Linear energy transfer dependence of a normoxic polymer gel dosimeter investigated using proton beam absorbed dose measurements

Abstract

Three-dimensional dosimetry with good spatial resolution can be performed using polymer gel dosimetry, which has been investigated for dosimetry of different types of particles. However, there are only sparse data concerning the influence of the linear energy transfer (LET) properties of the radiation on the gel absorbed dose response. The purpose of this study was to investigate possible LET dependence for a polymer gel dosimeter using proton beam absorbed dose measurements. Polymer gel containing the antioxidant tetrakis(hydroxymethyl)phosphonium (THP) was irradiated with 133 MeV monoenergetic protons, and the gel absorbed dose response was evaluated using MRI. The LET distribution for a monoenergetic proton beam was calculated as a function of depth using the Monte Carlo code PETRA. There was a steep increase in the Monte Carlo calculated LET starting at the depth corresponding to the front edge of the Bragg peak. This increase was closely followed by a decrease in the relative detector sensitivity (Srel = Dgel/Ddiode), indicating that the response of the polymer gel detector was dependent on LET. The relative sensitivity was 0.8 at the Bragg peak, and reached its minimum value at the end of the proton range. No significant effects in the detector response were observed for LET < 4.9 keV microm(-1), thus indicating that the behaviour of the polymer gel dosimeter would not be altered for the range of LET values expected in the case of photons or electrons in a clinical range of energies.

Capability of NIPAM polymer gel in recording dose from the interaction of 10 B and thermal neutron in BNCT

“…gamma ray inflicts damages mostly indirectly through producing free radicals, while neutron, in contrast, produces alpha particles, recoil protons and heavier nuclear fragments, inflicting 12 | P a g e damages directly (Hall and Giaccia, 2012). In this study, the observed low gel sensitivity in thermal neutron irradiation is in accordance with the results of studies were conducted to employ polymer gels for measuring dose resulting from high LET particles such as proton and heavy ions (Gustavsson et al, 2004;Heufelder et al, 2003;Jirasek and Duzenli, 2002;Ramm et al, 2000). In these studies, it was found that the gel sensitivity for high LET particles is significantly smaller than high-energy photons, and the gel sensitivity decreases as radiation LET increases.…”

MAGIC polymer gel for dosimetric verification in boron neutron capture therapy

“…This finding contradicts our previous results, which showed a decrease in the dose– response of polymer gel to high‐LET radiation. The BANG‐1‐type polymer gel has been reported to underestimate the absorbed dose at the Bragg peak of the proton beam by $20\%-30\%$ ( 4 , 5 , 11 ) and by $10\%-40\%$ at carbon ion beams of various energies (6) . The BANG‐3‐type gels underestimate dose under the same conditions by 50% and $40\%-60\%$ respectively.…”

“…The BANG‐3‐type gels underestimate dose under the same conditions by 50% and $40\%-60\%$ respectively. ( 4 – 6 , 11 ) …”

“…The various components and their relative share of total absorbed dose are of interest because the polymer gel response to absorbed dose depends on linear energy transfer (LET). ( 4 – 6 , 11 ) Studies have shown that gel response decreases with high‐LET particles.…”

Verification of proton range, position, and intensity in IMPT with a 3D liquid scintillator detector system

“…[1][2][3][4][5][6] However, the dynamic nature of IMPT as well as the necessity to use thousands of scanning proton beamlets makes treatment verification both time consuming and difficult to perform. [7][8][9][10][11] We have previously studied the feasibility of using a three-dimensional liquid scintillator (LS) detector system to rapidly verify proton treatments. 12,13 Using a tank of LS and a high sensitivity CCD camera, we have shown that monitoring the passage of a proton beam is feasible.…”