ses·ta·mi·bi 
(sĕs′tə-mēbē)
(sĕs′tə-mēbē)n.
An injectable drug containing an isotope of the radioactive element technetium, used in nuclear medicine imaging primarily to visualize the heart muscle, parathyroid glands, and breast tissue.
[sesta-, perhaps alteration (influenced by Latin sex, six) of hexakis-, prefix indicating six in chemical names (from the six ligands bound to its central technetium ion ) + m(ethoxy)i(so)b(utyl)i(sonitrile).]