Comments on "A cone-beam filtered backprojection reconstruction algorithm for cardiac single photon emission computed tomography" by G. T. Gullberg and G. L. Zeng

In the above-titled work by G. T. Gullberg and G. L. Zeng (ibid., vol.11, no.1, p.91-101, 1992), a fan-beam reconstruction formula of a noncircular scanning locus was derived and extended for half-scan cone-beam reconstruction. However, the reconstruction formula is not exact mathematically unless a necessary condition is satisfied. In this correspondence, the commenters derive this necessary condition and provide a geometrical explanation of the condition.<
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