Chapter 1 Doppler Sonography: A Brief History

Dev Maulik

The origins of modern medical technology may be appears, however, that Doppler never used his second traced to nineteenth-century europe, when the indus- name. trial revolution ushered in sweeping changes in every Doppler's father, a master stone mason, was a man aspect of life. Of all the momentous discoveries and in- of wealth and fame. Because of frail health Doppler ventions of this period, there was one relatively obscure was sent to school instead of joining the family trade. scientific event that laid the foundation for the subse- In 1822 Johann Doppler requested that Simon Stamp- quent development of Doppler technologies in the fer, a professor at the local Lyceum, evaluate his son's twentieth century ± the discovery of a natural phenom- aptitude. Stampfer was impressed with young Chris- enon that came to be known as the Doppler effect. An- tian's scholastic abilities in mathematics and science, 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 Fig. 1.1. Christian Andreas Doppler. The oil painting was them still preserved in the Church of St. Andra, done by an unidentified artist probably at the time of Doppler's marriage in 1836. The original is in the Austrian which had moved to a new location in Salzburg in Academy of Sciences to whom it was donated by Mathilda 1898. These documents conclusively established that von Flugl, the great granddaughter of Christian Doppler. Doppler had been christened Christian Andreas. It (Reprinted from [1], with permission) 2 D. Maulik

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)

and at his recommendation Doppler was sent to the Society of Sciences in Prague. Ironically, there were Polytechnic Institute of Vienna for further education. only five people and a transcriber in the audience. Doppler studied mathematics and physics in Vien- The paper was entitled ªOn the Colored Light of the na for 3 years and then returned to Salzburg where Double Stars and Certain Other Stars of the Heavensº he concluded his education and eventually graduated (Fig. 1.2) and was published in 1843 in the Proceed- in 1829. For 4 years he held the position of assistant ings of the society [2]. Of 51 papers Doppler pub- in higher mathematics at the Vienna Polytechnic In- lished, this one was destined to bring him lasting rec- stitute. Following this assitantship he experienced dif- ognition. ficulty finding an appropriate position, and in 1835 Doppler's work was based on the theory of the aber- he seriously considered emigrating to the United ration of light developed by Edmund Bradley, the eigh- States. At this point, however, he was offered and ac- teenth-century British Astronomer Royal. Doppler es- cepted the position of Professor of Elementary Mathe- tablished the principle of frequency shift and devel- matics and Commercial Accounting at the State Sec- oped the formula for calculating the velocity from the ondary School in Prague. The following year he was shift. For elucidating the theoretic background of the also appointed Supplementary Professor of Higher principle, Doppler used various analogies and exam- Mathematics at the Technical Institute in Prague. In ples primarily based on transmission of light and 1841 Christian Doppler became a full Professor of sound. Although his examples of sound transmission Mathematics and Practical Geometry at the latter in- were correct, those involving light transmission were stitution. One year later, on May 25, he presented his erroneous, as he presumed that all stars emitted only landmark paper on the Doppler effect at a meeting of pure white light. He postulated that the color of a star the Natural Sciences Section of the Royal Bohemian was caused by the relative motions of the star and the a Chapter 1 Doppler Sonography: A Brief History 3 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 Fig. 1.3. C.H.D. Buys Ballot (1817±1890). (From [40], with the other identifying the pitch of the tone. After this permission) 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 fute the Doppler theory ultimately confirmed it. Buys trackside perceived that the note blown by the musi- Ballot proved not only the existence of the Doppler cian on the train was half a note higher when the effect in relation to sound transmission but its angle train approached him and half a note lower when it dependency as well. Incredibly, Buys Ballot still re- moved away. Unfortunately, a raging blizzard forced fused to accept the validity of the theory for the pro- Buys Ballot to abandon his experiment and to resche- pagation of light and most of the scientific commu- dule it in a more temperate season. The results from nity of the nineteenth century did not acknowledge the first experiment were published within less than a the validity of Doppler's theory because of his erro- month in a music journal [5]. neous interpretation of astronomical phenomena. Buys Ballot conducted the experiment again in As translated by Eden [1], Doppler's response was early June of the same year [6]. Three teams were sta- impressive in its foresight: ªI still hold the trust ± in- tioned along the track. Each team was composed of a deed, stronger than ever before ± that in the course horn player, an observer, and a manager. A fourth of time, this theory will serve astronomers as a wel- team was on a flat car behind the locomotive. Buys come help to probe the happenings of the universe, at Ballot positioned himself on the foot plate next to the times when they feel deserted by all other methodsº engineer. This experiment was more sophisticated, [7]. This statement was prophetic. Since the begin- but it also encountered environmental complications ning of the twentieth century, the Doppler principle as the summer heat seriously interfered with the cor- has been used extensively not only in astronomy but rect tuning of the musical instruments. The musi- also in the immensely diverse fields of science and cians originally tried to use one-sixteenth of a single technology. note but failed, and the final experiment was done in Doppler lived only 10 years after publishing his eights. The results were remarkable despite all the paper on the frequency shift; however, these few years trials and tribulations. The study that set out to re- brought him well-deserved recognition and honor. He 4 D. Maulik

