History of Ultrasonography
For new parents who see their baby for the first time through an ultrasound, it's a moving experience. But ultrasound is used for many purposes other than obstetrics, including military defense and other areas of medicine. The high-tech, detailed images we see on ultrasounds today took several years of research and development all over the world to achieve.
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Development of Ultrasonography
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Ultrasonography developed from sonar technology, the measurement of distance underwater using sound waves, which was discovered as early as 1822 and used by ships in the early 1900s to avoid collision.
Underwater detection systems were developed for submarine navigation in World War I and to detect icebergs after the Titanic sank in 1912. Modern ultrasonics started with the use of high-frequency acoustic waves and quartz resonators for submarine detection in 1917. Since then, the field has grown enormously, with applications in science, industry and medicine. In the late 1920s, Russian physicist Sergei Sokolov developed a technique using ultrasonography to detect irregularities in solids. He demonstrated that sound waves could be used as a new form of microscope.
Early Uses in Medicine
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The use of ultrasonics in medicine initially started with applications in therapy by using heating and disruptive effects on animal tissues. In 1944, Lynn and Putnam successfully used ultrasound waves to destroy brain tissue in animals. Soon, doctors were able to perform craniotomies and destroy parts of the brain in patients with Parkinson's disease. Ultrasonics was also used extensively in physical and rehabilitation medicine In 1958, American pediatrician and physiologist Robert Rushmer experimented with Doppler ultrasound to characterize cardiovascular functions in intact unanesthetized animals.
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Ultrasound in Obstetrics
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In the early 1960s, the A-mode scan was used in early pregnancy to detect fetal heartbeat, but measurements were done without actually seeing inside the body. The B-mode ultrasound was the first to achieve visualization inside a patient in 1963, and it was used to measure gestational sac diameter to assess fetal maturity. One of the most important uses of the ultrasound is the ability to confirm the presence of a fetal heartbeat, which was successfully achieved as early as seven weeks in 1972. This breakthrough had profound implications in the management of early pregnancy complications. Despite its initial use in destroying body tissue, studies in the 1960s proved that there were no harmful effects from ultrasound use on patients or unborn babies. In the 1970s, doctors developed several measurements using ultrasound to study fetal growth and development as well as diagnose fetal abnormalities. As early as the 1970s, ultrasound was used in gynecology to diagnose various pelvic disorders, ranging from cancer to cysts.
Improvements in Image Quality
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Images produced by early ultrasound machines were poor. Early scanners registered echoes on screen as solid dots of light. Soon, the scan converter was developed, which featured a useful degree of gray scaling, creating a clearer and more accurate image.
Real-time scanners were first developed in 1965, and they completely changed the practice of ultrasound scanning, because they produced moving images. This new device was used to demonstrate fetal movements and cardiac motions as early as 12 weeks as well as diagnose tumors.
In 1973, the analog scan converter displayed information on a standard television monitor. Brand new computer-processor technology was applied to process the signal. With the advancement of computer electronics, the analog scan converter was soon replaced by the digital scan converter in the late 1970s, which resulted in great improvements in the quality and resolution of the image. Soon, DRAM memory boards substantially improved image clarity. However, ultrasound machines at this time were immobile and bulky because of the computers housed inside.
Other Medical Uses
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Ultrasounds were also successfully used in other medical fields besides obstetrics and gynecology. Cardiac valvular motion was first detected ultrasonically in 1954. The ultrasonic Doppler principle was first implemented in the study of cardiac valve motion and pulsations of peripheral blood vessels in 1955. Blood flow was detected by the ultrasonic Doppler technique in 1962. This enabled noninvasive localized measurements of blood velocity to diagnose blood flow inadequacies.
In 1972 and 1973, real-time 2D scanners made important advancements in echocardiography possible. Throughout the 1970s, ultrasounds were used to detect abdominal disorders such as gallbladder disease and kidney stones. In the 1970s, doctors began using ultrasound to guide needles used for biopsies, amniocentesis and fetal blood sampling, making these procedures safer.
In the late 1970s and early 1980s, engineers worked to miniaturize scanners to make them portable. In the 1980s, researchers developed scanners with smaller probes that could be used more successfully in echocardiographs because of their small contact surface on the patient's chest.
Developments in the 1980s
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By the mid 1980s, convex abdominal transducers came to the market, which had a better fit to the pregnant tummy and a wider field of view. Toshiba introduced the trapezoidal-shaped image, which became standard on every new scanner by 1987. Also at this time, researchers developed a new water-soluble gel medium to apply to the skin, allowing for better transmission of ultrasound waves than the oil medium used earlier.
The transvaginal or transrectal scanner, which had been introduced as early as 1955, could observe fetal heart pulsation as early as 6 weeks. In 1965, a transvaginal scanner was developed that could be rotated, producing good images of the pelvic organs. In 1985, Austrian scientists produced the first real-time mechanical vaginal scanner, which allowed transvaginal ovum retrieval in collaboration with early developers of in vitro fertilization. The advent of transvaginal scanning had a significant impact on the diagnosis of gynecological and early pregnancy disorders.
In 1975, 2D color flow imaging was added to ultrasound technology, which allowed doctors to see blood moving in different directions in either red or blue, which helped physicians diagnose congenital heart defects as well as cardiac problems in older patients. In 1985, Japanese bio-engineers developed the use of real-time color imaging, which is still used as color flow mapping today.
Continuing advances in electronics have permitted the development of faster color Doppler instruments, which have led to better understanding of blood flow and pathology in tissues. In 1986, real-time color flow images were used to study arteries. In the 1980s, ultrasound scanners developed the rather standard appearance they still have today: a portable console on four wheels with the monitor on top and rows of scanners on the bottom.
Improvements in the 1990s
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Image quality saw real improvements throughout the 1990s, due to advances in technology in other areas of science such as radar navigation, telecommunications and consumer electronics. With the advent of ultrasound use in clinics and private offices all over the world, it became apparent that special training was needed for technicians to be able to read and understand ultrasound images, and special training courses and accreditation boards were established.
The routine fetal scan at 20 weeks of pregnancy became an integral part of prenatal care in the early 1990s, because it enabled physicians to take more accurate and in-depth measurements of fetal growth as well as diagnose a myriad of fetal malformations that had not previously been possible in utero. With modern ultrasound, doctors are even able to perform surgery on a fetus.
Ultrasound proved useful in treating mothers as well as babies with advances in the 1990s. Doctors began using it to assess pre-eclampsia and placenta abnormalities, leading to early and effective treatment. Ultrasound also paved the way for advancements in the science of assisted reproduction in the 1980s and 1990s. Using transvaginal scanners, doctors are able to access the ovaries for egg retrieval in a safer and pain free way.
The first 3D ultrasound machine was developed in 1986, but it was slow and images were of low resolution. In 1991 and 1992, researchers produced scanners that could image cardiac and arterial structures in real-time 3D. In the mid-1990s, 3D ultrasounds were used to evaluate carcinomas in cancer patients, detect fetal surface and skeletal abnormalities, and calculate volumes of the gestational sac, and also the fetal lungs, heart and abdomen. Soon, 3D ultrasonography was increasingly available due to rapid advancement in computer technology and decreasing cost of microprocessor electronics. 3D ultrasounds also provided a new experience for parents by allowing them to more accurately see their babies' face and body, leading to early maternal-fetal bonding, which might contribute to better prenatal care.
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