Radio-physical properties of micelle leucodye 3D integrating gel dosimeters

J. Vandecasteele*, S. Ghysel, S. H. Baete, Y. De Deene

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Citations (Scopus)

Abstract

Recently, novel radiochromic leucodye micelle hydrogel dosimeters were introduced in the literature. In these studies, gel measured electron depth dose profiles were compared with ion chamber depth dose data, from which it was concluded that leucocrystal violet-type dosimeters were independent of dose rate. Similar conclusions were drawn for leucomalachite green-type dosimeters, only after pre-irradiating the samples to a homogeneous radiation dose. However, in our extensive study of the radio-physical properties of leucocrystal violet-and leucomalachite green-type dosimeters, a significant dose rate dependence was found. For a dose rate variation between 50 and 400 cGymin -1, a maximum difference of 75% was found in optical dose sensitivity for the leucomalachite green-type dosimeter. Furthermore, the measured optical dose sensitivity of the leucomalachite green-type dosimeter was four times lower than the value previously reported in the literature. For the leucocrystal violet-type dosimeter, a maximum difference in optical dose sensitivity of 55% was found between 50 and 400 cGymin-1. A modified composition of the leucomalachite green-type dosimeter is proposed. This dosimeter is composed of gelatin, sodium dodecyl sulfate, chloroform, trichloroacetic acid and leucomalachite green. The optical dose sensitivity amounted to 4.375 × 10-5cm-1 cGy-1 (dose rate 400 cGymin -1). No energy dependence for photon energies between 6 and 18 MV was found. No temperature dependence during readout was found notwithstanding a temperature dependence during irradiation of 1.90 cGy °C-1 increase on a total dose of 100 cGy. The novel gel dosimeter formulation exhibits an improved spatial stability (2.45 × 10-7cm 2 s-1 (=0.088 mm2 h-1) and good water/soft tissue equivalence. Nevertheless, the novel formulation was also found to have a significant, albeit reduced, dose rate dependence, as a maximum difference of 33% was found in optical dose sensitivity when the dose rate varied between 50 and 400 cGymin-1. By pre-irradiating the novel leucomalachite greentype dosimeter to 500 cGy, the apparent difference in dose response between 200 and 400 cGymin-1 was eliminated, similar to earlier findings. However, a dose response difference of 38% between 50 and 200 cGymin-1 was still measured. On the basis of these experimental results it is concluded that the leucodye micelle gel dosimeter is not yet optimal for dose verifications of high precision radiation therapy treatments. This study, however, indicates that the dose rate dependence has a potential for improvement. Future research is necessary to further minimize the dose rate dependence through extensive chemical analysis and optimization of the gel formulation. Some insights into the physicochemical mechanisms were obtained and are discussed in this paper.

Original languageEnglish
Pages (from-to)627-651
Number of pages25
JournalPhysics in Medicine and Biology
Volume56
Issue number3
DOIs
Publication statusPublished - 7 Feb 2011
Externally publishedYes

Fingerprint Dive into the research topics of 'Radio-physical properties of micelle leucodye 3D integrating gel dosimeters'. Together they form a unique fingerprint.

Cite this