. Author manuscript; available in PMC: 2018 Jan 1.

Published in final edited form as: IEEE Trans Med Imaging. 2016 Aug 31;36(1):236–250. doi: 10.1109/TMI.2016.2604568

TABLE II.

Computational costs per iteration.

method	computational cost
Gradient-based (classic adjoint)	𝒪(N^7/3) + 2𝒪(N^5/3)
Gradient-based (generalized adjoint)	2𝒪(N^7/3) + 2𝒪(N^5/3)
Gradient-based (straightforward)	𝒪(N^7/3) + (M + 1)𝒪(N^5/3)
Gauss-Newton	𝒪(N³) + 𝒪(N^7/3) + (M + 1)𝒪(N^5/3)