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Clinical/methodical Issue: Pulmonary carcinoids and carcinoids of the small intestine (jejunum and ileum) are often asymptomatic and can affect various parts of the body, which makes diagnosis difficult., Standard Radiological Methods: Contrast-enhanced computed tomography (CE-CT) is commonly used for primary diagnostics. In case of concomitant pulmonary consolidation (e.g., atelectasis or pneumonia), tumor lesions can be obscured. In addition, differentiation between atypical (AC) and typical carcinoids (TC) is not possible using CT. Small tumors of the small intestine are easily overlooked (sensitivity: 50-85%, specificity: 25-97%, based on the literature). Additional functional imaging evaluation using hybrid imaging techniques can be applied, e.g., positron emission tomography/computed tomography (PET/CT)., Methodical Innovations/performance: Depending on the histological characteristics of the tumor, PET/CT scans can be performed with different tracers. Since most carcinoids (e.g., TC) express somatostatin receptors (SSR), 68  gallium-radiolabeled PET tracers (e.g. 68  Ga-DOTA-TOC) are commonly used (sensitivity: 88-93%, specificity: 88-95%, based on the literature). Poorly differentiated carcinoids (e.g., AC) demonstrate lower SSR expression; thus, use of 18 F‑FDG (sensitivity: 37-72%, based on the literature) is indicated. In principle, these methods enable a noninvasive prognostic differentiation based on SSR expression and 18 F‑FDG uptake. However, the diagnosis must always be histologically confirmed., Achievements/practical Recommendations: Hybrid imaging with CE-CT and PET is useful to detect pulmonary carcinoids and carcinoids of the small intestine, respectively, and can be utilized for primary diagnostics and restaging.

Clinical/methodical Issue: Neuroendocrine tumors (NET) of the stomach, duodenum and pancreas are rare tumors with a low incidence but the exact tumor localization and staging diagnostics are of critical importance for further planning of treatment., Standard Radiological Methods: Standard primary diagnostic methods include multimodal imaging with computed tomography (CT) and magnetic resonance imaging (MRI) but in 20-50% of the cases the localization of the primary tumor cannot be identified., Methodical Innovations: Modern hybrid imaging procedures combine radiological procedures and functional imaging, e.g. using somatostatin receptor (SSR) positron emission tomography CT (PET)/CT imaging. For the exact diagnostics of the primary tumor and distant metastases morphological and functional aspects can be combined for targeted diagnostics. For primary tumor staging a sensitivity of 80.0% and a specificity of 88.4% are given in the literature., Performance: The application of SSR PET/CT led to a change in patient management in 44% of all cases according to a recently published meta-analysis and therefore had a significant influence on the further procedure., Assessment: The use of SSR PET/CT can provide critical information for further treatment and can lead to a significant change in treatment management in a relevant proportion of patients., Practical Recommendations: Radiological imaging diagnostics and in particular hybrid functional imaging procedures using PET/CT will become increasingly more relevant for the diagnostics, treatment and follow-up of NET patients.

Clinical Background: If pheochromocytoma (PC) or paraganglioma (PGL) is diagnosed based on serologic studies, imaging is required to locate the adrenal mass for further management. Besides pathognomonic hormonal findings, PC/PGL can exhibit typical imaging features. However, PC/PGL can also show morphological overlap with other pathologies., Standard Radiological Methods: The modality of choice for evaluation of PC is CT. In case of extra-adrenal location, MRI is superior to CT. Imaging with PET-CT provides complementary information in the differentiation of PC/PGL and is recommended as the imaging modality of choice for malignant PC/PGL. 68 Ga-DOTATATE (or 68 Ga-DOTATOC/ 68 Ga-DOTANOC) PET-CT has high sensitivity for SDHx-mutated PC/PGL and serves for planning of radioreceptor therapy with somatostatin analogues. In contrast, 123 I-metaiodobenzylguanidine (MIBG) scintigraphy is important in assessing the potential efficacy of radioreceptor therapy with MIBG., Methodical Details: The CT protocol for PC evaluation should include non-enhanced, arterial, portal-venous and late phases; the latter for the evaluation of wash-out. Recent studies indicate non-enhanced CT alone may be sufficient to rule out PC. For MRI, in- and opposed-phase sequences should be additionally acquired., Practical Recommendations: A relevant proportion of PC is diagnosed incidentally. Therefore, imaging of PC will gain further importance. Recent studies show better response rates of PC/PGL after radioreceptor therapy with somatostatin analogues ( 177 Lu-DOTATATE) than with MIBG. Therefore, 68 Ga-DOTATATE PET-CT gains further importance-for diagnostic imaging and therapy planning.

