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Gasthuisberg University Hospital raises fMRI to new level with Intera 3.0T

Best Practice
Sunaert, Stefan, M.D. Leuven, University of Leuven Belgium

SENSE critical for improving or enabling all 3.0T applications

Since December 2002, clinicians at Gasthuisberg University Hospital (Leuven, Belgium) have benefited from Intera 3.0T imaging in BOLD fMRI, MRA and high-resolution imaging studies. The Intera 3.0T is equipped with the Body coil and the eight-channel SENSE Head coil. fMRI examinations, in particular, have profited not only by the doubled BOLD effect at 3.0T, but also by using SENSE, which reduces the susceptibility artifacts more commonly seen at 3.0T. BOLD applications at Gasthuisberg include localization of the primary auditory cortex in tinnitus patients and pre-operative fMRI in avoidance of eloquent cortex, according to Stefan Sunaert, M.D., Professor of Radiology at the medical center.

The BOLD effect is doubled at 3.0T compared to 1.5T

A lesion in the auditory cortex often causes the brain to reorganize hearing functions to surrounding cortex. Abnormalities in this rearrangement can result in non-pulsatile tinnitus, in which sufferers subjectively experience continuous sound (e.g., ringing). Treatment involves electrode placement in the auditory cortex to stun the neurons responsible for symptoms. Functional MRI is used to characterize how the auditory cortex has reorganized.


In the fMRI experiment, the patient listens to music to stimulate the auditory tract nuclei and the primary and secondary auditory cortex, thereby evoking the BOLD effect. "The BOLD effect is doubled at 3.0T compared to 1.5T," Dr. Sunaert says. "Plus, this increased SNR allows increased resolution - to voxel sizes of two millimeters, or even 1.5 mm, isometrically in space. So, with 3.0T it's possible to visualize even tiny structures along the auditory pathway. We actually found two areas - the colliculus inferior and the medial geniculate body - on our 3.0T fMRI scans that have not been found at 1.5T."


BOLD imaging at 3.0T Increased BOLD contrast: the MR signal changes upon neuronal activation are roughly twice as large at 3.0T than those at 1.5T.
BOLD imaging at 3.0T
Increased BOLD contrast: the MR signal changes upon neuronal activation are roughly twice as large at 3.0T than those at 1.5T.

Increased BOLD contrast: the MR signal changes upon neuronal activation are roughly twice as large at 3.0T than those at 1.5T.



3.0T and SENSE - an ideal combination

In all 3.0T studies, SENSE has been indispensable, he adds. "We had been concerned about the larger susceptibility artifacts at 3.0T, but with SENSE [factor 2 or 3], we reduce distortion to the same level as on the 1.5T system without SENSE - our previous gold standard. SENSE also enables us to reduce RF deposition to permit better use of fast imaging sequences such as TSE, EPI and GRASE. Conversely, the higher signal of 3.0T has permitted the use of SENSE where it would have been impractical at 1.5T due to insufficient SNR."

BOLD imaging helps determine surgery risk

Functional MRI is a powerful tool in a protocol that also includes MRA and anatomical imaging for pre-surgical risk assessment of patients with frontal, parietal or temporal lobe brain tumors. At Gasthuisberg, the BOLD fMRI study helps confirm whether surgery is a safe option in one of every four of these patients. The goal is judging the lesion's distance from eloquent cortical areas, such as the primary motor cortex, the language areas of Broca and Wernicke and the visual cortex. Surgical damage to these regions could induce long-lasting deficits. In February 2003, all pre-operative work was shifted to the Intera 3.0T. "It became very clear that the increased SNR at 3.0T was extremely beneficial in this application," he says.


Half of the BOLD studies at Gasthuisberg are to determine lateralization of the brain's language center before surgery to remove a lesion. While the language center is found in the left hemisphere in 99 percent of the right-handed population, it may be in the left or right hemispheres, or distributed over both, in left-handed individuals. The lesion itself sometimes triggers the brain to reorganize language to the non-lesioned hemisphere. This cross-lateralization is often seen in patients with cortical dysplasia, epilepsy, or hippocampal sclerosis.


"For the last four years, patients at Gasthuisberg have undergone BOLD studies to assess operability of lesions that may be close to Broca's or Wernicke's areas," he says. "BOLD imaging helps determine surgery risk. If patients with a left hemispheric lesion successfully transferred their language to the right hemisphere, then it's completely safe to operate on them."



Gasthuisberg fMRI 3.0T:
Gasthuisberg fMRI 3.0T: "Binaural ..."

Binaural musical stimulation compared to no stimulation significantly (p<0.05 corrected for multiple comparisons) activates the primary and secondary auditory cortices, the colliculus inferior (arrowhead in A) and medial geniculate body (arrowhead in B).



Gasthuisberg fMRI 3.0T
Gasthuisberg fMRI 3.0T "fMRI activity du

fMRI activity during music listening versus rest (p<0.05 corrected for multiple comparisons) overlaid on structural images in transversal, coronal and sagittal planes, and on a 3D surface reconstruction of the patient's brain.The patient suffers from left lateralized tinnitus. Note the asymmetry in activation strength and extent of area A1 (L<R).



Gasthuisberg - fMRI 3.0T
Gasthuisberg - fMRI 3.0T "Activation obt

Activation obtained by a covert verb-to-noun generation task in a right handed patient with a left temporal malignant glioma, depicting the location of the primary (A1) and secondary (A2) auditory cortices, the expressive language area (Broca) and the receptive language area (Wernicke).The language centers are clearly left lateralized.



Gasthuisberg - fMRI 3.0T
Gasthuisberg - fMRI 3.0T "Patient with a

Patient with a Rolandic cavernous hemangioma. A: Motor network during a bilateral finger tapping task compared to rest. Note that the finger representation in the primary sensorimotor cortex is located laterally from the lesion, while the supplementary motor area is located anteriorly from the lesion. B: Activation during right toe's movements compared to rest: the toe's representation in the primary sensorimotor cortex is adjacent to the dorsal margin of the lesion.



Intera 3.0T scan protocols - Gasthuisberg University Hospital

Intera 3.0T scan protocols - Gasthuisber
Intera 3.0T scan protocols - Gasthuisber

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Nov 26, 2004

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