Summary:
The authors describe the tools that they have built for volume rendering heart data.  The details include segmentation and rendering.  All of the necessary processing steps are described along with how to built the code.

Hypothesis:
Not Applicable

Evidence:
The authors include, in great detail, the process to create segmented volumes and render them.  There is ample support also from the nice references provided.

Open Science:
This is completely open science.  Both the source code and data are provided.

Reproducibility:
I admit that I did not compile the code.  I did look at it and found there is not actually any code in it because it makes great use of other packages, so most of the files are cmake files for compiling existing tools.

Use of Open Source Software:
[Did the authors use Open Source software in their work? Do they describe their experience with it, advantages and disadvantages? Do they provide advice for future users of those Open Source packages?]

Open Source Contributions:
From my perspective, the primary contribution is the form and detail of the paper -- it is a nice template for others who would like to write a case study.  Having access to the code is also valuable.

Code Quality:
Unevaluated

Applicability to other problems:
At this point, I think it is probably applicable, but that has not yet been shown.  The specific algorithms are tuned for the application. 

Suggestions for future work:
More rendering examples and analysis will be beneficial.  I also think that this can be used to show the value of visualization to the clinician which requires a study all by itself.