A Study of Measurement of Relative Dose With Various Chamber for Small Field Dosimetry of 6 MV Photon Beam

Abstract

The new technologies intensity modulated radio therapy (IMRT), image guided radio therapy (IGRT) and stereotactic radio therapy (SRT) are the improved radiotherapy techniques where proper commissioning of Clinac is necessary to save patient’s healthy cells from adverse effect of radiation. The IAEA dosimetry protocol TRS-398 has been used to measure the absolute dose at 10 cm × 10 cm with CC13 (ionization) chamber. Later, the CC13 chamber was cross calibrated with CC01 (Ionization) and Razor (diode) chamber respectively for the measurement of dose in small fields. According Daisy Chaining Factor method, dose was measured for CC13 (ionization) to Razor (diode). On the other hand, the reference dose for small field was also measured for different field size(s) by applying newly proposed formalism (R. Alfonso et al. 2008) using CC13 (ionization) chamber and fitted with 4

th order polynomial fitting function where R

2=1. The variation of dose was observed as around 4% by CC01 (ionization) and Razor (diode) chambers for field sizes 1 cm × 1 cm field at reference

condition in the cross-calibration technique. The sources uncertainties were calculated as per IAEA guidelines for both Type-A and Type- B. The combined standard uncertainty lies within 1.51% (1σ).