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The effect of fluorescence on surface dose with superficial X-rays incident on tissue with underlying lead

  • John BainesEmail author
  • S. Zawlodzka
  • T. Markwell
  • M. Chan
Scientific Paper
  • 7 Downloads

Abstract

An Advanced Markus chamber on the surface of solid water phantom was used to determine surface dose reduction, with either a lead or air interface, as a function of surface-interface separation (t). The beam quality dependence of dose reduction was investigated using the 50 kV, 100 kV and 150 kV beams of an Xstrahl 150 superficial X-ray unit. For each beam the dose correction factor, DCF(t), namely the ratio of surface dose (t) to surface dose (t = 100 mm), was determined. Monte Carlo simulations of DCF(t) with a lead interface were compared with corresponding measured values. Simulated spectra were calculated at the phantom surface for full backscatter (t = 100 mm) and with either a lead or air interface at 2 mm or 8 mm depth. For each depth and beam quality lead fluorescent radiation at the surface was evident. The variation of DCF(t) for each beam and field size exhibits a minima at t ≈ 5 mm and in the range 1 mm ≤ t ≤ 40 mm surface dose reduction is larger for 100 kV than 150 kV. Monte Carlo simulated DCF(t) are consistent with corresponding measured DCF(t). From simulated spectra L-series fluorescent X-rays (≈ 15 keV) emanating from lead at t = 2 mm are evident for all beams and fluorescent K-series X-rays only occur with 100 kV and 150 kV beams.

Keywords

Superficial X-rays Backscatter reduction due to lead 

Notes

Compliance with ethical standards

Conflict of interest

John Baines declares that he has no conflict of interest. Sylwia Zawlodzka declares that she has no conflict of interest. Tim Markwell declares that he has no conflict of interest. Millicent Chan declares that she has no conflict of interest.

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Copyright information

© Australasian College of Physical Scientists and Engineers in Medicine 2019

Authors and Affiliations

  1. 1.Radiation Oncology Princess Alexandra HospitalBrisbaneAustralia

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