Advanced Brachytherapy Physics - Vienna 2016

Type A uncertainty  Recall that :

b h d f k , t e st ev o un nown quant ty m s not nown ut or N>> i i k b f

i approx mates m

and the square root of the variance

approximates b.

therefore forms precision confidence interval (k=3) of our tally and it must be

as low as possible.

 Type A uncertainty decreases ~ 1/sqrt(N)

 l ( h type A uncerta nty ecreases as voxe s ze ncreases or ana ogue MC at t e expense of volume averaging)  the only other way to decrease type A would be to reduce Var(k) which is in essence an efficiency gain and will be discussed later i d l i i f