PET, PET/CT scanner:

A small quantity of radioactive materials called radiotracers and using a special camera and a computer, your doctor can evaluate your organ and tissue functions. This technique is called Positron Emission Tomography (PET). The technique can identify body changes at the cellular level, Early signs of disease can be identified using the PET scanner before it is evident on other imaging tests.

Body functions, such as blood flow, oxygen usage, and glucose metabolism are used by PET scan to improve doctors evaluate how well organs and tissues are functioning.

On the other hand, CT imaging uses x-ray equipment and may use in some cases a contrast material, to generate multiple images or pictures of a specific organ or part of the body. These pictures are then shown on a computer monitor to be evaluated by a radiologist. CT imaging gives great anatomic information.

In several centers, a practice is known as image fusion or co-registration, in this technique, nuclear medicine images can be combined with Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) in one machine to produce special appearances. These aspects enable the information from two different exams to be fused together and interpreted on one image. This results in more accurate diagnoses. Moreover, several companies now are making single photon emission computed tomography/computed tomography (SPECT/CT).

Most PET scans today are performed on machines that combine PET and CT scanners. The combined PET/CT scans produce images that pinpoint the anatomic location of abnormal metabolic activity within the body. The combined scans have been shown to provide more accurate diagnoses than the two scans performed separately. The figure below shows compression of an image of a patient with residual Klatskin’s tumor produced :(A) Using native CT scanner, and (B) Using PET/CT Fused image (CT, 50%; PET, 50%). (A)  The native CT image shows a large hypodense area in liver hilus while PET/CT Fused image enables anatomic correspondence of increased glucose metabolism. [Michael Reinhardt, et. al. Detection of Klatskin’s tumor in extrahepatic bile duct strictures using delayed18F-FDG PET/CT: Preliminary results for 22 patient studies”, August 2005, Journal of Nuclear Medicine 46(7):1158-63]