TY - JOUR

T1 - Volume dose ratios relevant for alanine dosimetry in small, 6 MV photon beams

A1 - Cronholm,Rickard O.

A1 - Andersen,Claus Erik

A1 - Behrens,Claus F.

A1 - Helt-Hansen,Jakob

AU - Cronholm,Rickard O.

AU - Andersen,Claus Erik

AU - Behrens,Claus F.

AU - Helt-Hansen,Jakob

PB - Pergamon

PY - 2012

Y1 - 2012

N2 - The overall objective of this work is to establish alanine dosimetry for traceable measurements in clinical radiotherapy beams, in particular for non-reference situations such as small field sizes and composite beam delivery (e.g. intensity modulated radiotherapy and volumetric modulated arc therapy). To this end, we here present the results of a Monte Carlo simulation study with DOSRZnrc that investigated the influence of field and detector size for small 6 MV photon beams. The study focusses on doses averaged over the volume of the detector rather than point doses.The ratio of volume averaged doses to water (D¯W) and alanine (D¯det) was found to be approximately 1.025 for most situations studied, and a constant ratio is likely to be representative for many applications in radiation therapy. However, D¯W/D¯det was found to be as low as 0.9908 ± 0.0037 in situations where one might expect significant deviations from charged particle equilibrium (i.e. at shallow depths and when the field size was smaller than the range of the secondary electrons). These effects therefore need consideration when finite-size alanine dosimeters are used under such conditions.

AB - The overall objective of this work is to establish alanine dosimetry for traceable measurements in clinical radiotherapy beams, in particular for non-reference situations such as small field sizes and composite beam delivery (e.g. intensity modulated radiotherapy and volumetric modulated arc therapy). To this end, we here present the results of a Monte Carlo simulation study with DOSRZnrc that investigated the influence of field and detector size for small 6 MV photon beams. The study focusses on doses averaged over the volume of the detector rather than point doses.The ratio of volume averaged doses to water (D¯W) and alanine (D¯det) was found to be approximately 1.025 for most situations studied, and a constant ratio is likely to be representative for many applications in radiation therapy. However, D¯W/D¯det was found to be as low as 0.9908 ± 0.0037 in situations where one might expect significant deviations from charged particle equilibrium (i.e. at shallow depths and when the field size was smaller than the range of the secondary electrons). These effects therefore need consideration when finite-size alanine dosimeters are used under such conditions.

KW - Alanine

KW - Small field

KW - Correction factor

KW - Monte Carlo

U2 - 10.1016/j.radmeas.2012.07.009

DO - 10.1016/j.radmeas.2012.07.009

JO - Radiation Measurements

JF - Radiation Measurements

SN - 1350-4487

IS - 10

VL - 47

SP - 1014

EP - 1017

ER -