The Use of Radiolabeled Somatostatin Analogue in Medical Diagnosis. Introduction

Peptides have good characteristics as radiopharmaceuticals: they are small in size and have a fast renal clearance and easily penetrate into tissues with consequent low background blood pool activity after few minutes from injection. Somatostatin (SST) acts as a neurotransmitter in several organs, having a wide range of mainly inhibiting effects, such as the suppression of growth hormone release, as well as the inhibition of pancreatic and gastrointestinal hormone release. Five SST receptor (SSTR) subtypes have been cloned, of which SSTR1 and SSTR4 are grouped into one family and SSTR2, SSTR3, and SSTR5 into another. Molecular imaging by radiolabeled SST analogue highlights the presence of pathological tissues overexpressing SSTR. It can be used to characterize lesions with respect to the expression of SSTR for staging diseases by detecting or excluding sites of metastases.