The ultrasound boom.

Although diagnostic ultrasound has been used in many centers for obstetrical and gynecological diagnosis over the past twenty years, and there has been a slow but steady growth in cardiology investigation, until recently there have been few other clinical applications. The current exponential growth in diagnostic ultrasound was heralded by the introduction of a new technology which is known as "grey-scale ultrasound." This technology was pioneered by George Kossoff in Sydney, Australia, but was not commercially available in this country until 1974. The major advantages of this new technology are improved resolution, approximating 2-3 mm and the display of normal soft-tissue consistency. Thus, for the first time, it becomes possible to display diffuse parenchymal disease by a totally noninvasive method. In obstetrical examinations, it is now possible to identify all the major fetal organs, including heart, liver, kidneys, bladder and external genitalia. There are, however, two major limitations for the ultrasound technique: inability to penetrate aircontaining structures and inability to visualize through bone. Nevertheless, many applications exist in the eye, the thyroid, superficial arteries, the heart, liver, kidneys, spleen, great vessels, pancreas and the contents of the male and female pelves. Like the recently introduced computerized X-ray tomography scanners, ultrasound scanning results in the visualization of a space-occupying mass rather than inferring its presence from the distortion of the anatomy of the surrounding opacified structures. In comparison with most imaging equipment, ultrasound scanning is relatively inexpensive, does not involve ionizing radiation nor any discomfort to the patient and can produce highly accurate results in experienced hands. As with any new technique, there is a dearth of experienced personnel at both the technician and physician levels, but this situation will improve with time. Meanwhile, diagnostic ultrasound presents itself as an exciting modality with a promising future. The growth of the Ultrasound Service at Yale [Fig. 1] reflects the increasing interest in the technique which has resulted in a 400% increase in patient examinations within the last three years. We currently stand at the threshold of yet another era in the development of ultrasound. First, technical developments in transducer design promise to improve the resolution to 1 mm within the next year. Second, the manual scanning techniques currently requiring a highly skilled technician will at least partially be replaced by automated scanners, and these can be moved sufficiently fast to produce visualization of rapidly moving structures such as the heart in real-time. A seminar was held in July 1976, at Yale to describe and discuss the current position of ultrasound in these new applications and its potential for the near future. These papers are published in this issue (pp. 327-373). Current applications of diagnostic ultrasound in obstetrics are reviewed by Dr. John Hobbins and applications in the genitourinary system by Dr. Arthur Rosenfield. The relation of ultra-