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Ultrasound imaging is the method of obtaining images of the internal parts of the human body that extensively shows blood flow, heart valve function, and take images of organs. One of the greatest achievements of technology is echocardiography technology – an invention that prolongs and improves the lives of millions of patients – has been used in the medical field almost 60 years. A steep and rapid development of the history of ultrasound depicts remarkable achievements, constant evolvement, and improvement in this field, demonstrates impressive and dramatic transformation of simple hydrophone device into sophisticated ultrasound system with vast scope for diagnostic and treatment possibilities in medicine, and cardiology in particular.
The Origin of Ultrasound
Many important scientific advances and breakthroughs led to discovery of ultrasound. The talented scientists all over the world contributed to the state of the art, frequently used nowadays ultrasound technology. A brief timeline of major events in the history of ultrasound demonstrates the swift way of ultrasound discovery and evolution over the time:
1687 – Sir Isaac Newton first proposed his theory declaring that sound is a wave;
1794 – Physiologist Lazzaro Spallanzani was the first who studied echolocation among bats (animals navigate through the air using inaudible sound) what constitutes the basis for ultrasound physics. Lazzaro Spallanzani is supposed to be the “father” of ultrasound (Singh & Goyal, 2007);
1801 – Physicist Thomas Young, while working with light found that light waves can be shifted so two beams can either combine to become stronger or cancel each other out;
1880 – Brothers Pierre and Jacques Curie discovered the piezoelectricity. This breakthrough constitutes the basis of the early ultrasound systems, where ultrasound transducer emitted and received sound waves by the way of the piezoelectric effect;
1917 – After the Titanic sinking and with the help of Curie’s discovery, Paul Langevin developed one of the first use of underwater ultrasound at a frequency of about 150 kHz. His hydrophone, that detected objects at the bottom of sea, was the first transducer, a device able to send and then receive low frequency sound waves. According to J. Baker (2005),
“Ultrasound is no different from many other technological advances in that it owes its development to war, because the French government called upon Langevin to develop a device capable of detecting submerged enemy submarines during the World War 1.” (p. 4);
1930s – Sonography was firstly used to treat players of European soccer teams as a form of physical therapy, to soothe arthritic pain and eczema, and sterilize vaccines;
1941 – An Austrian psychiatrist Dr. Karl Dussik was first to use ultrasound for medical diagnoses and produced ultrasound pictures in an attempt to outline the ventricles of the brain detect brain tumors, transmitting an ultrasound beam through the human skull. Ultrasound imaging got its start with heat sensitive paper used to record echoes. “Dussik can be regarded the father of diagnostic ultrasound” (the European Society of Cardiology, 2001);
1942 – The idea to burn focal tissues deep in the body was proposed as a noninvasive neurosurgery technique by Lynn and Putman;
1948 – Dr. George Luwig, University of Pennsylvania, developed A-mode ultrasound equipment and was the first to record and study the difference in sound waves as they travelled through tissues, organs, muscles, and gallstones in animals;
1949-1951 – Douglas Howry and Joseph Holmes, the University of Colorado, were the leading pioneers of B-mode ultrasound equipment, including the 2D B-mode linear compound scanner. They invented a transducer that was put in direct contact with the patient and there was no need to submerge patient in water to produce images as it was before. That was the start of ultrasound pictures, as we know them today;
1953 – Physician Inge Edler and engineer C. Hellmuth Hertz conducted the first successful echocardiogram by employing an echo test control device from a Siemens shipyard;
1958 – Scottish professor Ian MacDonald, the University of Glasgow, invented and improved on many devices used in pregnancy and fetal development. He became the father of obstetric and gynecological ultrasound. He was able to detect a twin pregnancy;
1966 – D. Watkins, D. Baker, and J. Reid designed pulsed Doppler ultrasound device, that made possible visualizing blood flow in various layers of the heart;
1970s – The continuous wave, spectral wave, and color Doppler ultrasound technology was designed, that made duplex scanning possible;
1986 – Kazunori Baba of the University of Tokyo developed 3D ultrasound technology and captured three-dimensional images of a fetus in 1986;
1989 – Professor Daniel Lichtenstein commenced incorporating lung and general sonography in intensive care units;Want an expert to write a paper for you Talk to an operator now
1990s – Ultrasound technology became more sophisticated with improved image quality and 3D imaging capabilities. 4D capabilities were adopted and endoscopic ultrasounds began;
2000s – Present – ultrasound technologies continue evolving. A variety of compact, handheld devices have appeared in recent years. NASA has developed a virtual guidance program for non-sonographers to perform ultrasounds in space (Baker, 2005; Meyer, 2004; Singh & Goyal, 2007; the European Society of Cardiology, 2001).
