3 T Neuro Imaging Primate Chair Jennifer R

3 T Neuro. Imaging 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) f. MRI (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. 5 kg, 2832” prone (current cohort) Figure 2. Parameters of Philips 3 T 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. 4 b) 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 ~50 kg) 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 f. MRI 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 7 T 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 • Li. Min Chen, Vanderbilt University Department of Psychology • Bruce Williams, Kennedy Center Institute