Evaluation for Resolution Property of CT Image with Half-reconstruction Algorithm

Abstract

The aim of this study was to investigate the resolution property in XY-plane for half-reconstruction computed tomography (CT) image by measuring 360° multi-directional modulation transfer functions (MTFs). The 360° multi-directional MTFs were measured by use of a wire method to obtain line spread function with 15° interval in XY-plane. The MTFs of half-reconstruction CT image were measured with 100 mm off-center positions on the X- and Y-axis (X+100 mm, X-100 mm, Y+100 mm, and Y-100 mm) and compared with those of full-reconstruction CT image. We measured the MTFs of the half-reconstruction CT image at X+100 mm position with various X-ray tube positions of projection dataset. There were obvious differences for the MTFs of the half-reconstruction CT image between the tangential and radial directions at each measurement position. The dependences of the resolution property for the half-reconstruction CT image on positions and directions in XYplane were similar to those for the full-reconstruction CT image. The higher and the lower MTFs of the half-reconstruction CT image at X+100 mm position were measured with X-ray tube position of projection dataset at +X side and at -X side compared with those of the full-reconstruction CT image, respectively. We conclude that the half-reconstruction CT image had similar resolution property in XY-plane to the full-reconstruction CT image and showed dependency on the X-ray tube position of projection dataset for MTF in the tangential direction.