Will 1.5 T become the new Low field MRI? These new Ultra High field systems continue to amaze me. I saw this 12T system a few years ago being installed and really was amazed at how far we have come. The 7T scanner is actually more impressive because it is closer to being a production model. I can see it on the shelves in the next couple years. There will be a demand. I wouldn’t too be surprised to see it combined with a PET scanner. WOW!! that is where we are headed folks………Biograph 7T
High-field MRI reveals previously undetectable injuries in developing brain
High-field MRI at 12 Tesla (12T) is markedly more sensitive in detecting early white-matter injury — broad dark black area (arrow) — than is lower field MRI at 3 Tesla (3T) (credit: OHSU)
Pediatric neuroscientists at Oregon Health & Science University Doernbecher Children’s Hospital are the first to use high magnetic field strength (12 Tesla), MRI to reveal tiny white matter injuries in the developing brain previously undetectable using standard (3T) MRI.
Early, accurate identification of these lesions in the preterm human infant could prevent delays in therapy and enable physicians to inform families sooner of the potential for complications, including inability to walk and intellectual challenges.
White-matter injury is the most common cause of chronic neurologic disability in children with cerebral palsy, explains principal investigator Stephen Back, M.D., Ph.D., but babies with cerebral palsy often have MRIs that miss injury, which creates significant challenges, including delayed treatment intervention and rehabilitation.
White matter injury occurs during brain development when nerve fibers are actively being wrapped in myelin, the insulation that allows nerve fibers to rapidly transmit signals in the brain. The cells required to make myelin can be easily destroyed when blood flow to the developing brain falls below normal or when maternal infection occurs during pregnancy. The loss of these cells disrupts brain maturation and results in failure to make the myelin required for normal brain function.
In this study, using high-field MRI (12-Tesla), Back and colleagues were able to identify tiny brain lesions in preterm fetal sheep with characteristics previously unseen and unreported using a standard 3-T MRI.
AIRC 12T INSTRUMENT
The Bruker 12T instrument is located in the Biomedical Research Building. The 11.75 Tesla (T) horizontal magnet has a clear bore diameter of 31 cm and the ID of the large gradient set is 20 cm. Higher gradient strengths and faster slew rates are available from a gradient insert that has an 9 cm ID. The RF transmitter unit contains two broadband frequency synthesizers and two digital RF transmitters capable of producing 180-600 MHz and 6‑365 MHz pulses, respectively, with each amplifier capable of ≥1 kW peak power. This instrument is equipped with a Resonance Research, Inc high-bandwidth shim power supply for demanding quantitative imaging and spectroscopy studies.
- Field Strength/1H Frequency: 11.75 Tesla (T)/500 MHz
- Clear bore/Working bore [insert]: 31 cm/20 cm [9 cm]
- Gradient Strength/Slew Rate [20 cm insert]: ≥200 mT/m/ ≥1000 T/(m*s)
- Gradient Strength/Slew Rate [9 cm insert]: ≥750 mT/m/≥7500 T/(m*s)
- Transmit channels: 2
- Receiver channels: 2
- Length/Mass: 2.5m/12 tons (60 tons with iron shield)
RADIO FREQUENCY COILS
The system is equipped with two actively RF-decoupled 1H volume resonators with ID/OD of 7.2/8.9 cm and 15.4/19.7 cm, respectively, a 1H 2 cm diameter surface receiver coil, and a 1H/31P double-tuned mini surface coil.
SA Instruments Inc animal monitoring and gating system (model 1025)
- Ventilator (model CWE)
- Gas anesthesia
In vivo guinea pig MRI acquired at 12 T. In panel (A) is a 98 μm isotropic anatomical image showing the left cochlear of the live guinea pig. In panel (B) is a two-dimension T1-weighted gradient recalled echo image (100 μm in-plane 500 μm through-plane) collected as part of a dynamic contrast enhancement study to investigate cochlea perfusion. In this case a low-molecular weight gadolinium based contrast reagent (CR) was used. In panel (C) is shown signal intensity time course for different tissue regions of the DCE study. Significant CR uptake is observed for the four tissues investigated. (Selzer, Omelchenko, Nuttall, Rooney).
Iron labeled T-cell tracking at 12T. Feridex labelled T-cells were used to induce experiement allergic encephalomyelits in the mouse via adoptive transfer. The panel at the left shows a 12T T2-weighted MRI of the mouse spinal cord acquired 7 days post adoptive transfer. The large hypointense T2-weighted MRI areas indicated by the arrow corresponds to demyelination and iron accumulation as indicated by luxol-fast blue and Prussian blue coregistered histological sections.
Mouse Heart Beat acquired by Dr. James Goodman on AIRC 12T Instrument
Future studies are needed to determine if lower field MRI scanners, that are used for patients, can be adapted to achieve greater sensitivity to detect early injury to the white matter of the premature human infant, the researchers said.
AIRC 7T INSTRUMENT
The Siemens MAGNETOM 7T instrument is located in the Biomedical Research Building. The RF transmitter unit contains two independent digital RF transmitter channels, each capable of producing pulses with fully digital 1 MHz bandwidth,32 bit frequency resolution, ≥16 bit phase resolution, and ≤50 ns time resolution. Eight solid-state RF power amplifiers areincluded, each capable of producing ≥1kW over 270-305 MHz. If combined into one channel, these can produce ≥7 kW. This configuration also supports B1shimming when transmit phases and amplitudes are controlled independently and delivered to the phased array head coil. A second RF amplifier is broadband capable (40-305 MHz) with a single 7 kW output. The AVANTO gradient coil set (2000V/625A) is capable of producing field gradients of ≥45 mT/m, with high slew rates ≥200 T/(m*s).
- Field Strength/1H Frequency: 7 Tesla (T)/298 MHz
- Clear bore/Working bore: 90 cm/60 cm
- Gradient Strength/Slew Rate: ≥45mT/m/ ≥200 T/(m*s)
- Receiver channels: 32
- Length/Mass: 3.7m/30 tons (490 tons with iron shield)
RADIO FREQUENCY COILS
The 7T MRI is equipped with two transmit/receive quadrature 1H (300 MHz) RF coils [one suitable for human head studies, the other for extremity studies], an 8-channel phased-array transmit/receive 1H (300 MHz) head RF coil, and a 31P (121 MHz) transmit/receive quadrature head RF coil.
- LCD video projection system for visual fMRI studies
- Auditory system
- Medrad power injector
A comparsion of T1-weighted MPRAGE image quality at 3T (top row) and 7T (bottom row). Transverse, coronal and sagittal image orientations are shown in columns from left to right. Both images sets were acquired in ~9 min. The volume resolution is 1.1 μL and 0.34 μL at 3T and 7T respectively. (Grinstead and Rooney)
MRI image quality compared at 3T and 7T using nearly identical acquisitions and quadrature transmit volume radiofrequency coils. Signal/noise is improved ~2x at 7T compared to 3T. (Rooney andGrinstead).
Ref.: Art Riddle, et al., Histopathological correlates of magnetic resonance imaging–defined chronic perinatal white matter injury, Annals of Neurology, 2011; [DOI: 10.1002/ana.22501]