Ultrasound Speckle Reduction

after Coded Excitation and Pulse Compression

Ultrasound and this Study

Ultrasound has been used in the medical field in humans since the late 1940’s.  One of its common uses is for obtaining images of different regions of a person’s body.  The resulting images, however, are riddled with system dependent imperfections called speckle.

Speckle is multiplicative noise that distorts an image and looks very similar to television static placed on top of an image.  In ultrasound images, defects such as a lesion or a tumor may be small or similar in contrast to the surrounding tissue.  Consequently, the effects of speckle may reduce the visibility of these small or low-contrast targets.

The goal of this study was to reduce speckle in order to improve the contrast while attempting to preserve key features in the image.  The project was motivated by a recently-developed technique called eREC-FC, which uses pulse compression, coded excitation, and frequency compounding to improve the ultrasound imaging process.  The significance here lies in the improvement of diagnostic ultrasound, potentially resulting in earlier detection of cancer or other low-contrast lesions, easier identification of small but threatening lesions, etc.

This study assessed the application of post-processing despeckling filters on ultrasound images, especially when applied to the recently developed method of ultrasonic imaging known as eREC-FC.  All filters were designed and implemented during course of the project.  The despeckling filters assessed were:  median, homogeneous mask area, Lee, geometric, and speckle reducing anisotropic diffusion (SRAD).

The final culmination of this study is shown below.  Both images depict a conventional (CP) ultrasonic image of an object (speckle very prominent) and the effects of the despeckling filter SRAD applied to the eREC-FC ultrasonic image of the same object (speckle reduced).  The first image is of a +6 dB contrast lesion and the second, which really depicts the importance of despeckling, is of a +3 dB contrast lesion.

Despeckling 6 dB

Despeckling 3 dB

Note:  the perceived movement of the +3dB lesion is due to an error in deciding where the data began in the eREC-FC image.  What is of importance is to see the contrast improvement, speckle reduction, and edge preservation that leads to the sudden ability to identify the lesion's location and size as a result of eREC-FC and filtering the image.


Overview of ultrasound and this study.