Fig. 1.4. Model of the locomo- tive (named Hercules) used in the first experiments. (From [40], with permission)

was elected to the membership of the Royal Bohe- gradually emerged. The first sonar equipment for de- mian Society of Sciences in 1843 and of the highly tecting submarines was developed by Paul Langevin prestigious Imperial Academy of Sciences in Vienna of France, who also pioneered the use of piezoelectric in 1847. In 1850 he was appointed by Emperor Franz crystals for transmitting and receiving ultrasound Josef of the Austro-Hungarian Empire to the coveted waves. This technology was used to detect subma- position of the Chair of Experimental Physics at the rines, initially during World War I and more exten- University of Vienna. Sadly, however, he was in poor sively during World War II. The ensuing decades wit- health at this point because of the chronic respiratory nessed widespread application of the principle of the disease which was presumed to be ªconsumptionº or Doppler effect, from road-side radar speed detectors pulmonary tuberculosis and which he apparently had used by the police to the highly sophisticated military contracted in Prague years earlier. With the hope of defense and weather forecasting Doppler radar sys- recuperation he went to the warmer climate of Venice tems. Doppler radio signals are used for navigation, in the winter of 1852, where he died on March 17, surveying, monitoring animal migration, and estimat- 1853 at the age of only 49 in the arms of his wife ing crop yields. The development of diagnostic Dop- Mathilde. He was given a grand funeral at the Parish pler ultrasound technology offers yet another example Church of San Giovanni in Bragora and many aca- of the extensive use of the Doppler principle. 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- Development terested, I strongly recommend the excellent mono- of Spectral Doppler Ultrasonography graph written by Professor Alec Eden titled The Search For Christian Doppler [1]. The first medical applications of Doppler sonography were initiated during the late 1950s, and impressive technologic innovations have been continuing ever Technical Utilization since. Shigeo Satomura from the Institute of Scientific of Doppler's Principle and Industrial Research of Osaka University in Japan developed the first Doppler ultrasound device for Initial applications of the Doppler principle were medical diagnostic purposes and reported the record- mostly for astronomic studies. Over the years the ing of various cardiac valvular movements [8]. Based Doppler effect for light and radio waves has yielded on their experience, Satomura suggested the potential information on a cosmic scale, from orbital velocity use of Doppler ultrasonography for percutaneous of planets and stars to galactic rotation and an ever- measurement of blood flow. In 1960 he and Kaneko expanding universe. The principle still serves as a were the first to report construction of an ultrasonic major tool for cosmologic research. With the begin- flowmeter [9]. A significant amount of the pioneering ning of the twentieth century, other applications work occurred at the University of Washington in a Chapter 1 Doppler Sonography: A Brief History 5

