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

Purpose: 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).

Materials And Methods: 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, X, Y, and Y) and compared with those of full-reconstruction CT image. We measured the MTFs of the half-reconstruction CT image at X position with various X-ray tube positions of projection dataset.

Results: 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 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.

Conclusion: 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.