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The influence of antiscatter grids on soft‐tissue detectability in cone‐beam computed tomography with flat‐panel detectors
Author(s) -
Siewerdsen J. H.,
Moseley D. J.,
Bakhtiar B.,
Richard S.,
Jaffray D. A.
Publication year - 2004
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 - 10.1118/1.1819789
Subject(s) - flat panel detector , cone beam computed tomography , image quality , voxel , image resolution , optics , medical imaging , imaging phantom , contrast (vision) , detector , noise (video) , collimated light , physics , computed tomography , computer science , computer vision , artificial intelligence , medicine , radiology , image (mathematics) , laser
The influence of antiscatter x‐ray grids on image quality in cone‐beam computed tomography (CT) is evaluated through broad experimental investigation for various anatomical sites (head and body), scatter conditions (scatter‐to‐primary ratio (SPR) ranging from∼ 10 %to 150%), patient dose, and spatial resolution in three‐dimensional reconstructions. Studies involved linear grids in combination with a flat‐panel imager on a system for kilovoltage cone‐beam CT imaging and guidance of radiation therapy. Grids were found to be effective in reducing x‐ray scatter “cupping” artifacts, with heavier grids providing increased image uniformity. The system was highly robust against ring artifacts that might arise in CT reconstructions as a result of gridline shadows in the projection data. The influence of grids on soft‐tissue detectability was evaluated quantitatively in terms of absolute contrast, voxel noise, and contrast‐to‐noise ratio (CNR) in cone‐beam CT reconstructions of16 cm“head” and32 cm“body” cylindrical phantoms. Imaging performance was investigated qualitatively in observer preference tests based on patient images (pelvis, abdomen, and head‐and‐neck sites) acquired with and without antiscatter grids. The results suggest that although grids reduce scatter artifacts and improve subject contrast, there is little strong motivation for the use of grids in cone‐beam CT in terms of CNR and overall image quality under most circumstances. The results highlight the tradeoffs in contrast and noise imparted by grids, showing improved image quality with grids only under specific conditions of high x‐ray scatter( SPR > 100 % ), high imaging dose( D center > 2 cGy ), and low spatial resolution (voxel size⩾ 1 mm).