Medullary thyroid carcinomas can also be located by scintigraphy with 111In-DTPA (diethylenetriamine pentaacetic acid) -octreotide. In some studies, there is a sensitivity for the detection of these tumors by this method, 50-70%. The relationship of calcitonin and carcinoembryonic antigen levels were significantly higher in patients in whom scintigraphy was performed with 111In-DTPA-octreotide. This implies that somatostatin receptors can be detected "in vivo" for different forms of medullary thyroid carcinoma Based on the specific binding of the analogs of somatostatin receptors present on the membrane of some tumors such as medullary thyroid been possible to devise a therapy to target-directed using both beta-emitting radionuclides (which have therapeutic properties) coupled to such molecules. The main radiopharmaceuticals used for this purpose are currently 177 Lu-DOTA-Tyr3-OCTREOTATE or 90Yttrium-DOTA]-TOC.