Abstract
Parkinson disease is related to neurodegeneration and iron deposition in the substantia nigra pars compacta and nigrosome 1. However, visualization of nigrosome 1 via MR imaging is poor owing to the bilateral asymmetry, regardless of whether it is healthy. We focused on the magic angle and susceptibility effect and evaluated the anatomic slant structure of nigrosome 1 by tilting subjects' heads in the B0 direction. To investigate the effectiveness of the magic angle, we tilted the volunteers' heads to the right and left in the B0 direction or not at all for evaluating correlations between the degree of head tilting and visualization of the right nigrosome 1 and left nigrosome 1 using 3D spoiled gradient-echo sequences with multiecho acquisitions. We evaluated the susceptibility of nigrosome 1 and the local field using quantitative susceptibility mapping to assess static magnetic field inhomogeneity. The heads tilted to the right and left showed significantly higher contrasts of nigrosome 1 and the substantia nigra pars compacta than the nontilted heads. No significant differences were observed in the visualization and susceptibility between the right nigrosome 1 and left nigrosome 1 for each head tilt. The effect of the magic angle was remarkable in the nontilted heads. This finding was supported by quantitative susceptibility mapping because the anatomic slant structure of nigrosome 1 was coherent between the axis of nigrosome 1 and the magic angle. The asymmetric visualization of nigrosome 1 is affected by the magic angle and susceptibility. The anatomic slant structure of nigrosome 1 causes these challenges in visualization.
Highlights
BACKGROUND AND PURPOSEParkinson disease is related to neurodegeneration and iron deposition in the substantia nigra pars compacta and nigrosome 1
This finding was supported by quantitative susceptibility mapping because the anatomic slant structure of nigrosome 1 was coherent between the axis of nigrosome 1 and the magic angle
The asymmetric visualization of nigrosome 1 is affected by the magic angle and susceptibility
Summary
To investigate the effectiveness of the magic angle, we tilted the volunteers’ heads to the right and left in the B0 direction or not at all for evaluating correlations between the degree of head tilting and visualization of the right nigrosome 1 and left nigrosome 1 using 3D spoiled gradient-echo sequences with multiecho acquisitions. The volunteers participated in the study of their own free will, and informed consent was obtained from all the participants. Data Analysis The volunteers’ heads were tilted to the right (20.9° 6 5.8°) or left (18.9° 6 6.6°) in the B0 direction or not at all, to investigate the effectiveness of the magic angle (Fig 1). We evaluated the correlations between the degree of head tilting and visualization of the right nigrosome 1 and left nigrosome 1. To calculate the contrast of nigrosome 1 and the remaining SNc that was positioned around nigrosome 1 to assess its visualization, we used the following equation: Contrast 1⁄4
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