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Novel ultrahigh resolution data acquisition and image reconstruction for multi‐detector row CT
Author(s) -
Flohr T. G.,
Stierstorfer K.,
Süß C.,
Schmidt B.,
Primak A. N.,
McCollough C. H.
Publication year - 2007
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 - 10.1118/1.2722872
Subject(s) - detector , imaging phantom , optics , image resolution , optical transfer function , physics , flat panel detector , resolution (logic) , data acquisition , helical scan , aperture (computer memory) , iterative reconstruction , tomography , nuclear medicine , computer science , computer vision , artificial intelligence , acoustics , medicine , magnetic tape , tape recorder , operating system
We present and evaluate a special ultrahigh resolution mode providing considerably enhanced spatial resolution both in the scan plane and in the z ‐axis direction for a routine medical multi‐detector row computed tomography (CT) system. Data acquisition is performed by using a flying focal spot both in the scan plane and in the z ‐axis direction in combination with tantalum grids that are inserted in front of the multi‐row detector to reduce the aperture of the detector elements both in‐plane and in the z ‐axis direction. The dose utilization of the system for standard applications is not affected, since the grids are moved into place only when needed and are removed for standard scanning. By means of this technique, image slices with a nominal section width of 0.4 mm (measured full width at half maximum= 0.45 mm ) can be reconstructed in spiral mode on a CT system with a detector configuration of 32 × 0.6 mm . The measured 2% value of the in‐plane modulation transfer function (MTF) is 20.4 lp ∕ cm , the measured 2% value of the longitudinal ( z axis) MTF is 21.5 lp ∕ cm . In a resolution phantom with metal line pair test patterns, spatial resolution of 20 lp ∕ cm can be demonstrated both in the scan plane and along the z axis. This corresponds to an object size of 0.25 mm that can be resolved. The new mode is intended for ultrahigh resolution bone imaging, in particular for wrists, joints, and inner ear studies, where a higher level of image noise due to the reduced aperture is an acceptable trade‐off for the clinical benefit brought about by the improved spatial resolution.