Donald W. Baker was born in Skagway, Alaska in 1932. From 1951, he
served for 4 years in the United States Air Force in the Korean War. He
spent 2 years working at the Air Force Cambridge Research Center
investigating the detection of low-flying aircrafts and airborne bombers
basing on returned radar signals. During his Service he was able to acquire
knowledge on various electronic applications and in particular those
concerning the different types of radar devices. Discharged from the Air
force in 1955, Baker entered the University of Washington, Seattle
and graduated BScE from the Electrical Engineering Department in
1960.

Since 1958 and as a student he has started working under Robert
Rushmer in a Cardiovascular Instrumentation development program. He
was first introduced to Rushmer by his classmate Wayne Quinton, who
subsequently became bio-medical engineer and "instrument creator" at the
University of Washington, and founder of the Quinton Instruments Company.

Rushmer
was a trained Paediatrician and physiologist who was determined to
elucidate and document cardiovascular functions and parameters in
animals. At that time experiments were all conducted on open-chest
anesthetised specimens. These were impractical and time-consuming. Rushmer
felt that new instruments and methodologies are needed to look into such
functions in the intact un-anesthetised subjects. Having set his heart to
pursuing this Rushmer established facilities, secured funding and recruited
staff to embark on an instrumentation development program to design the
necessary 'hardware' and methodologies. Their aim was to look at
cardiovascular dimensions, pressures and flow. Rushmer was able to recruit
Dean Franklin, Dick Ellis and Baker, along with a
number of other students and technicians. Franklin was the pioneering
engineer who was behind the projects at the start. Ellis was
knowlegeable in sonar techniques which he had also acquired from the Navy.

Franklin, Ellis and Baker started with the design of a multichannel
transit-time flowmeter (which measured the velocity of blood flow in a
blood vessel by determining the time interval between two electric pulses
along the vessel). This was a device that was attached to the wall of the
animal's blood vessel. What were available as electronic components at that
time were basic analog components such as analog differentiators and
multipliers. Baker's next project was on an ultrasonic measuring device for
sensing the diameter of the left ventricle in experimental animals. The
group described "A pulsed ultrasonic flowmeter" in the IRE
Transections in Medical Electronics in 1959. These was an
invasive device being implanted and attached to the the blood vessel wall of
an unanaesthetised animal. Rushmer published their early findings in the
book "Cardiovascular Dynamics" in 1961. Because of the
invention of new instruments and the advent of better barium-titanate
transducers, the department at Washington attracted many new and budding
post-doctoral Fellows in their ultrasonic cardiovascular research programs.

Franklin left the University of Washington in the early
1960s to work at the Scripps Institute at La Jolla, California and later on
taking up a NASA grant project on implanted doppler radio control systems in
animals. In 1964 Franklin, Watson and Van Citters
published in "Nature" their telemeter system where the implanted doppler
device transmitted the flow signals to a receiver nearby. Baker went
on to become the chief of the technical team. Continuous wave applications
were further refined and applied to humans and made to work
transcutaneously. At that time instruments were all based on vaccum
tube designs, often cumbersome, operating at high voltages and with heavy
electronic hum. Subsequent developments led to the use of the newly
available FairChild 2484 silicon transistor circuitory which allowed for
much greater portablility in the instruments and lower electronic noise
generated. The shift in focus also had gone from animal experiments to
diagnostic human applications. Eugene
Strandness, a cardiovascular surgeon (became associate Professor in
1966), took on many of the clinical projects to look into the use of
transcutaneous doppler applications. Many of the earlier portable devices
are now on exhibit at the Smithsonian Museum in Washington DC.

By about 1963, Baker and his colleagues had developed spectral
analysis from the continuous wave doppler basing on the time-interval
histogram method. Working with HF Stegall, Baker published "a
sonic transcutaneous flow-meter" in 1964. Apart from
cardiovascular applications, other clinicians such as Wayne Johnson
worked with Rushmer and reported on the detection of fetal cardiac
pulsations with continuous wave doppler in 1964. The technology
was transferred to Smith Kline Instruments® and the first fetal
pulse detector, the Doptone was
marketed in 1965. With the instrument it was generally possible to detect
cardiac pulsations in the audio format in 100% of live fetuses after 12
weeks of gestation. In 1967, Rushmer, baker, Johnson and Strandness
published in the JAMA: "Clinical
applications of a Transcutaneous Ultrasonic Flow Detector", which
described the detection of fetal life, blood flow through the uterine
vasculature, fetal movements and placental location using continuous wave
doppler in an Obstetric situation.

The continuous wave doppler method however did not provide explicit
information about the distance between the ultrasonic transducer and the
moving target. Baker saw an article on the study of the motion of snow and
raindrops in the clouds using a pulsed-doppler
radar which inspired him to start working on pulsed-doppler
instrumentations. The initial device was of a phased-coherent
pulsed-doppler design with a reference frequency transmitting a sample of
the doppler signal into the target tissue and comparing the relative phase
to give a phased-modulated signal at a particular depth of the vessel that
can be range-gated to obtain flow and positional information at that
particular sample volume. Baker published the landmark articles: "A phase
coherent pulse Doppler system for cardiovascular measurement" in
1967 followed by "Pulsed Ultrasonic Blood Flow Sensing" in
1969.

