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White matter (WM) functional activity has been reliably detected through functional magnetic resonance imaging (fMRI). Previous studies have primarily examined WM bundles as unified entities, thereby obscuring the functional heterogeneity inherent within these bundles. Here, for the first time, we investigate the function of sub‐bundles of a prototypical visual WM tract—the optic radiation (OR). We use the 7T retinotopy dataset from the Human Connectome Project (HCP) to reconstruct OR and further subdivide the OR into sub‐bundles based on the fiber's termination in the primary visual cortex (V1). The population receptive field (pRF) model is then applied to evaluate the retinotopic properties of these sub‐bundles, and the consistency of the pRF properties of sub‐bundles with those of V1 subfields is evaluated. Furthermore, we utilize the HCP working memory dataset to evaluate the activations of the foveal and peripheral OR sub‐bundles, along with LGN and V1 subfields, during 0‐back and 2‐back tasks. We then evaluate differences in 2bk‐0bk contrast between foveal and peripheral sub‐bundles (or subfields), and further examine potential relationships between 2bk‐0bk contrast and 2‐back task d‐prime. The results show that the pRF properties of OR sub‐bundles exhibit standard retinotopic properties and are typically similar to the properties of V1 subfields. Notably, activations during the 2‐back task consistently surpass those under the 0‐back task across foveal and peripheral OR sub‐bundles, as well as LGN and V1 subfields. The foveal V1 displays significantly higher 2bk‐0bk contrast than peripheral V1. The 2‐back task d‐prime shows strong correlations with 2bk‐0bk contrast for foveal and peripheral OR fibers. These findings demonstrate that the blood oxygen level‐dependent (BOLD) signals of OR sub‐bundles encode high‐fidelity visual information, underscoring the feasibility of assessing WM functional activity at the sub‐bundle level. Additionally, the study highlights the role of OR in the top‐down processes of visual working memory beyond the bottom‐up processes for visual information transmission. Conclusively, this study innovatively proposes a novel paradigm for analyzing WM fiber tracts at the individual sub‐bundle level and expands understanding of OR function. [ABSTRACT FROM AUTHOR]

Background Purpose Method Results Conclusion Breath‐held electrocardiogram‐gated cardiac cine imaging (ECG‐CINE), as the gold standard for assessing cardiac function in magnetic resonance imaging (MRI), is prone to motion artifacts. Conventional golden‐angle (CGA) sampling has emerged as a promising technique for mitigating motion effects in real‐time cardiac cine imaging. However, in ECG‐CINE, the irregular re‐binning of radial k‐space profiles based on CGA can exacerbate k‐space non‐uniformity, resulting in severe streaking artifacts. The recently introduced segmented golden‐angle ratio (SGA) scheme aims to solve this problem; nevertheless, it sacrifices the desired motion insensitivity.The study aims to develop a more efficient k‐space sampling scheme for ECG‐CINE that guarantees both improved motion insensitivity and optimized k‐space coverage.Theoretically, to enhance motion insensitivity, it is essential that the single‐frame radial k‐space profiles acquired within each heartbeat (HB) span as close to a full 360‐degree range as possible. Meanwhile, to ensure uniform data coverage, the sequentially acquired k‐space profiles need to be evenly distributed both within each HB and across multiple HBs. In this study, we propose a Variable Initial value‐based tiny Golden‐Angle radial trajectory (VIGA) to achieve these two goals. Specifically, VIGA is a two‐step approach: First, the tiny golden‐angle ratio is applied to the k‐space profiles within each HB to maintain motion insensitivity and k‐space uniformity as in CGA. Second, a golden ratio of the golden angle used within each HB is applied to the initial k‐space profiles across adjacent HBs to optimize coverage further. We validated the proposed VIGA method through numerical simulations, phantom experiments, and prospective and retrospective in vivo cardiac cine experiments.Numerical simulations revealed that the k‐space uniformity of CGA is highly dependent on the number of spokes per HB, whereas VIGA and SGA maintained nearly optimal k‐space coverage regardless of this parameter. Both phantom and prospective studies demonstrated that VIGA outperforms CGA when the number of spokes per HB is suboptimal, and surpasses SGA in conditions with residual respiratory motion. The standard deviation of gradient scores indicates statistical significance between CGA and VIGA under free‐breathing conditions (p = 0.039) and between SGA and VIGA under all conditions tested (Free‐breathing, 200 spokes/HB: p = 0.028; Breath‐holding, 200 spokes/HB: p = 0.008; Free‐breathing, 200 spokes/HB: p = 0.013; Breath‐holding, 200 spokes/HB: p = 0.011). Retrospective results demonstrated that doctor ratings for SGA were lower than those for VIGA, and the ratings for systole images using VIGA were significantly higher than those using CGA (2.55 ± 0.45 vs. 3.29 ± 0.52; p = 0.04).A novel and efficient k‐space sampling scheme, named VIGA, was proposed to improve k‐space uniformity and motion insensitivity. VIGA facilitates robust image quality in both prospective and retrospective cardiac cine imaging, demonstrating its potential as a clinically viable alternative to CGA and SGA. [ABSTRACT FROM AUTHOR]

