The origins of modern medical technology may be traced to nineteenth-century europe, when the indus- trial revolution ushered in sweeping changes in every aspect of life. Of all the momentous discoveries and in- ventions of this period, there was one relatively obscure scientific event that laid the foundation for the subse- quent development of Doppler technologies in the twentieth century ± the discovery of a natural phenom- enon that came to be known as the Doppler effect. An- other critical event was the discovery of the piezoelec- tric phenomenon by Pierre Curie and Jacques Curie, which enabled the development of ultrasonic transdu- cers many decades later. This chapter briefly describes the origin of the Doppler theory during the nineteenth century and traces the development of diagnostic Dop- pler ultrasound technology during the second half of the twentieth century to the present.
Christian Andreas Doppler and the Doppler Theory
The Doppler effect is defined as the observed changes in the frequency of transmitted waves when relative motion exists between the source of the wave and an observer. The frequency increases when the source and the observer move closer and decreases when they move apart. The phenomenon bears the name of its discoverer, Christian Andreas Doppler, an Austrian mathematician and physicist (Fig. 1.1), born to Jo- hann Evangialist and Therese Doppler on November 29, 1803 in Salzburg, Austria. The house in which he was born and raised still stands across the square from the family home of Wolfgang Amadeus Mozart in the Markart Platz. For nearly a century Doppler's Christian name has been consistently misquoted in the literature as Johann Christian. Doppler was bap- tized on the day of his birth at the Church of St. An- dra, which was originally in close proximity of the Doppler home. Eden [1] conducted a thorough search for Doppler's birth and baptismal records and found them still preserved in the Church of St. Andra, which had moved to a new location in Salzburg in 1898. These documents conclusively established that Doppler had been christened Christian Andreas. It
appears, however, that Doppler never used his second name.
Doppler's father, a master stone mason, was a man of wealth and fame. Because of frail health Doppler was sent to school instead of joining the family trade.
In 1822 Johann Doppler requested that Simon Stamp- fer, a professor at the local Lyceum, evaluate his son's aptitude. Stampfer was impressed with young Chris- tian's scholastic abilities in mathematics and science,
Doppler Sonography: A Brief History
Dev Maulik
Fig. 1.1. Christian Andreas Doppler. The oil painting was done by an unidentified artist probably at the time of Doppler's marriage in 1836. The original is in the Austrian Academy of Sciences to whom it was donated by Mathilda von Flugl, the great granddaughter of Christian Doppler.
(Reprinted from [1], with permission)
and at his recommendation Doppler was sent to the Polytechnic Institute of Vienna for further education.
Doppler studied mathematics and physics in Vien- na for 3 years and then returned to Salzburg where he concluded his education and eventually graduated in 1829. For 4 years he held the position of assistant in higher mathematics at the Vienna Polytechnic In- stitute. Following this assitantship he experienced dif- ficulty finding an appropriate position, and in 1835 he seriously considered emigrating to the United States. At this point, however, he was offered and ac- cepted the position of Professor of Elementary Mathe- matics and Commercial Accounting at the State Sec- ondary School in Prague. The following year he was also appointed Supplementary Professor of Higher Mathematics at the Technical Institute in Prague. In 1841 Christian Doppler became a full Professor of Mathematics and Practical Geometry at the latter in- stitution. One year later, on May 25, he presented his landmark paper on the Doppler effect at a meeting of the Natural Sciences Section of the Royal Bohemian
Society of Sciences in Prague. Ironically, there were only five people and a transcriber in the audience.
The paper was entitled ªOn the Colored Light of the Double Stars and Certain Other Stars of the Heavensº (Fig. 1.2) and was published in 1843 in the Proceed- ings of the society [2]. Of 51 papers Doppler pub- lished, this one was destined to bring him lasting rec- ognition.