History of Ultrasound in Cardiology
Due to cooperative efforts of engineers, physicists and clinicians cardiac ultrasound has been the most important advance in diagnostic cardiology since the discovery of X-Rays by W. R. Röntgen. Acording to Meyer (2004), “Moreover, echocardiography had to be included among the top 10 greatest discoveries” (p. 1).
In the late 1940s, the German physicist, Wolfe Dieter Keidel, imagined as the future possibility the use of transmitted continuous ultrasound for recording the rhythmic volume variations of the heart, but he was not able to make his method quantitative (Singh & Goyal, 2007). This ‘sonocardiometric’ technique was later used by R. F. Rushmer in his cardiovascular experiments in awake animals.
The first experiments using ultrasonic echo-reflection for examining the heart were initiated by Inge Edler, a cardiologist at Lund University in Sweden, and Hellmuth Hertz, a Swedish physicist, who borrowed a sonar device from a local shipyard, modified it, and recorded echoes from Hertz’s own heart. In 1953, scientists recorded the first M-mode echocardiograms of the heart using an industrial reflectoscope for flaw detection. With the development of this ultrasonic “reflectoscope,” the new field of echocardiography began. Pamela S. Douglas (as cited in Singh & Goyal, 2007), president of the American Society of Echocardiography points out: “This team would bring about one of the truly groundbreaking and remarkable innovations of the 20th century” (p. 436). S. Singh and A. Goyal (2007) reveal the story how everything started:
“The first ultrasonic reflectoscope was delivered to Tekniska Rontgencentralen AB, a company that specialized in nondestructive testing at Kockum’s shipbuilding yard in Malmö. Hertz visited the company in May 1953 and, while there, applied the transducer to his precardium and observed pulsatile echo signals. Could this have been the first ultrasonic image of the heart? Unaware of the implications, the manager of the company was kind enough to lend Hertz the reflectoscope for the weekend — a small act of consideration that set the stage for a path-breaking discovery. At the cardiac laboratory at Lund University, I. Edler and C. Hertz put the ultrasonic probe over the latter’s heart and, to their fascination, saw an echo moving back and forth along the X-axis of the oscilloscope screen at a depth of 8 to 9 cm from the chest wall” (p. 433).
C. H. Hertz also devised the ink-jet recorder to produce a strip chart recording of the echoes originating from a selected structure (time-motion or M-mode recording), and the simultaneous recording of ECG (The European Society of Cardiology, 2000). I. Edler used this technique primarily for the preoperative study of mitral stenosis and diagnosis of mitral regurgitation. His work was carried forward by cardiologists all over the world, who developed Doppler, 2-dimensional, contrast, and transesophageal echocardiography. Singh and Goyal lay the stress on the following truism:
“To create a new and revolutionary diagnostic technique requires extraordinary qualities of interdisciplinary thinking, good judgment, and patience. I. Edler, it seems, had all of these. But as it often happens, the world recognized Edler’s contributions only after his retirement.” (p. 433).
The definitive breakthrough in echocardiography took place in the late 1960s, when the fiber-optic recorder was introduced, allowing the M-mode recording of all structures along the ultrasound beam. Nowadays, because of its high temporal resolution M-mode echocardiography allows accurate analysis of fast-moving structures and remains an important part of a complete cardiac ultrasound examination.
Echocardiography had been introduced in the United States by John Wild and John Reid, who had examined excised hearts ultrasonically earl, in1952. After their early works, including D. H. Howry (1960s), great progress was made in developing real-time two-dimensional (2D) echocardiography. The American effort was carried forward by Harvey Feigenbaum. He borrowed an ultrasonic instrument that neurologists were using to study the deviation of the midline of the brain and proceeded to identify pericardial effusion. Together, Feigenbaum and Dodge applied the M-mode technique to the measurement of ventricular dimensions, which is today one of the most common uses of echocardiography. This discovering turned out to be the necessary catalyst for the growth of that diagnostic method in the United States (Singh & Goyal, 2007).
In 1974, F. J. Thurstone and O. T. von Ramm constructed their electronic phased-array scanner, which marked the beginning of the revolutionary impact of ultrasound on clinical cardiology. Today, phased-array scanners are the most widely available and frequently used imaging instruments that have a greater impact on cardiac diagnosis than electrocardiography.
It was during the 1970s when the expanding interest in echocardiography led to striking advances in instrumentation, and numerous investigators have explored the feasibility of three-dimensional (3D) echocardiography. Many cardiologists, most notably Feigenbaum, were frustrated by a single sweep and tiny snapshot of heart motion. Hence, much effort was expended to transfer continuous M-mode data to multichannel recorders, which would produce long, continuous strips of the recorded data. In keeping with the advances in instrumentation, transducer design began assuming greater importance.
