Leadership:SlicerIGT 2007

This is a discussion about the requirements for Slicer for IGT. The blog is in reverse chronological order, most recent on top.

October 15

Sebastian

I'm definitely on the same page as David here actually. The hard-coded options and the huge list of #ifdef is getting hard to maintain; every once in a while I give a quick pass at Slicer3.cxx to fix the #ifdef, since there are at least 4 or 5 places to modify *per module* in Slicer3.cxx. Module maintainers can't really be blamed here, this solution is definitely not obvious unless you are familiar with Slicer3 initialization code: we could/should change that, especially now that we have sampled a decent variety of modules and can formalize the API to initialize them even tighter.

Now this was OK "so far" for the vast majority of Slicer3 users/developers but a few people have either adopted a different way to build Slicer3, or want to build on top of a "light Slicer3"; this has been my case for a while now, I try to help support the team when a GUI question arises, and I'd like to update Slicer3 SVN, build it "lean-and-mean", without the modules (especially the user-generated one which I trust), and fire my debugger. I actually recently added BUILD_MODULES and BUILD_CLI that can be turned off to get that "lightweight" Slicer3, shrinking my build tree from 2.5 GB to 500 MB: http://massmail.spl.harvard.edu/pipermail/slicer-devel/2007/001866.html

Very often though, Slicer3.cxx won't compile for me because of a missing #ifdefs, and I can relate to David when he expresses his concern about this file. This is, however, very much in the realm of what CMake can fix; a decent macro could be used to declare a module (and turn it on/off) and auto-generate the code necessary to initialize it. All those calls could then be compounded into a configured CXX file, compiled and linked against Slicer3.cxx, etc, reducing the size of this file to, indeed, 200 lines.

October 14

Ron

We should really explore the layout capability in Slicer3 as a way to present a simplified appearance in a clinical trial. We could even have a pop up that gives a warning if people want to go to a different layout. Something like:
Are you sure you want to do that?
If you switch to a different layout, you are not compliant with the clinical trial anymore!

October 12

David

There are a couple issues that I would like to address. One is architectural and the other is functional, but they both tie in together. Please bear with me, because it isn't until the very end that I get into the "multiple slicers" issue.

The architectural issue has to do with the current "Slicer3.cxx" file that comprises the front-end. It is absolutely full of hard-coded options relating to the modules. These options really should be controlled by CMake instead, and the module-specific code in Slicer3.cxx should be moved into separate files. This would reduce Slicer3.cxx to only 200 or so lines of code (instead of the current 2000 lines) which would be ideal. It would also make it easier for people to see what they have to do to add new modules.

The functional issue is that for clinical trials, if we cannot have our own front-end, then we at least want to be able to build a Slicer that only contains the relevant modules and GUI elements. This simplifies the training, decreases load time, and makes for a better technology demonstration.

Most of the hard work here has already been done: Slicer is exceedingly modular, various GUI elements can be hidden, etc. It's just a matter of improving the configurability via CMake, and tracking the dependencies between modules at build-time.

As for the multiple slicer front-ends, it has already been stated that we are not asking for a large number of new front-ends, if everyone doing IGT comes together we might be able to reduce our requirements to a couple new GUI layouts.

Will

It's good to have David on board. If I remember correctly from some past conversations, one of David's concerns was customizing the GUI. As it stands now, Slicer may not support the level of customization that David desires. It would be worth revisiting the Slicer GUI framework to see if we can't add additional flexibility. I'd like to hear (next engr tcon?) some discussion on this from Wendy, Sebastien and Stephen.

Gabor

I am inviting our David Gobbi into this discussion. As you may know, we are gearing up to multi-center clinical trials with an interventional robot system (MRI guided prostate biopsy) to run under Slicer. (David is our lead system architect, Csaba Csoma, also copied, is the software systems engineer who makes all the wonders actually happen.) The system, including Slicer and the robot, will be operated by techs and radiologists. We will not be able to ship an engineer with every system we replicate for clinical collaborators. This brings on some aspects that probably no Slicer user has faced before. David can explain the technical implications much more eloquently...

Noby

• I agree with Ron. See attached
  

  Slicer linked to commercial software
  file showing my work in Japan to link Slicer with a commercial navigation system to enjoy strength of Slicer (medical image processing) and stability of the commercial system. This helped me to publish (as scientific contribution!) in 2003 (Hata et al Academic Radiology).

About ctest --- Kevin and Will put a nice set of ctest in IGSTK. They are really nice and they can even test tracker interface. http://public.kitware.com/dashboard.php?name=igstk

One outstanding work to be done in Slicer-IGT is ctest-ing user-software interaction. This should be done once we implement the kwwidget-based workflow mechanism in neuroendoscope. The use of this kwwidget-based workflow was proposed by Sebastian and Stephen, and I love the idea.

I will develop ctest for robots. This will be part Japanese AIST project, and you and I will discuss our plan with Kiyo and Sakuma in our Tokyo meeting before MICCAI. Peter Kazanzides agreed to join our effort.

Initial email by Ron with comments from Will

R: IGT has special needs that we need to address. On the other hand, we can not, and should not compete with the commercial packages on their turf. The most significant value-add that Slicer can offer, are research capabilities. This requires easy access to the full Slicer.
W: Agreed, we want to keep our focus on pushing the limits of technology, and creating an environment where research can take place. There is a mistaken notion that research tools are inherently slow and unstable. Using test driven development, extreme programming, and designing appropriate flexible frameworks, this is not necessarily true anymore. We see this in VTK and ITK where both tools are used for research as well as embedded in applications, commercial and otherwise. And the same will be true of Slicer because it is built on the same foundation.

R: I am strongly opposed to a zoo of special versions that will inevitably drift apart and will soon become unmanagable. I have been there and do not care to go there again. Of course, I can only speak for NA-MIC, NAC and NCIGT. What people choose to do outside these efforts is none of my business.
W: If we design a framework that can be easily tailored, you get the flexibility and capability of a large system plus the ability to narrow down focus when necessary. Slicer modules are great for this, and I think the overall architecture will serve us well in this direction.

R: As far as the stability and performance are concerned: If I have ever seen an opportunity for the engineering core to be responsive to the needs of the DBP's, this is it. I am not sure that all of the IGT groups are fully aware of what is available to them inside the NA-MIC kit. -The workflow capablities in Slicer are not well documented. -Similarly, I am not sure how much the IGT people know about Ctest as a mechanism to improve stability (who will work with them on this?). -Finally, we should identify what performance issues are at hand and see how to address them (this is again something that will be beneficial to every user of slicer).
W: Workflow is an ongoing research topic. Currently there is good stuff there (e.g., EMSegmenter) and it is very useful at this point. I suggest that the dissemination people team with the engineering core to put some documentation together. Performance concerns can be addressed as long as we get feedback from the DBPs. Often users don't realize that certain algorithms and/or processes can be easily sped up by simple tweaks, or use of different components in a system. In VTK and ITK we routinely see cases where we realize speedups on the order of 10-100x when we work with a customer to make a fast path for a particular application. The hardest thing is to get people to communicate needs, often they give up early without enough communication.

R:Perhaps we should have some discussions in the engineering core about these issues and see if there are solutions that can be addressed with the resources available. I envision activities after the AHM and the release of slicer.
W: Agreed, this sounds good, and it will bring fresh energy to the engineering TCons.