A 3D Dual-Particle Imaging Algorithm for Multiple Imagers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors introduce a 3D dual-particle imaging algorithm designed for multiple images, focusing on the localization and imaging of radiation sources. This technology is particularly relevant for nuclear nonproliferation, treaty verification, nuclear safeguards, and homeland security applications.
Their method was validated using experimental data from a Cf-252 source. The three-dimensional representation of the imaging data provides a more intuitive and informative depiction of source positions.
The manuscript may make several significant contributions to radiation imaging. However, the reviewer finds space to improve it by addressing the following issues.
* The implementation of their technique needs to be clarified. They do not describe what kind of hardware and software they employed, the number of voxels, or the size of each voxel.
* As the authors mentioned, they validated their method for a single source. In reality, it is likely to have more than one source in the environment. What do the authors expect to get the 3D image using their technique if several volumetric sources exist in the field of view?
* In Figure 14, the pictures at the Top Left and Bottom seem to be the same. Please check the figure.
* In Figure 15, the caption says 'Top' and 'Bottom', but the two figures align left and right.

Author Response

Please see the attachment. Thank you for your comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The submitted manuscript describes a method for estimating the 3D-coordinates of a radioactive source by applying a multiple imager detector making use of double scattering for directional back projection.

In the following I list some critical points which I advice the authors to address before re-submission:

- p. 3: there is no information on the detection efficiency, both for double neutron and gamma scattering. The overall detection efficiency depends not only on the cross-sections, but also on the effective solid angles and detector quantum efficiencies. So, these numbers should be given and discussed as they determine the required measurement time for a given source activity.

- p. 4: the authors need to discuss the limits of their method for inhomogeneous objects: what if the attunation of the neutrons/gamma rays is different for the two dectector positions? Their presented back-projection does not take this into account and it leaves out the question whether not just the location, but also the source activity is of interest.

- p. 7: why are time-stamps taken, what is this information used for?

- p. 9, fig. 8, but also following figures: it is obvious that the data for the z-coordinate do not follow a perfect Gaussian, but this finding is not addressed at all. So, what is the reason for this deviation?

- p. 10: is it possible to give an analytical estimate on how to understand the found spatial resolution? Are these results surprising or is it possible to derive them with an analytical model?

- p. 11: the authors mention a possibly optimized algorithm, but give no hints with respect to what kind of improvements they have in mind.

Summing up, I would recommend publication after the above mentioned points have been clarified.

Author Response

Please see the attachment. Thank you for your comments.

Author Response File: Author Response.pdf