Doppler's work was based on the theory of the aber- ration of light developed by Edmund Bradley, the eigh- teenth-century British Astronomer Royal. Doppler es- tablished the principle of frequency shift and devel- oped the formula for calculating the velocity from the shift. For elucidating the theoretic background of the principle, Doppler used various analogies and exam- ples primarily based on transmission of light and sound. Although his examples of sound transmission were correct, those involving light transmission were erroneous, as he presumed that all stars emitted only pure white light. He postulated that the color of a star was caused by the relative motions of the star and the Fig. 1.2. Title page of Christian Doppler's paper titled ªOn the Coloured Light of the Double Stars and Certain Other Stars of the Heavens.º (Reprinted from [1], with permission)
earth causing apparent spectral shifts of the emitted white light. The spectrum would shift toward blue if the star approached the earth; conversely, the spectrum would shift to red if the star receded away from the earth. When describing these phenomena Doppler did not take into account preexisting research on light transmission and spectrum. Herschel [3] had already discovered infrared radiation, and Ritter [4] had de- scribed ultraviolet radiation; but it appears that Dop- pler was unaware of these important developments.
Verification of Doppler's Theory
As was to be expected, the paper generated critical responses. The most significant challenge came from a young Dutch scientist working at the University of Utrecht in Holland, Christoph Hendrik Diederik Buys Ballot (Fig. 1.3). In 1844 Buys Ballot proposed to re- fute the Doppler theory by designing an experiment involving sound transmission as his doctoral research project. Conveniently for him, a new railroad had just been established between Amsterdam and Utrecht, and the Dutch government gave him permission to use this railway system to verify the Doppler effect on sound transmission (Fig. 1.4). The first experi- ment was designed in February 1845. Two horn players who apparently had perfect pitch were chosen to participate in the experiment. The calibration was accomplished by one musician blowing a note and the other identifying the pitch of the tone. After this calibration was performed, one player was positioned on the train, and the other stood along the track. As the train passed, the stationary musician on the trackside perceived that the note blown by the musi- cian on the train was half a note higher when the train approached him and half a note lower when it moved away. Unfortunately, a raging blizzard forced Buys Ballot to abandon his experiment and to resche- dule it in a more temperate season. The results from the first experiment were published within less than a month in a music journal [5].
Buys Ballot conducted the experiment again in early June of the same year [6]. Three teams were sta- tioned along the track. Each team was composed of a horn player, an observer, and a manager. A fourth team was on a flat car behind the locomotive. Buys Ballot positioned himself on the foot plate next to the engineer. This experiment was more sophisticated, but it also encountered environmental complications as the summer heat seriously interfered with the cor- rect tuning of the musical instruments. The musi- cians originally tried to use one-sixteenth of a single note but failed, and the final experiment was done in eights. The results were remarkable despite all the trials and tribulations. The study that set out to re-
fute the Doppler theory ultimately confirmed it. Buys Ballot proved not only the existence of the Doppler effect in relation to sound transmission but its angle dependency as well. Incredibly, Buys Ballot still re- fused to accept the validity of the theory for the pro- pagation of light and most of the scientific commu- nity of the nineteenth century did not acknowledge the validity of Doppler's theory because of his erro- neous interpretation of astronomical phenomena.
As translated by Eden [1], Doppler's response was impressive in its foresight: ªI still hold the trust ± in- deed, stronger than ever before ± that in the course of time, this theory will serve astronomers as a wel- come help to probe the happenings of the universe, at times when they feel deserted by all other methodsº [7]. This statement was prophetic. Since the begin- ning of the twentieth century, the Doppler principle has been used extensively not only in astronomy but also in the immensely diverse fields of science and technology.
Doppler lived only 10 years after publishing his paper on the frequency shift; however, these few years brought him well-deserved recognition and honor. He Fig. 1.3. C.H.D. Buys Ballot (1817±1890). (From [40], with permission)
was elected to the membership of the Royal Bohe- mian Society of Sciences in 1843 and of the highly prestigious Imperial Academy of Sciences in Vienna in 1847. In 1850 he was appointed by Emperor Franz Josef of the Austro-Hungarian Empire to the coveted position of the Chair of Experimental Physics at the University of Vienna. Sadly, however, he was in poor health at this point because of the chronic respiratory disease which was presumed to be ªconsumptionº or pulmonary tuberculosis and which he apparently had contracted in Prague years earlier. With the hope of recuperation he went to the warmer climate of Venice in the winter of 1852, where he died on March 17, 1853 at the age of only 49 in the arms of his wife Mathilde. He was given a grand funeral at the Parish Church of San Giovanni in Bragora and many aca- demic and civil dignitaries were in attendance. A more comprehensive account of Doppler's life is be- yond the scope of this review. For those who are in- terested, I strongly recommend the excellent mono- graph written by Professor Alec Eden titled The Search For Christian Doppler [1].
