Pet scanner point source locator

An assembly for axially positioning a point source in front of a PET scanner for the purpose of transmission scanning, the scanner including a plurality of detectors arranged to form an annular cylinder about a cylindrical scanning region centered on a scanning axis, the assembly comprising:

• an annular rotating member positioned axially adjacent the scanning region and coaxially with the scanner;
• a support member having a distal end for supporting a point source, the support member moveable between at least a retracted position wherein the distal end is positioned axially adjacent and outside the scanning region and an extended position wherein the distal end is positioned within the scanning region;
• a first motivator linked to the annular member;
• a second motivator secured to the annular member for rotation therewith and linked to the support member for moving the distal end between the retracted and extended positions wherein, when the support member is in the extended position, the first motivator causes the annular member and second motivator secured thereto to rotate about the scanner axis;
• and
• first and second contacts, the first contact linked to the second motivator, as the annular member rotates about the scanning axis, the first contact sweeps through a path, the second contact stationary and adjacent the path and, when juxtaposed proximate the first contact, capable of transmitting control signals to the first contact for controlling the second motivator.