POSITRON EMISSION TOMOGRAPHY (PET)

Measures: blood flow, glucose metabolism, receptor binding, DNA and protein synthetic processes

Most commonly used tracers: FDG, methionine

Diagnostic Uses:

Distinguishing recurrent high grade tumors from radiation necrosis

Distinguishing lymphoma from infectious lesions in AIDS

Prognostic value

Advantages:

Non-invasive alternative to biopsy

Disadvantages:

Limited resolution (detection limited in lesions below 1cm)

Limited but growing availability

Third-party reimbursement variable

SINGLE PHOTON EMISSION TOMOGRAPHY (SPECT)

Measures: blood flow, sodium-potassium pump activity, receptor binding

Most commonly used tracers: Thallium, HMPAO

Diagnostic Uses:

Distinguishing recurrent high grade tumors from radiation necrosis

Distinguishing lymphoma from infectious lesions in AIDS

Advantages:

Non-invasive alternative to biopsy

Widely available

Third-party reimbursement

Disadvantages:

Poorer resolution and decreased sensitivity relative to PET