Impact of Ultrasound on Medical Imaging: 1967–2021

In 1967, a weekly feature for medical school seniors was the ‘bullpen’ in the Charity Hospital amphitheater. Students were assigned a patient and given 30 minutes to do a history and physical exam and then present their differential diagnosis and recommendations to an attending. Diagnosis was almost exclusively based on the history and physical examination. Laboratory studies were generally confined to basic electrolytes, a CBC, urinalysis, sputum stains, and a chest x-ray.

This prepared me well for internship and residency on the Osler Medical Service at Johns Hopkins Hospital. Interns were on call 24 hours a day for 6 days a week and usually spent 16 to 18 hours a day attending patients at the bedside.

On Osler, there were no computers and handwritten or typed paper records hung on a chart rack. The wards were not air-conditioned, and yellow curtains separated each of the 28 beds. There were no patient monitors, IV pumps, or respirators, and interns performed all of the basic lab work on their patients. Nursing care was excellent; the house staff and nurses worked as a team caring for the patients. Lack of technology was compensated for by close and direct interaction with the patients and their families, and the practice of medicine was extremely satisfying and filled with empathy and compassion.

The patient was the object of all of our attention. In the late 1960s, imaging was limited and played a relatively minor role in diagnosis and management. Defensive medicine was not a concern.

Following my internal medicine residency at Hopkins, I spent the next 3 years in the immunology branch of the National Cancer Institute in Bethesda. The research centered on the new field of bone marrow transplantation and treatment of graft vs. host disease.1 Whole-body radiation prepared candidates for transplantation and my experience in dealing with near-lethal doses of radiation led me to pursue a career in radiation oncology.

After completing a residency in general and therapeutic radiology in 1975, I joined the staff of the Ochsner Clinic in New Orleans, practicing a combination of radiation therapy and general radiography and fluoroscopy. Imaging was film-based, with studies hung on multipanel viewboxes for interpretation and a hot light for image processing. Cases were dictated directly to a transcriptionist in a cubicle next to the reading room and were typed and signed in real time. The daily workload included 40 to 50 barium studies along with numerous oral cholecystograms, intravenous urograms, and chest and bone radiographs. Specialized imaging consisted of polytomography, penumoencephalography, lymphangiography, and angiography. Evaluation of the aorta, runoff vessels, and carotid vessels was performed by direct puncture. Women’s imaging consisted of xeromammograms, hysterosalpingography, and pelvimetry. Image-guided intervention was nonexistent.

That year, ultrasound was in its early clinical development and I acquired a machine and placed it in the radiation therapy department and began scanning patients from the nearby emergency department. At that time there were no other sectional imaging modalities (CT was not yet available for clinical use.).

A large part of the challenge of ultrasound was learning anatomy in a completely new way. As a result, my groundwork in understanding sectional anatomy came from ultrasound. Ultrasound, unlike CT and MR, permitted imaging not only in standardized axial planes but allowed scan planes in virtually any orientation, requiring a very detailed knowledge of anatomy.

In 1976, upon the retirement of Dr. Seymour Ochsner, I became Chair of the department at Ochsner. This provided me with an opportunity to re-equip the department at a time that the entire field of imaging was undergoing immense change. With ultrasound, new findings were being reported regularly2, and the overall quality of ultrasound images often exceeded those of early body CT scans.

The development of Doppler ultrasound in the late 1970s further expanded the applications of ultrasound, although prior to the introduction of color Doppler, this was mainly of interest to vascular surgeons, and diagnosis was based on waveform analysis rather than imaging.

An important technological development at the end of the 1970s was real-time ultrasound, leading to the rapid development of new applications in obstetrical, abdominal, pediatric, and intraoperative imaging3,4.

Developments in computers in the early 1980s led me to an opportunity to participate in the development of exciting new technologies, including a breakthrough involving ultrasound and providing a method to image Doppler information. Working with a small company in Seattle and a large prototype device, we generated the first images of blood flow in the abdomen and peripheral vessels using color Doppler5,6. Color Doppler, by allowing Doppler information to be shown in an image rather than as a waveform, was important in getting radiologists interested in Doppler. Today, color Doppler is an integral part of the ultrasound examination.

A less successful application of ultrasound in the 1980s was in the evaluation of the breast. Early breast scanners produced quality images by scanning the breast, as the patient lay prone in a water tank. Unfortunately, breast ultrasound was promoted aggressively by many manufacturers and by the mid-1980s was discredited as a useful addition to mammography. By the mid-1990s, however, advances in breast ultrasound demonstrated an important role in the evaluation of breast masses, making ultrasound an indispensable part of breast imaging and leading to the BI-RADS breast imaging and reporting system for ultrasound7–9.

