Program Information

Effects of Gantry Rotation Time On CT Number Accuracy in Single-Source Dual Energy CT Imaging with Fast-KVp Switching

X Liu

X Liu*, D Cody , J Rong , U.T.M.D Anderson Cancer Center, Houston, TX

Presentations

SU-E-I-101 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
To investigate the effects of gantry rotation time on CT number accuracy in dual energy CT imaging with GE Discovery CT750 HD single-source 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.


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