IRC Scanning Hardware and Accessories

The Imaging Research Center operates two separate facilities – one for human imaging research, and one for preclinical imaging research. The scanners available for each, as well as their associated accessories, are described here.

Human Imaging Scanner

Siemens Skyra 3.0T MRI

The Siemens Skyra 3T enables high-resolution imaging capabilities at the UT IRC. This whole-body 3.0T device is configured with 64 receiver channels. It is capable of integrated parallel acquisition techniques and provides higher signal to noise in the parallel imaging mode than its predecessors. The maximum acceleration factor using parallel imaging is 16 using either mSENSE or GRAPPA, and 3D scanning can be accelerated in two directions (maximum acceleration factor of 4 in second direction). The gradients of the Skyra have a maximum amplitude of 45 mT/m and a maximum slew rate of 200 T×m-1×s-1, yielding a minimum rise time of 225μs. The vector gradient performance (vector summation of all three gradient axes) results in a maximum effective amplitude of 78 mT/m and a maximal effective slew rate of 346 T/m/s. All three gradient coils are force-compensated to reduce vibration and deliver superior eddy current performance. The water cooled gradient amplifier has a maximum amplitude potential of 2,250 volts and a maximum current output of 750 amps. The instrument has a minimum slice thickness (in two dimensions) of 0.1 mm and a minimum partition thickness (in three dimensions) of 0.05 mm. The instrument produces high sensitivity, with main field, or B0, homogeneity of 1.4 ppm VRMS for a 40 cm diameter spherical volume. Single shot EPI sequences for measuring diffusion-weighted data sets with up to 256 directions of diffusion weighting are also a part of this instrument’s capability. It provides diffusion tensor imaging and parametric maps derived from fractional anisotropy calculated in real time, automatically. Additional sequence options include Arterial Spin Labeling, and susceptibility weighted imaging (SWI) with both fully supported with parametric and phase map reconstructions.

Response Devices

The IRC uses a 932 Package provided by Current Designs, Philadelphia, PA. Currently, there is a four button bimanual box (2×2) available and an eight button bimanual box (2×4). The 932 interface accepts the TTL trigger output from the Skyra during EPI experiments for experiment and response synchronization.

Visual Stimulation

The PROPixx projector at the IRC has a native resolution of 1920 x 1080 and can be reliably driven with refresh rates up to 500 Hz. It uses high brightness LEDs as a light source, giving a larger color gamut and much longer lifetime than conventional bulbs. For stereo vision applications, a high speed circular polarizer allows for 3D displays using passive polarizing glasses, with interleaved binocular refresh rates up to 400 Hz.

The PROPixx also synchronizes virtually any input or output devices to the timings of the video signal with microsecond precision. These can include stereo audio, button boxes for precise reaction-time measurement, triggers for electrophysiology and eye-tracking equipment, and/or any custom analog I/O subsystem. You can now successfully synchronize all of your subject I/O to video refresh with microsecond precision. It is field upgradeable, allowing for custom features to be added via firmware update.
A software toolbox, PLDAPS, is shared by UT researchers and can be used in MATLAB (with the Psychophysics Toolbox) to take advantage of these functionalities with minimal additional programming overhead.

Physiological Monitoring and Recording

The Skyra is equipped with its own accessories for physiological monitoring and triggering. Users can select a 2, 3, or 4-lead ECG configuration. The acquired cardiac waveforms can be used to trigger most sequences or they can be recorded for retrospective image reconstruction and/or analysis. For studies not needing to trigger to a precise phase in the cardiac cycle, a plethysmographic finger clip can be used instead. This can provide adequate triggering for cine cardiac imaging without the need to attach ECG leads which some subjects see as overly intrusive. This method is also capable of providing real time pulse rate and retrospective analysis. Similar triggering and recording options are available via a respiratory bellows that is strapped to the subject’s abdomen over their clothing.
For those needed more control, a BioPac MP150 system is available for use. Controlled from a PC running Windows 7, the modular MRI-safe amplifiers and subject interface leads provide highly configurable and programmable external instrument triggering and recording. Amplifiers available include respiration, ECG, electrodermal activity, and two electromoygrams.

