[en] A pen pointer source is used as an image marker to signify the point of interested organ of the human body during diagnostic nuclear imaging studies or to trace the outline of anatomical features of a patient's organ. Cobalt-57 is used externally as a pointer marker standard source for nuclear imaging. Cobalt-57 is a preferred radioisotope for this purpose as it has a moderately long half-life of 270 days so that it can serve as a standard source for longer time and emits low energy γ-photon of 122 keV that simulates closer to the energy of 99m Tc of 140 keV. A facile electrochemical method has been employed for the preparation of 57 Co pen pointer marker source. Cobalt-57 cone source of 7.4 MBq (200 μCi) was prepared by cathodic electro-deposition on a conical electrode copper surface (∼ 1 mm (Φ) x 1 mm (L), 0.0025 cm 2 area) by passing a steady current (10 mA. cm-2 current density) through dilute cobalt chloride electrolyte for 4 h. The source was then mounted at the end of a specially designed cylindrical type brass holder support having overall dimensions of 8 mm (Φ) x 150 mm (L). Quality control tests were performed on the source and the results were found to be satisfactory.(author)