Background Purpose Methods Results Conclusions Magnetoencephalography (MEG) and magnetic resonance imaging (MRI) are non‐invasive imaging techniques that offer effective means for disease diagnosis. A more straightforward and optimized method is presented for designing gradient coils which are pivotal parts of the above imaging systems.A novel design method based on stream function combining an optimization algorithm is proposed to obtain highly linear gradient coil.Two‐dimensional Fourier expansion of the current field on the surface where the coil is located and the equipotential line of the expansion term superposition according to the number of turns of the coil are used to represent the coil shape. Particle swarm optimization is utilized to optimize the coil shape while linearity and field uniformity are used as parameters to evaluate the coil performance. Through this method, the main parameters such as input current distribution region, coil turns, desired magnetic field strength, expansion order and iteration times can be combined in a given solution space to optimize coil design.Simulation results show that the maximum linearity spatial deviation of the designed bi‐planar x‐gradient coil compared with that of target field method is reduced from 14% to 0.54%, and that of the bi‐planar z‐gradient coil is reduced from 8.98% to 0.52%. Similarly, that of the cylindrical x‐gradient coil is reduced from 2% to 0.1%, and that of the cylindrical z‐gradient coil is reduced from 0.87% to 0.45%. The similar results are found in the index of inhomogeneity error. Moreover, it has also been verified experimentally that the result of measured magnetic field is consist with simulated result.The proposed method provides a straightforward way that simplifies the design process and improves the linearity of designed gradient coil, which could be beneficial to realize better magnetic field in engineering applications. [ABSTRACT FROM AUTHOR]

Objective . Eye-tracking research has proven valuable in understanding numerous cognitive functions. Recently, Frey et al provided an exciting deep learning method for learning eye movements from functional magnetic resonance imaging (fMRI) data. It employed the multi-step co-registration of fMRI into the group template to obtain eyeball signal, and thus required additional templates and was time consuming. To resolve this issue, in this paper, we propose a framework named MRGazer for predicting eye gaze points from fMRI in individual space. Approach . The MRGazer consists of an eyeball extraction module and a residual network-based eye gaze prediction module. Compared to the previous method, the proposed framework skips the fMRI co-registration step, simplifies the processing protocol, and achieves end-to-end eye gaze regression. Main results . The proposed method achieved superior performance in eye fixation regression (Euclidean error, EE = 2.04°) than the co-registration-based method (EE = 2.89°), and delivered objective results within a shorter time (∼0.02 s volume -1 ) than prior method (∼0.3 s volume -1 ). Significance . The MRGazer is an efficient, simple, and accurate deep learning framework for predicting eye movement from fMRI data, and can be employed during fMRI scans in psychological and cognitive research. The code is available athttps://github.com/ustc-bmec/MRGazer., (© 2024 IOP Publishing Ltd.)

Objective: To explore the modulations of electroacupuncture in subjective tinnitus (ST) by comparing the difference of functional connectivity (FC) in ST patients and healthy volunteers between the insular (INS) and the whole brain region., Methods: A total of 34 ST patients were selected into electroacupuncture group (EG) and 34 age- and sex-matched normal subjects were recruited into control group (CG). The EG received acupuncture at SI19 ( Tinggong ), GB11 ( Touqiaoyin ), TE17 ( Yifeng ), GV20 ( Baihui ), GV15 ( Yamen ), GV14 ( Dazhui ), SJ13 ( Zhongzhu ), among which the points of SI19 and GB11 were connected to the electroacupuncture instrument with the density wave of 2/50 Hz, and 3 treatments per week for 10 sessions in total. The severity of tinnitus was evaluated by Tinnitus Handicap Inventory (THI), the hearing status was recorded using pure tone audiometry, and resting-state functional magnetic resonance imaging (rs-fMRI) was performed on the brain before and after treatment, the CG received no intervention yet only rs-fMRI data were collected., Results: With the electroacupuncture treatment, the total THI score, average air conduction threshold of patients of EG were significantly lower than before ( p  < 0.01), and the total effective rate was 88.24%. Compared with CG, FC of ST patients between INS and left superior temporal gyrus and right hippocampal significantly decreased before treatment, while FC of ST patients between INS and right superior frontal gyrus, left middle frontal gyrus and right anterior cuneus significantly decreased after treatment (voxel p  < 0.001, cluster p  < 0.05, corrected with GRF). FC of ST patients between the INS and right middle frontal gyrus, left superior frontal gyrus and right paracentral lobule showed a significant decrease after treatment (voxel p  < 0.001, cluster p  < 0.05, corrected with GRF). In addition, THI score in EG was negatively correlated with the reduction of FC value in INS-left superior frontal gyrus before treatment ( r  = -0.41, p  = 0.017). Therefore, this study suggests that abnormal FC of INS may be one of the significant central mechanisms of ST patients and can be modulated by electroacupuncture., Discussion: Electroacupuncture treatment can effectively reduce or eliminate tinnitus symptoms in ST patients and improve the hearing by decreasing FC between the INS and the frontal and temporal brain regions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zha, Zhang, Shi, Cheng, Rong, Yu, Liu, Xue, Ye, Yang, Qiu and Yang.)