link to lecture transcript - UT-H GSBS Medical Physics Class Site

What about the scatter coefficient? Remember when we have attenuation, two
things can happen. Some of the energy can be transferred to charged particles,
while some of the energy can go to a scattered photon. So the scatter coefficient is
going to be equal to the total coefficient minus the energy transfer coefficient.
At low energies, the energy transfer is small, so the scatter coefficient is
approximately equal to the total attenuation coefficient. Compton scatter is not a
good process for transferring energy to charged particles at low energies, but this is
also consistent with classical scatter, so we do wind-up getting the coherent scatter
in the limit of low energies.
At high energies, almost all of the energy gets transferred to charged particles.
Consequently, q y the scatter coefficient approaches pp zero. So the scatter coefficient
goes between the total attenuation coefficient at low energies and zero at high
energies.
Now, let’s use this information about coefficients to deduce some properties of
energy transfer and energy absorption.
17