Compared to SPECT, what best describes PET in terms of radiotracer energy, image resolution, and common clinical applications?

• A. PET uses gamma-emitting tracers with lower spatial resolution; SPECT uses positron-emitting tracers with higher resolution; PET is common in oncology and neurology; SPECT used for perfusion and bone imaging.
• B. SPECT uses gamma-emitting tracers with lower spatial resolution; PET uses positron-emitting tracers with higher spatial resolution; PET is common in oncology and neurology; SPECT used for perfusion and bone imaging.
• C. PET uses gamma emitters and is mainly for bone imaging; SPECT uses positron emitters and is used in oncology.
• D. PET has lower resolution than SPECT and relies on gamma photons; SPECT uses positron emission.

Answer: (B)

The main idea is that PET and SPECT differ in the type of radiotracer, the resulting image resolution, and typical clinical uses. PET uses positron-emitting tracers, and when the positron annihilates it produces two 511-keV gamma photons detected in coincidence, which gives higher spatial resolution and better sensitivity than SPECT. SPECT uses gamma-emitting tracers and single-photon detection, typically with lower resolution because it relies on collimation. Clinically, PET is widely used in oncology and neurology to image metabolic activity and receptor function, while SPECT is commonly used for perfusion imaging (such as myocardial and brain perfusion) and bone imaging. Therefore, the statement that PET uses positron-emitting tracers with higher spatial resolution, is commonly used in oncology and neurology, and that SPECT is used for perfusion and bone imaging best describes the contrast between the two modalities.