Immaculada Martínez-Rovira1,2, Wilfredo González1, Stephan Brons3, Yolanda Prezado1. 1. Laboratoire d'Imagerie et Modélisation en Neurobiologie et Cancérologie (IMNC), Centre National de la Recherche Scientifique (CNRS), Campus universitaire, Bât. 440, 1er étage - 15 rue Georges Clemenceau, 91406, Orsay Cedex, France. 2. Ionizing Radiation Research Group (GRRI), Physics Department, Universitat Autònoma de Barcelona, Campus UAB, Avinguda de l'Eix Central, Edicifi C, Cerdanyola del Vallès, 08193, Barcelona, Spain. 3. Heidelberg Ion Beam Therapy Center (HIT), Heidelberg University Clinic, Im Neuenheimer Feld 672, 69120, Heidelberg, Germany.
Abstract
PURPOSE: To perform dosimetric characterization of a minibeam collimator in both carbon and oxygen ion beams to guide optimal setup geometry and irradiation for future radiobiological studies. METHODS: Carbon and oxygen minibeams were generated using a prototype tungsten multislit collimator presenting line apertures 700 μm wide, which are spaced 3500 μm centre-to-centre distance apart. Several radiation beam spots generated the desired field size of 15 × 15 mm2 and production of a 50 mm long spread out Bragg peak (SOBP) centered at 80 mm depth in water. Dose evaluations were performed with two different detectors: a PTW microDiamond® single crystal diamond detector and radiochromic films (EBT3). Peak-to-valley dose ratio (PVDR) values, output factors (OF), penumbras, and full width at half maximum (FWHM) were measured. RESULTS: Measured lateral dose profiles exhibited spatial fractionation of dose at depth in a water phantom in the expected form of peaks and valleys for both carbon and oxygen radiation fields. The diamond detector and radiochromic film provided measurements of PVDR in good agreement. PVDR values at shallow depth were about 60 and decreased to about 10 at 80 mm depth in water. OF in the center of the SOBP was about 0.4; this value is larger than the corresponding one in proton minibeam radiation therapy measured using a comparable collimator due to a reduced lateral scattering for carbon and oxygen minibeams. CONCLUSIONS: Carbon and oxygen minibeams may be produced by a mechanical collimator. PVDR values and output factors measured in this first study of these minibeam radiation types indicate there is potential for their therapeutic use. Optimization of minibeam collimator design and the number and size of focal spots for irradiation are advocated to improve PDVR values and dose distributions for each specific applied use.
PURPOSE: To perform dosimetric characterization of a minibeam collimator in both carbon and oxygen ion beams to guide optimal setup geometry and irradiation for future radiobiological studies. METHODS:Carbon and oxygen minibeams were generated using a prototype tungsten multislit collimator presenting line apertures 700 μm wide, which are spaced 3500 μm centre-to-centre distance apart. Several radiation beam spots generated the desired field size of 15 × 15 mm2 and production of a 50 mm long spread out Bragg peak (SOBP) centered at 80 mm depth in water. Dose evaluations were performed with two different detectors: a PTW microDiamond® single crystal diamond detector and radiochromic films (EBT3). Peak-to-valley dose ratio (PVDR) values, output factors (OF), penumbras, and full width at half maximum (FWHM) were measured. RESULTS: Measured lateral dose profiles exhibited spatial fractionation of dose at depth in a water phantom in the expected form of peaks and valleys for both carbon and oxygen radiation fields. The diamond detector and radiochromic film provided measurements of PVDR in good agreement. PVDR values at shallow depth were about 60 and decreased to about 10 at 80 mm depth in water. OF in the center of the SOBP was about 0.4; this value is larger than the corresponding one in proton minibeam radiation therapy measured using a comparable collimator due to a reduced lateral scattering for carbon and oxygen minibeams. CONCLUSIONS:Carbon and oxygen minibeams may be produced by a mechanical collimator. PVDR values and output factors measured in this first study of these minibeam radiation types indicate there is potential for their therapeutic use. Optimization of minibeam collimator design and the number and size of focal spots for irradiation are advocated to improve PDVR values and dose distributions for each specific applied use.
Authors: Judith N Rivera; Thomas M Kierski; Sandeep K Kasoji; Anthony S Abrantes; Paul A Dayton; Sha X Chang Journal: PLoS One Date: 2020-06-22 Impact factor: 3.240
Authors: Alejandro Mazal; Juan Antonio Vera Sanchez; Daniel Sanchez-Parcerisa; Jose Manuel Udias; Samuel España; Victor Sanchez-Tembleque; Luis Mario Fraile; Paloma Bragado; Alvaro Gutierrez-Uzquiza; Nuria Gordillo; Gaston Garcia; Juan Castro Novais; Juan Maria Perez Moreno; Lina Mayorga Ortiz; Amaia Ilundain Idoate; Marta Cremades Sendino; Carme Ares; Raymond Miralbell; Niek Schreuder Journal: Front Oncol Date: 2021-01-21 Impact factor: 6.244