A PRELIMINARY STUDY OF RADIATION QUALITY CORRECTION FACTOR (KQ) DETERMINATION FOR WELL-TYPE IONIZATION CHAMBER

Assef Firnando F,Cahya Wulandari,Okky Agassy Firmansyah,R Pramuji Ramadhani S

doi:10.21009/spektra.052.05

Abstract

This paper deals with the determination of the radiation quality correction factor (kQ) well-type ionization chamber for the measurement of Co-60 brachytherapy. The measurement of the brachytherapy source has been done in the hospital brachytherapy facilities. The measurement of air Kerma has been done using three different ionization chambers 0.6 cm3, 30 cm3, 80 cm3, which have calibration factor traceability for Co-60 and one well-type ionization chamber which calibrated for Ir-192. The determination of the radiation quality correction factor (kQ) was determined based on the results of the air Kerma ratio between measurements using ionization chambers, which have traceability to Co-60 and Ir-192 sources. The results of the measurement of the reference air Kerma rate (RAKR) obtained from the three chambers were 21.36, 19.87, 19.34 mGy.m2.h-1, while the results of measurements with ionization chambers get a value of 19.01 mGy.m2.h-1. The kQCal results from 0.6 cm3 ionization chamber get a value of 1.07. The kQCal value was compared with the value of Andreas Schuller’s et al. kQreff of 1.05 and get a deviation of 2.2%. Implementation of the booth kQ value on the results of the RAKR from the HDR1000Plus well-type ionization chamber in the measurement of brachytherapy in two different facilities gets maximal deviation 1.7% with dose value from Treatment Planning System (TPS). The deviation was in the acceptable range of ±5%. Based on this, the use of radiation quality correction factor (kQ) value can be implemented as one method if it does not have the traceability factor calibration of the Co-60 brachytherapy source.

Highlights

Brachytherapy is one of the modalities of radiation therapy in addition to external radiotherapy
This paper describes the determination of the radiation quality correction factor for the Co-60 brachytherapy source using an high dose rate (HDR) 1000Plus well-type ionization chamber
By documents published by the International Atomic Energy Agency (IAEA), namely IAEA TEC-DOC 1274: Calibration of photon and beta ray sources used in brachytherapy, there were several methods to calibrate dosimeters used in the measurement of brachytherapy sources

Summary

INTRODUCTION

Brachytherapy is one of the modalities of radiation therapy in addition to external radiotherapy. Andreas Schűller, et al [15], in his research, investigated a value of the radiation quality correction factor (kQ) that can be used for measurement of Co-60 source brachytherapy using a well-type ionization chamber which has a calibration factor at the Ir-192 source. The reference paper [15] used the ionization chamber volume 1000 cm to measure the reference air Kerma rate from the PTB’s brachytherapy primary standard source. This paper describes the determination of the radiation quality correction factor (kQ) for the Co-60 brachytherapy source using an HDR 1000Plus well-type ionization chamber. Implementation of the results of the kQ value was carried out on two measurements of Co-60 brachytherapy source using a 1000Plus HDR well-type ionization chamber compared to the TPS value in different brachytherapy facilities. The 0.6 cm cm3, and 800 cm ionization chamber have the traceability of the Co-60 calibration factor

METHOD

EXPERIMENTAL SETUP

AND DISCUSSION

CONCLUSION