Supplementary Figure 1.

Schematic illustrating single photon emission computed tomography (SPECT) and positron emission tomography (PET). (a) In SPECT, a single photon is produced as the isotope decays and this single photon must be detected through rotating detectors using a collimator. (b) In PET, annihilation eventually occurs with the positron and electron to produce two high energy (511 keV) gamma rays at ~ 180° that are detected using a circular ring of detectors.