Reverse-time migration using multidirectional wavefield decomposition method

Reverse-time migration has attracted more and more attention owing to the advantages of high imaging accuracy, no dip restriction, and adaptation to complex velocity models. Cross-correlation imaging method is typically used in conventional reverse-time migration that produces images with strong low-frequency noise. Wavefield decomposition imaging can suppress such noise; however, some residual noise persists in the imaging results. We propose a 2D multidirectional wavefield decomposition method based on the traditional wavefield decomposition method. First, source wavefields and receiver wavefields are separated into eight subwavefields, respectively. Second, cross-correlation imaging is applied to selected subwavefields to produce subimages. Finally, the subimages are stacked to generate the final image. Numerical examples suggest that the proposed method can eliminate the low-frequency noise effectively and produce high-quality imaging profiles.

Altered amplitude of low-frequency fluctuations and default mode network connectivity in high myopia:a resting-state fMRI study

AIM:To analyze changes in amplitude of low-frequency fluctuations(ALFFs)and default mode network(DMN)connectivity in the brain,using resting-state functional magnetic resonance imaging(rs-fMRI),in high myopia(HM)patients.METHODS:Eleven patients with HM(HM group)and 15 age-and sex-matched non-HM controls(non-HM group)were recruited.ALFFs were calculated and compared between HM group and non-HM group.Independent component analysis(ICA)was conducted to identify DMN,and comparisons between DMNs of two groups were performed.Region-of-interest(ROI)-based analysis was performed to explore functional connectivity(FC)between DMN regions.RESULTS:Significantly increased ALFFs in left inferior temporal gyrus(ITG),bilateral rectus gyrus(REC),bilateral middle temporal gyrus(MTG),left superior temporal gyrus(STG),and left angular gyrus(ANG)were detected in HM group compared with non-HM group(all P<0.01).HM group showed increased FC in the posterior cingulate gyrus(PCC)/precuneus(preCUN)and decreased FC in the left medial prefrontal cortex(mPFG)within DMN compared with nonHM group(all P<0.01).Compared with non-HM group,HM group showed higher FC between mPFG and bilateral middle frontal gyrus(MFG),ANG,and MTG(all P<0.01).In addition,HM patients showed higher FC between PCC/(preCUN)and the right cerebellum,superior frontal gyrus(SFG),left pre CUN,superior frontal gyrus(SFG),and medial orbital of the superior frontal gyrus(ORB supmed;all P<0.01).CONCLUSION:HM patients show different ALFFs and DMNs compared with non-HM subjects,which may imply the cognitive alterations related to HM.

Selective image enhancement method for low energy target information area

A selective subband enhancement method based on biorthogonal wavelet base is proposed. This novel image enhancement method is just for those images in which the energy of target information area is relatively lower. It includes two parts: one is enhancing the low frequency subband by wavelet decomposition and the other is building a new criterion based on entropy window to image evaluation. Experimental results show that this new scheme may result in a perfect image processing.

Comparison of the effect of low-frequency electroacupuncture on serum leptin and NPY contents of male and female patients with simple obesity

Objective To explore the difference of low-frequency electroacupuncture in regulating serum leptin and neuropeptide Y（NPY） of male and female patients with simple obesity due to spleen deficiency and damp exuberance. Methods Eighty patients with simple obesity, including 37 males and 43 females, were included in this study. In both groups（male group and female group）, Yīnlíngquán（阴陵泉 SP 9）, Sānyīnjiāo（三阴交 SP 6）, Zúsānlǐ（足三里 ST 36）, Fēnglóng（丰隆 ST 40）, Qūchí（曲池 LI 11）, Tiānshū（天枢 ST 25）, Zhōngwǎn（中脘 CV 12）, Shuǐfēn（水分 CV 9）, Qìhǎi（气海 CV 6）, and Guānyuán（关元 CV 4）. were selected, and low-frequency electroacupuncture treatment was applied. Needles were retained for 30 min. The treatment was conducted once a day, and 10 times were considered as one course of treatment. Two courses were needed. The changes of weight, BMI（body mass index）, F%（fat percentage） and serum leptin and NPY contents of patients in the two groups before and after treatment were observed and analyzed comparatively. Results After treatment, in male group, the weight lost（9.24±2.55） kg, BMI reduced by 4.19±2.30, F% reduced by 3.98±2.13, serum leptin level reduced by（0.66±0.23） ng/m L, and serum NPY level reduced by（18.56±2.89） pg/m L; in female group, the weight lost（6.77±2.31） kg, BMI reduced by 2.65±0.93, F% reduced by 4.98±2.30, serum leptin level reduced by（3.49±1.09） ng/m L, and serum NPY level reduced by（11.21±1.97） pg/m L. The results reduced significantly when compared with the level before treatment（P〈0.05, P〈0.01）. The loss of weight, BMI and serum NPY content in male group was more obvious than that in female group（all P〈0.01）, and the loss of F% and serum leptin content in female group was more obvious than that in male group（both P〈0.01）. Conclusion Low-frequency electroacupuncture can significantly regulate the weight, BMI, F% and serum leptin and NPY contents of male and female patients with simple obesity, and there are gender differences. In terms of reducing weight, BMI and serum NPY content, the efficacy of low-frequency electroacupuncture in males is superior to that in females, while in terms of reducing F% and serum leptin content, the efficacy in females is superior to that in males.