Seattle in the United States. Major driving forces of The initial attempts involved various invasive and this group included Robert Rushmer, a physician, and noninvasive modifications of the existing echocardio- Dean Franklin, an engineer. They initiated the devel- graphic approach, including the use of a sonocontrast opment of a prototype continuous-wave Doppler de- agent to obtain information on blood flow patterns vice in 1959 and reported blood flow assessment during two-dimensional echocardiographic imaging using the ultrasound Doppler frequency shift [10]. [15] and the development of multichannel duplex The Seattle team refined this instrument into a small Doppler systems [16]. However, the spectral pulsed portable device, and the earliest clinical trials were Doppler ultrasound used in these techniques could undertaken during the mid-1960s by Eugene Strand- produce velocity information only along a single ness, who at the time was undergoing training as a beam line. The development of real-time two-dimen- vascular surgeon [11]. sional color Doppler ultrasonography therefore repre- The first pulsed-wave Doppler equipment was de- sents a major technologic breakthrough, which be- veloped by the Seattle research team. Donald Baker, came possible because of the introduction of two crit- Dennis Watkins, and John Reid began working on ical pieces of technology for processing the Doppler this project in 1966 and produced one of the first ultrasound signal. First was the Doppler sonographic pulsed Doppler devices [12]. Other pioneers of pulsed application by Angelsen and Kristofferson [17] of the Doppler include Wells of the United Kingdom [13] sophisticated filtering technique of ªthe moving tar- and Peronneau of France [14]. The Seattle team also get indicatorº used in radar systems. This filter allows pioneered the construction of duplex Doppler instru- removal of the high-amplitude/low-velocity clutter mentation based on a mechanical sector scanning signals generated by the movement of tissue struc- head in which a single transducer crystal performed tures and vessel walls. The second was development both imaging and Doppler functions on a time-shar- of the autocorrelation technique by Namekawa et al. ing basis. The duplex Doppler technique allowed the [18]. The autocorrelator is capable of processing ultrasound operator to determine for the first time mean Doppler phase shift data from the two-dimen- the target of Doppler insonation. This development is sional scan area in real time, so two-dimensional of critical importance in obstetric and gynecologic Doppler flow mapping is possible (see Chap. 5). In applications, as such range discrimination allows reli- 1983 the Japanese group, which included Omoto, able Doppler interrogation of a deep-lying circulation, Namekawa, Kasai, and others, reported the use of a such as that of the fetus and of the maternal pelvic prototype device incorporating the new technology organs. It must be recognized that many others also for visualizing intracardiac flow [19]. Extensive clini- have made immense pioneering contributions in the cal evaluation of this new approach was carried on in development and utilization of diagnostic Doppler so- the United States by Nanda and other investigators nography, a detailed discussion of which is beyond [20]. the scope of this chapter.

Development Introduction of Color Doppler Ultrasonography of Doppler Ultrasonography to Obstetrics and Gynecology Spectral Doppler ultrasound interrogates along the single line of ultrasound beam transmission. The The first obstetric application of Doppler ultrasonog- hemodynamic information thus generated is limited raphy consisted in detection of fetal heart movements to unidimensional flow velocity characterization from [21]. Originally developed for fetal heart rate detec- the target area. This limitation provided the impetus tion, the technique was further developed for nonin- to develop a method for depiction of flow in a two- vasive continuous electronic monitoring of the fetal dimensional plane in real time. Potential clinical utili- heart rate. Currently, they constitute the most com- ty of such an approach was obvious, particularly for mon uses of Doppler ultrasonography in obstetrics. cardiovascular applications to diagnose complex he- The systems are based on utilizing relatively simple modynamic and structural abnormalities associated continuous-wave Doppler ultrasound to determine with acquired and congenital cardiac disease. How- the fetal heart rate from the fetal cardiac wall or valv- ever, the unidimensional spectral pulsed Doppler ular motion. The first application of Doppler veloci- method was inadequate to cope with the processing metry in obstetrics was reported by FitzGerald and needs of real-time two-dimensional Doppler ultraso- Drumm [22] from Dublin and MacCallum et al. [23] nography, which involves analysis of an enormous from Seattle. The former are recognized as the first number of signals derived from multiple sampling group to publish a peer-reviewed article in this field. sites along multiple scan lines. These publications were followed by an era if impres- 6 D. Maulik

