Dependence of the thermoluminescent high-temperature ratio (HTR) of LiF:Mg,Ti detectors on proton energy and dose

Abstract

The high-temperature ratio (HTR) is a parameter quantifying changes of the shape of the high-temperature part of the LiF:Mg,Ti glow-curve after exposure to densely ionizing radiation. It was introduced in order to estimate the 'effective LET' of an unknown radiation field and to correct the decreased relative TL efficiency for high-Linear Energy Transfer (LET) radiation. In the present work the dependence of HTR on proton energy (14.5 -58 MeV) and dose (0.5 -30 Gy) was investigated. All measured HTR values were at the level of 1.2 or higher, therefore significantly different from the respective value for gamma-rays (HTR=1), but HTR was found to be insensitive to changes of proton energy above 20 MeV. As a result the relationship between HTR and relative TL efficiency is not unequivocal. The HTR was found to be dependent on absorbed dose even for the lowest studied doses.

Absorbed dose estimation using LET dependence in glow curve of thermoluminescent phosphor Li3B7O12:Cu in therapeutic carbon beams

“…The idea behind the HTR method is application of the LET dependence in glow curve. On the other hand, the reports on the feasibility of the HTR method are only concerned with commercially available TLD materials such as rods and powder [3][4][5]. These TLDs only offer point dose measurement and are unsuitable for verifying complex two-dimensional/three-dimensional (2D/3D) dose distribution in modern radiotherapy.…”