All unstable isotopes of molybdenum decay into isotopes of zirconium, niobium, technetium, and ruthenium. All unstable isotopes of molybdenum decay into isotopes of niobium, technetium, and ruthenium. Group 7 contains the two naturally occurring transition metals discovered last&colon; technetium and rhenium. Technetium, rhenium, and bohrium have no known biological roles. They are manganese (Mn), technetium (Tc), rhenium (Re), and bohrium (Bh). All other elements are either incredibly rare on earth (technetium, rhenium) or completely synthetic (bohrium). All isotopes of technetium must be handled carefully. Elements heavier than lead, and the elements technetium and promethium, exist only as radionuclides. Other volatile elements leave the fuel and must be recovered, especially iodine, technetium, and carbon-14. Technetium bone scans can detect regional blood flow and the amount of osseous uptake. Period 5 also includes technetium, the lightest exclusively radioactive element. The radioactive nature of technetium makes this corrosion protection impractical in almost all situations. Both of these decay modes rearrange the nucleons without transmuting the technetium into another element. Salivary scintiscanning using technetium is rarely used. A SPECT image can also be taken following an injection of Technetium labelled MAA.