ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: Radiological, Nuclear Medicine & Hybrid Imaging

Contrast-enhanced computed tomography (CT) of the neck-thorax-abdomen and pelvis, including three-phase examination of the liver, constitutes the basic imaging for primary NET diagnosis, staging, surveillance and therapy monitoring. CT characterization of lymph nodes is difficult because of inadequate size criteria (short axis diameter), and bone metastases are often missed. Contrastenhanced magnetic resonance imaging (MRI) including diffusion-weighted imaging is preferred for examination of the liver, pancreas, brain and bone. MRI may miss small lung metastases. MRI is less well suited than CT for examination of extended body areas, because of the longer examination
procedure. Ultrasonography (US) frequently provides the initial diagnosis of liver metastases and contrast-enhanced US is excellent to characterize liver lesions that remain equivocal on CT/MRI. US is the method of choice to guide the biopsy needle for the histopathological NET diagnosis. US cannot visualize thoracic NET lesions for which CT guided biopsy therefore is used. Endocopic US is the most sensitive method to diagnose pancreatic NETs, and additionally allows for iopsy. Intraoperative US facilitates lesion detection in the pancreas and liver. Somatostatin receptor imaging should be a part of the tumor staging, preoperative imaging and re-staging, for which 68Ga-DOTA-somatostatin analog-PET/CT is recommended, which is vastly superior to somatostatin receptor scintigraphy, and facilitates diagnosis of most types of NET lesions, for example lymph node metastases, bone metastases, liver metastases, peritoneal lesions and primary small-intestinal NETs.18FDG-PET/CT is better suited for G3 and high G2 NETs, which generally have higher glucose metabolism and less somatostatin receptor expression than low grade NETs.