Linear attenuation: actual fraction of photons interacting per unit thickness of an absorber, or the fraction of photons removed from the x-ray beam in a certain distance factoring in effects of compton scatter, PLE, and coherent scatter.
-In contrast to mass attenuation, linear of ice, water, and water vapor is different (different lengths for the same # of molecules).
-More attenuation occurs with denser object, higher Z material, and at k-edge.
-Lower attenuation occurs with higher kVp
Mass attenuation: fraction of photons interacting, scaled per gram of tissue. Supposed to reflect the attenuation.
-Mass attenuation of ice, water, and water vapor is the same.