title: In-vivo dosimetry for field sizes down to 6 × 6 mm2 in shaped beam radiosurgery with microMOSFET.
abstract: The aim of this study is to evaluate microMOSFET as in-vivo dosimeter in 6 MV shaped-beam radiosurgery for field sizes down to 6 × 6 mm2. A homemade build-up cap was developed and its use with microMOSFET was evaluated down to 6 × 6 mm2. The study with the homemade build-up cap was performed considering its influence on field size over-cover occurring at surface, achievement of the overall process of electronic equilibrium, dose deposition along beam axis and dose attenuation. An optimized calibration method has been validated using MOSFET in shaped-beam radiosurgery for field sizes from 98 × 98 down to 18 × 18 mm2. The method was detailed in a previous study and validated in irregular field shapes series measurements performed on a head phantom. The optimized calibration method was applied to microMOSFET equipped with homemade build-up cap down to 6 × 6 mm2. Using the same irregular field shapes, dose measurements were performed on head phantom. MicroMOSFET results were compared to previous MOSFET ones. Additional irregular field shapes down to 8.8 × 8.8 mm2 were studied with microMOSFET. Isocenter dose attenuation due to the homemade build-up cap over the microMOSFET was near 2% irrespective of field size. Our results suggested that microMOSFET equipped with homemade build-up cap is suitable for in-vivo dosimetry in shaped-beam radiosurgery for field sizes down to 6 × 6 mm2 and therefore that the required build-up cap dimensions to perform entrance in-vivo dosimetry in small-fields have to ensure only partial charge particle equilibrium.
authors.affiliation: Inserm Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Centre de Radiochirurgie Stéréotaxique, CHU Rangueil, Toulouse, France. Electronic address: sors.aurelie@hotmail.fr.
authors.forename: A
authors.initials: A
authors.lastname: Sors
authors.affiliation: Inserm Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Unité de Radiophysique et de Radioprotection, CHU Toulouse, France.
authors.forename: E
authors.initials: E
authors.lastname: Cassol
authors.affiliation: Centre de Radiochirurgie Stéréotaxique, CHU Rangueil, Toulouse, France; Groupe Oncorad Garonne, France.
authors.forename: I
authors.initials: I
authors.lastname: Latorzeff
authors.affiliation: Unité de Radiophysique et de Radioprotection, CHU Toulouse, France.
authors.forename: P
authors.initials: P
authors.lastname: Duthil
authors.affiliation: Centre de Radiochirurgie Stéréotaxique, CHU Rangueil, Toulouse, France.
authors.forename: J
authors.initials: J
authors.lastname: Sabatier
authors.affiliation: Inserm Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Centre de Radiochirurgie Stéréotaxique, CHU Rangueil, Toulouse, France.
authors.forename: J A
authors.initials: JA
authors.lastname: Lotterie
authors.affiliation: Centre de Radiochirurgie Stéréotaxique, CHU Rangueil, Toulouse, France; Groupe Oncorad Garonne, France.
authors.forename: A
authors.initials: A
authors.lastname: Redon
authors.affiliation: Inserm Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Centre de Radiochirurgie Stéréotaxique, CHU Rangueil, Toulouse, France.
authors.forename: I
authors.initials: I
authors.lastname: Berry
authors.affiliation: Inserm Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Université de Toulouse, UPS, INPT, LAPLACE Laboratoire Plasma et Conversion d'Energie, 118 route de Narbonne, F-31062 Toulouse cedex 9, France; Université de Toulouse, UPS, Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France.
authors.forename: X
authors.initials: X
authors.lastname: Franceries
mesh_terms: D006257:Head; D006801:Humans; D008670:Metals / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation*; D016634:Radiosurgery; D014173:Transistors, Electronic
chemical_list: D008670:Metals; D010087:Oxides
keywords: In-vivo dosimetry; Radiosurgery; Small-field dosimetry; microMOSFET