Experimentally determined backscatter factors for X-rays generated at voltages between 16 and 140 kV

Abstract

The backscatter factors computed by Grosswendt (1984) for x-rays generated at voltages between 10 and 100 kV using a Monte Carlo method differ significantly from the corresponding factors published in supplement 17 of the Brirish Journal ofRadiology (1983). The data of Grosswendt were subsequently used in the recently published International Code of Practice for Radiation Dosimetry by the IAEA (1987) in the section dealing with low-energy x-rays. The factors given in supplement 17 were obtained by a collation of experimental data from measurements performed by various investigators and include some extrapolated values. They may be subject to systematic uncertainties and it was therefore thought necessary to undertake a study of the backscatter in a uniform experiment in order to verify these data and the theoretical calculations of Grosswendt (1984).A special 3 mm thin plane-parallel ionisation chamber was constructed for this work and measurements were performed using water as a scattering medium. The experiments involved field sizes of 2.0 to 20 cm beam diameter and x-ray qualities between 0.1 and 4 mm AI for generating voltages between 16 and 140 kV. The results yielded backscatter factors which are in close agreement with those obtained by Monte Carlo calculations. The agreement with the supplement 17 data is only satisfactory at HVLS above 1 mm AI. The possible causes for the disagreement between the various published data are analysed.

The measurement of backscatter factors of kilovoltage X-ray beams using Gafchromic™ EBT2 film

“…It has been shown that B W are influenced by a wide range of factors including beam quality, field size, source-to-surface distance (SSD), and properties of the phantom material [6][7][8][9][10][11].…”

Radiochromic film for verification of superficial x-ray backscatter factors

“…Factors have been measured experimentally, previously by a number of authors. Klevenhagen [3,4] in particular developed a series of ionisation chambers specifically designed for measurement of backscatter factors using low atomic number material, plane parallel design and a phantom zero thickness extrapolation technique. Others (Coudin and Morunetto [5] and Podgorsak et al [6] ) have used thermoluminescent dosimeters, TLD's with success for these measurements.…”

“…Another approach which has provided data for backscatter factors is theoretical calculations using Monte Carlo techniques. The most recent and widely used data was performed by Grosswendt [7] and Knight in 1992 (cited in IPEMB 1996 [1]) and is the basis for backscatter factors used in the IPEMB along with experimental measurements performed by Klevenhagen [4].…”

Comparison of measured backscatter factors with Monte Carlo simulations for low energy X-ray

“…In principle, the dose at any point of an exposed phantom can be calculated using, for example, the Monte Carlo method by estimating the primary radiation reaching the point of interest and the corresponding contribution made by scattered radiation. However, because of the complexities of such calculations, this problem has been largely addressed using empirical approaches [1].…”