IMRT

DVH  NON-UNIFORM IRRADIATION

When considering non-uniform dose distributions (characterised by their DVH), the DVH has to be converted or reduced to an equivalent uniform dose distribution. The DVH can be reduced to an effective homogeneous dose (EUD) to total volume (DVH  {D=EUD, ν =1}). The EUD algorithm uses the power-law relationship:

n   

i    = ∑

n 1

EUD

D

i ν

⋅

i

where D i correspond to a point of the differential DVH (the sum is performed through the entire DVH) and n is a parameter that, for every organ, describes the volumetric dependence of the dose-response relationship: for small n (n  0) the EUD tends to the maximum dose, while for n equal to 1 the EUD is the average dose. and ν i