Speaker
Description
• Tomographic data collection methods (of which cryo-EM is an example) provide us with approximations of line integrals of some parameter.
• Reconstruction is the attempted recovery of the distribution of the parameter values from such data.
• The two major categories of reconstruction techniques are:
– transform methods such as weighted backprojection (WBP) and FBP; and
– series expansion methods such as the algebraic reconstruction techniques (ART) and SIRT.
• The former methods are in wide use because of their fast speed and simple implementation.
• The latter methods have been claimed to provide greater detail with incomplete or noisy data.
– Series expansion methods specify the distribution as a linear combination of some basis functions.
– They estimate the coefficients in such an expansion by an iterative reconstruction (IR) algorithm.
• In many fields of application of tomography (e.g., in medical CT), IR has become the norm.
• This has not happened in cryo-EM, where there seems to be a greater inertia against its use.
• The reluctance in the EM community to use IR goes back fifty years and is still strong.
• The purpose of this presentation is to discuss this phenomenon.
– Examples are given for the efficacy of IR in EM and other applications.
– Objections to the use of IR in cryo-EM are listed and critically examined.
