Nickel Isotopes are used for the production of several radioisotopes. Ni-64 is used for the production of Cu-64 which is used in radioimmunotherapy. Ni-61 can be used for the production of the PET radioisotope Cu-61. Ni-62 is used for the production of the radioisotope Ni-63 which can be used as an XRF source, as an electron capture source in gas chromatographs and as a power source in microelectromechanical systems. Ni-58 can be used for the production of the radioisotope Co-58. Ni-60 is used for the production of Co-57 which is used in bone densitometry and as a gamma camera reference source. Ni-60 is also used as an alternative for the production of Cu-61, but the route via Ni-61 is more common. Finally, most stable Nickel Isotopes have been used to study human absorption of Nickel. Ni 64 is currently in high demand.