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A CENTURY OF THORACIC RADIOLOGY. (31/50) Click here to see our objects about Lung, mediastinum and Pleura Introduction News of Wilhelm Conrad Röntgen's discovery of the X ray in Würzburg reached everywhere in the world through newspaper articles and long-distance telegraphy less than 1 month after its report in December 1895. The resulting great excitement led to early experimentation by a polyglot of engineers, physicians and lay persons whose attempts to reproduce X rays with highly evacuated Crooke tubes were met with variable success. PIONEERS OF CHEST RADIOLOGY (1896 – 1915). Because the early technology of X-ray generation was both rudimentary and unpredictable, the pioneers found fluoroscopy to be the most practical method available for X-ray imaging of the chest. Fluoroscopy had several advantages over radiography during this period. It was simpler, immediate, less expensive and more readily available. The additional capacity to demonstrate dynamic events led to many diagnostic breakthroughs and functional insights and helped to reinforce the correctness af many early clinical discoveries. Most of the basic technical and diagnostic precepts of clinical chest fluoroscopy were fully established during the first twelve months after Röntgen's discovery. Although fluoroscopy truly dominated clinical chest imaging in the early period, the pioneers periodically used chest radiography to document clinical findings. Because of the low power output of X-ray machines, the limited tolerance of gas-filled X-ray tubes, and the low sensitivity of emulsions to X-rays, the exposures required for chest radiography were excessively long. When radiography of the chest was needed, the long exposure demanded that the patient lie horizontally still on a cot (usually for exposures of several minutes) ! To enhance the exposure of a medical radiograph, the principle of the intensifying screen was first proposed by A. Battelli (1863-1916) and A. Garbasso (1871-1933) in Italy, January, 1896 (1). In Belgium, E. Van Melckebeke (pharmacist in Antwerp) successfully proposed, in early February 1896, the use of ammonium uranyl fluoride. M. Pupin (1858-1935) of Columbia University experimented, the first, different materials to use fluorescence ; he is considered as "father" of the discovery of the intensifying screen (2). Other ameliorations for radiography were proposed : high output tube that used a metallic anode rather than the glass envelope as the source of the X-rays, self-regulating tubes and high generators. Some pioneers, thought that camera images could document more permanent information than the fluoroscopic observer could absorb instantaneously. In 1896 the impracticality of large glass plates led J.M. Bleyer (1859-1915) in the United States (3) and J. MacIntyre (1857-1928) in Glasgow to develop camera photography of the fluorescent screen as an alternative to radiography for documenting fluoroscopy of the chest (4). These pioneering experiments set the stage for future large-scale photofluorographic screening and cineradiology. Within a few years of Röntgen's discovery, E. Thomson (1853-1937) in the United States (1896) (5), J.M. Davidson (1856-1919) in Britain (1898) (6), and A. Beclère (1856-1939) (7) in France (1901) independently laid the groundwork for stereoscopy by applying known photographic principles to X-ray imaging. Two slightly different image perspectives were created for each exposure to provide a depth dimension. Just after the turn of the century, E. Caldwell (1870-1918) developed an ingenious dual-focus tube coupled to a fluoroscope with a rapidly rotating shutter to obtain stereoscopic images. During the pioneering period chest stereoscopy was used primarily to localize foreign objects in the body. The pioneers made a number of unexpected observations about the diagnosis of the chest disease within only a few months of the X-ray discovery. In the first year after the discovery, several practitioners reported on the use of the X-ray in the diagnosis of chest disease. By 1901, there were three major texts on chest radiology : one in English by F.H. Williams (1852-1936) (8), one in French A. Béclère (9), and one in German by the Austrian G. Holzknecht (1872-1931) (10). These three men dominated chest radiology during the very early years. GROWING PERIOD (1916 – 1946). During the second period marked improvements were made in the technology of film emulsions, intensifying screens, and X-ray generation, leading to the replacement of fluoroscopy by radiography as the dominant mode of clinical chest imaging. Other new techniques in the period include bronchography, body section imaging, and pulmonary angiography. By the onset of the World War I a series of improvements had already occurred in the technology of X-ray generation and image formation. The war created an immediate demand for more serviceable X-ray tubes, generators, and efficient radiographic emulsions. The most pressing battlefield requirement during World War I was the facility to localize metallic