The use of gallium-68 labeled somatostatin receptors in PET/CT imaging

摘要

68Ga-DOTA-SSTRTs PET/CT has become the most promising noninvasive procedure to study well-differentiated NET. Although the excellent diagnostic accuracy of the procedure is well known, its use is limited to specialized centers in Europe as parts of clinical trials. Literature reports confirm the superiority of 68Ga-DOTA-SSTRTs PET/CT for the assessment of well-differentiated NET over morphologic imaging procedures, SRS, and even PET/CT using metabolic radiotracers. 68Ga-DOTA-SSTRTs provide good visualization of NET lesions at both the primary and the metastatic sites (node, bone, liver, and unusual localizations). The advantages of their use over metabolic tracers (18F-DOPA, 18F-FDG) are not only limited to a better overall detection rate but also to the fact that they also provide data on SSTR expression on target lesions, resulting a fundamental procedure before starting therapy with either hot or cold somatostatin analogues. Moreover, they can be used also in centers without an on-site cyclotron. To interpret 68Ga-DOTA-SSTRTs images correctly, it is crucial to understand the tracer's biodistribution as well as the conditions that may alter tracer uptake. Considering that SSTR are expressed on activated lymphocytes, all areas of inflammation show 68Ga-DOTA-SSTRTs uptake. Areas of increased uptake in frequent sites of inflammation (eg, thyroid, mediastinal nodes, inguinal nodes, and nodes adjacent to areas of recent surgery/trauma) should be interpreted with care. A detailed clinical history with particular attention to concomitant disorders (eg, sarcoidosis, chronic gastritis, chronic thryoiditis) and recent invasive procedures or trauma may often help image interpretation. The presence of uptake in the head of the pancreas should always be carefully evaluated because it may often be benign. Otherwise, because the pancreas is also a frequent site of NET onset, particular attention should be devoted to the evaluation of the uptake pattern (diffuse more likely to be benign) and to the comparison with other imaging techniques.