The Use of PET-CT in Rheumatology

Abstract

(bismuth germanium oxide, lutetium oxyorthosilicate, and cerium-doped gadollium oxyorthosilicate). These scintillators are used to detect the gamma rays emitted from those foci that concentrated with the radiolabeled glucose ( Figure 1). They will convert gamma rays to light signals and followed by electric signals that can be displayed on a monitor. However, photons originated from structures deeper in the body are more attenuated than those originating closer to the surface. This attenuation can leads to false interpretation. In order to correct this, the CT scan can generate an attenuation map or coefficients that can be used to correct this attenuation effect. Once scaled, they can be applied to the emission data to obtain the attenuation-corrected image. Apart from improving the image quality, this correction process is also essential Abstract: Positron emission tomography (PET) is a sensitive imaging tool that gives quantitative measure of underlying inflammation. Computed tomography (CT) scan used in combination with PET further helps to delineate the anatomical structure. PET-CT can be helpful for the early diagnosis of rheumatic diseases by pattern recognition, but its role in disease monitoring still needs further evaluation. It is not a fast track solution for all because of different sensitivity and specificity to different diseases, relative high cost, and radiation exposure to the patients. Keywords: PET-CT, inflammatory diseases Background and technical aspects of PET-CTPositron emission tomography-computed tomography (PET-CT) is the fusion of functional and anatomic scan that acquired almost simultaneously. It helps us to visualize the form and activity of potential diseases within the body. It is now a popular nuclear imaging modality for the evaluation of cancer, fever or inflammation of unknown origin. The differential diagnosis sometimes includes the rheumatic disorders. It is based on the fact that the glucose transporters are up regulated on cell membrane secondary to the hypoxic drive in the highly proliferative cells such as tumor or aggregated inflammatory cells. The increase in metabolism of these cells can be reflected by the increased uptake of radiolabeled glucose such as 18 fluorine-2-fluoro-2-deoxy-d-glucose ( 18 F-FDG) [1].Inside the machine, there is a PET portion which is physically mounted together with the CT system. PET images are fitted with various crystals called scintillators