Data for the dosimetry of low- and medium-energy kV x rays.

Data for the dosimetry of low- and medium-energy kV x rays. Phys Med Biol. 2019 Sep 06;: Authors: Andreo P Abstract Following the publication of the ICRU Report~90 (2016) on key data for measurement standards in radiation dosimetry, where ionometric air-kerma standards for kilovoltage (kV) x-ray beams are estimated to change by up to about 0.5\%, an update of the backscatter factors and water/air ratios of mass energy-absorption coefficients in kV dosimetry protocols was deemed necessary for consistency with the new ICRU key data. In addition, numerical methods and Monte Carlo (MC) systems that did not exist at the time when air-kerma protocols were developed, are currently available.
 
 Calculations of the chamber-independent quantities required for the dosimetry of low- and medium-energy kV x~rays have been carried out using a consistent set of key data throughout the complete process. The quantities are based on MC calculations of a database for a dense grid of monoenergetic photons for different beam diameters and source-to-surface distances, followed by a convolution procedure to compute water/air energy-absorption coefficient ratios and backscatter factors for 340 experimental and calculated kV spectra. 
 It has been found that for a given HVL and field size the variation of backscatter factors for different kVs can be up to about 5\%, a trend confirmed with independent calculations that show...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research