Recurring Meeting of Cleveland Clinic Core Team

Date: June 25, 2014

Time: 10:30 AM EST

Means: In person meeting

Attendees:

1. Ahmet Erdemir
2. Jason Halloran
3. Craig Bennetts
4. Snehal Chokhandre
5. Katie Stemmer
6. Robb Colbrunn
7. Tara Bonner

Agenda:

1. Discuss immediate action items from the last meeting.
2. Discuss tissue testing progress.
3. Discuss joint testing preparation progress.
4. Decide immediate action items for the next meeting.
5. Other.

Immediate Action Items:

• Ahmet
  • Update experimentation workflow figure.
  • Review tissue testing specifications.
  • Review tissue sampling section of specimen preparation specifications.
• Craig
  • Review specimen preparation specifications.
• Robb
  • Provide camera positioning system for thickness measurements.
• Tara
  • Review tissue testing specifications.
• Robb and Jason
  • Troubleshoot processing tools to move between "right knee abstraction" and "physical representation" of knee data collected during joint testing.
• Jason and Ahmet
  • Find appropriate foam material to conduct pressure calibration.
• Snehal
  • Complete writing a Python script to downsample number of video images collected during tissue testing.
  • Continue executing tissue testing procedures to finalize tissue testing specifications.

Notes:

1. Discuss immediate action items from the last meeting.
   • Ahmet e-mailed Martin from Biomomentum Inc. in regard to issues and new features related to software for tissue testing. The anticipation was that the new software version would have control over video collection. Specific features Ahmet asked about were i) automatic down-sampling to save every “nth” data point (displacement, force, video) and ii) the capability to turn on/off signal filtering in each sequence. Signal filtering would help smooth data and has implications for finding initial contact, which may be difficult to achieve with noisy data. There are workarounds for this issue but it would be convenient if there is an established way to handle this. For acquisition of stress relaxation data, it is desirable to collect raw signal to prevent any filtering artifacts.
   • Ahmet updated the imaging specifications protocol. Tables were completed to reflect the image settings for the chosen protocols. The imaging page is essentially complete and is ready for community review.
   • The experimentation workflow figure was not updated but will be for next week (Ahmet's task).
   • Tara reviewed the tissue preparation specifications. She added comments and will continue to review. Tara should also review the tissue testing specifications. Snehal covered her approach to develop the tissue testing specifications. She is actively prototyping, e.g. evaluating the protocols hands-on, and will populate the page with more details.
   • Robb will inform Snehal where an additional camera and a positioning system are for tissue thickness measurements.
   • Robb and Jason have been working out the approach to handle processing of robotics data (joint kinematics-kinetics) to streamline definitions of coordinate systems (based on registration markers and anatomical landmarks.
   • Robb, Ahmet, and Jason will determine an appropriate material for calibration of the Tekscan pressure measurement sensor. This will likely be based on a foam material that mimics cartilage behavior, ideally in stiffness and nonlinear behavior.
   • Snehal developed a Python script to read the tissue testing data. A sample test data file was uploaded to the utility folder. Down-sampling of the imaging data is still being worked on by Snehal.
   • The tissue testing system was moved into the new laboratory space. Setup is progressing and Snehal has made a list of items to order immediately. A crucial item is another manual adjustment stage to add another degree of freedom to align the specimen with loading axis.
2. Discuss tissue testing progress.
   • In the specifications page for tissue testing, Snehal summarized her progress and provided preliminary results. This information is provided at the bottom of the page as a discussion. Like the imaging specifications, this will serve as the preliminary outline for the final specifications. Another knee was dissected last week and a handful of tissue testing samples were obtained. Acquisition of compression samples for menisci can be “tricky.” Snehal suspects that our previous data on meniscus testing may have had related issues. Snehal summarized her approach to punch out meniscus samples. It may be difficult to obtain a uniform sample size given the complexity of the native meniscus geometry. Once a “wedge” shaped tissue is extracted, there is little material to actually work with, i.e. shaving it down to obtain a uniformly shaped sample may result in a very thin sample (1 mm or less). For soft and thin materials, testing can be problematic due to equipment resolution. The group discussed potential solutions, including indentation testing on a meniscus cross section (to acquire force-displacement data) followed by testing a sample to obtain stress-strain material response. The latter would provide material data (stress-strain) for a model of the meniscus cross section. Predictions of simulations using indentation boundary conditions can be compared against measurements of indentation force to confirm suitability of meniscus material properties obtained through proposed tissue testing approach.
   • The heater for the tissue bath was also discussed. Once the heating element is put in the bath, there is no room to subsequently put the tissue sample in. Snehal is concerned about the amount of time the sample might stay in a heated condition. If it is placed in before the desired bath temperature is stabilized, overheating the sample is a possibility. The question was raised as to whether the temperature bath is needed. This would need to be tested. The primary concern is consistency of the testing conditions, which a heated bath provides. One solution might be to preheat the saline outside of the testing bath and then pour it into the temperature controlled testing chamber once the testing starts. This would require less work by the installed heater as well as less time to stabilize the temperature of the sample.
   • Snehal made a list of all testing samples, which includes a total of 29 tests. Eight specific tests were identified for trial runs to fine tune the protocols. Snehal presented the list and the group agreed that the sample tests appeared to be adequate. Snehal performed compression testing on a cylindrical cartilage sample. She uploaded her notes about this test at the bottom of the specifications page for tissue testing. The protocols were updated to reflect what Snehal learned during this test. The data looks “good”, which means no spikes were observed and the protocol appeared to do what was desired. There was an “overshoot” when the loading rate was specified at 100%/second. Snehal's plan is to complete the 8 tests to inform the final tissue testing protocols. Snehal will find the group if she needs help.
3. Discuss joint testing preparation progress.
   • See relevant items above in the discussion of immediate action items from the last meeting.
4. Decide immediate action items for the next meeting.
   • Action items were assigned and agreed upon by the group. See Immediate Action Items above.
5. Other.
   • Robb, Craig, and Ahmet discussed the possibility to use the serial robot at Lutheran Hospital for the joint testing. This is as an alternative to our existing system (parallel robot). The motors of the current system cannot be replaced at this moment, which introduces the risk of loosing a specimen during testing when and if brakes fail. Ahmet proposed that during the last week of July a test run is performed on our robotics system to gain confidence in the setup and in the full testing protocols, which will include imaging and joint testing. This sample data would also provide a basis for cruciate ligament modeling. The team has a separate intact specimen (mid thigh to toes) for this purpose.

   • Katie covered her process for creating parametric surfaces in Rhino. This is document on her project page (see https://simtk.org/home/cruciate_model). This progress will serve as a basis for the details of model creation in Open Knee(s).