Tracking Internal Landmarks

Tracking Internal Landmarks

It is now possible to register CT-MRI scans for the tracking of internal landmarks both In-Vitro and In-Vivo during motion capture collection of activities. Use the data digitized with The MotionMonitor's® mesh file generator or from CT-MRI scans to define bone geometry; identify muscle and ligament insertion points; and to track bone separations during activity. The process is as follows:

  1. Specimens or subjects are instrumented with sensors.
  2. Registration landmarks are digitized during subject setup.
  3. Trials are collected pre & post surgical or rehabilitative interventions.
  4. Joints can then be disarticulated and surfaces digitized, or CT/MRI scans can be utilized for digitizing registration landmarks, other landmarks of interest and bone surfaces.
  5. Wire frames & mesh files are created from the digitized bone surfaces.
  6. The trials are played back synchronously with the point or mesh files.

CTExtractionIn the image on the right, CT scan of an intact cadaveric specimen (it could have been a live subject) was made with a flag of reflective markers attached to the bones. The MotionMonitor® software then extracted, in real-time, the important landmarks such as femoral head, condyle centers, long axis, mechanical axis, and joint center of rotation. While tracking the specimen with a passive optical camera system the distal end of the femur and proximal end of the tibia were resected to receive components for a total knee replacement. The components also were instrumented with passive markers so that their precise location on the resected bone could be monitored. By making the CT scan of the bone transparent it was possible to view the component attachment (see image to the right) and monitor component alignment, full leg alignment and range of motion post procedure.

 

In the series of images on the right, the femur and pelvis were instrumented and an activity was collected. The joint was then disarticulated to simulate an in-vitro experiment. The femoral head and pelvis were digitized using The MotionMontior’s® meshfile generator. The resultant point cloud and wireframe of the femoral head and pelvis were then played back synchronously with the previously collected activity. Then, the interaction of joint surfaces were observed during the activity.

In the image to the left, sensors were attached to a live subject’s scapula and humerus, registration landmarks were identified and an activity was collected. CT scans were taken following collection of the activity and then digitized. Using these digitized points and the registration landmarks, a point cloud and then mesh file were created. The previously collected activity was then played displaying the reconstructed CT scan and the location of various internal landmarks.

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