All the given statements are true about PET scan except :

Positron emission tomography (PET) Is a sensitive and specific functional imaging method that allows metabolic mapping of disease processes . The most widely used tracer, 18F-fluorodeoxyglucose (18FDG), acts as a glucose analogue allowing imaging of glucose utilization, a process that is enhanced in many malignant tumours. Various PET radionuclides, including 18 F-fluorine, 11 C-carbon, 13 N-nitrogen and 15 O-oxygen, provides the potential to investigate multiple aspects of tumour biology in addition to glucose utilization, including cellular proliferation, hypoxia, neo-angiogenesis and apoptosis. 18 FDG is the ideal isotope for PET scan with a half life of -110 minutes. 18-Fluoro-2-deoxy-D-glucose positron emission tomography (18-FDG PET) is highly sensitive for the detection of malignancy and can be used to detect small metastases or local recurrence that may not be obvious on CT. FDG PET is not specific and therefore cannot be used for differentiating few benign conditions from malignant lesions. Disadvantages Glucose utilization is not entirely specific to malignant tissue, some benign processes like inflammatory sites,infections,granulomas being associated with enhanced glycolysis. Normal variation of uptake of 18FDG in some tissues, including bowel, urinary tract, muscle and brown fat, can cause interpretative pitfalls