Physics Bucharest 2017

Helical Tomotherapy - treatment planning

Definitions:

• T = gantry rotation time: 10-60 s • w = longitudinal field width: 1, 2.5, 5 cm • pitch, p = (couch displacement in T)/w e.g., p = 0.2 → each point “sees” 5 rotations

p=0.5

w

• projection: each rotation is divided in 51 projections (‘fields’), 1 every 7 ° • for each projection 64 binary MLC leaves can be moved IN or OUT with a 0 – 100% intensity modulation

• modulation factor, MF= ratio between maximum intensity in a projection and the mean of the non-zero intensities