الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Positron emission tomography (PET) and CT are diagnostic modalities
usually combined in a PET/CT examination using 18F-flouro-deoxyglucose (18F-FDG). 18F-FDG-PET provides information about cellular
metabolism, and CT visualizes morphological details of organs and
tissues.
18F-FDG is used as a marker of glucose metabolism (wong et al.,
2011), and areas of increased uptake are suspect for malignancy,
especially if correlated with morphological CT changes. Non-malignant
disorders like infection and inflammation may also show abnormal 18FFDG accumulation, and physiological uptake mimicking pathological
accumulation can occur leading to PET misinterpretation.
18F-FDG-PET/CT is valuable in the detection, staging and control of
malignant diseases and is also sensitive for detection of incidental
clinically relevant foci. Thus, in a study evaluating infections and
inflammations by 18F-FDG-PET/CT, malignancy was detected in 6 of 26
patients (23.1%). The malignancies had not been detected by CT and Xray performed before the PET/CT.
Incidental abnormalities on 18F-fluorodeoxyglucose (FDG) positron
emission tomography PET/CT have been reported in 6.71-12.2 % of
scans. Accurate interpretation of incidental focal uptake and knowing
when to suggest further investigations therefore requires knowledge of its
differential diagnosis, the incidence of malignancy and any PET/CT
criteria which can be used to further characterize it.
As PET/CT imaging becomes more widely available, reporting
radiologists are encountering a large number of incidental findings. The
emphasis the reporter places on an incidental findings will influence
further management, as does the stage of the primary cancer and the
patient‟s comorbidity. Many clinicians are uncertain of the relevance of
the reported unexpected findings and require guidance relating to their
importance and the need for further investigation. All malignancies
should be discussed at local site-specific multidisciplinary team meetings
(MDTs). Increasingly, a PET/CT-trained radiologist and provide advice
on the probable significance of such findings in conjunction with the
clinical context.
Some parameters are used as diagnostic criteria for 18F-FDG PET/CT
to increase the accuracy of detecting malignancy. The most typical
diagnostic criterion parameter is the maximum standardized uptake value
(SUVmax). However, SUVmax has limitations, because it is also
increased in benign conditions related to physiologic variations,
degeneration, and infection or inflammation, as well as in malignant
lesions.
One of the methods to overcome this problem is to use dual-time point
PET imaging in the identification of malignant lesions. Various studies
have reported the effectiveness of dual-time point PET imaging in
different malignancies. They suggested the retention index (RI), the
percentage change between the 1-h SUVmax and the 2-h SUVmax, as a
diagnostic criterion.