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BACKGROUND Idiopathic rapid eye movement sleep behavior disorder is an early sign of neurodegenerative disease. This study aimed to quantitatively evaluate iron content in idiopathic rapid eye movement sleep behavior disorder patients using quantitative susceptibility mapping and to examine the potential of this technique to identify the prodromal stage of α-synucleinopathies. METHODS Twenty-five idiopathic rapid eye movement sleep behavior disorder patients, 32 Parkinson's disease patients, and 50 healthy controls underwent quantitative susceptibility mapping. The mean magnetic susceptibility values within the bilateral substantia nigra, globus pallidus, red nucleus, head of the caudate nucleus, and putamen were calculated and compared among groups. The relationships between the values and the clinical features of idiopathic rapid eye movement sleep behavior disorder and Parkinson's disease were measured using correlation analysis. RESULTS Idiopathic rapid eye movement sleep behavior disorder patients had elevated iron in the bilateral substantia nigra compared with healthy controls. Parkinson's disease patients had increased iron in the bilateral substantia nigra, globus pallidus, and left red nucleus compared with healthy controls and had elevated iron levels in the bilateral substantia nigra compared with idiopathic rapid eye movement sleep behavior disorder patients. Mean magnetic susceptibility values were positively correlated with disease duration in the left substantia nigra in idiopathic rapid eye movement sleep behavior disorder patients. CONCLUSIONS Quantitative susceptibility mapping can detect increased iron in the substantia nigra in idiopathic rapid eye movement sleep behavior disorder, which becomes more significant as the disorder progresses. This technique has the potential to be an early objective neuroimaging marker for detecting α-synucleinopathies. © 2019 International Parkinson and Movement Disorder Society.

By using the Huygens–Fresnel diffraction integral, we can obtain the analytical expressions of the chirped-Airy–Gaussian-vortex (CAiGV) beams propagating in the chiral medium. The distributions of the intensity, the phase and the gradient force of the CAiGV beams have been investigated analytically. Firstly, the CAiGV beams split into the left circularly polarized vortex (LCPV) beams and the right circularly polarized vortex (RCPV) beams when propagating in the chiral medium. We find that the values of the topological charges determine the focusing location, and the intensity distribution of the CAiGV beams is affected by the distribution factor χ 0 and the chiral parameter γ. With the increase of the chiral parameter γ, the parabolic deflection of the LCPV beams increases and that of the RCPV beams decreases, respectively. Similarly, if the chiral parameter γ increases, the evolution speed of the gradient force's distribution of the LCPV beams will speed up but that of the RCPV beams will slow down. In addition, the propagation trajectory and the diffraction effect of the beams are affected by the first-order and the second-order chirp parameters. Therefore, the propagation trajectory can be modulated effectively by adjusting the chiral parameter γ and the chirp parameters β 1 and β 2. Moreover, the phase distribution shows that the phase singularity moves outward and the trajectory approximates a straight line when the propagation distance increases. Finally, we find that the results of numerical experiments agree well with the analytical results.

We study both analytically and numerically nonparaxial propagation dynamics of the Chirped Airy vortex (CAiV) beams in uniaxial crystal orthogonal to the optical axis. The propagation trajectory, the intensity, the radiation forces, the Poynting vector and the angular momentum (AM) of the CAiV beams are illustrated by numerical examples. The influences of the ratio of the extraordinary refractive index to the ordinary refractive index, the linear chirp factor and the quadratic chirp factor on the nonparaxial evolution of the CAiV beams are examined in detail. Results show that the linear chirp factor provides an intensity concentration, which is totally different with the influence of the quadratic chirp. Besides, the uniaxial crystals with different refractive index ratios can be used to control the intensity of optical lobes. Moreover, the value and the direction of the radiation forces depend on the propagation distance and the chirp factor. The chirp factor acting on the Poynting vector and the AM mainly occurs in the direction of vectors. The nonparaxial propagation characteristics of the CAiV beams provide a convenient method to the intensity modulation and the optical manipulation of micro particles.