Ramp filter is named for its shape in the frequency domain. This filter is designed to reduce the star artifact resulting from backprojection. It is an example of a high-pass filter, which attenuates low spatial frequencies while letting high frequency pass attenuated. The filter is linearly proportional to the frequency and, as such to the mean frequency potential where not only the information of interest resides but also the high noise. It also serves to reduce some of the low and mid frequency noise.