Real-Time Enhancement of Medical Ultrasound Images

Ultrasound provides a useful means of obtaining real-time images of internal body tissues with non-ionizing radiation. The real-time capability of ultrasound imaging allows the operator to select desired images interactively. The images obtained represent the actual tissue structure being imaged quite well; and, since ultrasound is not ionizing radiation, it is safe. There are, however, some problems inherent to ultrasound imaging that require special processing. The large dynamic range of the return signal presents a problem that can be alleviated by using some type of logarithmic amplifier. Another common problem is echo attenuation as signals are returned from deeper portions of the imaging area. This problem is solved by increasing amplification as the depth increases (time/gain compensation). Additionally, an ultrasound image usually has low contrast, therefore details in the darker regions are often not perceptible. The contrast of the image can be stretched using any of a number of contrast-enhancement methods such as histogram modification. Finally, the ultrasonic beam, having a depth-variant width, causes the image to be somewhat blurred. The image may be high-pass filtered in order to sharpen the blurred features. Techniques for deblurring include inversion and local feature enhancement. The latter two problems will be addressed in this paper.