SUV correction for injection errors in FDG-PET examination.

OBJECTIVE: Many studies have documented the clinical usefulness of standardized uptake values (SUV) for diagnosis. However, in the event of injection error, accurate measurements cannot be obtained if the radioactivity of fluorodeoxyglucose (FDG) leakage is not subtracted from the administered dosage. Here, a correction formula for radioactivity estimation that takes into account the radioactivity of FDG leakage was derived on the basis of a phantom experiment. Furthermore, to determine whether SUV could be accurately calculated by the correction formula, we performed a volunteer study. METHODS: Images were displayed by altering the conversion constant from 1.0, 0.1 to 0.01, and the range of correctable counts was verified on the basis of image inversion. To estimate the radioactivity of FDG leakage by imaging, the count of the leakage was measured, converted into a radioactivity concentration using a cross-calibration factor (CCF), and multiplied by volume, as measured by imaging. Three factors that markedly affect count, i.e., count rate performance, partial volume effect and crosstalk, were assessed in phantom studies in order to derive a correction formula. In addition, to clarify the accuracy of the correction formula, we attached to the right elbow. RESULTS: With a conversion constant of 0.1, there was no image inversion at or=28 mm Leakage radioactivity (MBq)=positron emission tomography (PET) radioactivity (MBq)x0.9. For leakages of >or=15 mm but <28 mm Leakage radioactivity (MBq)=PET radioactivity (MBq)x0.9x(0.0517xleakage size (mm)-0.4029). In a volunteer study with 10 MBq leakage, SUV recalculated using the formula achieved 99.97% correction, whereas with 100 MBq leakage, SUV achieved 67.5% resulting in poor correction. CONCLUSIONS: The present correction technique can accurately calculate SUV and could be useful for the clinical diagnosis of malignant tumors.

[Paraneoplastic neurologic syndrome and small-cell lung cancer in a patient positive for anti-Hu antigen].

We encountered a case of small-cell lung cancer with paraneoplastic neurologic syndrome in a 68-year old man. Progressive dysesthesia had developed in his hands and legs over a period of 4 months. Chest radiography and chest CT scanning on admission showed a mass in the hilum of the left lung. Anti-Hu antibody was found in his serum and the subsequent histopathological diagnosis by TBLB was small cell lung cancer. The patient underwent complete remission, in terms of tumor size, as a result of concurrent chemoradiotherapy (cisplatin, etoposid) and the dysesthesia in his legs was alleviated.