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SU‐E‐I‐101: Effects of Gantry Rotation Time On CT Number Accuracy in Single‐Source Dual Energy CT Imaging with Fast‐KVp Switching
Author(s) -
Liu X,
Cody D,
Rong J
Publication year - 2014
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 - 10.1118/1.4888051
Subject(s) - imaging phantom , scanner , rotation (mathematics) , physics , hounsfield scale , nuclear medicine , monochromatic color , tomography , energy (signal processing) , medical imaging , optics , materials science , computed tomography , mathematics , geometry , computer science , medicine , artificial intelligence , radiology , quantum mechanics
Purpose: To investigate the effects of gantry rotation time on CT number accuracy in dual energy CT imaging with GE Discovery CT750 HD singlesource CT scanner. Methods: The CT number linearity section (CTP404) of the Catphan 600 phantom was imaged using the dual energy protocols equipped on a GE Discovery CT750 HD CT scanner. The imaging section of the Catphan phantom was surrounded with a fat‐equivalent oval ring to better approximate an adult body shape during the image acquisition. A series of dual energy (gemstone spectral imaging (GSI)) presets was selected to acquire images at a gantry rotation time of 0.5 – 1.0 second in an increment of 0.1 second. Images were reconstructed using “Standard” algorithm at different monochromatic energies of 40 — 140 keV in an increment of 10 keV. Two sets of phantom image were acquired with the Axial mode and 5 mm slice thickness for each GSI preset. Total eight images were averaged to compute the CT number of each material insert in the CTP404 section. A squared region‐of‐interest (ROI) of approximate 5 x 5 mm was placed at the center of each material insert to measure the CT number and to investigate the effects of gantry rotation time on CT number accuracy. Results: For LDPE (−100 HU), the CT number increases with rotation time and starts to decrease at 0.9 s for energies at 80 keV and above; while the CT number decreases with rotation time and starts to increase at 0.8 s for energies at 60 keV and below. For Teflon (990 HU), CT number increases with rotation time and starts to decrease at 0.8 s for energies at 80 keV and above; while the CT number decreases with rotation time and starts to increase at 1.0 s for energies at 60 keV and below. At 50 keV, the average CT numbers were −101 HU and 940 HU with maximum differences of 8.7 HU and 10.7 HU for LDPE and Teflon, respectively. The CT numbers were measured −57 HU for LDPE and 913 HU for Teflon for single energy imaging at 120 kVp. Conclusion: Effects of gantry rotation time on CT number accuracy in dual energy CT imaging depends on type of insert material and the monochromatic energy at which the images were reconstructed.