Technical Utilization of Doppler's Principle
Initial applications of the Doppler principle were mostly for astronomic studies. Over the years the Doppler effect for light and radio waves has yielded information on a cosmic scale, from orbital velocity of planets and stars to galactic rotation and an ever- expanding universe. The principle still serves as a major tool for cosmologic research. With the begin- ning of the twentieth century, other applications
gradually emerged. The first sonar equipment for de- tecting submarines was developed by Paul Langevin of France, who also pioneered the use of piezoelectric crystals for transmitting and receiving ultrasound waves. This technology was used to detect subma- rines, initially during World War I and more exten- sively during World War II. The ensuing decades wit- nessed widespread application of the principle of the Doppler effect, from road-side radar speed detectors used by the police to the highly sophisticated military defense and weather forecasting Doppler radar sys- tems. Doppler radio signals are used for navigation, surveying, monitoring animal migration, and estimat- ing crop yields. The development of diagnostic Dop- pler ultrasound technology offers yet another example of the extensive use of the Doppler principle.
Development
of Spectral Doppler Ultrasonography
The first medical applications of Doppler sonography were initiated during the late 1950s, and impressive technologic innovations have been continuing ever since. Shigeo Satomura from the Institute of Scientific and Industrial Research of Osaka University in Japan developed the first Doppler ultrasound device for medical diagnostic purposes and reported the record- ing of various cardiac valvular movements [8]. Based on their experience, Satomura suggested the potential use of Doppler ultrasonography for percutaneous measurement of blood flow. In 1960 he and Kaneko were the first to report construction of an ultrasonic flowmeter [9]. A significant amount of the pioneering work occurred at the University of Washington in Fig. 1.4. Model of the locomo- tive (named Hercules) used in the first experiments. (From [40], with permission)
Seattle in the United States. Major driving forces of this group included Robert Rushmer, a physician, and Dean Franklin, an engineer. They initiated the devel- opment of a prototype continuous-wave Doppler de- vice in 1959 and reported blood flow assessment using the ultrasound Doppler frequency shift [10].
The Seattle team refined this instrument into a small portable device, and the earliest clinical trials were undertaken during the mid-1960s by Eugene Strand- ness, who at the time was undergoing training as a vascular surgeon [11].
The first pulsed-wave Doppler equipment was de- veloped by the Seattle research team. Donald Baker, Dennis Watkins, and John Reid began working on this project in 1966 and produced one of the first pulsed Doppler devices [12]. Other pioneers of pulsed Doppler include Wells of the United Kingdom [13]
and Peronneau of France [14]. The Seattle team also pioneered the construction of duplex Doppler instru- mentation based on a mechanical sector scanning head in which a single transducer crystal performed both imaging and Doppler functions on a time-shar- ing basis. The duplex Doppler technique allowed the ultrasound operator to determine for the first time the target of Doppler insonation. This development is of critical importance in obstetric and gynecologic applications, as such range discrimination allows reli- able Doppler interrogation of a deep-lying circulation, such as that of the fetus and of the maternal pelvic organs. It must be recognized that many others also have made immense pioneering contributions in the development and utilization of diagnostic Doppler so- nography, a detailed discussion of which is beyond the scope of this chapter.
Development
of Color Doppler Ultrasonography
Spectral Doppler ultrasound interrogates along the single line of ultrasound beam transmission. The hemodynamic information thus generated is limited to unidimensional flow velocity characterization from the target area. This limitation provided the impetus to develop a method for depiction of flow in a two- dimensional plane in real time. Potential clinical utili- ty of such an approach was obvious, particularly for cardiovascular applications to diagnose complex he- modynamic and structural abnormalities associated with acquired and congenital cardiac disease. How- ever, the unidimensional spectral pulsed Doppler method was inadequate to cope with the processing needs of real-time two-dimensional Doppler ultraso- nography, which involves analysis of an enormous number of signals derived from multiple sampling sites along multiple scan lines.