The group recruited John (Jack)
Reid (one of the very earliest pioneers who worked with John J Wild)
from the University of Pennsylvania who brought along with him
technology for grayscale 2D and M-mode imaging. They went on
to implement "flow maping". The first 2D and M-mode cardiac
echographic machine were developed in 1970. By 1972, they
were able to publish 2D doppler images of femoral and carotid arteries. The
probe was moved manually by hand over the area of the underlying blood
vessel. Only where doppler signals are detected does the instrument cause
registrations to appear on the display. Their doppler shift information was
displyed as white dots overlaid on the B-mode image - the display method
used by modern color doppler instruments. This early instrument had the
disadvantage that it required many cardiac cycles to acquire an image and
was therefore difficult to operate.

Reid
and George Tome (an MSc student from Beirut) helped to develop their
first "rotor-mechanical" duplex scanner where 2D imaging and
pulsed-doppler interrogation can be performed together although not
simultaneously. Frank
Barber, another graduate student doing his Ph.D., developed with the
team a new rotor-transducer duplex device which commanded better
resolution of tissue and spectral flow although it was still incapable of
displaying both at the same time. The moving parts of the mechanical (rotor)
scanner cannot be stopped and started instantaneously and so only a stored
image can be available during doppler signal acquisition. Only through the
advent of the phased and linear arrays that finally allowed simultaneous
duplex operation.

Frank
Barber described the refined version of the Duplex scanner in
1974. A good digital scan-convertor was also a prerequisite to
dispense with the oscilloscope displays and strip chart recorders, and to
have a good overlay of the flow image over 2D images. The technology was
acquired through Fritz Thurstone at Duke University whose
group was heavily researching on linear and phased array
focusing electronics and scan convertors. David
Philips was recruited from the Thurstone group. In 1975, velocity
waveform and flow images were encoded in color and superimposed on M-mode
and gray scale 2-D anatomical images. Marco Brandestini from Zurich
who designed new and efficient Multi-gate circuitory made the project
come together. The team also included physician Geoffrey Stevenson
and engineer Mark Eyer. They had demonstrated quite clearly the value
of color flow imaging in the diagnosis of various cardiac
defects. Color doppler systems in the late 1970s and early 80s were
however limited by the processing power of the equipment, the lack of good
duplex arrays (as contrasted to the mechanical rotor systems) and the
agorithm and technique with which doppler frequency estimation was
performed.

Between 1973 and 1974 Baker effected a
technology transfer of the doppler instruments to a newly-founded
(1969) Seattle company ATL (Advanced Technology Laboratories, Bellevue,
WA). Howard Suskin, founder of the United Control Corporation was the
entrepreneur behind the business venture, the technology being introduced to
him and his engineer partner Ralph Astengo by Baker and his
wife Joan, who was a sonographer. "Technology
transfer", rather then simple transfer or licensing of 'patents'
included a range of formal and informal co-operations between the technology
developer and commercial enterprise. In addition, technology transfer
involved the transfer of knowledge and technical know-how as well as
physical devices and equipment. By agreement, the University of
Washington also received from ATL® a sum of money each year for a
number of years, basing on sales revenue.

ATL® started with 3 engineers and the first ATL pulsed
doppler scanner appeared in the fall of 1974. The Mark I was
soon commercially available in 1975. The 400B pulsed-doppler
unit (pictured above) developed slightly later became part of the well-known
ATL Mark V duplex scanner which debuted in 1978. Duplex
doppler was in fact way ahead of its time and most physicians did not
know what to do with it. A lot of ground data would need to be built. Baker
realized that in order to sell the duplex doppler to the cardiovascular
physicians they would need a better M-mode in their instruments. This
was done after bringing in new engineers in applied physics and ATL
soon boasted in their machines some of the best M-mode functions and traces
(incorporating grayscale) that was available at that time. By 1978, the
University of Washington Department of Surgery Carotid Laboratory was filled
with many talented research scientists and technologists. In 1980, the
Bioengineering Ultrasound Group came to an end of their project and
engineers and technologists including Larry Augustine, Marco Bradenstini,
Ron Daigle, Fred Forster, Jim Hossack, Arin Howard, George Keilman, Gordon
Kirkendahl, George Mahler, Craig Nelson, Bob Olson, Jeff Powers, and Vern
Simmons went over to work for ATL. David Phillips joined the Department of
Surgery to further develop duplex scanning and color flow imaging.

Baker travelled extensively around the world in 1980 to hold
seminars and to promote the duplex devices. ATL produced the Mk 300
and 500 in '80 and '81 respectively (followed by the MK 600 in '82 and the
MK 100 in '83). The Mk 500 and 600 had probably the best real time duplex
doppler at that time.

