Dose 2016

Stoichiometric calibration: An improved approach

U. Schneider et al PMB 1996

Relative proton stopping power

Calculate Relative Electron Density:

[

]

(

)

2 2

2

2

N

cm β

ρ β β β β = 2

2 log

1

I

ρ

− −

g

ρ ρ

K

e

m

ρ

=

=

[

]

(

)

e

2 2

2

s

e

e

water

water g

cm β

2 log

1

N

I

ρ

− −

e

w

Using chemical composition:

Zw N N N

∑ ∑ i i

i g

=

=

g

A

A

i

µ

Rutherford et al 1976

1000 =

H

~

{

} KN

µ

ˆ

ph

62.3

coh

86.1

w

) , (

K ZK ZKAZN +

=

+

ρ µ

g

By making measurements of H for different tissue substitutes of known composition one can get a fit of data to derive values for K ph/coh/KN which characterize the CT scanner

From this can plot a curve to predict H for range of tissues substitutes and real tissue