What are some notable differences between PET and SPECT?
See: What are the indications for PET vs. SPECT?
• In contrast with PET however the tracer used in SPECT emits gamma radiation that is measured directly whereas PET tracer emits positrons that annihilate with electrons up to a few millimeters away causing two gamma photons to be emitted in opposite directions.
• A PET scanner detects these emissions "coincident" in time which provides more radiation event localization information and thus higher spatial resolution images than SPECT (which has about 1 cm resolution).
• SPECT scans however are significantly less expensive than PET scans in part because they are able to use longer-lived more easily-obtained radioisotopes than PET.
If the answers is incorrect or not given, you can answer the above question in the comment box. If the answers is incorrect or not given, you can answer the above question in the comment box.