Ultrasound also has had a major impact in providing guidance for minimally invasive diagnostic procedures. Fine-needle biopsy of lesions of the liver, kidney, retroperitoneum, as well as peripheral lymph nodes and the thyroid, have become a standard part of the diagnostic workup.

A radiologist of 50 years ago would not recognize the field if he or she were to return today. In fewer than 50 years, the computer has changed the practice of medicine. More precise and early diagnosis are clear benefits of the technology of the 21st century, but are accompanied by the perils of over utilization prompted by defensive medicine with interests of the physician potentially overshadowing those of the patient.

Although the contribution of these advances has benefited countless patients, many of the rewards of the practice of medicine have been diminished. In looking back at my 50 years of practicing medicine, recalling my final grand rounds at Charity Hospital, I appreciate the diagnostic skills acquired through history and physical examination, as well as the relationship I had with my patients during my clinical years. To me, this represents the real definition of being a physician. In many cases, these simple tools were often as effective, and certainly more satisfying, than today’s tendency to view the patient as the result of an imaging test rather than a person.

Christopher R. B. Merritt, MD, is a Past President (1986–1988) of the American Institute of Ultrasound in Medicine (AIUM) where he led the development of the AIUM/NEMA/FDA Output Display Standard, and served as a founder of the Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL).


  1. Merritt CB, Mann DL, Rogentine GN Jr. Cytotoxic antibody for epithelial cells in human graft versus host disease. Nature 1971; 232:638.
  2. Merritt CRB. Ultrasound demonstration of portal vein thrombosis. Radiology 1979; 133:425–427.
  3. Merritt CRB, Coulon R, Connolly E. Intraoperative neurosurgical ultrasound: transdural and tranfontanelle applications. Radiology 1983; 148:513–517.
  4. Merritt CRB, Goldsmith JP, Sharp MJ. Sonographic detection of portal venous gas in infants with necrotizing enterocolitis. AJR 1984; 143:1059–1062.
  5. Merritt CRB. Doppler colour flow imaging. Nature 1987; Aug 20; 328:743–744.
  6. Merritt CRB. Doppler color flow imaging. J Clin Ultrasound 1987; 15:591–597.
  7. Mendelson EB, Berg WA, Merritt CRB. Towards a standardized breast ultrasound lexicon, BI-RADS: ultrasound. Semin Roentgenol 2001; 36:217–225.
  8. Taylor KWJ, Merritt C, Piccoli C, et al. Ultrasound as a complement to mammography and breast examination to characterize breast masses. Ultrasound Med Biol 2002; 28:19–26.
  9. Berg WA, Blume JD, Cormack JB, et al. Combined screening with ultrasound and mammography vs mammography alone in women at elevated risk of breast cancer. JAMA 2008; 299(18):2151–2163.

Pioneering Ultrasound Units

If you think your ultrasound machine is out-dated, imagine if you still had to use these from as long ago as the 1940s. 


Ultrasonic Locator
Dr G. D. Ludwig, a pioneer in medical ultrasound, concentrated on the use of ultrasound to detect gallstones and other foreign bodies embedded in tissues. During his service at the Naval Medical Medical Research Institute in Bethesda, Maryland, Dr Ludwig developed this approach that is similar to the detection of flaws in metal. This is A-mode in its operation and was Dr Ludwig’s first ultrasonic scanning equipment.




Ultrasonic Cardioscope
Designed and built by the University of Colorado Experimental Unit, the Cardioscope was intended for cardiac work.

Ultrasonic Cardioscope



Sperry Reflectoscope Pulser / Receive Unit 10N
This is an example of the first instrument to use an electronic interval counter to make axial length measurements of the eye. Individual gates for the anterior segment, lens, and vitreous compartment provided accurate measurement at 10 and 15 MHz of the axial length of the eye. This concept was the forerunner of all optical axis measurements of the eye, which are required for calculation of the appropriate intraocular lens implant power after cataract extraction. This instrument, which includes A-mode and M-mode, was developed by Dr D. Jackson Coleman and Dr Benson Carlin at the Department of Ophthalmology, Columbia Presbyterian Medical Center.

