Trade.Information

Topic Name: World's most powerful MRI, the 9.4 Tesla, ready to scan human brain

Category: Biomedical

Research persons: Ian Atkinson

Location: University of Illinois at Chicago, United States

Details

The world's most powerful medical magnetic resonance imaging machine, the 9.4 Tesla at the University of Illinois at Chicago, has successfully completed safety trials and may soon offer physicians a real-time view of biological processes in the human brain.

The safety study was published in the November Journal of Magnetic Resonance Imaging in an issue focused on MRI safety.

Researchers and physicians hope that the 9.4T will usher in a new era of brain imaging in which they will be able to observe metabolic processes and customize health care.

Oncologists, for example, may one day be able to tailor radiation therapy based on a brain tumor's real-time response to treatment. Currently, physicians often must wait weeks to see if a tumor is shrinking in response to therapy. With the 9.4T, it will be possible to see if individual cells within the tumor are dying long before the tumor has begun to shrink.

The 9.4T magnet has a field strength more than three times that of state-of-the-art clinical units. UIC's 9.4T is the first such device large enough to scan the head and visualize the human brain.

"Because the more powerful magnet allows us to visualize different types of molecules, we are seeing activity in the brain along a completely different dimension," said Dr. Keith Thulborn, director of UIC's Center for Magnetic Resonance Research.

Current MRI visualizes water molecules to track biochemical processes. By visualizing the sodium ions involved in those processes instead, the 9.4T permits researchers to directly follow one of the most important energy-consuming processes in the cellular machinery in the brain.

The strength of magnetic resonance scanners has increased from less than 0.5T up to the first 8T in 1998. As human safety data became available, the FDA limits were revised upwards accordingly -- to the current level of 8T in 2003.

In this safety trial, 25 healthy volunteers -- 12 men and 13 women -- were exposed, in random order, to the 9.4T scanner, in which they were exposed to a static magnetic field and to sodium imaging, and to a mock scanner with no magnetic field. An audio recording simulated the sound of a real scanner.

Vital signs and cognitive ability were measured in all volunteers before and after the sodium imaging at 9.4T and the mock scanning. There were no significant changes in heart rate, blood pressure, respiratory rate or other vital signs when volunteers were exposed to either the magnetic field or the imaging. There were no significant differences in the cognitive testing of volunteers following mock vs. real scanning.

The most frequently reported discomfort was lightheadedness or vertigo when being moved into the magnetic field. A few subjects reported a metallic taste, nausea, or a visual effect of seeing sparks. The sensations went away once they were stationary in the magnetic field.

The researchers concluded that exposure to a 9.4T static magnetic field does not present a safety concern.

With the FDA-required safety trials completed, UIC researchers will begin to put the 9.4T to use.

"This initial evaluation of safety is only the first step towards realizing metabolic imaging of the human brain," Thulborn said. "We are now moving towards patient studies of sodium imaging and towards safety testing for oxygen and phosphorus imaging in humans.

"These early metabolic signatures of cellular health have great potential to advance detection and monitoring of diseases in the earliest stages, when treatment can produce the greatest benefit."

Research specialist Ian Atkinson, data analyst Holly Burd, postdoctoral research associate Laura Renteria, and Neil Pliskin, director of the neurobehavior program and neuropsychology service at UIC, made major contributions to the study.

The study was supported by UIC and the State of Illinois Capital Fund.

Note for Magnetic resonance imaging

Magnetic resonance imaging (MRI) is primarily used in medical imaging to visualise the structure and function of the body. It provides detailed images of the body in any plane. MR has much greater soft tissue contrast than CT making it especially useful in neurological, musculoskeletal, cardiovascular and oncolological diseases. Unlike CT it uses no ionizing radiation. The scanner creates a powerful magnetic field which aligns the magnetization of hydrogen atoms in the body. Radio waves are used to alter the alignment of this magnetization. This causes the hydrogen atoms to emit a weak radio signal which is amplified by the scanner. This signal can be manipulated by additional magnetic fields to build up enough information to recontruct an image of the body.
MRI also has uses outside of the medical field, such as detecting rock permeability to hydrocarbons and as a non-destructive testing method to characterize the quality of products such as produce and timber.
MRI should not be confused with the NMR spectroscopy technique used in chemistry, although both are based on the same principles of nuclear magnetic resonance. In fact MRI is a series of NMR experiments applied to the signal from nuclei (typified by the hydrogen nuclei in water and body fat) used to acquire spatial information in place of chemical information about molecules. The same equipment, provided suitable probes and magnetic gradients are available, can be used for both imaging and spectroscopy.

Note for Magnetic field

In physics, the magnetic field is a field that permeates space and which exerts a magnetic force on moving electric charges and magnetic dipoles. Magnetic fields surround electric currents, magnetic dipoles, and changing electric fields.

When placed in a magnetic field, magnetic dipoles align their axes to be parallel with the field lines, as can be seen when iron filings are in the presence of a magnet. Magnetic fields also have their own energy and momentum, with an energy density proportional to the square of the field intensity. The magnetic field is measured in the units of teslas (SI units) or gauss (cgs units).

Note for Radiation therapy

Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiotherapy may be used for curative or adjuvant cancer treatment. It is used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit but is not curative) Total body irradiation (TBI) is a radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has a few applications in non-malignant conditions, such as the treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium, prevention of keloid scar growth, and prevention of heterotopic ossification. The use of radiotherapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers