Fig. 1

A schematic diagram of the 3D MT-GRE sequence. The sequence consists of an MT module and a 3D GRE imaging module. In the MT module, a spoiler gradient (black) is added following the Gaussian RF pulse (green) to spoil residual transverse magnetization. In the GRE module, a strong spoiler gradient (black) is applied to eliminate the residual transverse magnetization after all echoes are collected. α, flip angle for GRE imaging module; TR, repetition time; TE1, the first echo time; ΔTE, echo spacing

Fig. 2

Regions of interest (ROIs) for quantitative analysis of tissue contrast in neuromelanin (NM) sensitive images and susceptibility values in susceptibility maps. (a) ROIs for NM analysis. Red and orange circles were drawn for substantia nigra and reference areas, respectively. (b)~(d) ROIs for susceptibility analysis. CN, caudate nucleus; PUT, putamen; GP, globus pallidus; RN, red nucleus; SN, substantia nigra; DN, dentate nucleus

Fig. 3

The magnitude images of the first echo acquired by 3D GRE sequences with or without MT pulse. (a) MT RF pulse lasted for 5 ms (MT-5ms); (b) MT RF pulse lasted for 8 ms (MT-8ms); (c) MT RF pulse lasted for 10 ms (MT-10ms); (d) MT RF pulse lasted for 12 ms (MT-12ms); (e) MT RF pulse was not applied (MT-Off)

Fig. 4

The contrast-to-noise ratios (CNRs) between substantia nigra (SN) and surrounding reference area in neuromelanin sensitive images acquired with four different durations of MT pulse. The labels with different shape in the plot represent individual subjects

Table 1

Comparison of magnetic susceptibility values in deep gray matter nuclei acquired with and without MT pulses

Fig. 5

Quantitative comparison of the susceptibility values acquired with MT pulses of different durations and without MT pulse. (a), (c), (e), (g) scattered plots of the linear regression analysis of susceptibility values. The solid and dotted lines are the trend line of the linear regression and the line of equality, respectively. (b), (d), (f), (h) Bland-Altman plots. The solid and dotted lines indicate the mean difference and the mean difference ± 1.96 times the standard deviation of the difference, respectively. CN, caudate nucleus; PUT, putamen; GP, globus pallidus; RN, red nucleus; SN, substantia nigra; DN, dentate nucleus