Which test is not useful in a patient with history of syncopal attack

positron emission tomography (PET) scanning has enhanced the detection of localized infections and of occult neoplasms and lymphomasPET scanning appears to be superior to other forms of nuclear imaging. The FDG used in PET scans accumulates in tumors and at sites of inflammation and has even been shown to accumulate reliably at sites of vasculitis. Where available, FDG PET scanning should therefore be chosen over 67 Ga scanning in the diagnosis of FUO.PET scans using fluorodopa demonstrate diminished striatal dopamine formation and storage. In addition to hypometabolism in the putamen, severe caudate involvement on PET scanning distinguishes PSP from Parkinson's disease .PET scanning attempts to identify sites of malignancy based on glucose metabolism by measuring the uptake of fluorodeoxyglucose F18. Rapidly dividing cells, presumably in the lung tumors, will preferentially take up 18 F-FDG and appear as a "hot spot." To date, PET has been used for staging and detection of metastases in lung cancer and in the detection of nodules >15 mm in diameter. Combined 18 F-FDG PET-CT imaging has been shown to improve the accuracy of staging in NSCLC compared to visual correlation of PET and CT or either study alone. ref:harrison&;s principles of internal medicine,ed 18,pg no 1150