In this paper, four typical beamformers are explained according to the development process of ultrasound imaging systems. Comparison and analysis are made from several aspects, such as performance, integration, cost, and so on. Furthermore, characteristics of an analog and three digital beamformers are respectively summarized. At last, the development direction of beamformers is pointed out.
Ultrasonics ; instrumentation ; Ultrasonography ; methods

Objective To investigate the value of diffusion kurtosis imaging (DKI) in differential diagnosis of parotid gland disease and diagnosis of parotid adenolymphoma (PAL).Methods DKI and DWI data of 57 patients with parotid gland disease were etrospectively analyzed.Totally 57 cases were divided into infectious lesions group (n=10),pleomorphic adenoma group (n=19),PAL group (n=14),other benign parotid tumor group (n=4) and malignant parotid tumor group (n=10).Contralateral normal parotid glands in 19 patients with unilateral parotid gland lesions were treated as control group.The quantitative parameters including kurtosis concerning parameters (K Krad,Kax),diffusivity concerning parameters (D Drad,Dax),fractional anisotropy (FA) and conventional apparent diffusion coefficient (ADC) values were retrospectively reviewed.The binary Logistic regression method was used to confirm parameters with significant difference in diagnosing PAL.And Logistic regression equation was constructed to diagnose PAL.ROC analysis was conducted to evaluate the diagnostic value of the confirmed parameters and the Logistic regression equation.Results Significant difference of the parameters including K Krad,Kax,D Drad,Dax,FA and ADC values were found among different groups (all P＜0.05).ROC analysis demonstrated a higher area under the curve (AUC) for FA+Kax [0.88±0.06 (0.79-0.94)] than Kax[0.80±0.07 (0.70-0.88)] and FA [0.63±0.10 (0.52-0.73)],respectively (both P＜0.05).The sensitivity,specificity,accuracy,positive predictive value and negative predictive value was 71.43％,95.78％,91.77％,76.92％ and 94.44％.Conclusion DKI showed high diagnostic capacity in differential diagnosis of parotid gland disease.The combination of FA and Kaxcan improve the diagnostic accuracy in diagnosis of PAL.