Imaging of gastroenteropancreatic neuroendocrine tumors

Table 3 Summary comparison of the various imaging modalities

	Advantages	Disadvantages	Utility
Ultrasound	Widely available modality, dynamic visualization of lesions, no ionizing radiation	Limited to solid organ systems, inter-operator variability	Possible use as a screening tool for assessing the liver and pancreatic head
CT	Widely available modality, wide field of view, allowing evaluation of nodal disease and metastasis, good sensitivity	Ionizing radiation, non specific modality, low negative predictive value for small volume nodes	First line imaging modality
MRI	Superior to CT for assessment in solid organs, no ionizing radiation, gadolinium contrast agent safety profile better than CT agents in terms of allergic reaction and nephrotoxicity, ability to further characterize lesions using different sequencing	Not as widely available as compared with CT or ultrasound, more specialized diagnostic imaging expertise in interpretation, lower specificity in characterizing neuroendocrine lesions as compared with functional imaging modalities	Local staging of disease, including vascular involvement, use in pediatric age group in which ionizing radiation is of greater concern
SRS	Good sensitivity and specificity, able to accurately characterize lesions; single modality staging; allows for dosimetric evaluation of suitability for peptide receptor radionuclide therapy; proven impact on clinical management	Ionizing radiation; not as widely available as CT or ultrasound, requiring nuclear imaging capabilities; more specialized diagnostic imaging expertise in interpretation	Gold standard in the evaluation of neuroendocrine tumors
Flurodeoxyglucose PET	Possible use in disease prognostication and management stratification, possible use in post treatment assessment to evaluate for tumor dedifferentiation	Generally poor sensitivity for neuroendocrine tumors, ionizing radiation	Not routinely performed for neuroendocrine tumor assessment, possible utility in prognostication and post therapy assessment
Dihydroxyphenylalanine PET	Good sensitivities in the evaluation of neuroendocrine tumors, shows promise especially in assessments of insulinomas	Requires more specialized nuclear facilities (e.g. gaseous F18) for synthesis of the radioisotope, PET based SRS has generally similar or better accuracies in the detection and staging of neuroendocrine tumors, ionizing radiation	Possible clinical utility in the evaluation of insulinomas

CT: Computed tomography; MRI: Magnetic resonance imaging; PET: Positron emission tomography; SRS: Somatostatin receptor scintigraphy.