1681 / 1840
dV / dD (mm
3
.
cGy
-1
)
192
Ir point source, 100 cGy at 1 cm in tissue
A differential DVH of an
192
Ir point source
The Natural Dose Volume Histogram (NDVH)
Area = volume between 300 and 400 cGy
Area = volume between 160 and 177 cGy
Area = volume between 500 and 1000 cGy
100
200
300
400
127
dV / dD = –2
π
S
3/2
D
–5/2
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).