The initial attempts involved various invasive and noninvasive modifications of the existing echocardio- graphic approach, including the use of a sonocontrast agent to obtain information on blood flow patterns during two-dimensional echocardiographic imaging [15] and the development of multichannel duplex Doppler systems [16]. However, the spectral pulsed Doppler ultrasound used in these techniques could produce velocity information only along a single beam line. The development of real-time two-dimen- sional color Doppler ultrasonography therefore repre- sents a major technologic breakthrough, which be- came possible because of the introduction of two crit- ical pieces of technology for processing the Doppler ultrasound signal. First was the Doppler sonographic application by Angelsen and Kristofferson [17] of the sophisticated filtering technique of ªthe moving tar- get indicatorº used in radar systems. This filter allows removal of the high-amplitude/low-velocity clutter signals generated by the movement of tissue struc- tures and vessel walls. The second was development of the autocorrelation technique by Namekawa et al.
[18]. The autocorrelator is capable of processing mean Doppler phase shift data from the two-dimen- sional scan area in real time, so two-dimensional Doppler flow mapping is possible (see Chap. 5). In 1983 the Japanese group, which included Omoto, Namekawa, Kasai, and others, reported the use of a prototype device incorporating the new technology for visualizing intracardiac flow [19]. Extensive clini- cal evaluation of this new approach was carried on in the United States by Nanda and other investigators [20].
Introduction
of Doppler Ultrasonography to Obstetrics and Gynecology
The first obstetric application of Doppler ultrasonog- raphy consisted in detection of fetal heart movements [21]. Originally developed for fetal heart rate detec- tion, the technique was further developed for nonin- vasive continuous electronic monitoring of the fetal heart rate. Currently, they constitute the most com- mon uses of Doppler ultrasonography in obstetrics.
The systems are based on utilizing relatively simple continuous-wave Doppler ultrasound to determine the fetal heart rate from the fetal cardiac wall or valv- ular motion. The first application of Doppler veloci- metry in obstetrics was reported by FitzGerald and Drumm [22] from Dublin and MacCallum et al. [23]
from Seattle. The former are recognized as the first group to publish a peer-reviewed article in this field.
These publications were followed by an era if impres-
sive research productivity during which various investigators [24±36] extended the use of Doppler sonography for assessing the fetal and the maternal circulation (Table 1.1).
In contrast to the prolific publications on the ob- stetric uses of Doppler sonography, reports on gyne- cologic applications of the technique did not begin to appear until the mid-1980s. Taylor and colleagues were the first to characterize Doppler waves from the ovarian and uterine arterial circulations utilizing pulsed duplex Doppler instrumentation [37]. This work was followed by reports of transvaginal color Doppler studies [38] and transvaginal duplex pulsed Doppler studies [39] of pelvic vessels. Through the late 1980s and early 1990s, Doppler sonographic re- search in gynecology steadily expanded.
Conclusion
Discovery of the Doppler effect and its application to medical diagnostics after more than a century is a fascinating example of how our understanding and exploitation of natural phenomena can be translated into tangible advances in medicine. This is also rele- vant for obstetrics and gynecology as Doppler sonog- raphy has enabled us to explore and understand hu- man fetal hemodynamics, which was virtually inac- cessible before. As we continue to advance our knowledge, it is important to pause and acknowledge the immense contributions of the pioneers who made it all happen.
References
1. Eden A (1992) The Search for Christian Doppler.
Springer, Vienna
2. Doppler C (1843) Uber das farbige Licht der Doppler- sterne und einiger anderer Gestirne des Himmels. Ab- handl Konigl Bohm Ges Ser 2:465±482
3. Herschel JFW (1800) Experiments on the refrangibility of the invisible rays of the sun. Philos Trans R Soc Lond 90:284±292
4. Ritter JW (1801) Ausfindung nicht lichtbarer Sonnen- strahlen ausserhalbdes Farbenspectrums, an der Seite des Violetts. Widerhohlung der Rouppachen Versuche.