Purpose: To determine the value of MR enteroclysis (MRE) in the localization and characterization of primary carcinoid tumors of the small bowel and to describe typical imaging features., Material and Methods: Twenty patients with suspicion of primary small bowel carcinoid tumors (pCT) were recruited to undergo MRE following nasojejunal intubation and small bowel filling with 2.5 l of 0.5% methylcellulose solution under MR fluoroscopic guidance. MRE was performed on a 1.5 T MR scanner including T2w SSFSE, SSFP and contrast enhanced T1w GRE sequences with fat saturation. Fifteen patients, who subsequently had surgery for resection of their pCT, were retrospectively included in the study. All MRE were analyzed as for the presence, location, number, size, multiplicity and morphologic appearance of the pCT by two board certified radiologists in consensus. The conspicuity of the tumors was rated for each sequence type separately, according to a 4-point rating scale. Signal intensity measurements were performed in tumor and muscle. The presence of desmoplastic reaction, vascular involvement and lymph node metastases was also analyzed., Results: pCT were correctly identified and localized in 14/15 patients. Due to their hyperenhancement tumors was best detected on contrast-enhanced T1w fat saturated GRE sequences. SSFSE was clearly inferior with the tumors being either hyperintense or isointense to muscle. pCT appeared as nodular intraluminal masses in 40% of the cases, as focal wall thickening in 33.3% and in 20% with both. Mean size was 25 (7-46 mm) with a tendency to smaller size for ileal tumors. MRE failed to depict superficial micronodular peritoneal spread in one patient. Desmoplastic reaction was observed in 73.3% of the cases with mesenteric masses exhibiting lower signal than the pCT due to fibrotic changes., Conclusion: MRE is a valuable method for the detection and localization of primary carcinoid tumors, provided that appropriate bowel distension is achieved. Various characteristic morphologic features could be identified which may contribute to characterize pCT and their loco-regional metastases.

Introduction: Diseases of the parathyroids, the adrenals and of neuroendocrine tumors of the pancreas are primarily diagnosed by clinical and endocrinological evaluation. The requirements concerning various imaging techniques and their relative importance in localization strategies of the different tumors are complex., Materials and Methods: Current literature search, using PubMed., Results: Evaluation of primary hyperparathyroidism requires bone densitometry by DXA and search for nephrolithiasis by ultrasound or native CT examination. While ultrasound of the thyroid and parathyroids seems useful before any parathyroid surgery, more extensive preoperative localization strategies (sestamibi scintigraphy, MRI) should be restricted to minimal invasive parathyroid surgery or reoperations. For adrenal tumors CT and MRI are of similar diagnostic value. Imaging of pheochromocytomas should be completed by MIBG scintigraphy. Each adrenal incidentaloma requires an endocrinological work-up. A fine-needle aspiration or core needle biopsy of an adrenal tumor is rarely indicated. Before adrenal biopsy a pheochromocytoma has to be excluded. Successful localization strategies for neuroendocrine tumors of the pancreas include somatostatin receptor scintigraphy, endoscopic ultrasound and MRI., Discussion: Specific localization strategies have been established for the aforementioned tumors. The continuous progress of different imaging techniques requires a regular reevaluation of these localization strategies.