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. Author manuscript; available in PMC: 2018 May 21.
Published in final edited form as: Phys Med Biol. 2017 Mar 13;62(10):4183–4201. doi: 10.1088/1361-6560/aa6641

Figure 3.

Figure 3

Strength of signals reaching the detector from activity in the tumor remnant are depth dependent. The strength of all signals decreases with depth due to attenuation and reduction in solid angle. Gamma photons are least attenuated with depth, while e+ particles are most attenuated. Detection of Cerenkov optical photons depends on tissue optical properties. Grey matter, which has the lowest µa and µs’, is least depth sensitive, while white matter, which has higher µa and µs’ is more sensitive to depth.