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A dose reduction x‐ray beam positioning system for high‐speed multislice CT scanners
Author(s) -
Toth Thomas L.,
Bromberg Neil B.,
Pan TinSu,
Rabe Jerry,
Woloschek Steven J.,
Li Jianying,
Seidenschnur George E.
Publication year - 2000
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1323983
Subject(s) - collimator , collimated light , detector , scanner , tracking (education) , optics , beam (structure) , nuclear medicine , dosimetry , aperture (computer memory) , physics , medical physics , materials science , medicine , laser , psychology , pedagogy , acoustics
The introduction of multislice CT scanners and the associated dose increase compared to single and dual slice scanners has concerned many radiologists, health and medical physicists, as well as members of the regulatory community. Since multislice CT scanners are inherently post‐patient collimated, they are less dose efficient than single slice CT scanners, which use prepatient collimation. The x‐ray beam must be wide enough in the Z axis so that the beam remains on the detector in spite of typical movements due to thermal and mechanical flexing. We describe the x‐ray beam tracking system that is employed on a GE LightSpeed QX/i ® scanner to substantially reduce the multislice dose. The tracking system stabilizes the beam on the detector allowing a narrower x‐ray exposure profile compared to the x‐ray exposure profile without tracking. The tracking system measures the position of the beam every few milliseconds and continually repositions a source aperture to hold a narrow beam fixed on the detector. Using a standard LightSpeed QX/i ® source collimator and segmented detector, dose reductions of up to 40% were measured when tracking was employed. We also show that tracking has the potential to provide a dose efficiency approaching single slice scanners.