At that time, diagnostic ultrasound was in its infancy, and image quality was very limited. In fact, the bi-stable static images were so poor that it was difficult convincing my clinical colleagues that the anatomical structures they were looking at were not pictures of craters on the moon. Nevertheless, this new form of imaging drew much attention. In September 1965, a photograph of my lab appeared on the cover of LIFE magazine (the most popular magazine in the USA at that time) showing the ultrasonic image of a fetal head in the uterus of a pregnant wife of a medical student (Fig. 1). Since that time, the technology of ultrasound in medicine has continually improved throughout the years. Today, the imaging of anatomical detail is exquisite and diagnostic ultrasound has become indispensable to medical practice.

2. What were your ultrasound career highlights

In 1968, I returned to my alma mater, Temple University School of Medicine, in Philadelphia where I have remained to the present day, and where I am now Emeritus Professor of Radiology and Medical Physics. My earliest work at Temple involved studying the physiological meaningfulness of the Doppler signal. While performing blood flow studies in dogs, I noticed a dramatic amplification of the Doppler signal several seconds following the intravenous injections of fluids at distant sites. This, along with the work of Ray Gramiak and Robert Waag, ultimately led to the development of contrast agents for diagnostic ultrasonography.

Safety of Ultrasound

In 1972, because of concern for the safety of clinical ultrasound, I conducted an international survey of 68 clinical users, and found that in over 121,000 patient examinations there were no reported adverse effects from the ultrasound.
In 1974, the safety of ophthalmological ultrasonography was investigated using ultrasound exposures to the eyes of rabbits at levels used clinically. Even with exposures lasting four hours, no histological abnormalities could be detected by a skilled ophthalmological pathologist.
In 1977, I was a visiting scientist at the world renown Acoustics Laboratory in Sydney, Australia. Using equipment from the lab, and working with M.J. Edwards at the University of Sydney, I exposed pregnant guinea pigs to ultrasound at levels sufficient to raise the intrauterine temperature several degrees. In carefully controlled studies I was able to show that the fetal abnormalities caused by intrauterine temperatures greater than 2 ⁰C were the same if caused by ultrasound or by any other means of raising the intrauterine temperature to the same degree. Furthermore, it was shown that the most sensitive effect of intrauterine hyperthermia is microcephaly occurring at temperature elevations of 2 ⁰C for over 1 hour. By studying the world’s literature on the generation of fetal abnormalities by hyperthermia, I was able to establish how to avoid exposing the human fetus to potentially dangerous ultrasound intensities in clinical examinations. Working with other scientists, such as Wes Nyborg, Mort Miller, Ed Carstensen, Charlie Church, and truly excellent international colleagues from many countries, such as Australia and the UK, this work ultimately led to the development of the Thermal index (TI) and the Mechanical index (MI), which appear on the screens of present day diagnostic ultrasound scanners to help sonographers maintain the extraordinary safety record of diagnostic ultrasound. In fact, I don’t know of any other medical modality or procedure with a record as safe as ultrasound.

Later Studies

In 1982, I investigated the nature of image artifacts appearing in clinical ultrasonograms. I showed that an artifact with a tapering appearance seen distal to a highly reflecting object was due to ultrasonic reverberations between the transducer and object. Because of its shape, I coined the name “comet tail artifact”, which is a commonly used term in clinical ultrasonography today.