Sperry Reflectoscope Pulser


Sonoray Model No. 12 Ultrasonic Animal Tester (Branson Instruments, Inc.)
This is an intensity-modulated B-mode unit designed exclusively for animal evaluations. The instrument is housed in a rugged aluminum case with a detachable cover that contains the cables and transducer during transportation. The movable transducer holder on a fixed-curve guide was a forerunner of mechanical B-scan ultrasonic equipment.

Sonoray Animal Tester


Smith-Kline Fetal Doptone
In 1966, pharmaceutical manufacturer Smith Kline and French Laboratories of Philadelphia built and marketed a Doppler instrument called the Doptone, which was used to detect and monitor fetal blood flow and the heart rate. This instrument used the continuous wave Doppler prototype that was developed at the University of Washington. 

Smith Kline Fetal Doptone


Smith-Kline Ekoline 20
Working in collaboration with Branson Instruments of Stamford, Connecticut, Smith-Kline introduced the Ekoline 20, an A-mode and B-mode instrument for echoencephalography, in 1963. When B-mode was converted to M-mode in 1965, the Ekoline 20 became the dominant instrument for echocardiography as well as was the first instrument available for many start-up clinical diagnostic ultrasound laboratories. The A-mode was used in ophthalmology and neurology to determine brain midlines.

Ekoline 20


University of Colorado Experimental System
Developed by Douglas Howry and his team at the University of Colorado Medical Center, this compound immersion scanner included a large water-filled tank. The transducer moved back and forth along a 4-inch path while the carriage on which the transducer was mounted moved in a circle around the tank, producing secondary motion necessary for compound scanning. 

Compound immersion scannerCompound immersion scanner tub



Cromemco Z-2 Computer System (Bioengineering at the University of Washington)
This color-Doppler prototype, introduced in 1977, was the computer used for early color Doppler experiments. Z2 “microcomputers” were used for a variety of data acquisition and analysis applications, including planning combat missions for the United States Air Force and modeling braking profiles for the San Francisco Bay Area Rapid Transit (BART) system during actual operation.

Cromemco Z-2 Computer System


ADR-Model 2130
ADR of Tempe, Arizona, began delivering ultrasound components to major equipment manufacturers in 1973. Linear array real-time scanners, which began to be manufactured in the mid-1970s, provided greater resolution and more applications. Grayscale, with at least 10 shades of gray, allowed closely related soft tissues to be better differentiated. This 2-dimensional (2D) imaging machine was widely used in obstetrics and other internal medicine applications. It was marketed as an electronic linear array, which was faster and more repeatable without the need for a water bath as the transducer was placed right on the skin.

ADR Model 2130


Sonometrics Systems Inc, NY BR-400V
The first commercially available ophthalmic B-scanner, this system provided both linear and sector B-scans of the eye. The patient was examined in a water bath created around the eye by use of a sterile plastic ophthalmic drape with a central opening. Both A-scan and B-scan evaluations were possible with manual alignment of the transducer in the water bath. The instrument was developed at the Department of Ophthalmology, Columbia Presbyterian Medical Center by Dr D. Jackson Coleman, working with Frederic L. Lizzi and Louis Katz at the Riverside Research Institute.

Sonometrics Systems Inc, NY BR-400V


Unirad GZD Model 849
Unirad’s static B-scanner, allowing black-and-white anatomic imaging, was used with a scan arm and had similar controls as those used today, including processing, attenuation compensation, and gain.

Unirad GZD Model 849



American Flight Echocardiograph
This American Flight Echocardiograph (AFE) is a 43-pound off-the-shelf version of an ATL 400 medical ultrasonic imaging system, which was then modified for space shuttle compatibility by engineers at the Johnson Space Center to study the adaptations of the cardiovascular system in weightlessness. Its first journey to space was on the space shuttle Discovery in 1985 and its last on the Endeavour in 1992. The AFE generated a 2D cross-sectional image of the heart and other soft tissues and displayed it in video format at 30 frames per second. Below, Dr Fred Kremkau explains more about it.


To check out even more old ultrasound machines, visit the American Institute of Ultrasound in Medicine’s (AIUM’s) An Exhibit of Historical Ultrasound Equipment.


How old is the ultrasound machine you use now? What older ultrasound equipment have you used? Did it spark your desire to work with ultrasound? Comment below, or, AIUM members, continue the conversation on Connect, the AIUM’s online community.


The AIUM is a multi-disciplinary network of nearly 10,000 professionals who are committed to advancing the safe and effective use of ultrasound in medicine.