The instantaneous frequency (IF) image is proposed in this work. It is obtained by the differentiation of the instantaneous phase (IP) image, which in turn is calculated by replacing the amplitude information with the IP in the delay-and-sum beamforming. The IP image is a coherence factor that reduces artifacts and sidelobes influence, and it will be shown that the IF image will keep these same positive characteristics. In amplitude images the reflector representation level varies according to the experimental conditions, even using time-gain compensation. In IP images, the reflector is represented by a $- \pi $ to $\pi $ rad variation. An important feature of the IF image is that a reflector is represented by a constant level that is determined by the central frequency of the signal. Farther reflectors are represented with similar magnitudes as closer ones, being less influenced by distance than IP images and resulting in better contrast. Amplitude, IP, and IF images are obtained from point spread function simulations and a medical phantom in different experimental cases: vertical distances, contrast reflectors, axial and lateral separation, and a sparse array. The improper choice of dynamic range can result in low contrast or nondetection of a reflector. For the IF image, the dynamic range is determined by the central frequency of the signal and the zero-mean Gaussian distribution of the IF of noise. The IF image can be used to improve reflector detection, as additional information to assist the interpretation of pixels intensities in conventional amplitude images, or as a new coherence factor.

中文翻译：

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瞬时频率图像

这项工作中提出了瞬时频率（IF）图像。它是通过瞬时相位（IP）图像的微分获得的，而瞬时相位（IP）图像又是通过在延迟和求和波束成形中用IP替换幅度信息来计算的。IP图像是一个减少伪影和旁瓣影响的相干因子，将显示出IF图像将保持这些相同的正特性。在振幅图像中，即使使用时间增益补偿，反射镜的表示水平也会根据实验条件而变化。在IP图像中，反射器用 $-\ pi $ 至 $ \ pi $ rad变化。IF图像的一个重要特征是反射镜由恒定水平表示，该恒定水平由信号的中心频率确定。较远的反射器以与较近的反射器相似的幅度表示，与IP图像相比，受距离的影响较小，并产生更好的对比度。振幅，IP和IF图像是通过点扩散函数模拟和医学模型在不同实验情况下获得的：垂直距离，对比反射器，轴向和横向分离以及稀疏阵列。动态范围的选择不当会导致对比度低或无法检测到反射镜。对于IF图像，动态范围取决于信号的中心频率和噪声IF的零均值高斯分布。IF图像可用于改善反射器检测，