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SUMMARYBrain dysfunction in erectile dysfunction (ED) has been identified by multiple neuroimaging studies. A recent MRI study indicated grey matter alterations in ED patients. This study aims to investigate the microstructural changes of cerebral white matter (WM) in psychological ED patients and their possible correlations with clinical variables. Twenty-seven psychological ED patients and 27 healthy subjects (HS) were included and underwent a magnetic resonance (MR) diffusion tensor imaging (DTI) scan. The tract-based spatial statistics were employed to identify the WM structure alterations in psychological ED patients. The multiple DTI-derived indices′ [fractional anisotropy (FA), axial diffusivity (AD) and mean diffusivity (MD)] correlations with the symptoms and their durations, respectively, were analysed. The IIEF-5, quality of erection questionnaire (QEQ) and the self-esteem and relationship (SEAR) questionnaire were used to assess the symptoms of psychological ED patients. Compared with HS, the psychological ED patients showed increased FA values, reduced MD values and reduced AD values in multiple WM tracts including the corpus callosum (genu, body and splenium), corticospinal tract, internal capsule, corona radiata, external capsule and superior longitudinal fasciculus (p < 0.05, threshold-free cluster enhancement corrected). Both of the IIEF scores and QEQ scores of ED patients showed a significantly negative correlation with the average FA values, and positive correlation with average AD values and MD values in the splenium of the corpus callosum (p < 0.05). The results provided preliminary evidence of WM microstructural changes in patients with psychological ED. The morphological alterations in the splenium of the corpus callosum were related to the symptom severity.

A low angle estimation method in the presence of the multipath for multiple-input multiple-output (MIMO) radar is proposed. The multipath signal model for MIMO radar is constructed with both transmitted multipath and received multipath signals being considered. To reduce the computational burden and retain estimation precision, the beamspace maximum likelihood algorithm is developed for angle estimation. This method overcomes multipath effects for low angle measurement, and only requires one one-dimension search procedure. Simulation results are presented to verify the effectiveness of the proposed method.Introduction: Multiple-input multiple-output (MIMO) radar has been widely investigated in recent years, owing to its potential benefits over the conventional phased-array radar [1,2]. For low angle estimation, multipath propagation plays a large part in degrading the accuracy of angle estimation systems [3,4]. In MIMO radar, received multipath signals and transmitted multipath signals should be considered simultaneously [5]. Since multipath signals are different from coherent signals in MIMO radar, the method using the virtual sub-array spatial smoothing techniques in [6] is unavailable. The maximum likelihood (ML) algorithm is a good candidate for angle estimation, since it can handle correlated sources directly, apply to the case of a single snapshot, and in a sense achieve asymptotically the Cramer Rao bound (CRB). However, it requires very high computational cost. The beam-space algorithm is effective and eases the computational burden [4]. In this Letter, we show how the beam-space maximum likelihood (BSML) algorithm is exploited to obtain angle estimation in MIMO radar with the multipath propagation.