Paraneoplastic encephalitis associated with cystic teratoma is detected by fluorodeoxyglucose positron emission tomography with negative magnetic resonance image findings.

The role of fluorodeoxyglucose (FDG) positron emission tomography (PET) as a functional imaging technique used in the evaluation of a variety of malignancies has been well known. Paraneoplastic encephalitis is a rare central nervous complication, which has been reported in some tumors. Traditionally, magnetic resonance imaging of the brain is performed to aid in its diagnosis. The authors report a case of paraneoplastic encephalitis, associated with cystic teratoma, which had positive FDG-PET findings but appeared normal on magnetic resonance imaging.

Unrecognized renal transplants as a potential source of false-positive interpretation of FDG PET.

Renal transplantation has become an effective therapy for patients with late-stage renal disease. Fluorodeoxyglucose (FDG) positron emission tomography (PET) is accepted as an important diagnostic technique in the evaluation of suspected or known malignancies or other disorders in the day-to-day practice of medicine. Because FDG is excreted from the kidneys into the urine, unrecognized renal transplants can appear as malignant lesions. Familiarity with the clinical history is a prerequisite in the correct interpretation of FDG PET images in this setting. In addition, FDG PET images should be correlated with anatomic images when such studies are available. When neither clinical history nor anatomic images are available, a combination of "abnormal" activity in the pelvis and absence of normal renal activity should raise suspicion of the existence of a renal transplant.

Rapid normalization of osseous FDG uptake following traumatic or surgical fractures.

It is known that following a traumatic fracture or surgical intervention, bone scintigraphy reveals positive results for an extended period of time, posing a challenge when evaluating patients for possible malignancy or superimposed osteomyelitis. Previous reports indicate that acute fractures can also result in increased fluorine-18 fluorodeoxyglucose (FDG) accumulation and therefore cause difficulties when patients are evaluated for other indications by FDG-PET. The purpose of this study was to assess the pattern and time course of abnormal FDG uptake following traumatic or surgical fracture. A total of 1,517 consecutive patients who underwent whole-body FDG-PET imaging were retrospectively studied. A history of fractures or orthopedic intervention was obtained from an interview prior to scanning. The FDG-PET results were compared with the results of other imaging studies, including bone scans, radiographs, CT, and MRI, as well as surgical pathology reports. Thirty-seven patients with a known date of traumatic or surgical fracture were identified. Among these, 14 had fractures or surgery within 3 months prior to FDG-PET, while 23 had fractures or surgical intervention greater than 3 months prior to FDG-PET. FDG-PET showed no abnormally increased uptake at the known fracture or surgical sites in 30 of these patients. Notably, in the 23 patients with fractures more than 3 months old, all but one showed no abnormally increased uptake. Furthermore, the positive FDG uptake in this exception was a result of complicating osteomyelitis. In the 14 patients with a history of fracture less than 3 months old, only six had abnormally increased FDG uptake. Following traumatic or surgical fractures, FDG uptake is expected to be normal within 3 months unless the process is complicated by infection or malignancy.