Prog Med Phys.  2015 Sep;26(3):178-184. 10.14316/pmp.2015.26.3.178.

Determination of Beam Quality Correction Factors for the PTW-Markus Chamber for Electron Beam Qualities R50=1.0 and 1.4 g/cm2

• Kim MY
• Rhee DJ
• Moon YM
• Jeong DH

• KMID: 2069481
• DOI: http://doi.org/10.14316/pmp.2015.26.3.178

Abstract

The Markus ionization chamber(R) is a small plane parallel ionization chamber widely used in clinical electron beam dosimetry. Plane parallel chambers were recommended for low energy electron dosimetry with the beam quality at R50<4.0 g/cm2 (E approximately 10 MeV) according to TRS-398 protocol. However, the quality correction factors (k(Q,Q0)) of the Markus chamber was not presented in TRS-398 protocol for electron beam quality at R50<2.0 g/cm2 (Eapproximately4 MeV). In this study, the k(Q,Q0) factors of the Markus chambers (PTW-34045) for beam qualities at R50=1.0, 1.4, 2.0, 2.5, 3.0, and 5.0 g/cm2 were determined by Monte Carlo calculations (DOSRZnrc/EGSnrc) and the dosimetric formalism of quality correction factor. The derived k(Q,Q0) values were evaluated using the produced data based on TRS-398 and TG-51 protocols and known values for the Markus chamber.

Keyword

Markus chamber; Quality correction factor; Electron dosimetry

Figure

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  Fig. 1. Monte Carlo calculated quality correction factors for electron beams with mean energies between 2 and 12 MeV.

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  Fig. 2. Determined quality correction factors for Markus type ionization chamber for electron beams with beam qualities R50=1.0∼5.0 g/cm2.

Reference

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