foreign bodies with fluoroscopy and radiography. During this period more efficient hot cathode (W.D. Coolidge 1873-1975) (11) and rotating anode (A. Bouwers 1893-1972) (12) and more powerful X-ray generators began to appear. Glass X-ray plates began to be replaced by a more practical cellulose acetate film base, supporting more uniform and more sensitive emulsions (Eastman, later Kodak, 1914). By 1918 double-coated X-ray film and purer, fine-grain calcium tungstate intensifying screens of high luminosity had greatly reduced exposure time. The introduction of rigid radiographic cassettes further improved image quality by maintaining tight contact between the intensifying screens and double-emulsion film. During this period a large reservoir of patients suffering from post-pneumonic bronchiectasis provided a strong impetus for development of surgical intervention based on accurate localization of the affected lobes and segments. Early bronchographic experiments with iodoform and bismuth subcarbonate powder proved to be impractical. J.A. Sicard (1890-1978) and J. Forestier (1872-1929) introduced the first practical clinical contrast medium for bronchography, Lipiodol in 1922 (13). Interest in the pulmonary vasculature began at the turn of the century with speculation that the normal linear opacities in the perihilar regions of the chest were caused by pulmonary vasculature rather than bronchi. The initial attempt of experimental pulmonary angiography in 1910 consisted of fluoroscopic viewing of animals after intravenous injections of bismuth suspension (O. Franck and W. Alwens) (14). The possibility of pulmonary angiography in humans was promoted by W. Forssmann's (1904-1979) demonstration of percutaneous cannulation of the right chambers (by on himself) in 1929 (15). The introduction of timed serial radiographic exposures and the use of concentrated iodinated contrast media just before World War II were important milestones in the development of clinical angiography of the lungs, hile, and mediastinum. The Portuguese, pioneers in the field of angiography, were early leaders in the radiographic demonstration of the lung vasculature. In 1931 E. Moniz (1874-1955) et al. demontrated the pulmonary vessels in several conditions (16). From 1915 to 1931 numerous independent investigators such as G. Grossman (1878-1957) (17), A. Vallebona (1899-1987) (18), B. Ziedses des Plantes (1902-1993) (19), and others experimented projection tomography. But A. Bocage (1892-1953) is considered as the "father" of tomography. The technique played an increasingly important role in clinical chest diagnosis during this period, especially in localizing studies of tuberculosis and lung cancer.(20) The first systematic thoracic examination for mainly tbc screening was maded by L. Kelsch, in Lyon, already in 1896 (21). The technical amelioration maded by J.M. Bleyer and J. MacIntyre had not many clinical applications. To be able to fight the danger of tuberculosis, from 1937 on, special "mass fluorography systems" were developed by M.D. de Abreu (1892-1962) et al. for screening the lungs (22). Particular emphasis was given to radiation exposure and protection, as well as to easy and fast working procedures for the assistants. The optical image intensifier was a natural choice, because it required a smaller dose than a film-screen combination and also – because it made use of a small format on rollfilm – lower film costs. Mass fluorography systems could also be installed in a coach, suitable for public health offices and for the military. The coach was used in communities without a hospital, in schools, and a large companies for the chest screening to detect tuberculosis at an early stage. AFTER WORLD WAR II : (1946 – 1965) During the third period chest diagnosis advanced, and technology was further refined. Film-screen radiography greatly improved as a result of high-kilovoltage technique, phototiming, scatter-absorbing grids, and automatic film processing. The increased volume of x-ray examinations led to the introduction in 1942 of the Pako automatic film processor. The first commercial model (1945) used conventional x-ray films square-cut corners, which were unloaded in the darkroom and impaled by a stamper on the sharp retainer (23). In May 1942 R. Morgan (1911-1986), then at the University of Chicago, reported the development of a new phototiming system (24). Morgan's phototimer was initially designed for use with photofluorographic units, which were commonly used at that time as sreening tools ; it soon became standard equipment through-out radiology. Acceptance of the technique in general radiography began some years later with the introduction of multifield ionization chamber detector. Altrough I. Langmuir (1881-1957) was given the original patent for an intensifier (1937) his design would not have provided sufficient intensification for clinical use. J.W. Colman (1915- ? ) of the Westinghouse Corporation announced the design of a practical image intensifying system in 1948, but it was not until 1953 that the first commercial