Auditory Systems

In addition to the built-in headphone system of the MRI scanner, an Optoacoustics OptoACTIVE system is available, which provides active noise cancellation for both headphones and microphone, allowing high-fidelity stimulus presentation as well as collection of spoken responses.

Liquid Delivery

A gustometer system (designed by Dr. Eric Stice) is available for studies involving liquid delivery. The gustometer system is a portable device that consists of a laptop computer that can control up 7 independently programmable BS-8000 syringe pumps to deliver precise amounts of liquid stimulus to the supine subject at precisely timed intervals and durations. The pumps, which infuse liquids at rates of 6- 15 mL/min, are controlled by programs written using MATLAB. The gustometer mouthpiece is a collar capable of holding up to 7 beverage tubes and was designed to deliver tastants or tasteless solution to a consistent place on the tongue. Each tube is attached to one-way syringe activated check valves to prevent dripping and participants sucking on the tubes.

Preclinical Imaging Scanners

Bruker BioSpec 7.0T MRI10_biospec1

The MRI is a Bruker BioSpec 7.0 Tesla, 16cm bore (B-C 70/16) platform. It is equipped with a Bruker B-GA 9S high duty cycle gradient coil, capable of delivering 30 G/cm maximum amplitude with a 80 microsecond rise (3,375 T×m-1×s-1) time along any individual axis and a up to 69 G/cm amplitude combined. The 12 shim gradient coils are integrated into the liner gradient coil, providing a total of 15 shim channels. This gradient coil provides a 9cm operational inner diameter. The system is equipped with three 1H CP volume coils and a volume transmit, surface receive RF coil set – all made by Bruker. The inner diameters of the three volume coils are 72mm, 38mm, and 23mm. The transmit-only volume resonator has an 80mm inner diameter, and the surface coil is 30mm in diameter, and both are actively-detuned. The system has two independent, fully broadband 1,000W (pulsed), 50W (CW) RF amplifiers. The receive-chain has a single broadband receiver equipped with 1H, 19F, and X filters. The system is capable of operating with either of two host computers – one running ParaVision 5.1 and the other with ParaVision 6.0. Both software configurations include all options available. The system is maintained under a parts service contract from Bruker.

Xenogen IVIS Spectrum12_optical_room

The facility has an IVIS Spectrum system made by Xenogen/Perkin Elmer. It is capable of simultaneously imaging 5 mice under isoflurane anesthesia on a bed maintained at physiological temperature. The system has 8 excitation filters (410-760nm) and 12 emission filters (475-850nm). It is operated by a host computer running Living Image 4.1. The anesthesia is metered by an XGI-8 isoflurane vaporizer/evacuator.

Siemens Inveon PET-CT

The PET-CT is a Siemens Inveon scanner. It is equipped with all available options, including a variable focus X-ray source, and an extra-large
165mm detector. The PET is capable of achieving 1.6 × 1.6mm pixel spacing with its 4 rings of 16 blocks (each with 20 × 20 LSO crystal arrays) and iterative reconstruction techniques. The PET detectors provide 10-bit dynamic range at 100MHz sampling and 312ps time bins. The maximum single-position axial PET field of view is 12.7cm, but with continuous table motion, 30cm is possible. The X-ray source operates
between 35-50kVp and is specified to provide a 50 micometer focal spot. However, this particular instrument is capable of achieving ~7 micrometer isotropic CT voxels. Using a separate physiological monitoring system, it is capable of gating acquisition to respiratory or cardiac cycle. CT-based attenuation correction is available. The host computers have all available software options and run Acquisition Workplace 4.0. There is a standalone computer that runs Research Workplace version 4.0 that can be used to process data offline.