3.0-T functional brain imaging: a 5-year experience

Abstract

The aim of this paper is to illustrate the technical, methodological and diagnostic features of functional imaging (comprising spectroscopy, diffusion, perfusion and cortical activation techniques) and its principal neuroradiological applications on the basis of the experience gained by the authors in the 5 years since the installation of a high-field magnetic resonance (MR) magnet. These MR techniques are particularly effective at 3.0 Tesla (T) owing to their high signal, resolution and sensitivity, reduced scanning times and overall improved diagnostic ability. In particular, the high-field strength enhances spectroscopic analysis due to a greater signal-to-noise ratio (SNR) and improved spectral, space and time resolution, resulting in the ability to obtain high-resolution spectroscopic studies not only of the more common metabolites, but also--and especially--of those which, due to their smaller concentrations, are difficult to detect using 1.5-T systems. All of these advantages can be obtained with reduced acquisition times. In diffusion studies, the high-field strength results in greater SNR, because 3.0-T magnets enable increased spatial resolution, which enhances accuracy. They also allow exploration in greater detail of more complex phenomena (such as diffusion tensor and tractography), which are not clearly depicted on 1.5-T systems. The most common perfusion study (with intravenous injection of a contrast agent) benefits from the greater SNR and higher magnetic susceptibility by achieving dramatically improved signal changes, and thus greater reliability, using smaller doses of contrast agent. Functional MR imaging (fMRI) is without doubt the modality in which high-field strength has had the greatest impact. Images acquired with the blood-oxygen-level-dependent (BOLD) technique benefit from the greater SNR afforded by 3.0-T magnets and from their stronger magnetic susceptibility effects, providing higher signal and spatial resolution. This enhances reliability of the localisation of brain functions, making it possible to map additional areas, even in the millimetre and submillimetre scale. The data presented and results obtained to date show that 3.0-T morphofunctional imaging can become the standard for high-resolution investigation of brain disease.

Functional BOLD MRI: comparison of different field strengths in a motor task

“…Also, as described in previous studies a statistically highly significant gain in functional sensitivity (number of activated voxels) and BOLD CNR (t score) was found with 3.0-T imaging [6,8,26]. This finding is likely to be an effect of the higher field strength as with increasing B 0 the field gradient around capillaries becomes larger and extends into parenchyma, thus including more signal-producing brain tissue [27]. The amplitude of the BOLD signal change increased by a higher factor compared to the increase of SNR.…”

A comparative study of brain activation patterns associated with sexual arousal between males and females using 3.0-T functional magnetic resonance imaging

“…7,16 The use of an MRI system with a higher magnetic field provides higher signal intensity in fMRI because of its stronger magnetic susceptibility effects. 17 All of the fMRI studies [11][12][13] concerning gender differences of sexual arousal have been performed on a 1.5-T MRI system and these studies were not able to investigate the smaller brain centres, such as the septal area, because of the dominant effect of large vessels at such a low magnet field (1.5 T). As shown in Table 2, our study demonstrated the predominant activation areas observed in males rather than females: the hypothalamus, the globus pallidus, the head of the caudate nucleus, the parahippocampal gyrus, the amygdala and the septal area.…”

The Role of Functional MRI in Intracranial Glioma Resection

“…The wide clinical application of higher magnetic fields may increase fMRI's quality. It has been demonstrated that higher magnetic fields change the relaxation rate R2 and thus provide better BOLD signal and more accurate fMRI studies [Hoenig et al, 2005;Krasnow et al, 2003;Tieleman et al, 2007] Higher strength magnets allow fMRI studies to be performed in shorter times, and provide the opportunity for almost real time imaging of cortical activation during stimulation [Scarabino et al, 2007]. The development of advanced software packages, allowing further decrease of susceptibility artifacts, may well improve the quality and the accuracy of fMRI [Li et al, 2010].…”