The use of ultrasound for diagnosis of patient pathology is one of the most rapidly advancing fields of medical imaging. Prior to 1972, ultrasound images were black and white displays with essentially no gray scale variation depicting the amplitude of echoes from interfaces within the body. In 1972, Kossoff introduced the methodology for gray scale display, and improvements over the last four years have yielded ultrasound images with excellent gray scale characteristics and good rendition of anatomic detail. With these improvements, the ability to resolve fine detail is now limited primarily by the frequency and geometrical characteristics of the ultrasound beam, motion of the patient during the scanning interval, and refraction of the ultrasound beam as it travels through the body. Within the constraints imposed by reduced penetration of ultrasound energy with increasing, frequency, limitations introduced by the ultrasound beam can be reduced with the use of higher frequency ultrasound and with careful selection of transducer diameter and focusing characteristics.