Towards two-dimensional brachytherapy dosimetry using plastic scintillator: localization of the scintillation process

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Vol. 439; no. 1; pp. 178 - 188
• Main Authors: Kirov, A.S, Binns, W.R, Dempsey, J.F, Epstein, J.W, Dowkontt, P.F, Shrinivas, S, Hurlbut, C, Williamson, J.F
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2000
• Subjects: Medical radiation dosimetry; Scintillation detectors; 29.40.Mc; Scintillation detectors; 87.53.Dq; 87.53.Jw; Medical radiation dosimetry
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/S0168-9002(99)00894-3

Detecting the scintillation light coming from a thin sheet of plastic scintillator (PS) provides a promising fast and precise tissue equivalent method for radiation dose measurements in two dimensions. The successful implementation of such technique requires high efficiency, dosimetric tissue equivalence and high localization of the scintillation process. The last is needed to assure that the light photons originating from a pixel of the scintillator sheet correspond to energy deposited in the same pixel. Since no such information is available for PS material with standard or modified chemical composition we have developed two experimental methods for assessing the scintillation locality by measuring the optical spectra and the scintillation light profile (SLP) of PS samples with different thickness. The results of the two types of measurements are consistent with each other and with a simple theoretical model of the energy conversion process. We have demonstrated that comparing the relative intensities of the primary and secondary photon peaks in the optical spectra of the scintillator is a sensitive approach to determine the delocalization of the secondary photon emission. The ratio of the number of primary to secondary photons shows strong dependence on PS dye composition. Two types of plastic scintillator materials were tested and the advantages of one of them for radiation dosimetry are demonstrated.