Abstract
This paper aims to explain the phenomenon of laser light trapping (LLT) in a 3D polymer gel dosimeter. A VIC-T polymer gel dosimeter containing 17% N-vinylpyrrolidone, 8% N,N′-methylenebisacrylamide, 12% tert-butyl alcohol, 5% gelatine, 0.02% hydroquinone and 14 mM tetrakis(hydroxymethyl)phosphonium chloride was used in this study. It was exposed to green laser light with a wavelength of 532 nm. A film was recorded during the exposure. After exposure, Raman spectroscopy was used to study the reactions taking place inside the dosimeter. The obtained results were used to explain what the LLT phenomenon is, what are the consequences for the dosimeter in which such a phenomenon occurs, and what dosimeter components play an important role in the occurrence of LLT. In addition, the conditions under which 3D polymer gel dosimeters can be measured using optical computed tomography at short wavelengths of visible laser light are indicated.
Highlights
Only after the development of magnetic resonance imaging (MRI) scanners and computers was it possible to switch to advanced 3D dosimetry, as proposed by Gore et al [3], using a Fricke dosimeter [4] inserted into a polymer matrix with MRI reading
VIC-T is an acronym that originates from VIPARCT, where “CT” stands for computed tomography, and VIPARCT has been abbreviated to VIC [11], whereas “-T” in VIC-T corresponds to tetrakis(hydroxymethyl)phosphonium chloride used in this composition as oxygen scavenger
The aim of this work was to investigate and explain the phenomenon observed in the VIC-T gel dosimeter irradiated with green laser light
Summary
Only after the development of magnetic resonance imaging (MRI) scanners and computers was it possible to switch to advanced 3D dosimetry, as proposed by Gore et al [3], using a Fricke dosimeter [4] inserted into a polymer matrix with MRI reading. The dosimeter belongs to the family of 3D radiation therapy dosimeters containing Nvinylpyrrolidone (NVP). The results of the VIC-T [16] provided an optimal new composition of the gel dosimeter containing NVP, demonstrated the broad dose-response characteristics and thermal stability of the VIC-T, and indicated chemical (THPC-induced) and physical cross-linking of gelatine occurring in parallel after the manufacture of the Academic Editor: Tien-Chang Lu. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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