Development of a phantom and analysis of brachytherapy dosimetry using the sulfamic acid/electron paramagnetic...

Design and develop an epoxy resin-based cylindrical phantom to simulate cancer treatment conditions in high dose rate (HDR) brachytherapy and evaluate the spatial dose distribution around a ¹⁹²Ir source using an Sulfamic Acid/EPR system.

A cylindrical phantom was fabricated from epoxy resin, allowing the precise insertion of a ¹⁹²Ir HDR brachytherapy source and multiple sulfamic acid dosimeters at predefined positions. The dosimetric system used in this study combined sulfamic acid detectors with EPR readout to quantify absorbed doses. Dosimeters were irradiated with doses ranging from 1 to 8 Gy, and the EPR signal intensities were measured to construct a calibration curve. Several dosimeters were then strategically positioned at various distances from the source to experimentally determine the dose distribution within the phantom.

The EPR dosimetry system showed a linear dose-response relationship within the 1-8 Gy range. The absorbed dose values at different locations were derived from the established calibration curve. A steep dose gradient was observed near the ¹⁹²Ir source, in agreement with theoretical expectations for HDR brachytherapy. The overall uncertainty in the dose evaluation process was estimated to be approximately 8% (k = 2).

This study demonstrates that the EPR/sulfamic acid dosimetry system provides a reliable and accurate method for dose evaluation in HDR brachytherapy. The developed epoxy resin phantom offers a practical and reproducible platform for experimental dose verification and quality assurance in brachytherapy treatments.