C Peucelle1, C Nauraye2, A Patriarca2, E Hierso2, N Fournier-Bidoz2, I Martínez-Rovira1, Y Prezado1. 1. IMNC-UMR 8165, CNRS; Paris 7 and Paris 11 Universities, 15 rue Georges Clemenceau, Orsay Cedex 91406, France. 2. Institut Curie - Centre de Protonthérapie d'Orsay, Campus Universitaire, Bât. 101, Orsay 91898, France.
Abstract
PURPOSE: Proton minibeam radiation therapy (pMBRT) is a new radiotherapy (RT) approach that allies the inherent physical advantages of protons with the normal tissue preservation observed when irradiated with submillimetric spatially fractionated beams. This dosimetry work aims at demonstrating the feasibility of the technical implementation of pMBRT. This has been performed at the Institut Curie - Proton Therapy Center in Orsay. METHODS: Proton minibeams (400 and 700 μm-width) were generated by means of a brass multislit collimator. Center-to-center distances between consecutive beams of 3200 and 3500 μm, respectively, were employed. The (passive scattered) beam energy was 100 MeV corresponding to a range of 7.7 cm water equivalent. Absolute dosimetry was performed with a thimble ionization chamber (IBA CC13) in a water tank. Relative dosimetry was carried out irradiating radiochromic films interspersed in a IBA RW3 slab phantom. Depth dose curves and lateral profiles at different depths were evaluated. Peak-to-valley dose ratios (PVDR), beam widths, and output factors were also assessed as a function of depth. RESULTS: A pattern of peaks and valleys was maintained in the transverse direction with PVDR values decreasing as a function of depth until 6.7 cm. From that depth, the transverse dose profiles became homogeneous due to multiple Coulomb scattering. Peak-to-valley dose ratio values extended from 8.2 ± 0.5 at the phantom surface to 1.08 ± 0.06 at the Bragg peak. This was the first time that dosimetry in such small proton field sizes was performed. Despite the challenge, a complete set of dosimetric data needed to guide the first biological experiments was achieved. CONCLUSIONS: pMBRT is a novel strategy in order to reduce the side effects of RT. This works provides the experimental proof of concept of this new RT method: clinical proton beams might allow depositing a (high) uniform dose in a brain tumor located in the center of the brain (7.5 cm depth, the worst scenario), while a spatial fractionation of the dose is retained in the normal tissues in the beam path, potentially leading to a gain in tissue sparing. This is the first complete experimental implementation of this promising technique. Biological experiments are needed in order to confirm the clinical potential of pMBRT.
PURPOSE: Proton minibeam radiation therapy (pMBRT) is a new radiotherapy (RT) approach that allies the inherent physical advantages of protons with the normal tissue preservation observed when irradiated with submillimetric spatially fractionated beams. This dosimetry work aims at demonstrating the feasibility of the technical implementation of pMBRT. This has been performed at the Institut Curie - Proton Therapy Center in Orsay. METHODS: Proton minibeams (400 and 700 μm-width) were generated by means of a brass multislit collimator. Center-to-center distances between consecutive beams of 3200 and 3500 μm, respectively, were employed. The (passive scattered) beam energy was 100 MeV corresponding to a range of 7.7 cm water equivalent. Absolute dosimetry was performed with a thimble ionization chamber (IBA CC13) in a water tank. Relative dosimetry was carried out irradiating radiochromic films interspersed in a IBA RW3 slab phantom. Depth dose curves and lateral profiles at different depths were evaluated. Peak-to-valley dose ratios (PVDR), beam widths, and output factors were also assessed as a function of depth. RESULTS: A pattern of peaks and valleys was maintained in the transverse direction with PVDR values decreasing as a function of depth until 6.7 cm. From that depth, the transverse dose profiles became homogeneous due to multiple Coulomb scattering. Peak-to-valley dose ratio values extended from 8.2 ± 0.5 at the phantom surface to 1.08 ± 0.06 at the Bragg peak. This was the first time that dosimetry in such small proton field sizes was performed. Despite the challenge, a complete set of dosimetric data needed to guide the first biological experiments was achieved. CONCLUSIONS:pMBRT is a novel strategy in order to reduce the side effects of RT. This works provides the experimental proof of concept of this new RT method: clinical proton beams might allow depositing a (high) uniform dose in a brain tumor located in the center of the brain (7.5 cm depth, the worst scenario), while a spatial fractionation of the dose is retained in the normal tissues in the beam path, potentially leading to a gain in tissue sparing. This is the first complete experimental implementation of this promising technique. Biological experiments are needed in order to confirm the clinical potential of pMBRT.
Authors: F Avraham Dilmanian; Bhanu P Venkatesulu; Narayan Sahoo; Xiaodong Wu; Jessica R Nassimi; Steven Herchko; Jiade Lu; Bilikere S Dwarakanath; John G Eley; Sunil Krishnan Journal: Br J Radiol Date: 2020-01-24 Impact factor: 3.039
Authors: Y Prezado; M Dos Santos; W Gonzalez; G Jouvion; C Guardiola; S Heinrich; D Labiod; M Juchaux; L Jourdain; C Sebrie; F Pouzoulet Journal: Sci Rep Date: 2017-12-11 Impact factor: 4.379
Authors: Harald Paganetti; Chris Beltran; Stefan Both; Lei Dong; Jacob Flanz; Keith Furutani; Clemens Grassberger; David R Grosshans; Antje-Christin Knopf; Johannes A Langendijk; Hakan Nystrom; Katia Parodi; Bas W Raaymakers; Christian Richter; Gabriel O Sawakuchi; Marco Schippers; Simona F Shaitelman; B K Kevin Teo; Jan Unkelbach; Patrick Wohlfahrt; Tony Lomax Journal: Phys Med Biol Date: 2021-02-26 Impact factor: 4.174