Colon Cancer Mimicking Physiologic FDG Uptake: with Using of Negative Oral Contrast / 핵의학분자영상

A 64-year-old female with glioblastoma multiforme (GBM) was assigned to our department for whole body PET/CT scan. She ingested 1 liter of pure water as negative oral contrast just before PET/CT examination. FDG-PET/CT images showed a very intense hypermetabolic, focal lesion in the abdominal cavity around descending colon. The SUVmax of the lesion was 17.2. But there was no abnormal lesion corresponded to the area of PET scan in the combined contrast enhanced CT scan. We suggested considering a malignant lesion due to very intense glycolytic activity. Conventional abdominal CT scan and colonoscopy were accomplished within one week after PET/CT evaluation. There was no abnormality in both examinations. We executed follow-up PET/CT evaluation after 1 month and couldn't find any abnormality around the corresponding area. So we concluded the hypermetabolism was colonic physiologic uptake. A colonic physiologic uptake is a well known cause of false positive finding. Nuclear physicians should be considered the possibility of malignancy when interpret focal colonic uptake, especially incidental finding.1-3) There are a few reports that using of negative oral contrast is able to reduce gastrointestinal physiologic uptakes.4,5) But as we can see in this case, although we used negative oral contrast, intense physiologic uptake is detected and maxSUV is able to up to 17.2. So, it is important to keep a fact in mind. Even though there is a colonic physiologic uptake in PET/CT image, it may be able to show very intense hypermetabolism regardless of using negative oral contrast.

Usefulness of Superparamagnetic Iron Oxide (SPIO) as a Negative Oral Contrast Agent in MR Cholangiopancreatography

PURPOSE: To evaluate value of superparamagnetic iron oxide (SPIO) as a negative oral contrast agent in MR cholangiopancreatography (MRCP). MATERIALS AND METHODS: Forty-eight patients with suspected biliary tract or pancreatic diseases and six healthy volunteers were enrolled in this study. All MR images were obtained using a 1.5 T MR unit. MRCP using fat-suppressed half-Fourier acquisition single-shot turbo spin echo (HASTE) and turbo spin echo (TSE) techniques were performed and reconstructed with maximal intensity projection (MIP). To determine the most optimal concentration of SPIO to obliterate the high signal intensity of water, a phantom experiment was conducted with various concentrations of SPIO-water mixture. Two radiologists evaluated pre- and postcontrast MRCPs. The contrast enhancement was assessed on the basis of loss of signal intensity in the stomach and duodenum. RESULTS: In the phantom experiment, a significant increase of percentage of signal intensity loss (PSIL) occurred in concentration of 22.4 ugFe/ml (Feridex 1 ml diluted with water 500 ml). Postcontrast MRCP showed an improved image quality compared with precontrast images. The rate of improvement in the diagnosis of diseases of the common bile duct and pancreatic duct was 25% (12/48). CONCLUSION: In patients with suspected biliary tract and pancreatic diseases, the SPIO is useful as a negative oral contrast agent for MRCP and provides an improvement of image quality.