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Achieva 7.0T research yields impressive imaging results at Nottingham

Best Practice
Prof. Morris, Peter, Ph.D. Nottingham, University of Nottingham United Kingdom

Not only is Achieva 7.0T significantly more sensitive than 3.0T in functional MRI brain studies, as expected, but the ultra-high field research system also produces unexpectedly sharp structural images across the FOV unhindered by major RF distortions. The images are especially striking in the centrally-located deep gray matter, where the B1 field is pristine, according to the University of Nottingham's Professor Peter Morris, who is leading investigations on the institution's Achieva 7.0T system, the world's first clinical site installation. Researchers also are eager to test the system's capabilities in multi-nuclear imaging by exploring elements such as carbon-13 and phosphorous-31 and learning more about their role in biological processes.

 

 Prof. Peter Morris, <br>University of Nottingham The high SNR available at 7.0T enables excellent spatial resolution. T1-weighted 3D TFE with TR 19 ms, TE 9.5 ms, slices 1 mm, FOV 240 mm, matrix 700.<br><br>Click image to enlarge. The increased iron content of deep gray matter structures, such as the red nucleus, render them clearly visible due to decreased relaxation times
at 7.0T. T2-weighted IR-TSE with TR 3.5 s, TE 7.2 ms, slices 3 mm, FOV 240 mm, matrix 277.
Prof. Peter Morris,
University of Nottingham
The high SNR available at 7.0T enables excellent spatial resolution. T1-weighted 3D TFE with TR 19 ms, TE 9.5 ms, slices 1 mm, FOV 240 mm, matrix 700.

Click image to enlarge.
The increased iron content of deep gray matter structures, such as the red nucleus, render them clearly visible due to decreased relaxation times at 7.0T. T2-weighted IR-TSE with TR 3.5 s, TE 7.2 ms, slices 3 mm, FOV 240 mm, matrix 277.

 

While many MR centers globally are enthusiastically comparing the performance of their new 3.0T systems with that of 1.5T scanners, University of Nottingham is presently pitting a 7.0T system against a 3.0T unit. Nottingham researchers are equally enthusiastic as results of their trials pour in.

 

"Our main reason for wanting Achieva 7.0T was to do functional imaging at very high field, because - as in 3.0T - we expected that contrast-to-noise would scale upward with field strength by more than SNR," says Peter Morris, Professor of Physics and Head of the Sir Peter Mansfield Magnetic Resonance Centre, which has been conducting experiments with Achieva 7.0T for a year. "We're seeing activations that are above 10%, when in the past we were looking at a few percent and just above noise level. We've done a preliminary comparison across 1.5T, 3.0T and 7.0T field strengths and you can see a clear improvement as you scale up in field strength."

Superb image quality of deep brain anatomy

As functional imaging studies continue, Nottingham scientists are applying equal efforts to Achieva 7.0T structural imaging and determination of tissue relaxation times throughout the brain. "We knew we might encounter some B1 effects, but we acquired very beautiful anatomical images despite these effects, particularly in the deep gray matter structures," Prof. Morris says. "They really stand out. It's almost as if you had an anatomical coloring book - the contrast makes the different tissues so much easier to see. We attribute this to the tissues' different iron content, giving them different relaxation time values."

 

The superb image quality, particularly of deep brain anatomy (e.g. red nucleus, substantia nigra) has convinced Nottingham clinicians to create an atlas of detailed brain maps featuring T1, T2 and T2* tissue contrasts.

Achieva 7.0T to examine other nuclei

Building on multi-nuclear studies using their Achieva 3.0T, Nottingham researchers are eager to begin exploring how the extra SNR at 7.0T can improve functional studies that focus on elements other than Proton-1, such as Carbon-13 and Phosphorous-31, to study biological processes. At 3.0T, Prof. Morris continues his studies that use Carbon-13 to analyze the metabolism of carbohydrate and lipid in the muscle and liver of diabetic subjects.

 

In the brain, investigators use labeled substrates of Carbon-13 and Phosphorous- 31 to conduct 3.0T brain bioenergetic studies that measure regional energy consumption per unit of time based on the rate at which the nuclear label is used.

 

"It's absolutely clear that these brain experiments will work much better at 7.0T," he says. "Already, several pharmaceutical companies are extremely interested, because this will provide a mechanism by which they can monitor the efficacy of new drugs under development for diabetes."

"Single-trial" functional studies possible

Due to the abundance of SNR at 7.0T, University of Nottingham will embark on single-trial functional brain studies in early 2006. "Instead of repeating a paradigm many times and looking for an average response, we will be able to see responses to individual trials," Prof. Morris explains. "In one case, we look at schizophrenics and auditory hallucinations. Although they may experience many of these, they might actually all be different - so it's important to look at them on an individual basis.

 

"Alternatively, this capability opens the door to examinations of how we learn," he continues. "There are many cases in which you only have to do something a few times and it's committed to memory - you can do it almost subconsciously, whereas the first time you do it you have to really think hard. If you have to average 30 of these responses, you will never be able to assess the activation that occurs in the first few trials."

Searching for white matter in gray matter

Bringing studies of patients with multiple sclerosis from 3.0T to 7.0T could help researchers to demonstrate the brain's full burden of MS lesions by revealing their presence in gray matter as well as white matter. At 3.0T, using standard pulse sequences, clinicians can detect MS lesions in white matter fairly easily, yet often there is a poor correlation between these lesions and the patient's symptoms, Prof. Morris explains.

 

"At least 50% of MS lesions, post-mortem, occurred in the gray matter and were undetected," he says. If we could find MS lesions in the gray matter of living patients, perhaps we could correlate these lesions with the patients' symptoms. We think that research studies on 7.0T may show these cortical lesions due to the enhanced anatomical resolution."



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Best Practice
Achieva 7.0T
Brain, Neuro, Spectroscopy
 

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