intensifier was made available for clinical use (25). With this innovation fluoroscopy of all areas of the body including the thorax took a giant step forward, and television display of the image became possible. Meaningful recording of images in motion became a reality ; practical cineradiography was introduced in 1954. The 1950s were years of rapid technological development, although many of the progress could be considered equipment refinements rather than true technological breakthroughs. Shorter exposures became possible, largely as a result of the development of more powerful generators and tubes, and film processing was better controlled. These improvements were, of course, felt throughout diagnostic radiology, but chest radiographs, in particular, improved in quality with a concomitant decrease in patient exposure. Tomography was upgraded by the advent of pluridirectional tube movements. The "Polytome" was developed by G. Massiot (1901-1962) in France in 1951 (26). In Belgium, De Man ( ? – 1959) developed an other important pluridirectional apparatus : "Stratomatic". It was S.I. Seldinger ( ? - ? ) in Sweden who in 1953 introduced a technique for percutaneous catheter placement (27). This innovation, presently known as the Seldinger technique, revolutionized angiography, including thoracic angiography. B. Nordenstrom ( ? - ? ), also from Sweden, described contrast studies of the bronchial and mediastinal arteries in 1967 (28). THE MODERN PERIOD : (1965 – ) Without doubt, however, the major advances in the 1970s were related to the development of new cross-sectional imaging teniques. Computed tomography (CT) evolved during this decade, and Magnetic Resonance (MR) imaging had its beginnings. During the 1950s A.M. Cormack (1924-1998), a South African physicist, noted that radiation therapy dose distributions could be predicted if the distribution of attenuation coefficients was known across a body region. He also realized that such a distribution could be displayed as a gray-scale image (29). Sir G. Hounsfield (1919-2004), who was not aware of Cormack's work, was almost solely responsible for taking basic physical information and creating a practical CT unit (30). His first image of the brain, made at the Atkinson-Morley Hospital in London in October 1971, had a slice thickness of 1 cm. and an acquisition time of four and one-half minutes ; it clearly demonstrated a frontal lobe tumor. Cormack would share the 1979 Nobel prize in medicine and physiology with Hounsfield. During the 1980s technological advances in radiology included improvements in conventional radiographic devices, sonographic equipment, and in CT and MR devices. Major advances occurred in digital radiography, digital fluoroscopic equipment, and in computer storage, viewing, and recording systems. In all digital systems the X-ray beam exiting from the patient is captured by a detector. The information is digitized by an analog-to-digital converter, processed, and displayed. During the 1980s several variants of this technology were developed. In 1981s a prototype for a scanned-projection digital chest X-ray unit was described by M.M. Tesic et al. of Picker International and G.T. Barnes of the University of Alabama (31). The device passed a fan beam through fore and aft slit collimators before striking a detector array. A variant of this system is available commercially in 1987 by H. Vlasbloem et al. of Odeleca and is sold as the AMBER system (Advanced Multiple Beam Equalization Radiography)(32) Early experience with AMBER technology suggests a major improvement in film quality, due to scattering. In 1983 M. Sonoda et al, of the Fuji Photo Film Co, introduced a scanning-laser-stimulated luminescence technique using photostimulable phosphors (33). Already in 1973, Luckey of Kodak Co. had developed a theorical method for dosimetric application (Patented in 1975) : this had no clinical application. During exposure, the phosphor captures electrons ; the energy is released as light when scanned by a high-intensity laser. This technique has been rather widely used for portable chest radiography, where repeat examinations have essentially been eliminated. A.W. Templeton et al. described an image intensifier-based system in 1987 (34). This system uses a large field-of-view image intensifier ; images are recorded on a video display terminal or on film. Film digitization; another technology to insert picture in a digital environment, requires that a film be made and its information content digitized. These approaches to digital radiography have not achieved wide popularity. In 1980 Philips introduced the first digital subtraction angiography system, the DVI (Digital Vascular Imaging) to the market (35). This system ushered in the digital age of conventional radiology. It made use of image intensifier and television technology and converted its analogue signal to digital format. In this way the image information could be further processed digitally. The result was then displayed in analogue form on the monitor screen. Some DSA systems were capable of generating