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Imaging Systems
The Kirby Center has three whole-body magnetic resonance imaging systems dedicated for research use:
- Scan Room
Each MR scan room has been optimally designed for fMRI with attention to RF shielding, stimulus and response interface and environmental control.
- Magnetic Resonance Imaging Systems
- 3.0T MRI Systems
These two systems ("MR1" and "MR2") have many advanced features for optimizing MRI studies.
- 7.0T MRI System
One of only 35 ultra-high field MRI systems worldwide and 18 in the U.S. this system ("MR3") was opened to the research community in April of 2009.
- Simulator
This "mock scanner" can be used to acclimatize subjects preparing for an MRI.
- fMRI Paradigm Presentation
Subjects can be exposed to both video and audio stimuli, which can be synchronized with the scanner imaging. We have fiber-optic response boxes and several other resources for monitoring subjects' responses.
- Physiologic Monitoring
MR compatible devices for measuring pulse, blood pressure, brain activity, etc. are available.
- Computing Resources
Dedicated PCs and Macintosh computers control stimuli introduction, scanner operation, data storage, etc.
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Known as "MR2", this was the first 3T whole-body MR scanner delivered by Philips Medical Systems worldwide.
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Each MR scan room has been optimally designed for fMRI with attention to RF shielding, stimulus and response interface and environmental control:
- Optimum radio-frequency (RF) shielding: Soldered, monolithic copper shielding with air-sealed door is used to provide maximum protection from outside RF interference sources with long-term reliability. The rooms exceed the manufacturers specification for RF attentuation by as much as 30 dB.
- Two lab penetration panels with a variety of waveguides and filtered connectors provide the means to interface devices between the scan rooom and outside areas without compromising the RF shield. No RF-producing equipment is used in the scan rooms without proper shielding.
- 3T Scanners: The scan rooms are lined with layers of silicon steel sheet to reduce the influence of low frequency magnetic fields on imaging.
- 7T Scanner: A 400 metric tonne magnetic shield is used to limit the stray field generated by the magnet. The shield forms a six sided box encompassing most of the scan room varying in thickness from 8 to 16 inches.
- Air conditioning and power conditioning: Humidity and temperature in the scan rooms is controlled and monitored by dedicated equipment. Each scanner's power is supplied by a dedicated uninterruptable power system (UPS) providing stable power condition and battery backup operation during brownouts or total power loss.
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These systems are defined by the strength of their magnetic field, namely 3.0 Tesla or 7.0 Tesla. One Tesla is about 20,000 times stronger than the Earth's magnetic field. Each scanner has a thirty-two-channel receiver system and high-sensitivity multi-element receive-only head coils, allowing for parallel imaging, including sensitivity encoding (SENSE) for faster scanning.
These Philips 3.0 Tesla MRI scanners have many advanced and unique features to optimize functional MRI studies, including:
- Short bores: 60 cm in diameter, 60 cm straight bore. Each bore flares in the front and back for a total magnet length of 179 cm cover-to-cover. A short bore provides a comfortable scanning environment, especially valuable for studies involving children, the elderly, and subjects with neurological and psychiatric disorders.
- Excellent field homogeneity: Even with the shorter bore, the main field is very homogeneous, which allows us to implement many modern imaging techniques.
- Modern imaging capabilities: Including echo planar imaging (EPI), fast spin echo (FSE), diffusion imaging with EPI and navigator echoes, single voxel MR spectroscopy (MRS), multi-slice spectroscopic imaging (MRSI).
- A second radiofrequency channel: Allows heteronuclear and homonuclear spectroscopy with decoupling, interleaved with fast imaging.
- Gradients: Dual mode gradients run at 80mT/m with a slew rate of 110mT/m/s, or at 40mT/m with a slew rate of 220mT/m/s. They have exceptional linearity.
- Coils: These receive the magnetization signal.
- Eight channel head coil - standard coil for fMRI studies with 8 elements radially positioned around the head. Allows SENSE in anterior-posterior (AP) or right-left (RL) direction.
- Thirty-two channel head coil - first of it's kind, being tested for advanced fMRI use. Coil layout allows SENSE in AP, RL or head-foot direction with higher SENSE factors and 2 direction SENSE during 3D scans.
- Sixteen channel head and neck coil - excellent for neurovascular studies.
- Dual Flex-M coil - flexible surface coil, can be use in pairs.
