Radiology: A Historic Perspective

CHAPTER 5


Radiology


A Historic Perspective






Few discoveries have so profoundly affected the world as the discovery of the x-ray. This development has changed almost every aspect of medical practice. However, the diagnosis and treatment of disease is not the only area influenced by this discovery. Other uses have also had a dramatic effect on the way we live and work and include, for example, providing security at airports, developing improved strains of grain, controlling some kinds of insects, detecting flaws in industrial materials and equipment, identifying counterfeit art, and, recently, irradiating food to extend its shelf-life.



Pioneers of radiology


The development of radiology is, in large measure, a story of the development of technical hardware. The work of early scientists and craftsmen made possible the production of x-rays. Evidence of experimentation with the chemical, as well as the physical properties of matter, has been found as early as the first century ad. Archimedes, for example, explained the reaction of solids when they are placed in liquids. Democritus described materials as being composed of ultimate particles, and Thales discovered some of the effects of electricity.


More recently, three specific aspects of physical science helped pave the way for the discovery of x-rays—electricity, vacuums, and image-recording materials. Evangelista Torricelli produced the first-recognized vacuum when he invented a barometer in 1643. In 1646, through many hours of scientific experiments, Otto van Guericke invented an air pump that was capable of removing air from a vessel or tube. This experiment was repeated in 1659 by Robert Boyle and in 1865 by Herman Sprengel. Their techniques considerably improved the amount of evacuation, thus making better vacuum tubes available for further experimentation by other scientists.


From the seventeenth century forward, the main interest of scientists seemed to be experimentation with electricity. William Gilbert of England was one of the first to extensively study electricity and magnetism. He was also noted for inventing a primitive electroscope. Robert Boyle’s experiments with electricity earned him a place among the serious investigators. Most such scientists had to build their own equipment. Isaac Newton built and improved the static generator. Charles du Fay, working with glass, silk, and paper, distinguished two different kinds of electricity.


Abbé Jean-Antoine Nollet made a significant improvement in the electroscope, a vessel for discharging electricity under vacuum conditions. The electroscope was a forerunner of the x-ray tube. Of course, Benjamin Franklin conducted many electrical experiments and should be mentioned in any discussion of the pioneers in electricity. William Watson demonstrated a current of electricity by transmitting electricity from a Leyden jar through wires and a vacuum tube.


While conducting experiments with electrical discharges, William Morgan noticed the difference in color of partially evacuated tubes. He noted that when a tube cracked and some air leaked in, the amount of air in the tube determined the coloration.


In 1831, Michael Faraday induced an electric current by moving a magnet in and out of a coil. From this experiment evolved the concept of electromagnetic induction, which led to the production of better generators and transformers and high voltages for use in evacuated tubes. The most significant improvement on induction coils was made by Heinrich Daniel Ruhmkorff of Paris.


Johann Wilhelm Hittorf conducted several experiments with cathode rays, which are streams of electrons emitted from the surface of a cathode. William Crookes furthered the study of cathode rays and demonstrated that matter was emitted from the cathode with enough energy to rotate a wheel placed within a tube. Hittorf’s works were repeated and further developed by Crookes. Philipp Lenard furthered the investigation of the cathode rays. He found that cathode rays could penetrate thin metal and would project a few centimeters into the air. Lenard did a tremendous amount of research with cathode rays and determined their energies by measuring the amount of penetration. He also studied the deflection of rays as a result of magnetic fields.


William Goodspeed produced a radiograph in 1890. However, his achievement was recognized only in retrospect and after the discovery of x-rays by Wilhelm Conrad Roentgen; Goodspeed was not credited with the discovery of x-rays.


The image-recording materials (i.e., the photographic recording techniques) were very important to the investigators of the cathode rays. The first photographic copy of written material was produced by Johann Heinrich Schulze in 1727. This technique was tested further and greatly improved in later years. In 1871, Richard Leach Maddox produced a film with a gelatin silver bromide emulsion that has remained the basic component for film. In 1884, George Eastman produced and patented roll-paper film. With this significant improvement of image-recording material and the improvement in the cathode ray tube, the basis for modern-day radiography was established.



Wilhelm Roentgen


Wilhelm Conrad Roentgen was born on March 27, 1845, in Lennep, a small town near the Rhine River in Germany (Fig. 5-1, A). He was the only child of Friedrich Conrad Roentgen, a textile merchant whose ancestors had lived in or near Lennep for several generations. Wilhelm Roentgen married Bertha Ludwig in 1872 (Fig. 5-1, B), and in 1888 he was offered employment at the University of Wurzburg. He readily accepted the offer, knowing of the university’s new physics institute and its impressive facilities. Roentgen was elected rector at the university, although he continued to work in the physics department and on his personal research projects. He became interested in cathode ray experiments with the Crookes tube, which he worked with until his discovery of x-rays.





Discovery of X-Rays


On November 8, 1895, Wilhelm Roentgen discovered x-rays while working in his modest laboratory at the university. While operating a Crookes tube at high voltage in a darkened room, he noticed a piece of barium platinocyanide paper on a bench several feet from the Crookes tube. He observed a glowing or fluorescence of the barium platinocyanide after he passed a current through the tube for only a short period. Knowing the parameters of this particular experiment, Roentgen realized that the fluorescence was some kind of ray, rather than light or electricity, escaping the Crookes tube.

Mar 2, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on Radiology: A Historic Perspective

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