" ....... The program was instrument and hardware orientated,
because in those days, medical research was carried out in little the same
way as wars are fought. Wars are fought according to the weapons you have,
and the rules of the game will be according to the weapons you have. I think
a lot of researches are in the same way. If you have the tools that nobody
else has you can create a new game that nobody else can play........ People
saw this as an opportunity. ...... They saw an opportunity to get ahead of
their colleagues and publish ....... ."  --- Baker speaking on his
early work in doppler instrumentations and his efforts in popularising them
at ATL.

In 1970, Donald Baker was married to Joan
Baker, who was founder & first president of the Society of
Diagnostic Medical Sonographers ( SDMS) in the same year and first chair of the
American Registry of Diagnostic Medical Sonographers (ARDMS).
Donald Baker retired from the University of Washington in 1979
and subsequently was out of the Ultrasound field in 1984. Prior to
that, he was a full-time consultant to Squibb Medical Systems®, the
International division of ATL and had taught in numerus seminars on the
application of doppler ultrasound. Among other accolaides he was given the
Pioneer award from the AIUM in 1987 and the Pioneer
Award from the Society of Vascular Technology in 2000.
Baker holds a number of important patents and has authored over 30 articles
and book chapters on Ultrasonic Instrumentations. A few of his original
continuous wave doppler and the pulsed-doppler devices are now exhibited in
the Smithsonian Museum of American Medical History.

The University of Washington Center for Bioengineering, of
which Robert Rushmer was the founding director in 1967, became a
department in 1997 and was jointly administered by the schools of Medicine
and Engineering. Rushmer became Professor Emeritus of Bioengineering. Since
1989 a Robert F. Rushmer lecture was given annually at the university
in honor of him. Dr. Rushmer passed away in July 2001at the age of 86.
Donald Baker is retired. In 2002 he received the Alumnus Summa Laude
Dignatus award from the University of Washington for "an outstanding
alumnus, distinguished for service and achievement over a period of years
since graduation". Eugene Strandness retired from the Head of
Vascular Surgery in 1995. He passed away in January 2002 at the age of 73.
John Reid is Emeritus and Research Professor at Drexel University,
and Affiliate Professor of Bioengineering at the University of Washington.
Other engineers who took part in the early development of doppler ultrasound
at the University in the 1970s such as Barber, Eyer,
Brandestini and others, also had very promising careers in various
fields of advanced engineering and inventive technology.

Some of the Landmark articles:

D. L. Franklin, D. W. Baker and R. W. Ellis, "A pulsed ultrasonic
flowmeter." IRE Trans Med Electron, 6, 204, 1959
D. L. Franklin, W.
A. Schlegal, and R. F. Rushmer, "Blood flow measured by Doppler
frequency shift of backscattered ultrasound," Science, vol. 132, pp.
564-565, 1961
Franklin DL, Watson NW, Van Citters RL (1964) Blood
velocity telemetered from unanaesthetised animals. Nature 203:528-530.

D. L. Franklin, D. W. Baker, and R. F. Rushmer, "Pulsed
ultrasonic transit time flowmeter," IRE Transactions on Biomed. Electronics,
vol. 9, pp. 44-49, 1962
D. E. Strandness, J. W. Kennedy. et al,
"Transcutaneous directional flow detection: A preliminary report". Am Heart
J. 78: 65-74, 1969.
D. W. Baker and Watkins, " A phase coherent
pulse Doppler system for cardiovascular measurement",in Proc. 20th Ann.
Conf. on Eng. in Med. and Biol., 1967
D. W. Baker, "Pulsed
Ultrasonic Blood Flow Sensing", IEEE Trans Sonics Ultrasonics, vol. 17, pp.
170, 1969
J. M. Reid and M. P. Spencer, "Ultrasonic Doppler
technique for imaging blood vessels," Science, vol. 176, pp. 1235, 1972

Barber FE, Baker DW, Nation AWC, Strandness DE Jr., Reid JM.
Ultrasonic duplex echo-Doppler scanner. IEEE Trans. Bio-Medical Engineering,
March 1974; BME-21, 2:109-113.
Barber FE, Baker DW, Strandness DE Jr,
Ofstad JM, Mahler GD. Duplex Scanner II: for simultaneous imaging of
artery tissues and flow. 1974 Ultrasonics Symposium Proceedings, IEEE Press,
1974; 744-748.
F. L. Thurstone and O. T. v. Ramm, "A new
ultrasound imaging technique employing two- dimensional electronic
beamsteering", in Acoustic Holography, P.S. Green, Editor. 1974, Plenum
Press: New York. pp. 149

Read also "D. Eugene Strandness, Jr, MD, and the Revolution in
Noninvasive Vascular Diagnosis" Part
1, Part
2 and Part
3, by Kirk W. Beach, PhD, MD, Department of Surgery, University of
Washington, Seattle, Washington USA, published in the Journal of Ultrasound
in Medicine, 2005. Copyrighted the American Institute of Ultrasound in
Medicine.

And: A brief
history of the pioneering work in Doppler applications in Japan for
important developments in doppler ultrasound preceeding those in the United
States.

Baker, Rushmer and Strandness' pictures courtesy of the University of
Washington, Seattle. Baker's picture in the middle courtesy of Dr. Eric Blackwell.

Back to History of Ultrasound in
Obstetrics and Gynecology.