Phantom Laboratory Catphan 503 - Page 16

16
An excel le with the linear attenuation coefcient µ [units cm
-1
] for the sensitometry
materials can be downloaded from our web site.
Contrast Scale (CS) is formally dened as
CS = µ
m
(E) - µ
w
(E)
CT
m
(E) – CT
w
(E)
where m is reference medium, and w is water, and E is the effective energy of the CT
beam.
Alternatively, CS = µ
1
(E) - µ
2
(E)
CT
1
(E) – CT
2
(E)
where 1,2 are two materials with low z effective, similar to water (eg. acrylic & air).
Linear attenuation coefcient µ [units cm
-1
]