As a final step, we can use a high pass filter to sharpen the image and ensure if we are going to reduce the size to use it for the web we are not going to lose any information and definition.

In medical Doppler ultrasound systems, a high-pass filter is usually employed to remove wall clutter components which may also remove the information of the low velocity blood flow.

Based on the design fundamental of digital LDI ladder filter, a digital LDD ladder high-pass filter is designed by using the frequency transformation in this paper.