Ionization chamber dosimetry based on < sup > 60 < /sup > Co absorbed dose to water calibration for diagnostic kilovoltage x-ray beams.

Ionization chamber dosimetry based on ⁶⁰Co absorbed dose to water calibration for diagnostic kilovoltage x-ray beams.
Phys Med Biol. 2018 Aug 13;:
Authors: Araki F, Ohno T, Umeno S
Abstract
The purpose of this study was to develop a new ionization chamber dosimetry formalism for diagnostic kilovoltage x-ray beams based on a 60Co absorbed dose-to-water calibration coefficient . To validate the new chamber dosimetry, 39 fluence spectra of kilovoltage x-rays were calculated, using a SpekCalc program, for Al half-value-layer (Al-HVL) values of 1.4 8.5 mm and tube voltages of 50 137.6 kVp. We used these spectra to calculate the beam quality conversion factor for kilovoltage x-ray beams Qx to a 60Co beam for a PTW 30013 Farmer ionization chamber in a reference geometrical setup (depth = 1 cm in water, field size = 20 × 20 cm2). The absorbed dose to water for kilovoltage x-rays was obtained using and . Meanwhile, the water surface dose based on the air kerma calibration coefficient NK was obtained using a Monte Carlo-calculated correction factor CF (corresponding to in AAPM TG-61) for the 39 x-ray fluence spectra. The absorbed dose based on was validated by comparing the water surface dose for the 39 x-ray fluence spectra with the water surface dose based on NK. The water surface dose based on was obtained using Monte Carlo-calculated percentage depth doses. For Al-HVL ranging from 1.4 to 8.5 mm, ranged from 0.884...

Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Araki F, Ohno T, Umeno S Tags: Phys Med Biol Source Type: research