Compensation for Influence on Image Deterioration Occurring Because of Gantry Inclination—Compensation of image quality obtained by a newly devised phantom—

Abstract

The influence of gantry inclination on image quality was examined in the Y and Z directions and an increase in the volume of a scan part. FWHM (full width at half maximum) in the Y direction decreased at the rate of 2.53%, which was caused by leaving the center of the gantry, and spatial resolution was improved. FWHM (y) in the Z direction increased at a rate of y=2.4× (1/cosθ)+0.91 which was caused by an increase in the gantry angle of inclination, and spatial resolution was declined. The relation between FWHM (y) and pitch (x) was y=0.19x+3.12. The increase in FWHM caused by the increase in the gantry angle of inclination was revised with pitch from two formulae, and it became constant. Noise was corrected in the same way, and it became constant. The increase in the noise that occurs due to the increase in the volume of the body caused by the gantry tilt angle was corrected with the tube current, and applied to AEC (automatic exposure control). The influence of gantry inclination on image quality was adjusted, and image quality was improved.