Revisit to Derivative-Free Noncircular Fan-Beam Reconstruction - Responses to "iscussions on a Noncircular Fan-Beam Reconstruction Formula"by Huang, et al.

Huang <i<et al.</i< identified an error in the derivation of a derivative-free noncircular fan-beam reconstruction formula published in 1993. They concluded that the derivative-free formula is not exact under the assumed conditions, but it is a very good approximate reconstruction formula. In this report, the author analyzes the impacts of that error, discuss on remedy for exact derivative -free noncircular fan-beam reconstruction, and pose some open questions.