Biomedical subjects

Wang Zhan

Publications and source records attributed to Wang Zhan.

6 recordsLinked to original sources

PubMed2025

Exploring the causal association between television viewing and meniscal injuries: A two-sample Mendelian randomization analysis.

The aim of this study was to assess whether there is a potential causal relationship between sedentary behavior and meniscal injuries based on the Mendelian randomization (MR) method. This study used a two-sample MR design to integrate pooled data from a large-scale genome-wide association studies (GWAS). Single nucleotide polymorphisms (SNPs) that were significantly associated with sedentary behavior (represented by daily TV-viewing time) and independent of each other were selected as instrumental variables, while focusing on data from populations of European ancestry. To ensure the robustness and reliability of the analyses, 3 mainstream MR analysis methods were combined in this study: inverse variance weighted (IVW), weighted median estimation (WME) and MR-Egger regression. Heterogeneity test, horizontal multivariate analysis, and leave-one-out sensitivity test were also conducted to further validate the stability of causal estimation. The results of the IVW method showed that sedentary behavior was significantly associated with the risk of meniscus injury, with an OR (95% CI) of 2.93 (1.89-4.52), and a P-value of < .001, suggesting that sedentary behavior may be an important risk factor for meniscus injury. No significant bias was found in the heterogeneity test and the assessment of multiple validity, and the sensitivity analysis showed that the effect of individual SNPs on the overall estimation was small, and the results had good robustness. This study provides genetic epidemiological evidence of a positive causal effect of sedentary behavior on meniscal injuries based on a causal inference approach with genetic instrumental variables. The results suggest that reducing sedentary time, especially prolonged TV watching behavior, may reduce the risk of meniscus injury to some extent.

Humans↗

PubMed2003

Circular spectrum mapping for intravoxel fiber structures based on high angular resolution apparent diffusion coefficients.

A method is presented for mapping intravoxel fiber structures using spectral decomposition onto a circular distribution of measured apparent diffusion coefficients (ADCs). The zeroth-, second-, and fourth-order harmonic components of the ADC distribution on the circle spanned by the major and median eigenvectors of the diffusion tensor can be used to provide quantitative indices for isotropic, linear, and fiber-crossing diffusion, respectively. A diffusion-weighted MRI technique with 90 encoding orientations was implemented to estimate the circular ADC distribution and calculate the circular spectrum. A digital phantom was used to simulate various diffusion patterns. Comparisons were made between the circular spectrum and regular DTI-based index maps. The results indicated that the zeroth- and second-order circular spectrum maps exhibited a strong consistency with the DTI-based mean diffusivity and linear indices, respectively, and the fourth-order circular spectrum map was able to identify the fiber crossings. MRI experiments were performed on seven healthy human brains using a 3T scanner. The in vivo fourth-order maps showed significantly higher densities in several brain regions, including the corpus callosum, cingulum bundle, superior longitudinal fasciculus, corticospinal tract, and middle cerebellar peduncle, which indicated the existence of fiber crossings in these regions.

Adult↗

PubMed2002

Simultaneous perfusion and BOLD imaging using reverse spiral scanning at 3T: characterization of functional contrast and susceptibility artifacts.

Reverse spiral scanning with arterial spin-labeling was developed at 3T to simultaneously detect perfusion and BOLD signals in the brain by subtracting or adding the control and labeled images, respectively, in the same dataset. BOLD contrast was improved with the longer effective echo time achieved in the reverse spiral scan compared to conventional forward spiral scans. Susceptibility artifacts near air-tissue interfaces in the brain were substantially reduced in the reverse spiral images due to their early data acquisition time and, hence, less signal attenuation. Brain activation experiments with the reverse spiral scan were performed on normal subjects and were compared to forward spiral imaging in the same subjects. The experiments demonstrated that reverse spiral imaging was able to detect perfusion and BOLD signals simultaneously and reliably, even in the brain regions with severe susceptibility-induced local gradients, while forward spiral scans were either not optimal for detecting the two functional signals at the same time or were vulnerable to susceptibility artifacts.

Adult↗

PubMed2002

Single-shot interleaved z-shim EPI with optimized compensation for signal losses due to susceptibility-induced field inhomogeneity at 3 T.

A new single-shot echo-planar imaging (EPI) sequence with interleaved z-shim and optimized compensation for susceptibility-induced signal loss is proposed in this paper. Experiments on human brain demonstrated that the new method is able to regain signal dropout in brain areas with severe susceptibility-induced local gradients, while its image acquisition speed is comparable to that of conventional single-shot EPI techniques. Significant signal-to-noise ratio improvements were demonstrated in the ventral prefrontal and lateral temporal lobes with the new technique compared to a conventional EPI. Brain activation experiments with a bilateral finger-tapping task were performed with intentionally introduced local gradients near the left sensorimotor cortex, by a small gadolinium (Gd)-doped bottle placed on the left side of the head. The results of the functional experiments showed that the interleaved z-shim EPI sequence effectively recovered the signal loss caused by the Gd-doped bottle and reliably detected activation signals in bilateral sensorimotor regions, while the activation signals on the left side diminished considerably in a conventional EPI technique. The new technique, with the capability of reducing susceptibility artifacts and rapid scanning speed, may be particularly useful for event-related functional MRI experiments in the base of the brain, which are of great importance in neuropsychiatric studies.

Adult↗

PubMed2002

Inversion profiles of adiabatic inversion pulses for flowing spins: the effects on labeling efficiency and labeling accuracy in perfusion imaging with pulsed arterial spin-labeling.

The inversion profile of adiabatic inversion pulses is essential to the accuracy of perfusion measurement with pulsed arterial spin-labeling (ASL). In this paper, the inversion profiles for flowing spins were investigated using a numerical solution of the modified Bloch equations including a term for moving spins. Inversion profiles for spins flowing at a constant or varying velocity were examined for hyperbolic secant (HS) and frequency-offset corrected inversion (FOCI) pulses. Distortions of the inversion profiles were found for both pulses with spins flowing within physiological velocity range. The effects of the distorted profiles on labeling efficiency and labeling accuracy in the application of pulsed ASL perfusion imaging were analyzed. These effects should be taken into account in ASL techniques, in order to obtain robust and accurate perfusion measurements.

Blood Flow Velocity↗

PubMed2002

[Effect of the endoexpander pressure of continuous and constant pressure expansion on the drug permeability].

OBJECTIVE: To investigate the effect of the endoexpander pressure of continuous and constant pressure expansion on the drug permeability. METHODS: The expanders were divided into two groups, the normal expansion and the continuous and constant pressure expansion (4.6 kPa). Each expander was filled with 0.2% Metronidazole, then the expanders were immersed wholly in normal saline and sealed totally. At several intervals over 72 hours, the surrounding saline was sampled and the drug concentration of the sample was measured respectively. RESULTS: Both groups were permeable to the Metronidazole and the concentration outside the expander would reach the effective concentration in 48 hours. The drug concentration of the continuous and constant pressure expansion was higher than that of the normal one and there was significant difference between the two groups (P < 0.01). CONCLUSION: The endoexpander pressure in continuous and constant pressure expansion can enhance the drug permeability. In view of this, in the course of continuous and constant pressure expansion, 0.2% Metronidazole can be used to prevent and control the infection.

Humans↗