In Memoriam-M.P. Spencer

Merrill P. Spencer, M.D. 1922-2006

　　Merrill P. Spencer died on July 3, 2006 at the age of 84. As well known pioneer in the field of cerebrovascular ultrasound, he is credited with the introduction of a carotid ultrasound methodology into clinical medicine. He also made important contributions in the development of transcranial Doppler ultrasound and went on to describe a number of important observations regarding the role of embolic particles carried into the cerebral circulation, and their role in stroke.

Merrill completed his medical degree at Baylor University in Houston in 1945. Immediately after World War II he served as a Flight Surgeon in the Army Air Corps.

Then he received a fellowship at Western Reserve Hospital in Cleveland, and later became an Associate Professor of Physiology & Pharmacology at Bowman Gray School of Medicine at Wake Forest University in Winston/Salem. There he performed research in the dynamics of blood flow in coronary arteries utilizing the electromagnetic flowmeter, which he had invented and patented.

In 1963 he became Director of the Virginia Mason Research Center in Seattle, Washington where he established the leading Hyperbaric Laboratory in the Northwest United States.

Merrill co-founded in Seattle the Institute of Applied Physiology & Medicine (IAPM), along with Dr. Jack Reid. Together they created first a Doppler ultrasound device to detect nitrogen bubbles to be applied in divers. This work is the basis for the algorithms used in today’s sport diving decompression tables and computers.

Merrill and Jack developed the so called Dopscan, a device to record the Doppler signals first by listening the audiosignal, later supported by spectrum analysis. This was combined with a two dimensional (c-mode) image of the carotids taken from the Doppler signals during the scanning process. This resulted in an improved documentation which allowed physicians to read the exam offline after the recording by well trained technicians. Following this invention the IAPM offered many courses in Doppler sonography for technicians and physicians. Today we still use as the most informative teaching material Spencer and Reid’s scheme illustrating the relation between Doppler frequencies recorded at the site of a carotid stenosis, the degree of narrowing and flow volume (Stroke 1979, 326 ff)

Merrill opened the first vascular laboratory in Seattle at Providence Hospital. In 1987 he co-founded Pacific Vascular Inc., which expanded the laboratory business to 14 locations in Western Washington.

The transcranial Doppler (TCD) was invented by Dr Rune Aaslid in 1981. He used the transtemporal approach. Merrill on the other hand tried to explore the intracranial arteries through the orbital window.

In 1992 Dr. Spencer co-founded, with Scott Seidel, David Dobson, RVT, and Mark Moehring, PhD, a new company called Spencer Technologies, with a mission to improve upon Doppler technology to detect emboli in flowing blood. A special clinical application for the detection of microemboli is the detection of PFO, Merrill was very interested in this clinical field. This led to the Spencer grading system for the severity of the shunt through a PFO.

As a result of his world known research in hemodynamic physiology, neurovascular diagnosis and Doppler sonography in cardiology Merrill received many medical honors. He was a member of the Neurosonology Research Group of the World federation of Neurology from the beginning and did not miss one of the meetings. He organized 10 International Symposia on Cerebral Hemodynamics 1987-1996 as satellite to the yearly International Stroke Conference. From this series of meetings originated the European Society of Neurosonology and cerebral Hemodynamics (ESNCH). Merrill became honorary president of this society and was presented Mai this year at the meeting in Düsseldorf, Germany a lifetime award for his achievements in the field of Neurosonology.

Merrill was not only an exemplary and respected curious scientist but also a man with plenty of kindness and humor. He was taking part in countless international meetings all over the word especially in Europe and became a friend of many other researchers and clinicians. Despite his own extensive experience he was open for new ideas from others and ready to discuss papers in a helpful manner. He always talked about the future and exciting projects. He did continue his activities and research indefatigably up to the end of his life even after knowing that there was no more help against his final disease.

All his achievements would not be possible without Joanne his beloved wife of 34 years. They always traveled together. It is also due to her warm-hearted personality that both were most welcome everywhere in the scientific community.

Our deep feelings go to Joanne and the children.

G.-Michael von Reutern and David W. Newell

Nidda Bad Salzhausen, Germany and Seattle, US, August 2006