023] [Indexed: 11/04/2023]
Abstract
Objective. Carbon ion radiotherapy is a promising radiation technique for malignancies like pancreatic cancer. However, organs' motion imposes challenges for achieving homogeneous dose delivery. In this study, an anthropomorphicPancreasPhantom forIon-beamTherapy (PPIeT) was developed to simulate breathing and gastrointestinal motion during radiotherapy.Approach. The developed phantom contains a pancreas, two kidneys, a duodenum, a spine and a spinal cord. The shell of the organs was 3D printed and filled with agarose-based mixtures. Hounsfield Units (HU) of PPIeTs' organs were measured by CT. The pancreas motion amplitude in cranial-caudal (CC) direction was evaluated from patients' 4D CT data. Motions within the obtained range were simulated and analyzed in PPIeT using MRI. Additionally, GI motion was mimicked by changing the volume of the duodenum and quantified by MRI. A patient-like treatment plan was calculated for carbon ions, and the phantom was irradiated in a static and moving condition. Dose measurements in the organs were performed using an ionization chamber and dosimetric films.Main results. PPIeT presented tissue equivalent HU and reproducible breathing-induced CC displacements of the pancreas between (3.98 ± 0.36) mm and a maximum of (18.19 ± 0.44) mm. The observed maximum change in distance of (14.28 ± 0.12) mm between pancreas and duodenum was consistent with findings in patients. Carbon ion irradiation revealed homogenous coverage of the virtual tumor at the pancreas in static condition with a 1% deviation from the treatment plan. Instead, the dose delivery during motion with the maximum amplitude yielded an underdosage of 21% at the target and an increased uncertainty by two orders of magnitude.Significance. A dedicated phantom was designed and developed for breathing motion assessment of dose deposition during carbon ion radiotherapy. PPIeT is a unique tool for dose verification in the pancreas and its organs at risk during end-to-end tests.
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Affiliation(s)
- Christina Stengl
- Medical Faculty Heidelberg, Heidelberg University, Im Neuenheimer Feld 672, Heidelberg D-69120, Germany
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Kathrin Panow
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Eric Arbes
- Biomedical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Department for Physics and Astronomy, Heidelberg University, Im Neuenheimer Feld 226, Heidelberg D-69120, Germany
| | - Iván D Muñoz
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Department for Physics and Astronomy, Heidelberg University, Im Neuenheimer Feld 226, Heidelberg D-69120, Germany
| | - Jeppe B Christensen
- Department of Radiation Safety and Security, Paul Scherrer Institute (PSI), Forschungsstrasse 111, Villigen PSI 5232, Switzerland
| | - Christian Neelsen
- Department of Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Department of Nuclear Medicine, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Department of Radiology, Charité-Universitätsmedizin Berlin, Charitéplatz 1, Berlin D-10117, Germany
| | - Fabian Dinkel
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Artur Weidner
- Medical Faculty Heidelberg, Heidelberg University, Im Neuenheimer Feld 672, Heidelberg D-69120, Germany
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Armin Runz
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Wibke Johnen
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - Jakob Liermann
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Im Neuenheimer Feld 400, Heidelberg D-69120, Germany
- Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Im Neuenheimer Feld 450, Heidelberg D-69120, Germany
- National Center for Tumor Diseases (NCT), Im Neuenheimer Feld 460, D-69120 Heidelberg, Germany
| | - Gernot Echner
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - José Vedelago
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Im Neuenheimer Feld 400, Heidelberg D-69120, Germany
| | - Oliver Jäkel
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg D-69120, Germany
- Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
- Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital (UKHD), Im Neuenheimer Feld 450, Heidelberg D-69120, Germany
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Ahern V, Adeberg S, Fossati P, Garrett R, Hoppe B, Mahajan A, Orlandi E, Orecchia R, Prokopovich D, Seuntjens J, Thwaites D, Trifiletti D, Tsang R, Tsuji H. An international approach to estimating the indications and number of eligible patients for carbon ion radiation therapy (CIRT) in Australia. Radiother Oncol 2023; 187:109816. [PMID: 37480996 DOI: 10.1016/j.radonc.2023.109816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Revised: 07/13/2023] [Accepted: 07/15/2023] [Indexed: 07/24/2023]
Abstract
BACKGROUND AND PURPOSE To establish the treatment indications and potential patient numbers for carbon ion radiation therapy (CIRT) at the proposed national carbon ion (and proton) therapy facility in the Westmead precinct, New South Wales (NSW), Australia. METHODS An expert panel was convened, including representatives of four operational and two proposed international carbon ion facilities, as well as NSW-based CIRT stakeholders. They met virtually to consider CIRT available evidence and experience. Information regarding Japanese CIRT was provided pre- and post- the virtual meeting. Published information for South Korea was included in discussions. RESULTS There was jurisdictional variation in the tumours treated by CIRT due to differing incidences of some tumours, referral patterns, differences in decisions regarding which tumours to prioritise, CIRT resources available and funding arrangements. The greatest level of consensus was reached that CIRT in Australia can be justified currently for patients with adenoid cystic carcinomas and mucosal melanomas of the head and neck, hepatocellular cancer and liver metastases, base of skull meningiomas, chordomas and chondrosarcomas. Almost 1400 Australian patients annually meet the consensus-derived indications now. CONCLUSION A conservative estimate is that 1% of cancer patients in Australia (or 2% of patients recommended for radiation therapy) may preferentially benefit from CIRT for initial therapy of radiation resistant tumours, or to boost persistently active disease after other therapies, or for re-irradiation of recurrent disease. On this basis, one national carbon ion facility with up to four treatment rooms is justified for Australian patients.
