Design And Development Of A Collimator And Robot For Use In Detector/collimator Studies

Abstract

As part of a project aimed at understanding and accounting for collimator effects in SPECT (single photon emission computed tomography) and PET (positron emission tomography) images, a robot and collimator system is being constructed to accurately position a narrow beam of radiation. The beam from the collimator will have a diameter of no more than 5 mm FWTM (full width tenth maximum) at a distance of 30 cm and will improve, due to penumbra effects, as the distance decreases. Positioning will be done by a wrist (two degrees of angular motion) on a Cartesian arm (three degrees of linear motion) controlled by a CAMAC (Computer Automated Measurement and Control) system and LabView software on the Macintosh. Beam positioning error should be less than 2.5 mm at a distance of 30 cm. While the majority of the use will be in a bench environment, the design will also function within the tunnel of a whole body PET scanner or with a SPECT camera. With this in mind, the stepping motor drivers will toggle a signal, compatible with standard cardiac gating signals, to signify if the arm is stationary or in motion. This will allow sorting of many positions taken during the same acquisition on most PET and SPECT scanners. As a further convenience, the collimator assembly will have an internal laser that will aid in calibration of the robot and accurate positioning of the beam.