title: Fiber background rejection and crystal over-response compensation for GaN based in vivo dosimetry.
abstract: For dosimetric measurements using an implantable optical fiber probe with GaN (Gallium Nitride) scintillator as radioluminescence (RL) transducer, a bi-channel method is proposed to reject the background contribution of the irradiated fiber segment. It is based on spectral differences between the narrow-band light emission from GaN and the large-band background from the irradiated optical fiber. Experimental validation of this method using 6 MV photon beam has shown that the remaining background contribution after subtraction is below 1.2% for square field sizes ranging from 3 cm to 20 cm. Furthermore, a compensation method for the over-response of GaN is also proposed, since GaN is not tissue equivalent. The over-response factor of GaN exhibits a linear increase with square field aperture and depends on depth from phantom surface. This behaviour is modelled to allow compensation in specific conditions. The proposed method has been evaluated and has shown a maximum deviation of 3% for a 6 MV photon beam and 1% for an 18 MV photon beam at a depth beyond the build-up region.
authors: INL, CNRS UMR5270, Université Lyon 1, Villeurbanne F-69622, France. patrick.pittet@univ-lyon1.fr
authors: P
authors: P
authors: Pittet
authors: A
authors: A
authors: Ismail
authors: J
authors: J
authors: Ribouton
authors: R
authors: R
authors: Wang
authors: J-M
authors: JM
authors: Galvan
authors: A
authors: A
authors: Chaikh
authors: G-N
authors: GN
authors: Lu
authors: P
authors: P
authors: Jalade
authors: J-Y
authors: JY
authors: Giraud
authors: J
authors: J
authors: Balosso
mesh_terms: D016477:Artifacts; D002138:Calibration; D005708:Gallium / Q000737:chemistry*; D055100:Optical Fibers; D011874:Radiometry / Q000295:instrumentation*; D015203:Reproducibility of Results
chemical_list: C473348:gallium nitride; D005708:Gallium
keywords: Background rejection method; Over-response of GaN (Gallium nitride); Real-time implantable dosimetry