The
AIM Frame is a bone-attached miniature parallel robot for
minimally-invasive neurosurgical procedures, in particular
cochlear implant (CI) surgery. The AIM Frame project of Vanderbilt's
Computer-Assisted Otologic Surgery (CAOS)
laboratory in cooperation with the MED Lab.
Cochlear
implants are electronic devices that restore hearing
to individuals who have severe or total hearing loss and
cannot benefit from traditional hearing aids, which amplify
external sounds. A cochlear implant bypasses non-functioning
parts of the ear by directly stimulating the auditory nerve
with electrical signals. The signals are transmitted to the
auditory nerve through an electrode array implanted in the
cochlea, a spiral-shaped structure of the inner ear.
Surgeons currently gain access to the cochlea by performing
a mastoidectomy,
requiring tedious creation of a cavity in the temporal bone
behind the ear using a hand drill. To avoid damaging
sensitive structures such as the facial nerve, surgeons must
rely on hand-eye coordination and spatial memory to execute
the mastoidectomy procedure with submillimetric accuracy.
A Cochlear Implant. (Image: National Institutes of Health/ Department of Health and Human Services)
A Cochlear Implant. (Image: National Institutes of Health/ Department of Health and Human Services)
A
new procedure, Percutaneous Cochlear Implantation (PCI) has
been pioneered at the CAOS laboratory as a
minimally-invasive alternative to traditional CI surgery. A
rigid fixture called a "Microtable" is custom manufactured
for each patient and attached to the skull using bone
screws. The Microtable guides a drill and electrode
insertion tool to the cochlea through a single drill hole
behind the ear. The shape of the Microtable is automatically
designed by custom software that calculates an optimally
safe drill path from patient CT scans. By eliminating the
mastoidectomy from CI surgery, PCI promises to reduce patient trauma,
shorten procedure time, and reduce reliance on a surgeon's
skill.
Microtables have been shown to be a safe solution for PCI surgery, but each surgery requires on-site machining. The purpose of the AIM Frame is to remove the need to machine a Microtable, by using a rapidly configurable parallel robot to perform the same targeting function as the Microtable but with a reduction in total procedure time. High accuracy and mechanical rigidity is achieved by use of a parallel robot design, the Gough-Stewart platform.
The AIM Frame system for Percutaneous
Cochlear Implantation
PCI surgery with the AIM Frame begins with attaching a rigid
platform called Pre-Positioning Frame (PPF) to the patient's
head using bone screws and then taking a CT scan. Metal
spheres on the PPF are automatically identified in a CT scan
and allow planning software to automatically plan a safe
drill trajectory to the cochlea. After the robot is adjusted
to position, it is detached from its power source and
the spheres on the PPF. During surgery, the drill and
electrode insertion tool attach to a coupling on top of the
robot.
Two views from a CT scan of a drill tip (5/64" diameter) guided by the AIM Frame to the cochlea of a human cadaver. The AIM Frame successfully avoided all critical anatomy and placed the drill tip 0.38 mm from its planned target.
In addition to
Percutaneous Cochlear Implantation surgery, the AIM Frame
is being considered for other neurosurgical applications
including electrode placement for deep brain stimulation
and drainage of the petrous apex.
Videos:
Publications:
- L. B. Kratchman, G. S. Blachon, T. J. Withrow, R. Balachandran, R. F. Labadie, and R. J. Webster III. Design of a Bone-Attached Parallel Robot for Percutaneous Cochlear Implantation. IEEE Transactions on Biomedical Engineering. (In Press).
- L. B. Kratchman, G. S. Blachon, T. J. Withrow, R. Balachandran, R. F. Labadie, and R. J. Webster III. Toward Automation of Image-Guided Microstereotactic Frames: A Bone-Attached Parallel Robot for Percutaneous Cochlear Implantation. Robotics, Science and Systems 2010 - Workshop on Enabling Technologies for Image-Guided Robotic Interventional Procedures. (Poster)