Clinical Magnetic Resonance Imaging of Brain Tumors at Ultrahigh Field

Abstract

With the advancement of the magnetic resonance (MR) technology, the whole-body ultrahigh field MR system operated from 7 to 9.4 T becomes feasible for the routine patient imaging in clinical settings. The associated potentials and challenges from the perspectives of technology, physics, and biology as well as clinical application of the ultrahigh field MR systems are different from those systems operated at 3 T, 1.5 T, or lower field strength. In this article, we will present our initial experiences of brain tumor imaging using the 7 and 8 T whole-body MR systems at the Ohio State University Medical Center and provide a brief overview pertinent to the ultrahigh field clinical MR systems. Keywords ultrahigh field whole-body MR; 7 and 8 Tesla clinical MR; brain tumorIn this article, ultrahigh field (UHF) is defined as the magnetic field strength (B 0 ) of 7 T or higher. Imaging systems for humans are currently used from 7 to 9.4 T. We will focus on the clinical aspects of ultrahigh-field whole-body human magnetic resonance imaging (MRI) systems.Since the introduction to clinical utility back in the 1980s, human whole-body MR scanners with various field strength have contributed significantly to patient care and became an indispensable tool for the management of most diseases of the central nerve system (CNS), including the focus of this issue, brain tumor imaging. For the past decades, the technical development for clinical MR scanners also has been making remarkable progress particularly in coil design, gradient, and radiofrequency (RF) performance as well as software development. The field strength, or B 0 , of the MR scanners increased constantly from the initial ultralow (<0.1 T) to low field (0.1-0.5 T) around the 1980s and from mid (0.5-1.5 T) to high field (3 T) during the early 1990s to 2000s. Meanwhile, the clinical experiences and applications for various CNS pathologies expand constantly as the field strength of the whole-body MR systems scanners continues to grow.Until recently, clinical MR scanners operating at field strength (B 0 ) of 1.5 T have been considered as the optimal means to evaluate neurological diseases. Just few years ago, there were many doubts about the worthiness and cost-effectiveness to develop a 3-T human system mostly because of technical challenges and cost perspectives. Fortunately, most of the technical problems have been resolved, and 3-T human scanners now become the stateof-the-art imaging modality for CNS diseases. With the improved signal-to-noise ratio (SNR) from the increased magnetic field strength, 3-T whole-body MR systems provide superior neuroimaging and functional capability as compared with those of the commonly available 1.5-T systems. Because the 3-T clinical systems have established tremendous credibility and clinical acceptance for the last few years, currently, the enthusiasm in building even higher field-strength clinical systems becomes the fastest growing segment of the MR marketplace. After the initial demonstration of feasibility at few academic ...

Imaging of adult astrocytic brain tumours with 7 T MRI: preliminary results

“…With increasing field strength, susceptibility contrast of paramagnetic substances (e.g. deoxyhaemoglobin) is amplified and allows a superior depiction of venous vasculature and microhaemorrhages [1,13].…”

“…With the increased magnetic field, the signal-tonoise ratio (SNR) rises in an almost linear fashion and can be used to improve image quality especially in the field of neuroimaging. Ultrahigh-field MRI allows improved spatial resolution without sacrificing SNR and contrast-tonoise ratio (CNR) compared with low-field MRI [1]. Ultrahigh-field MR whole-body scanners for humans are currently available at 7 to 9.4 T.…”

“…Since its clinical introduction in the 1980s, the magnetic field of magnetic resonance imaging (MRI) systems has increased gradually from low (0.1-0.5 T), through mid (0.5-1.5 T), to high fields (3 T) during the early 1990s and 2000s [1]. With the increased magnetic field, the signal-tonoise ratio (SNR) rises in an almost linear fashion and can be used to improve image quality especially in the field of neuroimaging.…”

“…vessels of less than 100 µm in size [1,5]. The sensitivity for susceptibility contrast increases with the applied magnetic field and allows the direct visualisation of microvasculature and blood products (e.g.…”

New brain atlas—Mapping the human brain in vivo with 7.0 T MRI and comparison with postmortem histology: Will these images change modern medicine?

“…Ugurbil and coworkers at the University of Minnesota (Moeller et al, 2006) and Knopp and coworkers at Ohio State University (Yuh et al, 2006) have attempted 7.0 T or higher, i.e., ultra high field (UHF) MR imaging and have obtained many excellent images that were not previously available by low field MRI. More recent activities of the research prototype 7.0 T at Massachusetts General Hospital, University of New York, and NIH at Washington DC, as well as at our institute NRI (Neuroscience Research Institute, Gachon University of Medicine & Science, Incheon, Republic of Korea) have also brought numerous new and interesting results that we thought would be of interest to the neuroscience community (Wiggins et al, 2006;Duyn et al, 2007;Fischl and Wald, 2007;.…”