Wien, Mathemat-Naturw Klasse Sitzungsbericht 79:
365±380
5. Buys Ballot CHD (1845) Bedrog van het gehoororgaan in het bepalen van de hoogte van een waargenomen toon. Caecilia. Algemeen Muzikaal Tijdschrift van Ne- derlandl Tweede Jaargang No 7:78±81
6. Buys Ballot CHD (1845) Akustische Versuche auf der Niederlandischen Eisenbahn nebst gelegentlichen Be- merkungen zur Theorie des Herrn Prof Doppler. Pogg Ann 66:321±351
7. Doppler C (1846) Bemerkungen zu meiner Theorie des Farbigen Lichtes der Doppelsterne etc, mit vorzuglicher Rucksicht auf die von Herrn Dr Buys Ballot zu Utrecht dagegen erhobenen Bedenken. Pogg Ann 68:1±35 8. Satomura S (1957) Ultrasonic Doppler method for the
inspection of cardiac functions. J Acoust Soc Am 29:1181±1183
9. Satomura S, Kaneko Z (1960) Ultrasonic blood rheo- graph. In: Proceedings of the 3rd International Confer- ence on Medical Elect, London, IEEE, p 254
10. Franklin DL, Schlegel W, Rushmer RF (1961) Blood flow measured by Doppler frequency shift of back scat- tered ultrasound. Science 134:564±565
11. Strandness DE, Schultz RD, Sumner DS, Rushmer RF (1967) Ultrasonic flow detection ± a useful technic in the evaluation of peripheral vascular disease. Am J Surg 113:311±314
12. Baker DW (1970) Pulsed ultrasonic Doppler blood flow sensing. IEEE Trans Sonic Ultrasonics SU-17(3):170±
13. Wells PNT (1969) A range gated ultrasonic Doppler185 system. Med Biol Eng 7:641±652
14. Peronneau PA, Leger F (1969) Doppler ultrasonic pulsed blood flowmeter. In: Proceedings of the 8th Conference on Medical and Biological Engineering, pp 10±11
15. Gramiak R, Shah PM, Kramer DH (1969) Ultrasound cardiography: contrast studies in anatomy and func- tion. Radiology 92:939±948
16. Fish PJ (1975) Multichannel direction resolving Dop- pler angiography (abstract). Presented at the 2nd Euro- pean Congress of Ultrasonics in Medicine, p 72 17. Angelsen BAJ, Kristofferson K (1979) On ultrasonic
MTI mearement of velocity profiled in blood flow.
IEEE Trans Biomed Eng BME-26:665±771
18. Namekawa K, Kasai C, Tsukamoto M, Koyano A (1982) Imaging of blood flow using autocorrelation (abstract).
Ultrasound Med Biol 8:138±141
19. Omoto R, Yokote Y, Takamoto S et al (1983) Clinical significance of newly developed real time intracardiac Table 1.1. Feasibility of Doppler velocimetry of fetal and
uteroplacental circulations
Circulation Year Author
Umbilical artery 1977 FitzGerald and Drumm [22]
Umbilical vein 1979 Gill and Kossoff [24]
Fetal aorta 1980 Eik-Nes et al. [25]
Uteroplacental 1983 Campbell et al. [26]
Fetal inferior vena
cava 1983 Chiba et al. [27]
Fetal cardiac 1984 Maulik et al. [28]
Fetal cerebral 1986 Arbeille et al. [29]
1986 Wladimiroff et al. [30]
Fetal ductus
arteriosus 1987 Huhta et al. [31]
Fetal renal 1989 Vyas et al. [32]
1989 Veille and Kanaan [33]
Fetal ductus venosus 1991 Kiserud et al. [35]
Fetal coronary artery 1996 Gembruch et al. [36]
two dimensional blood flow imaging system (2-D-Dop- pler) (abstract). Jpn Circ J 47:191
20. Omoto R (1989) History of color flow mapping tech- nologies. In: Nanda NC (ed) Textbook of color Doppler echocardiography. Lea & Febiger, Philadelphia, pp 1±5 21. Callaghan DA, Rowland TC, Goldman DE (1964) Ultra-
sonic Doppler observation of the fetal heart. Obstet Gy- necol 23:637±641
22. FitzGerald DE, Drumm JE (1977) Noninvasive measure- ment of the fetal circulation using ultrasound: a new method. BMJ 2:1450±1451
23. McCallum WD, Olson RF, Daigle RE, Baker DW (1977) Real time analysis of Doppler signals obtained from the fetoplacental circulation. Ultrasound Med 3B:1361±
