Radio-Fluorogenic Gel Dosimetry with Coumarin.

Peter Sandwall,Henry Fenichel,Henry Spitz,Brandt Bastow,Howard Elson,William Connick,Michael Lamba

doi:10.3390/bioengineering5030053

Abstract

Gel dosimeters are attractive detectors for radiation therapy, with properties similar to biological tissue and the potential to visualize volumetric dose distributions. Radio-fluorogenesis is the yield of fluorescent chemical products in response to energy deposition from ionizing radiation. This report shares the development of a novel radio-fluorogenic gel (RFG) dosimeter, gelatin infused with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission following ultra-violet (UV) to near UV (365–405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated. The response of the RFG was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship independent of energy and type, with a dose-rate dependency. This report demonstrates increased photo-yield with high pH and the utility of gelatin-RFG for phantom studies of radiation dosimetry.

Highlights

Advancements in radiation therapy technology have supported study of tissue-equivalent gels containing active chemical sensors for the measurement of absorbed dose of radiation
Radio-fluorogenic sensors are chemical elements that allow for dosimetry and quantification of energy deposition from of ionizing radiation through measurement of molecular fluorescence
Numerous aromatic compounds are recognized as radio-fluorogenic, with hydroxylation producing fluorescent products

Summary

Introduction

Advancements in radiation therapy technology have supported study of tissue-equivalent gels containing active chemical sensors for the measurement of absorbed dose of radiation. Polymer-RFG production involves a nitrogen-flushed glove box and pre-irradiation prior to use as a dosimeter. With strict fabrication methods and sometimes toxic constituents, the hunt for the ideal sensor element and gel substrate continues. Slow gelation yields increased organization and orientation of chain elements with greater lateral bonding, resulting in the formation of fine well-ordered lattices [13].

Results

Conclusion