- Magnetic resonance image. Within approximately two weeks of the PET study, anatomical MRIs will be acquired at the Yale University MRI Center. Subjects will be taken through a ferromagnetic metal detector before entering the scan room. The purpose of the MRI scan is to direct the region of interest placement on the lower resolution PET images. The T1 weighted images will be acquired on a 3 Tesla Siemens Scanner. There will also be an additional resting state scan with subjects in the scanner, eyes open, fixating on a cross.