This system was opened for use to our Center in April of 2009.
- 58 cm bore.
- A second radiofrequency channel: Allows heteronuclear and homonuclear spectroscopy with decoupling, interleaved with fast imaging.
- Gradients: On this system, these run at 33 mT/m at a slew rate of 166 mT/m/s.
- Shims: 3 first order (gradient), 5 second order and 7 third order shims plus 2 dynamically controlled shims
- Coils: We receive the magnetization signal from these coils in order to create an image.
- Transmit/receive head coil - primarily used for QA.
- Volume TR head coil - normally used asthe transmitter for 16 or 32 channel head coils (NovaMedical).
- Sixteen-channel receive head coil (NovaMedical).
- Thirty-two-channel receive head coil - permits higher SENSE factors (NovaMedical).
- Eight-channel receive spine coil - not yet delivered (NovaMedical).
- Dual-tuned proton/C13 leg coil.
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This "mock scanner" allows researchers to do "practice runs" in order to acclimatize subjects to the sights and sounds of an MRI. It is especially useful for "training" children, the elderly, and persons with psychiatric disorders to perform an fMRI task and to reduce head motion during scanning. Our simulator includes:
- Model: A similarly-sized scanner cover by Philips Medical Systems.
- Surround sound audio system: This simulates the scanner sounds.
- Audio and video paradigm presentation system: The response buttons for these are identical to those used in the MRI scanner.
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fMRI Resources
Dedicated Windows PCs are provided in each control room for fMRI stimulus presentation and response collection. They are connected to the scanners via custom triggering circuits. Macintoshes are available in both 3T control rooms.
Paradigm presentation software packages on our systems include:
- E-Prime Stimulus Presentation Software
- Neuro-Behavioral Systems Presentation
- MATLAB with the Psychophysics toolbox
- Superlab 1.7 (Macintosh)
Visual stimulation equipment:
- Video Projector - Epson 3 LCD projector, 1024x768 native resolution
- Computer connections
- DVD Recorder/Player connections
- Located in Equipment Room, projects into back end of scanner through 7 inch waveguide
- Remote control from Control Room
Audio stimulation equipment:
- Amplifier and equalizer
- Computer-generated sound
- DVD/CD player/recorder
- Philips in-bore speakers
- MR-compatible headphones
Response monitoring equipment includes:
- Custom triggering circuits: providing a stimulus triggers the scanner and is synchronized with scanner pulses
- fMRI-compatible button boxes: using fiber optic communication
- Auditory equipment: using air-tube conduction or an electrostatic headset
- fMRI-compatible EEG equipment
- Eye-tracking of subjects inside the magnet: using infrared imaging
- Easily accessible interfaces: allowing investigator-owned computers to present paradigms to subjects
- Wave Guide Passthru connection: which is MR-compatible
- Filtered DB25 connector
- Filtered BNC coaxial connector
- Fiber optic connector
fMRI Software Packages
For either presenting stimuli or analyzing data, these include:
- E-Prime Stimulus Presentation Software
- SuperLab Stimulus Presentation Software
- MEDx, Medical Image Processing
- AFNI
- Stimulate
- SPM (running under MATLAB)
- EvIdent (running under IDL)
For software developed at the Kirby Center, please refer to our Software page.
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We have several MR-compatible physiologic monitoring devices:
Philips devices for MR triggering and can be stored for fMRI correction
- Vector-electrocardiogram (VCG)
- Finger pulse
- Respiration pneuomgraph
Invivo Millennia 3500 MR compatible monitor
- Electrocardiogram (ECG)
- Peripheral pulse oximeter
- End tidal CO2
- Non-invasive blood pressure
- Invasive blood pressure
- Anesthetic inhalation gases
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We have many computers, for storing data, and operating the scanner. Some specific details:
- Fast Gigabit Ethernet network
- File and compute server: SunFire V880 Server
- Parallel processors: 8
- Memory: 16GB of RAM
- Storage capability: 8.7TB of RAID storage, with 20TB tape "jukebox"
- Installed software: AFNI, FIDAP, FSL, GIFT, IDL, MATLAB, MEDx, SPM
- Workstations running:
- Solaris (UltraSparc 10, SunBlade 100, SunFire V880z)
- Windows & Linux (Dells)
- MacOSX (Macintoshes)
For several image analysis tools, please see the website for the Center for Imaging Science.
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