Gil Schwarzband and Nahum Kiryati 2005 Phys. Med. Biol. 50 5307 doi:10.1088/0031-9155/50/22/007
Gil Schwarzband and Nahum Kiryati
Show affiliationsComputed tomography (CT) scanners are usually described by their in-plane resolution and slice-sensitivity profile (SSP). Other imaging systems are characterized by their point spread function (PSF). The PSF is an excellent basis for the analysis, design and enhancement of imaging systems. The 3D PSF of CT systems has rarely been considered, and has usually been approximated by a 3D Gaussian. We present mathematical analysis of the PSF of single-slice and multi-slice fan-beam and cone-beam CT, for major reconstruction algorithms. We show that the PSF has a complicated, non-separable 3D shape. It is anisotropic in the xy plane and twisted in the z direction. Furthermore, the PSF is space variant in all three axes. In particular, it rotates as the input impulse function moves in the z direction. The PSF may also have effective discontinuities that can lead to streaking artefacts. Indirect measurements of the PSF can be misleading. We support the theoretical results by direct experimental measurements of the PSF.
Issue 22 (21 November 2005)
Received 16 June 2005, in final form 29 August 2005
Published 2 November 2005
Gil Schwarzband and Nahum Kiryati 2005 Phys. Med. Biol. 50 5307
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