Transcript Poster Presentation - Research

3T NeuroImaging Primate Chair
Jennifer R.
*
Pryweller ,
Professor Malcolm J.
‡
Avison
*Vanderbilt
University, Department of Biomedical Engineering
‡Vanderbilt University Institute of Imaging Science, Department of Radiology
Methods
Background
The synergistic activity of large neural populations remains largely
unexplored in the visual cortex. Hemodynamic metabolic approaches to
exploring this activity are based on the fact that energy metabolism
(measured as a function of cerebral blood flow and volume change) is
coupled to neuronal activity. Studies explore the brains of rhesus macaques
by presenting the monkey with a visual stimulus while simultaneously
collecting imaging and electrophysiological data from the occipital lobe.
Specifically, the correlation of BOLD (blood oxygen level dependent) fMRI
(functional magnetic resonance imaging) brain data and neuron action
potential signal localization is used to map the visual cortex. Since these
investigations require the use of awake monkeys, it is necessary to develop a
device to restrain animal movement in an ethical manner while performing
simultaneous data acquisition.
Cost Analysis
Design Constraints & Specifications:
• Bore Constraints: loading of chair into
elevated bore, patient bed restricts
available bore radius; gradient induced
vibrations
• Cohort Specifications: 6.5-8.5kg, 2832” prone (current cohort)
Figure 2. Parameters of Philips 3T
Achieva bore (without patient bed).
• Materials Selection: MRI compatible,
cost effective, resistant to monkey
strength, provide isolation, permit
viewing of monkey
Objectives
To create an MRI compatible device that restrains rhesus macaques while
minimizing head movement. The device must conform to high ethical
standards and:
• Provide a comfortable position for the monkey
• Be adjustable/customizable for individual variation in monkey weight, body
size and head size
• Restrict monkey paws while allowing for their use in task response
• Be Compatible with functional components:
• stimulus presentation equipment
• behavioral monitoring equipment
• simultaneous electrophysiological monitoring of neural activity
Figure 3. Materials selection criterion for chair siding, boot piece and hardware assuming temperature
variation of 10-35 degrees Celsius. Based on analysis polycarbonate was chosen for chair siding.
Brass and nylon screws will be used – nylon near isocenter to prevent distortion artifacts in images,
and brass for vertex hinging in areas further from isocenter.
Discussion & Results
The portion of this project specified to be completed for Senior Design was
the design and construction of the physical chair, while accounting for the
addition of functional components in the future.
Previous Design
Figure 1. Headbar and chair design by Wim Vanduffel
(2001) (a); Primate chair design by Mark Pinsk (2005) (b);
Crist Instruments stock manufactured chair (2005) (c).
Ethics
• Non-human primate of
choice is rhesus macaque
for: anatomical and
physiological likeness, ease
of maintaining and breeding
• IACUC (Institutional Animal
Care and Use Committee)
approved
• IRB (Institutional Review
Board) approved
• Ethics research training
exam (#1102055)
Figure 4. Cross-section of chair fit to parameters of bore (a); Side-view of
chair (b); boot piece of chair fit to bore parameters (c).
• Monkeys will be exposed to the chair and
imaging conditions (i.e. noise, darkness) during
training to minimize emotional distress
• Boot piece (Fig. 4b) fits chair tightly in place
inside bore, minimizing effects of animal
movement
• A headpost restraint, functionally similar to
those seen in Fig.1, will be constructed using the
highest quality MRI compatible material, Peek.
• Removal of patient bed from bore
during imaging allows for more height
between base of chair and isocenter,
where monkey’s head will be
positioned.
• Gradient vibration and potential animal
movement is minimized by securing
the chair to a customized patient bed
outside the bore. A lip will be
constructed to secure the chair to the
external bed through a series of
screws.
• An adjustable neckplate piece and a
headbar with six degrees of freedom
were developed to account for variable
monkey size.
• Lightning holes will be drilled in siding
to decrease the weight of the chair
(siding weight alone ~50kg) and
provide more air flow to the monkey
• A chest plate will be used to support
the monkey sitting in sphynx position
Figure 6. Cost analysis of primate chair construction
including parts and labor.
Conclusions
• Primate chair conforms to high ethical standards and provides the macaque
with physical comfort and minimal emotional distress
• Primate chair provides physical restraint of rhesus macaques to obtain
BOLD fMRI images with minimal motion artifacts
• Primate chair promotes a high level of safety for both the monkey and
human investigators
• The addition of functional components to the primate chair:
• allows for increased monitoring of the monkey’s well-being
• provides for the acquisition of additional data
• implements positive-reinforcement through a reward system
• increases control for subject movement, minimizing artifact
• Weight of chair can be reduced up to 20% using lightning holes in siding
• Chair is easily modifiable and allows for the future addition of functional
components
Future Direction
• Finish machining and construction of primate chair
• Add functional components and electrophysiological monitoring devices
• Train current macaque cohort and begin imaging studies
• Build custom RF head coils to fit around headpost
• Insure compatibility of chair with 7T Varian MRI bore
• Explore options for complete isolation of monkey for safety compliance up
to BSL 4
References
• Andersen, AH et al. Functional MRI studies in awake rhesus monkeys:
Methodological and analytical strategies. J Neurosci Methods 2002;118:141-52.
• Pfeuffer, J et al. Anatomical and functional MR imaging in the macaque monkey
using a vertical large-bore 7 Tesla setup. Magn Reson Imaging 2004;22:1343-59.
• Pinsk, MA et al. Methods for functional magnetic resonance imaging in normal and
lesioned behaving monkey. Journal of Neuroscience Methods 2005;143(2):179-95.
• Prof. Malcolm J. Avison, Vanderbilt University Institute of Imaging Science
• Dr. Paul King, Vanderbilt University Department of Biomedical Engineering
• Ken Wilkens, Vanderbilt University Institute of Imaging Science
• LiMin Chen, Vanderbilt University Department of Psychology
• Bruce Williams, Kennedy Center Institute