Studying Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis with 7-T magnetic resonance

Abstract

Ultra-high-field (UHF) magnetic resonance (MR) scanners, that is, equipment operating at static magnetic field of 7 tesla (7 T) and above, enable the acquisition of data with greatly improved signal-to-noise ratio with respect to conventional MR systems (e.g., scanners operating at 1.5 T and 3 T). The change in tissue relaxation times at UHF offers the opportunity to improve tissue contrast and depict features that were previously inaccessible. These potential advantages come, however, at a cost: in the majority of UHF-MR clinical protocols, potential drawbacks may include signal inhomogeneity, geometrical distortions, artifacts introduced by patient respiration, cardiac cycle, and motion. This article reviews the 7 T MR literature reporting the recent studies on the most widespread neurodegenerative diseases: Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis.

Keywords: Alzheimer disease; Amyotrophic lateral sclerosis; Magnetic resonance imaging; Neurodegenerative diseases; Parkinson disease.

Fig. 1

Structural and vascular hippocampal and medial temporal lobe imaging at 7T in an older adult. a T2-weighted coronal 7-T MRI scan through the body of the hippocampus, immediately distal to the hippocampal head. Color legend of segmented regions: entorhinal cortex brown, Brodmann area 35 (transentorhinal) teal, Brodmann area 36 dark blue, subiculum mauve, CA1 red, CA2 green, CA3 yellow, dentate gyrus blue. b High-resolution time of flight imaging of hippocampal vascularization allowing to identify supplying vessels from the anterior choroidal artery (solid arrow) and the posterior cerebral artery (dashed arrow). c A structural T1-weighted coronal 7-T MRI in a patient with mild cognitive impairment and markedly enlarged perivascular spaces, particularly in the insular regions (long arrow) but also in the hippocampus (middle arrow). The scan also shows linear perivascular spaces alongside vessels (short arrow). d A microbleed in the anterior temporal lobe (white arrow) in a patient with cerebral amyloid angiopathy imaged with QSM at 7T. e A microbleed with a venous connection, as visualized with a QSM based venography

Fig. 2

Ex vivo and in vivo MR imaging of the SN. The oval-shaped hyperintense formation indicated by arrows corresponds to nigrosome 1 (N1). a Proton density axial image of an ex-vivo sample. b Gradient echo imaging at high resolution allows to define the N1 formation with typical “swallow tail appearance” in healthy subjects in vivo

Fig. 3

3D multi-echo T2*-weighted images of the substantia nigra at the level of the nigrosome 1 (arrow) in a an RBD patient with a normal imaging of the substantia nigra who has not developed symptoms or signs of parkinsonism in the follow-up; b an RBD patient with abnormal findings at imaging (the nigrosome 1 was not visible), who eventually converted to PD

Fig. 4

T2*-weighted images and QSM images of the primary motor cortex in a healthy subject (a–c) and an ALS patient (d–f). a In healthy subjects, two strips are recognisable in the primary motor cortex: a thin superficial hyperintense strip (arrow) and a thicker and slightly hypointense deep band (*). In many ALS patients, the deep strip is abnormally hypointense in T2*-weighted images (arrows in d and e), and the hypointensity corresponds to higher values of magnetic susceptibility (arrow in f)