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The advances in the medical imaging technologies have created both the powerful diagnostic solutions and practical means for the patients’ treatment. Magnetic Resonance Imaging (MRI), Computed Tomography (CT), and Ultrasound imaging tools enable the early diagnosis of the various diseases with great precision. This paper presents the chronological perspective on the medical imaging solutions along with the brief technology outlines. All three technologies are explored with regard to their value in the medical practice, as well as their potential development in the near future.
Dr. George Ludwig and Francis Struthers were the first researchers who used an ultrasound technology for the medical purposes in 1949. In order to diagnose foreign bodies and gallstones, they have used the pulse-echo method. Ludwig and Struthers were building on the experience of the Austrian scientist Dr. Dussik, who tried to apply the ultrasound diagnosing cerebral ventricles during the World War II (Gupta & Sahu, 2007). Also in 1949, Dr. Dorothy Howry and engineer Roderick Bliss have conducted a number of experiments aimed at detecting shadows in the soft tissues while the patient was submerged in the water. They have succeeded in getting the cross-section image of the tissues using the same reflection technique with pulse-echo ultrasound. According to Gupta and Sahu (2007), in 1950 Dr. Gilbert Baum has created an ultrasound scanner that was capable of detecting the orbital and intraocular tumor. Shortly afterward, Dr. Ian Donald has introdused a direct skin contact scanner that used an ultrasound beam. Starting from 1960’s, the ultrasound imaging technologies were developing rapidly, benefitting different areas of the medical knowledge. The quality of the ultrasound images has imroved significantly once the portable computers became available during 1980’s. The precision of ultrasonic scanning devices combined with the computing power of modern imaging systems made the ultrasound application an indispensable part of the medical practice.
The creation of the X-ray computed tomography has its roots back in 1895, when a German physicist Wilhelm Röntgen had discovered the radiation. The medical application of this discovery was apparent from the very beginning, as two-dimensional bone images have caused a sensation in the scientific world. However, the major issue in obtaining the correct image was the so-called inverse problem. Due to this problem, the exact spatial placement of the different objects could not be determined on the two-dimensional picture. Two major steps toward olving this issue were made by Johann Radon and Arthur Eddington (Buzug, 2008, p. 6). In 1917, Radon has published his work that offered a solution to the image reconstruction with regard to the inverse problem. Two decades later, Eddington solved the reconstruction problem in his work related to the astrophysics studies. Although the fields of astrophysics and medicine are widely separated from each other, the mathematical principles remain the same. Allan MacLeod Cormack and Godfrey Newbold Hounsfield independently transformed those principles into the first CT scanners.
A theoretical physicist, Cormack has started his tomography experiments in 1963 when he worked for the Harvard University. He addressed the image reconstruction problem with the X-ray projections using the experimental apparatus and horsemeat cutlets (Cierniak, 2011, p. 14). During the same time, Hounsfield worked for the Central Research Laboratories of EMI Ltd. He already had an experience developing the radar air defense systems during World War II, which eventually was helpful with the tomography concepts. Hounsfield started his research on tomography in 1967, using the gamma radiation instead of X-rays. He was the first scientist who actually applied computers in the course of the image reconstruction, building the prototype CT scanner. In 1968, Hounsfield has patented his device, which by then had 80x80 pixels screen and was able to produce an image after 2.5 hours of calculations (Cierniak, 2011, p. 15). Eventually, X-rays replaced the gamma radiation as Hounsfield has started to experiment on living tissues. This approach has reduced the measurements’ time to nine hours, and the image reconstruction was performed in 20 minutes.
The prototype scanner EMI Mark I, installed at the Atkinson Morley’s Hospital in Wimbledon, has produced the first brain image in October 1971. Hounsfield and his team achieved 4.5 minutes scan time and 20 seconds reconstruction time with 13 mm cross-section thickness (Cierniak, 2011, p. 17). The first commercial CT scanner EMI CT 1000, based on the Mark I computer, has appeared on the market in 1973. As the new technology successfully found its way into numerous medical practices, Hounsfield and Cormack received the Nobel Prize for Medicine in 1979. Since then, CT technology progressed in the slice count and performance, producing images with the constantly increasing quality. The general technology advancements have resulted in the portable CTs that appeared by the late 1990s.
The nuclear medicine had started its development in 1958, when Hal Anger invented the first gamma camera. A year later, hhis colleague at the University of California at Berkeley Jerome Singer has proposed to use NMR (Nuclear Magnetic Resonance) for the in vivo blood flow measurements (McRobbie, Moore, Graves, & Prince, 2007, p. 2). In 1971, Raymond Damadian has noticed that in vitro mouse tumors have the high contrast compared to the normal tissues under the NMR influence. Paul Lauterbur in 1973 proposed the image reconstruction approach based on the magnetic field gradients, which differ in objects’ actual locations and their respective projections in NMR signal. The works of Damadian and Lauterbur gave the start to the modern MRI technology, which still uses the magnetic field gradients as the main image reconstruction tool. In July 1977, Damadian and his colleagues Michael Goldsmith and Larry Minkoff have performed the first MRI human body scan. Since then, the technology evolved only in terms of the more powerful computers and higher magnetic field energy. By the late 1996, there were more than 10.000 MRI scanners worldwide (McRobbie et. al, 2007, p. 3).
Neither of MRI, CT, or ultrasound tools could have gained their effectiveness without the progress in computer technologies. Early computers were extremely unreliable and could not be used for the medicine purposes. The ENIAC machine (Electronic Numerical Integrator and Calculator) was built in 1946 and can be recognized as the first ever computer (Cierniak, 2011, p. 14). The Mark I machine that had been used in 1973 by Hounsfield was partially semiconductor-based, which significantly improved the operational reliability. The microcontrollers’ introduction in the late 1970s permitted the creation of the small-factor computers, powerful enough to run the CT and MRI applications. As the modern computing equipment has benefited from the electronic miniaturization, portable microcomputers are often integrated directly into the scanning equipment.
There is a number of potential improvements that may influence the CT, MRI, and ultrasound equipment in the near future. Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) promise new advancements in the tomographic imaging. Apart from the high-quality images and top precision, these technologies will offer the improved radiation doze measurements. With the introduction of the nanomaterials, the operational precision can be shifted from the micron-level even deeper. The microchip agents also could be used more widely in order to enhance the images’ contrast in the most complex cases. Finally, a variety of portable scanners can benefit the emergency medicine, reducing the reaction time in severe cases treatment.