Radiological Imaging: Computed Tomography, Magnetic Resonance Imaging and Ultrasonography

Neuroendocrine tumor (NET) imaging is generally performed by a combination of radiological and functional methods. Conventional radiological imaging of morphology (anatomy) is usually performed by computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound, whereas functional imaging of somatostatin receptor expression generally utilizes scintigraphy, but recently also positron emission tomography (PET). Because of the large variations in tumor characteristics (for example primary location, presence or absence of hormonal production, proliferation and metastatic spread) and disease presentation, the imaging requirements in different patients are very diverse. Imaging also needs to be adapted according to the imaging application in the individual patient (tumor localization, staging, detection of recurrent disease, monitoring of therapy). Familiarity with the contrast-enhancement technique for CT and MRI is important in the interpretation and understanding of the radiological findings. The choice of the optimal imaging techniques also needs to be considered in the light of the department's local availability and expertise. In this review, methodological aspects of radiological imaging are described, imaging requirements for various types of NETs are discussed, and typical image findings are illustrated.