Table 1.1. Feasibility of Doppler velocimetry of fetal and References uteroplacental circulations 1. Eden A (1992) The Search for Christian Doppler. Circulation Year Author Springer, Vienna 2. Doppler C (1843) Uber das farbige Licht der Doppler- Umbilical artery 1977 FitzGerald and Drumm [22] sterne und einiger anderer Gestirne des Himmels. Ab- Umbilical vein 1979 Gill and Kossoff [24] handl Konigl Bohm Ges Ser 2:465±482 Fetal aorta 1980 Eik-Nes et al. [25] 3. Herschel JFW (1800) Experiments on the refrangibility Uteroplacental 1983 Campbell et al. [26] of the invisible rays of the sun. Philos Trans R Soc Fetal inferior vena 1983 Chiba et al. [27] Lond 90:284±292 cava 4. Ritter JW (1801) Ausfindung nicht lichtbarer Sonnen- Fetal cardiac 1984 Maulik et al. [28] strahlen ausserhalbdes Farbenspectrums, an der Seite Fetal cerebral 1986 Arbeille et al. [29] des Violetts. Widerhohlung der Rouppachen Versuche. 1986 Wladimiroff et al. [30] Wien, Mathemat-Naturw Klasse Sitzungsbericht 79: Fetal ductus 1987 Huhta et al. [31] 365±380 arteriosus 5. Buys Ballot CHD (1845) Bedrog van het gehoororgaan Fetal renal 1989 Vyas et al. [32] in het bepalen van de hoogte van een waargenomen 1989 Veille and Kanaan [33] toon. Caecilia. Algemeen Muzikaal Tijdschrift van Ne- Fetal ductus venosus 1991 Kiserud et al. [35] derlandl Tweede Jaargang No 7:78±81 Fetal coronary artery 1996 Gembruch et al. [36] 6. Buys Ballot CHD (1845) Akustische Versuche auf der Niederlandischen Eisenbahn nebst gelegentlichen Be- merkungen zur Theorie des Herrn Prof Doppler. Pogg sive research productivity during which various Ann 66:321±351 investigators [24±36] extended the use of Doppler 7. Doppler C (1846) Bemerkungen zu meiner Theorie des sonography for assessing the fetal and the maternal Farbigen Lichtes der Doppelsterne etc, mit vorzuglicher circulation (Table 1.1). Rucksicht auf die von Herrn Dr Buys Ballot zu Utrecht dagegen erhobenen Bedenken. Pogg Ann 68:1±35 In contrast to the prolific publications on the ob- 8. Satomura S (1957) Ultrasonic Doppler method for the stetric uses of Doppler sonography, reports on gyne- inspection of cardiac functions. J Acoust Soc Am cologic applications of the technique did not begin to 29:1181±1183 appear until the mid-1980s. Taylor and colleagues 9. Satomura S, Kaneko Z (1960) Ultrasonic blood rheo- were the first to characterize Doppler waves from the graph. In: Proceedings of the 3rd International Confer- ovarian and uterine arterial circulations utilizing ence on Medical Elect, London, IEEE, p 254 pulsed duplex Doppler instrumentation [37]. This 10. Franklin DL, Schlegel W, Rushmer RF (1961) Blood flow measured by Doppler frequency shift of back scat- work was followed by reports of transvaginal color tered ultrasound. Science 134:564±565 Doppler studies [38] and transvaginal duplex pulsed 11. Strandness DE, Schultz RD, Sumner DS, Rushmer RF Doppler studies [39] of pelvic vessels. Through the (1967) Ultrasonic flow detection ± a useful technic in late 1980s and early 1990s, Doppler sonographic re- the evaluation of peripheral vascular disease. Am J search in gynecology steadily expanded. Surg 113:311±314 12. Baker DW (1970) Pulsed ultrasonic Doppler blood flow sensing. IEEE Trans Sonic Ultrasonics SU-17(3):170± Conclusion 185 13. Wells PNT (1969) A range gated ultrasonic Doppler Discovery of the Doppler effect and its application to system. Med Biol Eng 7:641±652 14. Peronneau PA, Leger F (1969) Doppler ultrasonic medical diagnostics after more than a century is a pulsed blood flowmeter. In: Proceedings of the 8th fascinating example of how our understanding and Conference on Medical and Biological Engineering, exploitation of natural phenomena can be translated pp 10±11 into tangible advances in medicine. This is also rele- 15. Gramiak R, Shah PM, Kramer DH (1969) Ultrasound vant for obstetrics and gynecology as Doppler sonog- cardiography: contrast studies in anatomy and func- raphy has enabled us to explore and understand hu- tion. Radiology 92:939±948 man fetal hemodynamics, which was virtually inac- 16. Fish PJ (1975) Multichannel direction resolving Dop- pler angiography (abstract). Presented at the 2nd Euro- cessible before. As we continue to advance our pean Congress of Ultrasonics in Medicine, p 72 knowledge, it is important to pause and acknowledge 17. Angelsen BAJ, Kristofferson K (1979) On ultrasonic the immense contributions of the pioneers who made MTI mearement of velocity profiled in blood flow. it all happen. 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 a Chapter 1 Doppler Sonography: A Brief History 7

