How can I generate image from Delay and Sum algorithm?

I am trying to find the pixel vales by using DAS algorithm, I have calculated the envelope of the signals by using Hilbert transform and then calculated the arrival time of a signal traveling from the actuator to the arbitrary pixel value (x,y) and then to the sensor, they actually form multiple ellipse but I cant figure out the next step to obtain the image value, E(x, y). The general formula of DAS is attached. Someone please help me.