Modern Bt Techniques - Florence 2016

The Natural Dose Volume Histogram (NDVH)

A differential DVH of an 192 Ir point source

192 Ir point source, 100 cGy at 1 cm in tissue

dV / dD (mm 3 . cGy

-1 )

dV / dD = –2 π S 3/2 D –5/2

400

Area = volume between 160 and 177 cGy

300

Area = volume between 300 and 400 cGy

200

127

Area = volume between 500 and 1000 cGy

100

200 300 400 500 600 700 800 900 1000 1100 1200 Dose (cGy) 100 0

A differential DVH of a volume implant behaves as a single point source for very low doses and for very high doses (see figure at the right).