Radiant energy – Calibration or standardization methods
Patent
1994-07-28
1996-03-26
Willis, Davis L.
Radiant energy
Calibration or standardization methods
25036309, G01T 1164, H01J 3706
Patent
active
055023037
ABSTRACT:
A slow positron source having a cylindrical geometry which permits increased conversion efficiency from high energy into low energy positrons. A thin walled inner cylinder is filled with a positron emitting liquid radioisotope and is separated from an outer cylinder by an annular cavity. The outer cylinder surrounds the inner cylinder and is coated with a high atomic number material thick enough to stop all the positrons while providing a high fraction of backscattered positrons. A thin layer of moderator is also deposited on the inner surface of the outer cylinder. A positively biased pusher disk is placed at one end of the cylinders, while a negatively biased extraction grid is placed at the other end of the cylinders for extracting the low energy moderated positrons from the cavity so as to form a substantially monoenergetic positron beam. The positron beam is directed to impinge upon an annihilation screen at selected points using standard CRT focusing and deflection arrangements. The positron beam is controlled to create a desired phantom image on the annihilation screen. The gamma rays produced by the impingement of the positron beam on the annihilation screen are advantageously measured by a PET or SPECT camera and may be used to calibrate resolution, field of view, and the like of such gamma ray cameras.
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Hanig Richard
Trustees of the University of Pennsylvania
Willis Davis L.
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