Dose Course 2018_Flipping book

Dose per MU formalisms: factor-based dose calculations

d Reference normalisation conditions: choice of reference depth

ref

Reference depth in water of 10 cm recommended irrespective of beam quality index

– Previous recommendations where 5 cm for BQI < 0.70 and 10 cm for BQI > 0.70

Avoids unpredictable influence of contaminating electrons as far as possible – Rule of thumb: depth of influence ~ 2·d Dmax

MM22, 20 MV , SSD=100cm

or MV/3

 10cm depth chosen for consistency in reference depth for beam calibration and MU calculation

Sjögren and Karlsson, Med, Phys, 25(6), p916, 1998