X-rays By Adam Lustig

Overview Physics History Trivia Modern Day Overview:

What are X-Rays? Wavelength: 0.01 to 10 nm Frequency: 3 x 1016 to 3 x 1019 Hz Wavelength: 0.01 to 10nm Frequency: 3 x 1016 to 3 x 1019

Wilhelm Röntgen Born 1845 in Prussia Vacuum tubes Considered to be the Father of Diagnostic Radiology Was studying properties of the electric discharge from a vacuum tube

Crookes Tube - Explain the Crookes Tube - Rontgen was in a dark room The tube was covered in black paper, but observed elsewhere in the room that a cardboard screen with barium platinocyanide became illuminated He soon discovered that other objects were able to be penetrated such as books, wood, metal sheets—and--once he interposed his hand between the source and the luminescent board, he saw the bones of his living hand projected as a silhouette. When high voltage is applied to the tube, the electric field accelerates the small number of electrically charged ions always present in the gas, created by natural processes like radioactivity. These collide with other gas molecules, knocking electrons off them and creating more positive ions in a chain reaction. All the positive ions are attracted to the cathode or negative electrode. When they strike it, they knock large numbers of electrons out of the surface of the metal, which in turn are repelled by the cathode and attracted to the anode or positive electrode. These are the cathode rays.

Wilhelm Röntgen Born 1845 in Prussia Vacuum tubes “A New Kind of Ray” – 1895 “X” for unknown Röntgen ray Röntgen's original paper, "On A New Kind Of Rays”, published on 28 December 1895. On 5 January 1896, an Austrian newspaper reported Röntgen's discovery of a new type of radiation. Röntgen was awarded an honorary Doctor of Medicine degree from the University of Würzburg after his discovery. He published a total of three papers on X-rays between 1895 and 1897. Today, Röntgen is considered the father of diagnostic radiology

Wilhelm Röntgen Born 1845 in Prussia Vacuum tubes “A New Kind of Ray” – 1895 “X” for unknown Röntgen ray 1901 Nobel Prize for Physics Röntgen's original paper, "On A New Kind Of Rays”, published on 28 December 1895. On 5 January 1896, an Austrian newspaper reported Röntgen's discovery of a new type of radiation. Röntgen was awarded an honorary Doctor of Medicine degree from the University of Würzburg after his discovery. He published a total of three papers on X-rays between 1895 and 1897. Today, Röntgen is considered the father of diagnostic radiology

Henri Becquerel Discovered radioactivity

Henri Becquerel Discovered radioactivity Uranium salts Inherited some uranium salts from his father and wanted to investigate florescent substances He placed the minerals on photographic plates and wrapped them in light-tight black paper, exposed them to sun, but did not observe any images on the plate In February 1896, poor weather prevented sunlight exposure to several prepared plates that he placed in a drawer. A month later when he developed the unexposed plates he saw silhouetted images in the same shape as the uranium salts.

Marie Curie Discovered the element Radium – 1898 1/10 of a grain of radium from two tons of blend Pierre Curie died in MVC in 1906 at 47 yo Marie died in 1934 at 67yo from aplastic anemia - By taking the work of Becquerel, Curie showed that radiation intensity was proportional to the amount of uranium. She then observed that a uranium mineral blend showed a higher radiation intensity than could be explained by uranium alone In December 1898, the Curies discovered Radium by refining the blend

Radium Surface plaques for skin cancer Lupus Permanent cures not achievable “Radiumgraph” Cervical cancer – 1920s Radium needles

Thomas Edison Investigated fluorescence to X-rays Calcium tungstate Developed the fluoroscope Clarence Dally (RIP 1904) - Early fluoroscopes were simply cardboard funnels, open at narrow end for the eyes of the observer, while the wide end was closed with a thin cardboard piece that had been coated on the inside with a layer of fluorescent metal salt. The fluoroscopic image obtained in this way is rather faint.  - Thomas Edison quickly discovered that calcium tungstate screens produced brighter images and is credited with designing and producing the first commercially available fluoroscope. Scientists and physicians would often place their hands directly in the x-ray beam resulting in radiation burns. Edison's assistant (and glassblower) Clarence Madison Dally (1865-1904) died as a result of exposure to radiation from fluoroscopes. Dally had a habit of testing X-ray tubes on his hands, and acquired acancer in them so tenacious that both arms were amputated in a futile attempt to save his life. In 1903, Edison abandoned his work on fluoroscopes, saying "Don't talk to me about X-rays, I am afraid of them.“ Trivial uses for the technology also resulted, including the shoe-fitting fluoroscope used by shoe stores in the 1930s-1950s.

William Coolidge Coolidge tube “hot” tube rather than “cold” Tungsten emits electrons when heated The characteristic features of the Coolidge tube are its high vacuum and its use of a heated filament as the source of electrons. There is so little gas inside the tube that it is not involved in the production of x-rays, unlike the situation with cold cathode gas discharge tubes. The key advantages of the Coolidge tube are its stability, and the fact that the intensity and energy of the x-rays can be controlled independently.  Increasing the current to the cathode increases its temperature.  This increases the number of electrons emitted by the cathode, and as a result, the intensity of the x-rays. As a bonus, the Coolidge tube could function almost indefinitely unless broken or badly abused.

William Coolidge Coolidge tube “hot” tube rather than “cold” Thermionic emmission

William Coolidge Coolidge tube “hot” tube rather than “cold” Thermionic emmission

Modern Day X-ray Tube Converts electrical energy into: Heat (99%) X-rays (1%) Converts electrical energy into: Heat (99%) X-rays (1%)

Modern Day X-ray Tube filament target 1. Cathode (filament) and Anode (target) 2. Coil of tungsten wire - similar to light bulb filament Tungsten advantages - high melting point - little tendency to vaporize - long life expectancy Tungsten disadvantages - not as efficient at emitting electrons as some other materials

Modern Day X-ray Tube Rotating - Target is annular track - spreads heat over large area of anode - speeds - 3600, 9600 rpm - Faster = much better heat ratings

Modern Day X-ray Tube

Sources Coolidge, W. D. “Vacuum Tube.” US Patent 1,203,495. Oct 1916. "Diagnostic Medical Physics." Medical College of Georgia Department of Radiology. 8 Oct. 2010. Web. 21 Oct. 2010. <http://www.radiology.mcg.edu/RadiologyPhysics/ResidentPhysicsCourse.p hp>. "Henri Becquerel - Biography." Nobelprize.org. Web. 21 Oct. 2010. <http://nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel- bio.html>. Thomas, A. M. K. Invisible Light: 100 Years of Medical Radiology. Great Britain: Blackwell Science, 1995.

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