Focal F-18 FDG Uptake Mimicking Malignant Gastric Localizations Disappearing After Water Ingestion on PET/CT Images

Abstract

Diffuse, increased gastric wall F-18 FDG uptake is widely observed during PET/CT examinations, frequently unrelated to malignant findings, but simply caused by inflammatory disease, physiological emptying, or visceral thickening. Hence, elevated F-18 FDG gastric uptake can lead to equivocal misinterpretation, especially in patients with known gastric malignant disease, at posttherapy reevaluation. Gastric wall contraction can increase F-18 FDG uptake, especially for a remnant stomach, increasing the percentage of false-positive results with a direct impact on therapeutic management. One field PET/CT acquisition centered on the hypochondrial regions a few minutes after water ingestion should be performed routinely if standard images are doubtful (increased tracer uptake and visceral thickening) to differentiate benign from malignant uptake.

Dual time point [18F]Flurodeoxyglucose (FDG) Positron Emission Tomography (PET)/Computed Tomography (CT) with water gastric distension in differentiation between malignant and benign gastric lesions

“…Difficult evaluation of the stomach especially if it is contracted on conventional 18 F-FDG PET/CT requires some novel modifications to the standard oncologic protocol to reduce the number of false-positive or false negative results, predominantly related to physiological gastric wall or mucosal uptake. Expanding the stomach with gas, liquids, diluted barium or foods are simple and rapid methods that had been utilized to achieve gastric distention, thinning of the gastric wall and to reduce the physiological 18 F-FDG uptake in the gastric wall [ 4 , 6 , [20] , [21] , [22] , [23] ]. These maneuvers help to delineate the lesions more clearly, however the improvement in diagnostic accuracy is still controversial [ 23 , 24 ].…”

“…Early PET/CT images (upper panel) revealed a gastric pyloric FDG avid focal lesion (arrows) with SUVmax of 5.7 that increased to 6.9 in post gastric distension delayed images (lower panel). utilized to achieve gastric distention, thinning of the gastric wall and to reduce the physiological 18 F-FDG uptake in the gastric wall [4,6,[20][21][22][23]. These maneuvers help to delineate the lesions more clearly, however the improvement in diagnostic accuracy is still controversial [23,24].…”

“…As in a fasting state, the stomach is collapsed and wall is thickened; ingestion of water reduces the wall thickness, and tumor involvement of the gastric wall can be visualized more accurately in CT studies [5]. In a similar way, water intake just before 18 F-FDG PET/CT scanning will result in gastric distention and thinning of the gastric wall, which in turn may lead to a reduction in the physiological 18 F-FDG uptake in the gastric wall [4,6].…”