Uptake in the pancreatic uncinate process on the 111In-octreotide scintigraphy: How to distinguish physiological from pathological uptake?

BACKGROUND: The aim of this study was to assess the relevance of physiological In-octreotide uptake in the head of pancreas and to establish its imaging features in comparison with pathological uptake in patients with neuroendocrine tumors (NET).

PATIENTS AND METHODS: We retrospectively reviewed all patients that underwent In-octreotide single-photon emission tomography (SPECT) scintigraphy in our institution. Only patients with an isolated uptake in the head of the pancreas were included. In-octreotidescintigraphy consisted in planar whole-body and abdominal SPECT/computed tomography (CT) images acquired at 6 and 30 h' postinjection. Different imaging features of the pancreatic focalized uptake were assessed: its precise location on the pancreas head, shape, intensity [visually and quantitatively by calculating the pancreatic to hepatic uptake ratio (L/H ratio)] and intensity changes.

RESULTS: Thirteen patients out of 230 were included. Among them, a pancreatic NET was confirmed in five patients. On In-octreotide SPECT/CT, two of these had uptake located in the uncinate process, and three had uptake focused in the right lateral borders or in the whole head. SPECT images demonstrated high uptake (L/H ratio >2) in four patients out of five. In the eight remaining patients, pancreatic NET was ruled out. For all of these physiological cases, SPECT/CT acquisitions revealed that the uptake was both located in the uncinate process and with an L/H ratio below 2.

CONCLUSION: The simple criteria of localization and uptake quantification can help to discriminate between a possible physiological uptake in the uncinate process of the pancreatic head and a pathological uptake induced by a NET.