R.A. Meyer (2004) points out that the “evolution of echocardiographic instrumentation has been nothing less than phenomenal over the past 50 years” (p. 9). During the 1970s, invaluable collaboration between engineers and physicians culminated in the development of 2-dimensional echocardiography, Doppler echocardiography, color flow Doppler echocardiography, and even transesophageal echocardiography (Meyer, 2004). The Austrian C.A. Doppler made a new great advance in ultrasound evolution. Investigation of blood flow velocity using Doppler frequency shifts to measure motion of cardiac structures, and later, the velocity of red blood cells become possible. This method achieved great clinical acceptance in combination with imagining that ultimately led to the integration of pulsed-wave Doppler with 2D phased-array systems, and allow blood flow to be studied at selected regions within the image plane (The European Society of Cardiology, 2000).
Eventually, technologies to use duplex imaging, or Doppler in conjunction with B-mode scanning, to view vascular structures in real-time were developed. In 1978, the Swiss-born M. A. Brandestini et al. produced a 128-channel digital multigate Doppler instrument, allowing the imaging of cardiac structures and blood flow in colour and in real-time. Based on similar principles, C. Kasai et al. constructed in 1982 the revolutionary colour Doppler flow imaging system based on autocorrelation detection, providing a non-invasive ‘angiogram’ of normal and abnormal blood flow on a ‘beat-to-beat’ basis.
At present, M-mode, 2D, pulsed-wave, continuous-wave and colour Doppler flow are all combined in one diagnostic console, and represent the most comprehensive cardiac diagnostic modality by providing integrated structural, functional and haemodynamic information. The mono- and biplane electronic phased-array probes developed by J. Souquet in 1982 and his multiplane probe in 1985 represented the definitive clinical breakthrough of transoesophageal echocardiography (Singh & Goyal, 2007; the European Society of Cardiology, 2001).
Over the past 2 decades, there has been an explosion of publications and interest in the application of all forms of cardiac ultrasound. In 1985, colour flow imaging gave a fresh impetus to echocardiography. In parallel with the main developments, intravascular and transoesophageal scanning have gained clinical popularity within the last decade, and became the ideal method of evaluating the heart.
What is more, ultrasonic technology, like progress, is always changing for the better. The wide variety of transducers, frequencies, and applications that are available for the echocardiographer is unlimited now, and will be so in the foreseeable future. Clearly, all the techniques have a room for improvement. Most notably, among these is 3-dimensional echocardiography. Today, it is possible to produce real-time 3-dimensional images that are believable by using an electronic array consisting of thousands of closely packed crystals (Meyer, 2004).
Today, more than 25 million echocardiograms are performed each year throughout the world. According to Prof. Petros Nihoyannopoulos (2003), “Never before has the pace of innovations in echocardiography been so swift. . . . technological innovations are put into clinical practice at such a speed that it has become very difficult to follow, even for dedicated echocardiographers.” (p. 363).
R. Meyer (2004) gives his remarks as for ultrasound instrumentation development:
“The potential of ultrasonic application is limitless, and the evolution of echocardiography has been dramatic, to say the least, it has been particularly gratifying to appreciate how integral echocardiography has become to the practice of cardiology. As always, with any technology, we must learn how to use it to our advantage and how not to abuse and misuse the technology that can provide so much information” (p. 9).
In conclusion, the application of ultrasound in medicine started during, and shortly after World War 2, in various centres all around the world. “The Father of ultrasound” Lazzaro Spallanzani, “the father of medical diagnostic ultrasound” Dr. Karl Dussik, “the fathers of echocardiography” I. Edler and C.H. Hertz, and scientists from different countries did much to facilitate the development of practical technology and its use that led to wide spread of ultrasound in medical practice in the subsequent decades. Actually, simple hydrophone constructed by P. Langevin within several decades transformed into sophisticated ultrasound system performance equipped with real-time compound imaging, tissue harmonic and contrast harmonic imaging, vascular assessment, matrix array transducers, pulse inversion imaging, 3D and 4D ultrasound with panoramic view. At the current pace of development, echocardiography is able to provide complete assessment of the heart in terms of its anatomy, coronary flow, and physiology. Proposed brief account illustrates only major events in the history of ultrasound. Many key people, who had a hand in these discoveries, are overlooked in our paper not due to lower level of their priority, but because of our limitation in space and time. Our omission of any of the many individuals, who have so contributed, does not minimize their efforts and contributions. Nevertheless, we feel gratitude to all the contributors to this dynamic and important field in diagnostic medicine, because due to them millions of lives and hearts are saved nowadays.