A direct comparison of Positron Emission Tomography (PET) (11C-Raclopride) and Single Photon Emission Computed Tomography (SPECT) (123I-IBZM) D2 RO measurements would allow GSK to gain understanding on the SPECT results obtained with SB773812, and to accurately interpret future D2 RO results from either PET or SPECT studies with new compounds.