MAGNETIC RESONANCE SCANNERS
GE High-Field Actively-Shielded 7T/90 cm Whole-Body Imaging System
Supported by the state, a GE High-Field Actively-Shielded 7T/90 cm Whole-Body Imaging System was ordered by the Medical College of Wisconsin on November 23, 2010, and will be delivered in 2013. Specifically, the imaging system contains a 7T actively shielded magnet and superconducting shims manufactured by Varian (Magnex), weighs (excluding cryogens) 38 tons, and has a clear bore size of 900 mm, with first-, second-, and third-order superconducting shims. The resistive shim subsystem has a total of six zero- and first-order shim coils and two second-order shim coils with shim drivers (amplifiers) of 4 A maximum current. The magnet enclosure/facade and patient-handling subsystem include a dock-able (removable, mobile) table, vibration isolation, acoustic damping, and physiological acquisition controller.
The gradient system includes an XRMb (eXtreme resonance module) gradient coil, driven by XGD (eXtreme gradient driver) amplifiers (1600 V and 600 A). The gradient coil cooling system is capable of extracting more than 25 kW of heat from the coils. The gradient system provides a max amplitude per axis of 50 mT/m and maximum slew rate per axis (T/m/sec) of 200 T/m/sec and full eddy current compensation including Bo and cross-terms.
For exciter, receiver, and power RF subsystems, the transmitter is configurable from 70 to 300 MHz for 1H imaging and X nucleus imaging/spectroscopy experiments. 10 × 1 kW RF power amplifier comprised of 10 × 1 kW modules, configurable as 2 × 4 kW or 8 × 1 kW Tx channels. The receiver has the high linearity of an MR750 receiver system, supporting imaging and spectroscopy of 1H, 31P, 23Na, and 13C with X-nucleus and 1H decoupler kit. Thirty-two independent 1H receivers and a 32-channel receiver coil are provided.
A host computing platform, reconstruction engine, and software will be provided. Version-20.x-based software will include all commercially available pulse sequences, spectroscopy, and imaging options, nominally equivalent in form and function to the MR750 (3T) platform. Dual CPU host-computer includes Linux OS, dual- core Volume Reconstruction Engine 2.0, operating at 5400 2D FFT/s (or better), wide-screen, 23-inch high- definition 1920 × 1200 flat panel monitor, with 500:1 contrast ratio and 85 Hz refresh rate.
This 7T scanner will enhance shared use of the centralized MRI resources, enrich ongoing research, promote new research, foster a cooperative and interactive research environment and stimulate multidisciplinary approaches to neuroscience. MCW has provided a strong institutional commitment to the 7T imaging facility and its maintenance. It is anticipated that the installation of the 7T scanner and its operation for translational research will not only significantly enhance technology development but also bring new scientific discoveries to the next level and benefit patient care.
Experiments will be conducted by the applicants of this proposal to evaluate the feasibility of this instrument for real-time fMRI and fcMRI.
GE 3T MR750 MRI System
Supported by the state, a newly purchased GE 3T scanner (Model: DiscoveryTM MR750 32-Channel MR System) has been installed and is in operation. A more detailed description of the system is given below:
Third Generation Magnet Design. Contains 18 superconducting higher-order shim coils, active-shielding technology and stainless steel foundation. The magnet’s high homogeneity delivers excellent fat-saturation away from isocenter and ensures image quality over a full 48-cm field of view. Zero boil-off technology and remote magnet monitoring technology are incorporated.
High-Performance Whole-Body Gradients. The MR750 incorporates the eXtreme Resonance Module (XRM). XRM gradients deliver 50 mT/m peak amplitude and 200 T/m/s maximum slew rate on each axis simultaneously. The gradients are water-cooled and equipped with integrated thermo-electric cooling panels to provide 100% duty-cycle and stability for advanced studies, such as fMRI. Acoustic noise is minimized, using a passive acoustic barrier material that reduces acoustic transmission by an average of 6 dB for enhanced patient comfort without compromising imaging performance.
Higher-Order Shimming. The MR750 is equipped with five higher-order shim-resistive shim coils to minimize patient-induced field perturbations. In addition to the linear terms (X, Y, Z), the shim set includes XY, XZ, YZ, Y2, X2-Y2 compensation coils.
RF Amplifier. To drive the MR 750 body coil, the system utilizes a water-cooled, solid-state 35 kW RF amplifier design. The amplifier supports a 100 W continuous-wave output mode for advanced proton- decoupling and spin-labeling research.