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Affiliation(s)
- Verity Ahern
- Sydney West Radiation Oncology Network, Westmead, Australia; Westmead Clinical School, The University of Sydney, Australia.
| | - Sebastian Adeberg
- Marburg Ion-Beam Therapy Center (MIT), Department of Radiation Oncology, Heidelberg University Hospital, Marburg, Germany; Department of Radiation Oncology, Marburg University Hospital, Marburg, Germany
| | - Piero Fossati
- MedAustron Ion Therapy Center, Austria; Karl Landsteiner University of Health Sciences, Austria
| | - Richard Garrett
- Australian Nuclear Science and Technology Organisation, Australia
| | | | | | - Ester Orlandi
- National Center for Oncological Hadrontherapy (Fondazione CNAO), Pavia, Italy
| | - Roberto Orecchia
- Scientific Directorate, European Institute of Oncology, IRCCS, Milan, Italy
| | | | - Jan Seuntjens
- Department of Medical Physics, Princess Margaret Cancer Centre, Toronto, Canada; Radiation Oncology, University of Toronto, Toronto, Canada
| | - David Thwaites
- Institute of Medical Physics, School of Physics, University of Sydney, Australia; Radiotherapy Research Group, Leeds Institute of Medical Research, University of Leeds, Leeds, UK
| | | | - Richard Tsang
- Radiation Oncology, University of Toronto, Toronto, Canada; Department of Radiation Oncology and Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada
| | - Hiroshi Tsuji
- National Institutes for Quantum Science and Technology, Chiba, Japan
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Endo M. Creation, evolution, and future challenges of ion beam therapy from a medical physicist's viewpoint (Part 2). Chapter 2. Biophysical model, treatment planning system and image guided radiotherapy. Radiol Phys Technol 2023; 16:137-159. [PMID: 37129777 DOI: 10.1007/s12194-023-00722-5] [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: 12/02/2022] [Revised: 04/13/2023] [Accepted: 04/13/2023] [Indexed: 05/03/2023]
Abstract
When an ion beam penetrates deeply into the body, its kinetic energy decreases, and its biological effect increases due to the change of the beam quality. To give a uniform biological effect to the target, it is necessary to reduce the absorbed dose with the depth. A bio-physical model estimating the relationship between ion beam quality and biological effect is necessary to determine the relative biological effectiveness (RBE) of the ion beam that changes with depth. For this reason, Lawrence Berkeley Laboratory, National Institute of Radiological Sciences (NIRS) and GSI have each developed their own model at the starting of the ion beam therapy. Also, NIRS developed a new model at the starting of the scanning irradiation. Although the Local Effect Model (LEM) at the GSI and the modified Microdosimetric Kinetic Model (MKM) at the NIRS, the both are currently used, can similarly predict radiation quality-induced changes in surviving fraction of cultured cell, the clinical RBE-weighted doses for the same absorbed dose are different. This is because the LEM uses X-rays as a reference for clinical RBE, whereas the modified MKM uses carbon ion beam as a reference and multiplies it by a clinical factor of 2.41. Therefore, both are converted through the absorbed dose. In PART 2, I will describe the development of such a bio-physical model, as well as the birth and evolution of a treatment planning system and image guided radiotherapy.
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Affiliation(s)
- Masahiro Endo
- Association for Nuclear Technology in Medicine, Nikkei Bldg., 7-16 Nihombashi-Kodemmacho, Chuo-Ku, Tokyo, Tokyo, 103-0001, Japan.
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Wang W, Huang Z, Sun W, Wang X, Zhao J, Shen H. Calibration and evaluation of the relative biological effectiveness for carbon-ion radiotherapy in a new relative to a clinically applied treatment planning system. Radiat Oncol 2022; 17:219. [PMID: 36587224 PMCID: PMC9805684 DOI: 10.1186/s13014-022-02181-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 12/15/2022] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND The study objective was to validate the relative biological effectiveness (RBE) in RayStation for carbon-ion radiotherapy (CIRT) using the Syngo treatment planning system as reference. METHODS Local effect model I was established in RayStation (Ray-LEM) with the same parameters as in LEM I in Syngo (Syngo-LEM). Three cube plans covering most of the tumors treated at our center were generated with Syngo-LEM. Ray-LEM re-calculated the Syngo plans and compared the RBEs to the Syngo counterparts. The results showed that RayStation RBE was smaller than Syngo RBE. To ensure that Ray-LEM reproduced Syngo RBE, the observed deviations were used to scale the maximum RBE (RBEmax) in Ray-LEM. After this calibration, we further compared the RayStation RBE to Syngo RBE using additional plans in both homogeneous phantoms and patients, to ensure that the calibrated Ray-LEM reproduced Syngo RBE even with more complex planning features. RESULTS The calibration increased the RBEmax by 2.3% to raise the Ray-LEM RBE. The target mean RBE deviations in the phantom evaluation plans were median: 0.0 (minimum: - 1.1 to maximum: 0.7) %, and the target mean RBE deviations of the clinical target volumes of 16 patient cases were - 0.4 (- 1.5 to 0.2) %. CONCLUSIONS The residual RBE difference between RayStation and Syngo was found to be ≤ 1.0%. Thus, we can propose to use RayStation for clinical CIRT treatment planning. However, the potential differences due to the absorbed beam model warrants further exploration.
