Speckle reduction in ultrasonic imaging for medical applications

The application of SAR speckle reduction filters for the purpose of ultrasonic imaging is introduced. A new adaptive filter is proposed which yields a significant improvement of sharpness in edge areas and better smoothing in homogeneous regions. The new filter incorporates high statistical moments which are weighted by their normalized local entropy determined by a moment window around the central pixel. Furthermore, a recursive version, which is algorithmically more efficient, is suggested. The results are illustrated by applying the filter to noise-corrupted artificial edge areas and ultrasonic agar phantoms. As a practical application the diagnosis of immune rejections in transplanted kidneys is demonstrated