Modern Bt Techniques - Florence 2016

Uniformity Index UI

The Uniformity Index UI which can be extracted from the natural volume dose histogram (Anderson 1986), is defined as:

V(PD) HD) - V(PD = UI

u(HD) - u(PD) u(PD)

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With PD the prescription dose, HD the dose at half maximum of the peak at the high dose side, V(PD-HD) the volume receiving a dose between PD and HD, V(PD) the volume receiving at least the prescription dose PD and u(D)= D -3/2 . This uniformity index, thus, depends not only on the uniformity of the dose distribution but also on the choice of the reference isodose. It expresses the amount of the treatment volume which is concentrated between the prescription dose, PD, and the high dose side of the peak, HD.