Image-guided biopsy: what the interventional radiologist needs to know about PET/CT.

Positron emission tomography (PET)/computed tomography (CT) with fluorine 18 fluorodeoxyglucose (FDG) is increasingly used in evaluation of oncology patients. Because PET/CT can demonstrate malignancy before morphologic changes are evident, application of PET/CT information to image-guided biopsy can facilitate early histologic diagnosis and staging. However, because FDG uptake is not specific to cancer, PET/CT findings may raise questions about whether uptake in a lesion is an indication for biopsy. To properly select patients for image-guided biopsy, interventional radiologists should be familiar with the biologic significance of FDG uptake and various causes of false-positive uptake. PET/CT images may also become a source of confusion in the interpretation of biopsy results. Various causes of false-positive and false-negative FDG uptake need to be considered, especially when there is a discrepancy between biopsy results and PET/CT findings. False-negative FDG uptake can result from cancers that are too small to be observed or not FDG avid. False-positive FDG uptake can be due to underlying inflammation from recent treatment. Conversely, complete resolution of FDG uptake in a treated lesion does not necessarily indicate absence of viable cells. When questions about PET/CT findings arise in the context of image-guided biopsy, discussion with experienced nuclear imaging physicians is essential.

Clinical and radiologic review of the normal and abnormal thymus: pearls and pitfalls.

At imaging, the thymus appears in a variety of shapes and sizes, even in the same individual. It gradually involutes with age and may acutely shrink during periods of bodily stress. During the recovery period, it grows back to its original size or even larger, a phenomenon known as thymic rebound hyperplasia. These anatomic variations and dynamic changes appear to be the main source of confusion with pathologic conditions. In turn, these misinterpretations may lead to prolongation or alteration of the chemotherapy regimen or to unnecessary radiation therapy, biopsy, or thymectomy. Familiarity with the embryology, anatomy, and dynamic physiology of the thymus is essential to avoid unnecessary imaging or invasive procedures. Radiologists play a major role in differentiating normal thymic variants, ectopic thymic tissue, and nonneoplastic thymic conditions such as rebound hyperplasia from neoplastic conditions. Knowledge of the imaging findings of thymic tumors and their mimics may help radiologists arrive at the correct diagnosis.

Imaging of the Postoperative Orbit.

Imaging evaluation of the postoperative orbit remains challenging even for the expert neuroradiologist. This article provides a simplified framework for understanding the complex postoperative appearances of the orbit, in an attempt to enhance the diagnostic accuracy of postoperative computed tomography and MR imaging of the orbit. Readers are familiarized with the normal appearances of common eye procedures and orbit reconstructions to help avoid interpretative pitfalls. Also reviewed are imaging features of common surgical complications, and evaluation of residual/recurrent neoplasm in the setting of oncologic imaging surveillance.

Large Multilocular Thymic Cyst: A Rare Finding in an HIV Positive Adult Female.

Multilocular thymic cysts with follicular hyperplasia are uncommon masses that occur in Human Immunodeficiency Virus (HIV) positive individuals. These cysts mostly present in HIV positive children. Here we report a rare case of multilocular thymic cyst in an HIV positive adult female. In this case report, the radiologic findings of multilocular thymic cyst, management and prognosis are discussed.

A unique case of intraventricular hemorrhage associated with posterior reversible encephalopathy syndrome in an adolescent.

Intraventricular hemorrhage is a rare finding in patients with the posterior reversible encephalopathy syndrome and generally carries a poor prognosis. We report a unique case of an 18-year-old girl with glomerulonephritis who developed posterior reversible encephalopathy syndrome without hypertension but with a primary intraventricular hemorrhage and subarachnoid blood without demonstrable parenchymal blood. The normotensive presentation of posterior reversible encephalopathy syndrome and intraventricular hemorrhage in association with systemic vasculitis is rare. Our patient had a good initial outcome and was discharged with resolution of her symptoms and signs of raised intracranial pressure.