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Affiliation(s)
- Weiwei Wang
- grid.8547.e0000 0001 0125 2443Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai, 200433 China ,grid.452404.30000 0004 1808 0942Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai Key Laboratory of Radiation Oncology (20dz2261000), Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, 4365 Kangxin Road, Pudong District, Shanghai, 201315 China
| | - Zhijie Huang
- grid.452404.30000 0004 1808 0942Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai Key Laboratory of Radiation Oncology (20dz2261000), Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, 4365 Kangxin Road, Pudong District, Shanghai, 201315 China
| | - Wei Sun
- grid.452404.30000 0004 1808 0942Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai Key Laboratory of Radiation Oncology (20dz2261000), Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, 4365 Kangxin Road, Pudong District, Shanghai, 201315 China
| | - Xufei Wang
- grid.8547.e0000 0001 0125 2443Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai, 200433 China
| | - Jingfang Zhao
- grid.452404.30000 0004 1808 0942Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai Key Laboratory of Radiation Oncology (20dz2261000), Shanghai Engineering Research Center of Proton and Heavy Ion Radiation Therapy, 4365 Kangxin Road, Pudong District, Shanghai, 201315 China ,grid.452404.30000 0004 1808 0942Department of Medical Physics, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, 270 Dongan Road, Xuhui District, Shanghai, 200032 China
| | - Hao Shen
- grid.8547.e0000 0001 0125 2443Institute of Modern Physics, Applied Ion Beam Physics Laboratory, Fudan University, Shanghai, 200433 China
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Molinelli S, Vai A, Russo S, Loap P, Meschini G, Paganelli C, Barcellini A, Vitolo V, Orlandi E, Ciocca M. The role of multiple anatomical scenarios in plan optimization for carbon ion radiotherapy of pancreatic cancer. Radiother Oncol 2022; 176:1-8. [PMID: 36113776 DOI: 10.1016/j.radonc.2022.09.005] [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: 03/28/2022] [Revised: 08/17/2022] [Accepted: 09/07/2022] [Indexed: 12/14/2022]
Abstract
PURPOSE /OBJECTIVE To quantify benefits of robust optimization on multiple 4DCT acquisitions combined with off-line treatment adaptation for neoadjuvant carbon ion therapy (CIRT) of pancreatic cancer. MATERIAL/METHODS For 10 previously treated patients, 4DCTs were acquired around -15 (CTPlan), -5 (RE1), -1 (RE2) and +6 (RE3) days from RT start. Treatment plans were newly optimized to a dose prescription of 38.4 Gy(RBE) (8 fractions) with a constraint of 38 Gy(RBE) to 1% of the gastrointestinal organs at risk volume (D1%). Three strategies were tested: (A) robust optimization on CTPlan maximum exhale (0Ex) with 3 mm set-up, 3% range uncertainty, including 30%-inhale; (B) addition of the RE1-0Ex scenario; (C) plan recalculation at each REi and adaptation (RPi) according to deviation thresholds from clinical goals. The cumulative variation of target coverage and GI-OARs doses was evaluated. Duodenum contours of all 4DCTs of each patient were registered on CTPlan-0Ex. The capacity of pre-RT acquisitions to predict duodenum position was investigated by computing the intersection of contours at CTplan, RE1, or their union, with respect to subsequent 4DCTs and the CTV, coupled with increasing margin. RESULTS (A) No recalculation exceeded the D1% constraint. (B) The inclusion of RE1-0Ex in the optimization problem improved inter-fraction robustness on a patient-specific basis, but was non-significant on average. (C) Half of the plans would be re-optimized to recover target coverage and/or minimize duodenum dose, at least once. A significant difference was observed between pre-RT duodenum contours when intersecting subsequent contours, either with a margin expansion. CONCLUSION Anatomical variations highlighted at multiple REi proved that a fast and efficient online adaptation is essential to optimize treatment quality of CIRT for pancreatic cancer.
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Affiliation(s)
| | | | | | - Pierre Loap
- Institut Curie, Department of Radiation Oncology, Paris, France
| | - Giorgia Meschini
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy
| | - Chiara Paganelli
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milano, Italy
| | | | | | | | - Mario Ciocca
- Dipartimento Clinico, Fondazione CNAO, Pavia, Italy
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