24. Gill RW, Kossoff G (1979) Pulsed Doppler combined1364 with B-mode imaging for blood flow measurement.
ContribGynecol Obstet 6:139±141
25. Eik-Nes SH, Bruback AO, Ulstein MK (1980) Measure- ment of human fetal blood flow. BMJ 28:283±287 26. Campbell S, Diaz-Recasens J, Griffin DR et al (1983)
New Doppler technique for assessing uteroplacental blood flow. Lancet 1:675±677
27. Chiba Y, Utsu M, Kanzaki T, Hasegawa T (1983) Changes in venous flow and intra-tracheal flow in fetal breathing movements. Ultrasound Med Biol 11:43±49 28. Maulik D, Nanda NC, Saini VD (1984) Fetal Doppler
echocardiography: methods and characterization of normal and abnormal hemodynamics. Am J Cardiol 53:572±578
29. Arbeille P, Tranquart F, Body G et al (1986) Evolution de la circulation arterielle ombilicale et cerebrale du foetus au cours de la grossesse. Prog Neonatal 6:30 30. Wladimiroff JW, Tonge HN, Stewart PA (1986) Doppler
ultrasound assessment of cerebral blood flow in the human fetus. Br J Obstet Gynaecol 93:471±475
31. Huhta JC, Moise KJ, Fisher DJ, Sharif DS, Wassersturm N, Martin C (1987) Detection and quantitation of con- striction of the fetal ductus arteriosus by Doppler echocardiography. Circulation 75:406±412
32. Vyas S, Nicolaides KH, Campbell S (1989) Renal artery flow-velocity waveforms in normal and hypoxemic fetuses. Am J Obstet Gynecol 161:168±172
33. Veille JC, Kanaan C (1989) Duplex Doppler ultrasono- graphic evaluation of the fetal renal artery in normal and abnormal fetuses. Am J Obstet Gynecol 161:1502±
34. Maulik D, Nanda NC, Hsiung MC, Youngblood J (1986)1507 Doppler color flow mapping of the fetal heart. Angiol- ogy 37:628±632
35. Kiserud T, Eik-Nes SH, Blaas HG, Hellevik LR (1991) Ultrasonographic velocimetry of the fetal ductus veno- sus. Lancet 338:1412±1414
36. Gembruch U, Baschat AA (1996) Demonstration of fe- tal coronary blood flow by color-coded and pulsed wave Doppler sonography: a possible indicator of se- vere compromise and impending demise in intrauterine growth retardation. Ultrasound Obstet Gynecol 7:10±16 37. Taylor KJW, Burns PN, Wells PNT, Conway DI, Hull MGR (1985) Ultrasound Doppler flow studies of the ovarian and uterine arteries. Br J Obstet Gynaecol 92:240±246 38. Kurjak A, Zalud I, Jurkovic D, Alfrevic Z, Miljan M
(1989) Transvaginal color Doppler for the assessment of pelvic circulation. Acta Obstet Gynecol Scand 68:131±135
39. Thaler I, Manor D, Brandes J, Rottem S, Itskowvitz J (1990) Basic principles and clinical applications of the transvaginal Doppler duplex system in reproductive medicine. J In Vitro Fertil Embryol Transfer 7:74±75 40. Jonkman EJ (1980) A historical note: Doppler research
in the nineteenth century. Ultrasound Med Biol 6:1±5
