Recurring Meeting of Cleveland Clinic Core Team

Date: May 20, 2014

Time: 10:30 AM EST

Means: In person meeting

Attendees:

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

Agenda:

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

Immediate Action Items:

• Jason
  • Outline details of patella marker registration and provide scripts for registration in the utility folders of source code repository.
  • Modify extensor mechanism preparation images in the specimen preparation page.
• Snehal
  • Rewrite harvesting tissue section of specimen preparation based on her recent experience.
  • Use the vibratome to prepare cartilage and meniscus tensile test samples to evaluate tissue preparation.
  • Conduct thickness measurements using a rubber band as a test problem.
• Tara
  • Add relevant images and update existing ones in the specimen preparation page to reflect latest changes in robotics testing.
• Craig
  • Complete post-processing test problem for cloud computing prototype.

Notes:

1. Discuss immediate action items from the last meeting.
   • Jason summarized results from the patella registration, including comparisons. It appears that patella registration errors will be similar to that of femur and tibia.
   • Snehal summarized the tissue testing laboratory setup. Besides installing the eye wash station, the setup is nearly complete. After eye wash installation and floor cleaning, the testing equipment can be moved to the new space.
   • In regard to fixtures for tissue testing, Snehal reported that the old clamps are still being used for tensile testing, the tall bath with flat sides is under construction, both the the short and tall cylindrical baths are currently used. Tony Shawan, from Prototype Core, will provide an estimate for the new clamps for tensile testing. All other accessories are made, e.g., an acrylic base fixture for confined compression.

   • In regard to tissue testing, Elvis's tensile tests will need to start this week in order to finish before his departure. Snehal has talked with Martin Garon at BioMomentum, Inc. about the apparent erroneous displacement reporting during hold cycle of tensile testing. He mentioned that it may be a sampling problem but will explore this behavior and report back. Regarding sequence specific sampling frequency, Ahmet noted that the experimental results can be down sampled by skipping steps, and possibly only during relaxation portion of the testing. The stress relaxation test can be broken up so that the instantaneous response is sampled at the highest possible frequency. Video recording will also need to be downsampled or the file size will be unmanageable (approximately 250 gigabytes if sampled at 640 by 480 pixels and 10 hz). Additional discussion centered around how to resample the video data to capture the appropriate response. Options include higher sampling rate during the instantaneous loading followed by a lower sampling rate during relaxation if the interface of mechanical testing system allows. Note that, time stamps are used to align the transducer and video samples.

   • Snehal made some changes to the tissue preparation specifications. The tissue harvesting section will be rewritten based on the most recent testing sessions with Elvis. Snehal has developed a sequence of dissection procedures and this will be reflected in the description. Sample preparation is adequate with the exception of an addition to describe preparation of cartilage tensile samples.
   • Regarding specimen preparation in general, Jason will update the patella registration images and description. Tara will update description of the new Optotrak probe.
   • Snehal also updated the specifications for tissue mechanics experimentation to include all the tissue types and the primary outcomes. Ahmet would like Snehal to provide an illustration of the various loading sequences that will be used during the testing. These graphs could be generated in Inkscape to reflect the expected time-displacement-loading curves.Loading rates of 100% strain/second will be attempted though this will be evaluated in terms of necessity for tissue response, i.e. is a high frequency response expected? and capability of the machine, e.g., potential overshoot at higher loading rates. Confined and unconfined testing of cartilage and meniscus will be attempted. Secondary tissue tests will be populated if needed but as of now, the first set of knee(s) will focus on the primary restraining tissues. Specifications for preparing secondary tissues will be needed before tissue harvesting starts.
   • Snehal also tested two different approaches to quantify thickness measurements (optical and constant pressure LVDT). Results are summarized on the wiki. Inconsistency between and within methods were noted. Additional testing to evaluate reproducibility of tissue thickness measurements is necessary.
   • Craig will provide a post-processing test problem for the meeting with Stanford tomorrow.
   • Robb and Jason met to discuss/test the approach to pressure calibration of the Tekscan pressure sensor. An approach was summarized on the wiki but the actual geometry of the specimens used for calibration needs to be determined. It was decided that a candidate “foam” material with a similar indentation stiffness as cartilage will be cut into an appropriately sized dome, e.g., half sphere, and thickness to provide an approximate approach to calibration.
2. Review of specimen preparation specifications.
   • See relevant section above in the discussion of immediate action items from the last meeting.
3. Discuss tissue testing progress.
   • See relevant section above in the discussion of immediate action items from the last meeting.
4. Decide immediate action items for the next meeting.
   • Action items were discussed and agreed on, see Immediate Action Items above.
5. Other.
   • Craig, Jason and Ahmet met about providing details in the specifications of various modeling steps. Craig summarized the potential hierarchical approach to defining the topology of models which will also indicate modeling workflow and assembly. This is a strategy to abstract the connections between modeling components and the required relationship(s) between these pieces. With this, individual components or the desired assembly (up to the whole model) could be developed with the appropriate input(s)/output(s). Craig will summarize this on the wiki.
   • Ahmet had the biannual meeting with the scientist/engineer members of the Advisory Board. Current progress was found to be good. Ahmet would like to establish open collaboration with outside groups and Yasin Dhaher suggested reaching out to specific laboratories to setup cross-institutional internships. Both Open Knee(s) and the collaborative group would likely benefit from such an arrangement.