A Simple Contrast Matching Rule for OSEM Reconstructed PET Images with Different Time of Flight Resolution

Round 1

Reviewer 1 Report

Dear authors,

The work is very interesting and provides very useful results given that nowadays all PET scanners have TOF capabilities and further improvements are expected in this area. It is really a very good new that a stoping rule demostrated for MLEM works properly in the case of OSEM and experimental data. I think it would be useful for the readers that the authors could explain at the theory section or at the discussion section why it is valid for OSEM the rule demostrated for MLEM, since the convergence characteristics of both algorithms are not exactly the same.

Best regards

Author Response

We thank the reviewer for highlighting this point.

In literature it has been shown that OSEM and MLEM behaviour are slightly different at convergence, since OSEM converges to a limit cycle rather than to a unique solution (Hudson and Larkin 1994, Browne and De Pierro 1996). This does not impact on the convergence trend at first iterations, which are the ones considered in this work. We inserted this point in the revised discussion.

Reviewer 2 Report

This is an interesting and significant investigations on the suggestion of EM updates for contrast matching between many cameras with different TOF time resolution. Methods and materials are sound not only scientific but also to the point of clinical unmet needs of applied physics in nuclear medicine. This reviewer recommend the paper published as is. 

Author Response

We thank the reviewer for reading and appreciating our work.