unsubtracted single-frame images but the system was too expensive because subsystems for substraction were not used, which led to the appearance of digital systems designed specifically for spot-film radiography replacing 70-mm and 100 / 105-mmm cameras. In 1989, von Dölken et al. introduce the thoracic digital image intensifier (36). The technical quality improved with the introduction of the flat-panel electronic detectors. Digital radiograms proved of great advantage when acquired, diagnosed, and distributed within a digitally networked hospital (37). CONCLUSION : Since Röntgen's discovery in 1895, history has witnessed an unparalleled century of development in the science of imaging technology. Radiology is now positioned in the forefront of medical diagnosis. Thoracic imaging, of course, plays a major role in the dominant position held by diagnostic imaging. We can confidently predict that the future will lead medical imaging to new, exciting, and even more valuable height. BIBLIOGRAPHY 1. Batelli A. and Garbasso A. : Sopra I Raggi del Röntgen. Il Nuovo Cimento, 1896, 4 : 40-61. 2. Pupin M. : From immigrant to inventor. Scribner's, New-York. 1923. 3. Bleyer J.M. : On the photo-fluoroscope. Laryngoscope. 1896, 1 : 1-20. 4. MacIntyre J. : Experiments on röntgen rays ; the introduction of use the camera to reduce the size of plates. Nature 1896, 55 : 64-65. 5. Thomson A. : Stereoscopic roentgen pictures. Electrical Engineer 1896, 21 : 256. 6. Davidson J.M. : Remarks on the value of stereoscopic photography and skiagraphy : records of clinical and pathological appearances. Brit Med J 1898, 2 : 1669-1671. 7. Béclère A. : Présentation de radiographies stéréoscopiques. Soc Méd d Hôp de Paris 1901, 18 : 532-537. 8. Williams F.H. : The X-rays in the diagnosis of chest troubles, with an exhibition of a fluoroscope. Boston Med Surg J 1896, 134 : 621. 9. Béclère A. : Les rayons de Röntgen et le diagnostic de la tuberculose. Baillière, Paris. 1899. 10. Holzknecht G. : Die röntgenologische Diagnostik der Erkrankungen der Brusteingeweide. Gräfe und Sillem, Hamburg. 1901. 11. Coolidge W.D. : A powerful Roentgen ray tube with a pure electron discharge. Phys Rev Ser 1913, 2 : 409-430. Coolidge W.D. : Vacuum tube. US Patent 1, 203. 495, issued October 31 1916. 12. Bouwers A. : X-ray tube. US Patent 1, 893. 759 issued January 10, 1933. Bouwers A. : Self-protecting tubes and their influence on the development of X-ray technique. Radiology 1929, 13 : 191-196. 13. Sicard J.-A., and Forsetier J. : L'huile iodée en clinique : applications thérapeutiques et diagnostiques. Bull et mém. Soc Méd d Hôp de Paris 1922, 46 : 463-469. 14. Franck O. and Alwens W. : Kreislaufstusien am Röntgenschirm. Münch Med Wschr 1910, 950. 15. Forssmann W. : Die sondierung des rechten herzen. Klin Wschr 1929, 81 : 2085-2087. 16. Moniz E., de Carvalho L. and Lima A. : Angiopneumographie. Presse Med (Paris) 1931, 39 : 996-999. 17. Grossmann G. : Tomographie 1 : Röntgenographische Darstellung von Körperschnitten. Forschr Röntgenstr 1935, 51 : 61-80. Grossmann G. : Tomographie 2 : Theoretisches über Tomographie. Forschr Röntgenstr 1935, 51 : 191-208. 18. Vallebona A. : Una modalità di tecnica per la dissiciazione radiografica delle ombre applicata allo studio del cranio. Radiol Med 1930, 17 : 1090-1097. 19. Ziedes Des Plantes B.G. : Een bijzondere methode voor het maken van Röntgenphoto's van schedel en wervelkolom. Ned Tijdschr Geneesk 1931, 75 : 5218-5222. 20. Bocage A.E.M. : Procédé et dispositif de radiographie sur plaque en mouvement. Brevet français n° 534 464, 1922. 21. Camelin A. : Les premières radioscopies systématiques par L. Kelsch – (Lyon, Hôpital Militaire Desgenettes; 1897). Lyon Med 1969, suppl. 175-4. 22. de Abreu M., : Verfahren und Apparatur zur kollektiven Röntgenphotographie. (indirekte Röntgenaufnahme). Z Tuberk 1938, 80 : 70. 23. Angus W.M. ; A commentary on the development of diagnostic imaging technology. RadioGraphics 1989, 9 : 1225-1244. 24. Morgan R.H. : A photoelectric timing mechanism for the automatic control of roentgenographic exposure. AJR 1942, 48 : 220-228. 25. Coltman J.W. : Fluoroscopic image brightening by electronic means. Radiology 1948, 51 : 359-367. 26. Massiot M.J. : Présentation du biotome du Dr Bocage et du planigraphie du Dr Ziedes Des Plantes. Bull Mém Soc Électrol Radiol Méd Fr 1938, 26 : 520-523. 27. Seldinger S.I. : Catheter replacement of the needle in percutaneous arteriography : a new Technique. Acta Radiol 1953, 39 : 368-376. 28. Nordenstrom B. : Selective catheterization and angiography of bronchial and mediastinal arteries in man. Acta Radiol 1967, 6 : 13-25. 29. Cormack A.M. : Representation of a function by its integrals with some radiological applications. J App Phys 1963, 34 : 2722-2727. 30. Hounsfield G.N. : Computerized transverse axial scanning (tomography) : Part I. Description of system. Br J Radiol 1973, 46 : 1016-1022. 31. Tesic M.M., Mattson R.A., Barnes G.T. et al. : Digital radiography of the chest : design features and consideration for a prototype unit. Radiology 1983, 148 : 259-264. |