Aids in indicating anatomical location for SPECT Imaging. Aids in indicating organ size or region of interest by counting the number of visible “hot and cold” segments for SPECT Imaging. Sources contain 460 microcuries of Co-57 (20 microcuries per segment). Each source contains 23 “hot” 1 cm segments and 24 “cold” 1 cm stainless steel segments, total length is 18.9 inches (48 cm). Custom sources can be made containing a maximum activity 1.2 millicuries (44.4 MBq).