Minimum variance adaptive beamforming combined with coherence factor weighting applied to ultrafast active cavitation imaging

The ultrafast active cavitation imaging(UACI)based on plane wave transmission and delay-and-sum(DAS)beamforming has been developed to monitor cavitation events with a high frame rate.However,DAS beamforming leads to images with limited resolution and contrast.In this paper,minimum variance(M V)adaptive beamforming and coherence factor(CF)weighting are combined to achieve an MVCF-based UACI,which can improve the cavitation imaging quality.The detailed algorithm evaluation has been investigated from both simulation and experimental data The simulation data include10point targets and a cyst,while the experimental data are obtained by detecting the dissipation of cavitation bubbles in water excited by a single element transducer with frequency of1.2MHz.The advantages of the proposed methodology as well as the comparison with conventional B-mode,DAS?M V,DAS-CF and MV on the basis of compressive sensing(CS)(called MVCS)beamformers are discussed.The results show that MVCF beamformer has a significant improvement in terms of both resolutions and signal-to-noise ratio(SN R).The MVCF-based UACI has a SNR at21.82dB higher,lateral and axial resolution at2.69times and1.93times?respectively,which were compared with those of B-mode active cavitation mapping.The MVCF-based UACI can be used to image the residual cavitation bubbles with a higher SNR and better spatial resolution

TFM imaging of aeroengine casing ring forgings with curved surfaces using acoustic field threshold segmentation and vector coherence factor

The aeroengine casing ring forgings have complex cross-section shapes,when the conventional ultrasonic or phased array is applied to detect such curved surfaces,the inspection images always have low resolution and even artifacts due to the distortion of the wave beam.In this article,taking a type of aeroengine casing ring forging as an example,the Total Focusing Method(TFM)algorithms for curved surfaces are investigated.First,the Acoustic Field Threshold Segmentation(AFTS)algorithm is proposed to reduce background noise and data calculation.Furthermore,the Vector Coherence Factor(VCF)is adopted to improve the lateral resolution of the TFM imaging.Finally,a series of 0.8 mm diameter Side-Drilled Holes(SDHs)are machined below convex and concave surfaces of the specimen.The quantitative comparison of the detection images using the conventional TFM,AFTS-TFM,VCF-TFM,and AFTS-VCF-TFM is implemented in terms of data volume,imaging Signal-to-Noise Ratio(SNR),and defect echo width.The results show that compared with conventional TFM,the data volume of AFTS-VCF-TFM algorithm for convex and concave is decreased by 32.39%and 73.40%,respectively.Moreover,the average SNR of the AFTS-VCF-TFM is gained up to 40.0 dB,while the average 6 dB-drop echo width of defects is reduced to 0.74 mm.

Adaptive Virtual Source Imaging Using the Sequence Intensity Factor:Simulation and Experimental Study

Virtual source(VS)imaging has been proposed to improve image resolution in medical ultrasound imaging.However,VS obtains a limited contrast due to the non-adaptive delay-and-sum(DAS)beamforming.To improve the image contrast and provide an enhanced resolution,adaptive weighting algorithms were applied in VS imaging.In this paper,we proposed an adjustable generalized coherence factor(aGCF)for the synthetic aperture sequential beamforming(SASB)ofVS imaging to improve image quality.The value of aGCF is adjusted by a sequence intensity factor(SIF)that is defined as the ratio between the effective low resolution scan lines(LRLs)intensity and total LRLs strength.The aGCF-weighted VS(aGCF-VS)images were compared with standard VS images and GCF-weighted VS(GCF-VS)images.Simulation and experimental results demonstrated that the contrast ratio(CR)and contrastto-noise ratio(CNR)of aGCF-VS are greatly improved,compared with standard VS imaging.And in comparison with GCF-VS,aGCF-VS can obtain better CNR and speckle signal-to-noise ratio(sSNR)whilemaintaining similar CR.Therefore,aGCF is suitable for VS imaging to improve contrast and preserve speckle pattern.

Real-life experience of ranibizumab therapy for neovascular age-related macular degeneration from Turkey

AIM： To report the real-life experience and clinical results of intravitreal ranibizumab injections to neovascular agerelated macular degeneration（nAMD） in a single institution in Turkey.METHODS： A total of 101 eyes of 89 patients with nAMD treated with intravitreal ranibizumab injection, followed up for at least 24 mo between 2009 and June 2014, which were evaluated retrospectively. A pro re nata（PRN） treatment protocol was performed after the patients had received three, monthly loading injections. Best corrected visual acuity（BCVA） and central macular thickness measurements were evaluated at baseline and 3, 6, 12, 18, and 24 mo. Number of injections and visits were also recorded.RESULTS： Of the 89 patients, 34（38.2%） were male and 55（61.8%） were female and the mean age was 74.0±9.5（52-91）y. The mean follow-up period was 24.82±4.4（24-29）mo. Mean number of visits was 8.4±1.12（7-12） in the first year and 6.6±1.33（4-12） in the second year. The mean number of injections was 5.8±1.6（3-10） and 4.2±2.2（0-9） in the first and second year, respectively. The mean BCVA was 59±15.8 letters at baseline by the Early Treatment Diabetic Retinopathy Study（ETDRS） chart. The mean BCVA at 3, 12, and 24 mo was 70.3±15.9, 67.9±14.3 and 67.3±16.9 letters, respectively. Improvement in visual acuity for each of the visits from baseline was found to be statistically significant（P〈0.01）. Visual acuity in 9 eyes at month 3, 7 eyes at month 12, and 13 eyes at month 24 did not change. The mean central macular thickness（CMT） was 437.99±164.78 μm at baseline. The mean CMT was 348.05±138.47 μm, 349.27±139.79 μm, and 344.13±146.30 μm at months 3, 12, and 24, respectively. The decrease in CMT for each of the visits from baseline was found to be statistically significant（P〈0.01）.CONCLUSION： Anatomical and functional achievement are obtained in our study, but the mean number of injections and visits are found to be lower than the findings reported in randomized controlled clinical trials in the literature. However, the mean number of injections and visits in our study are compatible with the findings reported in real-life experience studies in the literature.

High enhancement factor of Au nano triangular prism structure for surface enhanced coherent anti-Stokes Raman scattering

Coherent anti-Stokes Raman scattering spectroscopy（CARS） is a well-known detecting tool in biosensing and nonlinear spectroscopy. It can provide a non-invasive alternative without the need for exogenous labels,while the enhancement factor for surface plasmon resonances（SPR） are extensively used to increase the local field close to the oscillators and which can obtain high enhancement. In this work, we investigate the enhancement factor of our structure for surface-enhanced coherent anti-Stokes Raman scattering. The absorption spectrum of the structure has been studied, a wide range of absorption has been realized. The enhancement can be as high as 10^（16） over standard CARS. Our design is very useful for improving the enhancement factor of surface-enhanced coherent anti-Stokes Raman scattering.