two dimensional blood flow imaging system (2-D-Dop- 31. Huhta JC, Moise KJ, Fisher DJ, Sharif DS, Wassersturm pler) (abstract). Jpn Circ J 47:191 N, Martin C (1987) Detection and quantitation of con- 20. Omoto R (1989) History of color flow mapping tech- striction of the fetal ductus arteriosus by Doppler nologies. In: Nanda NC (ed) Textbook of color Doppler echocardiography. Circulation 75:406±412 echocardiography. Lea & Febiger, Philadelphia, pp 1±5 32. Vyas S, Nicolaides KH, Campbell S (1989) Renal artery 21. Callaghan DA, Rowland TC, Goldman DE (1964) Ultra- flow-velocity waveforms in normal and hypoxemic sonic Doppler observation of the fetal heart. Obstet Gy- fetuses. Am J Obstet Gynecol 161:168±172 necol 23:637±641 33. Veille JC, Kanaan C (1989) Duplex Doppler ultrasono- 22. FitzGerald DE, Drumm JE (1977) Noninvasive measure- graphic evaluation of the fetal renal artery in normal ment of the fetal circulation using ultrasound: a new and abnormal fetuses. Am J Obstet Gynecol 161:1502± method. BMJ 2:1450±1451 1507 23. McCallum WD, Olson RF, Daigle RE, Baker DW (1977) 34. Maulik D, Nanda NC, Hsiung MC, Youngblood J (1986) Real time analysis of Doppler signals obtained from Doppler color flow mapping of the fetal heart. Angiol- the fetoplacental circulation. Ultrasound Med 3B:1361± ogy 37:628±632 1364 35. Kiserud T, Eik-Nes SH, Blaas HG, Hellevik LR (1991) 24. Gill RW, Kossoff G (1979) Pulsed Doppler combined Ultrasonographic velocimetry of the fetal ductus veno- with B-mode imaging for blood flow measurement. sus. Lancet 338:1412±1414 ContribGynecol Obstet 6:139±141 36. Gembruch U, Baschat AA (1996) Demonstration of fe- 25. Eik-Nes SH, Bruback AO, Ulstein MK (1980) Measure- tal coronary blood flow by color-coded and pulsed ment of human fetal blood flow. BMJ 28:283±287 wave Doppler sonography: a possible indicator of se- 26. Campbell S, Diaz-Recasens J, Griffin DR et al (1983) vere compromise and impending demise in intrauterine New Doppler technique for assessing uteroplacental growth retardation. Ultrasound Obstet Gynecol 7:10±16 blood flow. Lancet 1:675±677 37. Taylor KJW, Burns PN, Wells PNT, Conway DI, Hull MGR 27. Chiba Y, Utsu M, Kanzaki T, Hasegawa T (1983) (1985) Ultrasound Doppler flow studies of the ovarian Changes in venous flow and intra-tracheal flow in fetal and uterine arteries. Br J Obstet Gynaecol 92:240±246 breathing movements. Ultrasound Med Biol 11:43±49 38. Kurjak A, Zalud I, Jurkovic D, Alfrevic Z, Miljan M 28. Maulik D, Nanda NC, Saini VD (1984) Fetal Doppler (1989) Transvaginal color Doppler for the assessment echocardiography: methods and characterization of of pelvic circulation. Acta Obstet Gynecol Scand normal and abnormal hemodynamics. Am J Cardiol 68:131±135 53:572±578 39. Thaler I, Manor D, Brandes J, Rottem S, Itskowvitz J 29. Arbeille P, Tranquart F, Body G et al (1986) Evolution (1990) Basic principles and clinical applications of the de la circulation arterielle ombilicale et cerebrale du transvaginal Doppler duplex system in reproductive foetus au cours de la grossesse. Prog Neonatal 6:30 medicine. J In Vitro Fertil Embryol Transfer 7:74±75 30. Wladimiroff JW, Tonge HN, Stewart PA (1986) Doppler 40. Jonkman EJ (1980) A historical note: Doppler research ultrasound assessment of cerebral blood flow in the in the nineteenth century. Ultrasound Med Biol 6:1±5 human fetus. Br J Obstet Gynaecol 93:471±475