PET/CT Diagnostics in Oncology
Nowadays, positron emission tomography (PET) is known
to be one of the most advanced medical functional imaging methods. It provides
images of biochemical processes of the body with the help of molecules labeled
with positron emitting isotopes. The most frequently used 252c29c radiopharmaceutical
is the 18F-fluoro-deoxyglucose (FDG), which accumulates in cells
with increased glucose metabolism. Tissue distribution of FDG and other PET
tracers is closely related of various cell functions (i.e. metabolism, receptor
expression), allowing pathological processes to be identified and localized.
Functional imaging techniques are able to identify diseases much earlier than
it is possible through the observation of obvious anatomical changes. Today PET
scanners are equipped with multi-detector computer tomographs, thus functional
information is merged with anatomical information into a single multi-modality
image during a fast imaging session. FDG PET/CT is mainly used in Oncology
(approx. 85-90% of indications), and in lesser extent in neuro-psychiatry
(5-10%) and cardiology (~5%). This is due to the fact that most tumor types
accumulate more glucose (and hence FDG) than normal cells. In the past years,
PET/CT has brought about major changes in oncological diagnostics.
FDG PET/CT provides more accurate tumor detection and
localization for a variety of cancers, including lung, esophageal, colorectal,
breast, cervical, ovarian and head and neck cancer, as well as melanoma and
lymphoma. PET/CT is also an excellent method for early detection of recurrence, that is revealing tumors that may otherwise be
obscured by scar tissue remaining after surgery and radiation therapy. It may
be also indicated for the earliest possible evaluation of response to therapy.
Furthermore it can be used to check the degree of malignancy non-invasively and
for the determination of biopsy sites in case of multiple or large lesions. In
addition, PET/CT can be useful in localizing occult tumors not identified by
any other diagnostic imaging modality.
Although PET/CT is still a relatively new medical
imaging technique, it is becoming the preferred method for whole-body oncology
imaging and plays an increasingly important role in clinical molecular imaging.