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Caltech Brain Imaging Center
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Human Neuroimaging

man and woman

The CBIC provides state-of-the-art facilities for human functional and structural neuroimaging in support of research ranging from visual psychophysics to social decision making.

3 Tesla Siemens Prisma.Fit
This upgraded, state-of-the-art human scanner is used for all human neuroimaging experiments and offers state-of-the-art structural, functional, and diffusion MRI. The system provides a variety of head coils (CP transmit-receive, 20 channel and 32 channel receive arrays and a 64 channel head-neck array), multipurpose flexible coil arrays and a two-channel parallel transmit body coil. This system has been augmented with remote eye tracking, a variety of physiological transducers and subject response devices including optical button boxes, a track ball and joystick (Current Designs, Philadelphia PA). Immediately adjacent to the scanner is training room simulating the in-bore experience for subject training.

Visual and Auditory Stimulation
Experimental stimuli are controlled by Windows and Linux workstations running a variety of standard stimulation software including Psychophysics Toolbox, PsychoPy, and Cogent. Visual stimulus presentation is via a low-noise LCD back-projection system outside the magnet fringe field and audio stimulus presentation is via high-quality in-ear headphones (Sensimetrics Inc, Gloucester, MA). Caltech has an active Master Research Agreement with Siemens Medical Systems allowing research modification of pulse sequences and RF coil hardware development.

Physiological Monitoring and Stimulation: Cardiac and respiratory waveforms during scanning are captured automatically by the functional imaging sequences and recorded in DICOM format for subsequent processing. Pupil dilation responses are captured during eye tracking. Auxiliary physiological measurements including skin conductance and electromyography can be recorded using appropriate amplifier modules for our MR-compatible Biopac system (MP150, Biopac Systems, Goleta, CA). Low voltage electrical stimulation is also supported by the Biopac system.

Eye tracking: Functional MRI with visual stimuli or required fixation performed in the CBIC frequently include gaze estimation including pupil response measurements. In-bore gaze estimation and pupilometry are acquired using an MR-compatible Eyelink 1000+ remote monocular IR camera (SR Research Ltd, Ottawa, Ontario, Canada). IR illumination and video capture of the participants eye employ a front-silvered hot mirror mounted to the MR head coil. Eye tracking acquisition control and data capture are integrated with stimulation scripts via the Eyelink API for Psychophysics Toolbox and PsychoPy.

Quality Control
Quality control (QC) for the human Prisma.Fit system is implemented at three levels:

  1. Manufacturer quality assurance during routine preventative maintenance and continuously via Siemens Remote Service management.
  2. Routine QC imaging fBIRN sphere phantom in the 32 channel head coil consists of a 15 minute single-band EPI sequence analyzed offline using the CBICQC analysis package.
  3. In Vivo QC of fMRI acquisitions using MRIQC (Stanford Center for Reproducible Neuroscience). The phantom and in vivo QC address coil element stability and the main imaging artifacts of concern for neuroimaging, such as dynamic Nyquist ghosting and gradient spiking.