Host Computing Platform, Reconstruction Engine, and Software. Version 22.x based software. The MR750 utilizes 2.6 GHz processing technology with VRE2.0 recon architecture. With its expansive 32 GB memory, acquisition-to-disk technology, and 5400 2D FFT/s frame rate, the VRE 2.0 delivers the processing power to reconstruct 32 channels of high-resolution 3D volumetric data.
This 3T scanner will enhance the shared use of the centralized MRI resources, enrich ongoing research, promote new research directions, foster a cooperative and interactive research environment, and stimulate multidisciplinary approaches to neuroscience. MCW has provided strong institutional commitment toward the 3T imaging facility and maintenance.
3.0T GE Long-Bore Excite MRI System
The long-bore GE Signa Excite MRI system is a 55-cm-bore, whole-body MRI system with a high homogeneity, actively shielded magnet with resistive, passive and superconducting shims. The gradient subsystem is a shielded gradient coil (CRM) capable of operating at slew rates up to 150 mT/m/sec and peak gradient amplitudes up to 40 mT/m. This performance allows high-resolution echo-planar and diffusion- weighted imaging to be conducted anywhere in the body. The system computer-architecture is based on Linux workstation operating as host with a dedicated signal acquisition subsystem — the Transceiver Processing System. The RF system contains an eight-channel receiver module, low-noise digital RF subsystem, and RF frequency synthesizer, quadrature transmit/receive body RF coil, quadrature transmit/receive head RF coil and eight-channel array head RF receive coil. This allows improved high-resolution, high-speed echo-planar imaging through parallel imaging. This system allows imaging resolutions up to 256 × 256, oblique plane imaging, graphics prescription, and automated reconstruction with echo-planar imaging sequences. These features make the system ideal for fMRI. This scanner is housed in the Department of Biophysics at the Medical College of Wisconsin (MCW).
Additional Equipment for Real-Time Acquisition
Units to create an arbitrary number of different tailored pulses; a stand-alone system containing: Two kW RF pulse amplifiers 10-140 MHz LPPA 14029Transmit pulse mixer with a bypass and 80 dB attenuator (1 dB step) made at MCWPentek 78621 transmit/receive PCIe card with three ADCs and two DACs
9.4T Bruker Biospec 94/30 USR In Vivo Spectroscopy Imaging System
The Bruker Biospec system has an actively shielded 9.4T magnet with a 31 cm warm bore. This system has a magnetic field uniformity of 0.1 ppm over a 70 mm DSV, and 10 ppm over a 180 mm DSV. To keep such high levels of magnetic field uniformity, there are 12 user-adjustable shim coils. The infrastructure is in place to augment the vendor-supplied shims with six additional shim coils, which will be used to further enhance magnetic field uniformity for imaging and spectroscopic studies. Gradients up to 100 mT/m can be generated along all three axes. The RF system has two transmission channels capable of experiments on 1H, 19F, 13C, 14N, and 31P nuclei, and two matching receiver channels capable of 16-bit resolution at a 2 MHz sampling rate. This collection of hardware will allow gathering of high quality imaging and spectroscopic data, since the shim system should be able to generate extremely uniform fields, and the gradients, in conjunction with the RF transmission and receiver subsystems, allow collection of data at extremely high rates necessary for functional magnetic resonance studies. This scanner is housed in the Department of Biophysics at MCW.
This facility mimics the spatial and aural environment of a functioning scanner. It is used for subject training and psycho-physical studies. It is operated by the MCW General Clinical Research Center.
• E5505A Agilent Phase Noise System
• HP3577A Network Analyzer (5 Hz–200 MHz)
• HP8712ES Network Analyzer (300 kHz–1.3 GHz)
• E8363B Agilent PNA Network Analyzer (10 MHz–40 GHz)
• N5242A Agilent PNA-X (10 MHz–26.5 GHz) with two Oleson V10VNA2-T/R W-band heads (75–110 GHz)
• two V06VNA2-T/R D-band heads (110–170 GHz)
• V03VNA2-T/R-A WR-3 head (220–325 GHz)
• N9030A-544 Signal Analyzer (10MHz-44GHz)
• HP8596E Spectrum Analyzer (9 kHz–12.8 GHz)
• HP8564E Spectrum Analyzer (9 kHz to 40 GHz to 110 GHz with external mixers)
• HP E4418B Series (with heads to 110 GHz) and other microwave power meters
• 578B Phase Matrix EIP Source Locking Microwave Counter (10 Hz–26.5 GHz, to 110 GHz with external mixers)
• Frequency counters to 40 GHz
• Digital and analog oscilloscopes to 1 GHz
• General purpose synthesizers for test purposes, Pulse, delay, and signal generators for test purposes, 33220A Agilent Function/Arbitrary Waveform Generator