The Science of Radiology and Radiologic Technology

Core Terminology and Key Concepts in Medical Radiology

  • Key Definitions:

    • Radiology: A branch of medicine that uses imaging technology to diagnose and treat disease.

    • Radiologist: A physician who applies any form of radiation in the diagnosis and treatment of disease.

    • Radiography: An imaging modality that uses x-ray film and usually an x-ray tube mounted from the ceiling on a track that allows the tube to be moved in any direction; provides fixed images.

    • Radiographer: A radiologic technologist who deals specifically with x-ray imaging.

    • Radiologic Technology: The art and science of using radiation to provide images of the bones, organs, soft tissue, and vessels that comprise the human body.

    • Radiologic Technologist: Health care professionals who perform diagnostic imaging procedures, such as X-ray examinations, magnetic resonance imaging (MRI) scans, and computed tomography (CT) scans.

  • Scope and Applications of Radiologic Technology:

    • Provides diagnostic images of four main anatomical structures:

    • Bones

    • Organs

    • Soft tissue

    • Vessels

    • Images are recorded on x-ray film or displayed on a video monitor and used as a tool to diagnose disease, injury, or congenital deformity.

    • Clinical diagnostic capabilities:

    • Aligning broken bones

    • Detecting ulcers

    • Diagnosing various injuries, traumas, and diseases

    • Diagnosis and treatment of a patient depend on the accurate and precise production of a radiographic (x-ray) examination.

    • Radiologic technologists are essential healthcare team members who work closely with physicians, nurses, and allied health professionals.

Historical Foundations and Early Scientific Discoveries

  • Early Chemical and Physical Foundations (First Century AD Onward):

    • Physical science foundations paving the way for x-ray discovery center around three specific aspects: electricity, vacuums, and image recording materials.

    • Archimedes: Explained the reaction of solids when placed in liquids.

    • Democritus: Described materials as being composed of ultimate particles.

    • Thales: Discovered some of the effects of electricity.

  • Scientific Pioneers in Vacuum, Electricity, and Imaging Hardware:

    • Evangelista Toricelli: Produced the first recognized vacuum when he invented the barometer.

    • Otto Van Guericke: Invented an air pump capable of removing air from a tube.

    • William Gilbert: First to study electricity and magnetism in detail.

    • Isaac Newton: Built and improved the static generator.

    • Charles du Fay: Distinguished two kinds of electricity using glass, silk, and paper.

    • Abbe Jean-Antoine Nollet: Improved the electroscope, which is a vessel for discharging electricity under a vacuum; considered the forerunner of the x-ray tube.

    • Benjamin Franklin: Pioneer in the study of electricity.

    • William Watson: Demonstrated electrical current through transmission of electricity from a Leyden jar through wires in a vacuum tube.

    • Michael Faraday: Induced an electric current by moving a magnet in and out of a coil, developing electromagnetic induction used to produce better generators and transformers.

    • Johann Wilhelm Hittorf: Conducted several experiments with cathode rays, which are streams of electrons emitted from the cathode.

    • William Crookes: Demonstrated that matter was emitted from the cathode which had enough energy to rotate a wheel placed within the tube.

    • William Godspeed: Produced a radiograph in 1890; however, his achievement was recognized only in retrospect and after the discovery of x-rays by Roentgen.

The Discovery of X-Rays and Wilhelm Conrad Roentgen

  • Nature and Context of the Discovery:

    • X-rays were not intentionally made; they were discovered by accident.

    • During the 1870s and 1880s, physics laboratories investigated the conduction of cathode rays through partially evacuated glass tubes known as Crookes tubes.

    • The Crookes tube is the forerunner of modern fluorescent lamps and x-ray tubes used today.

  • Wilhelm Conrad Roentgen Biography and Discovery Details:

    • Date of Birth: March 27, 1845 in Lennep, Germany.

    • Family Background: Only child of Friedrich Conrad Roentgen, a textile merchant.

    • Personal Life and Career: Married Bertha Ludwig in 1872. Offered employment at the University of Wurzburg in 1882.

    • Administrative & Academic Position: Became rector of the University of Wurzburg while continuing to work in the physics department and on his personal research project.

    • Discovery Circumstances: On November 8, 1895 (also cited as November 8, 1985 in Wurzburg laboratory notes), Roentgen was working in his laboratory at Wurzburg University in Germany.

    • Experimental Setup: Darkened his laboratory and wrapped the Crookes tube in black photographic paper to better observe the effect of cathode rays in the tube.

    • Observation of Fluorescence: A plate coated in barium platinocyanide, a fluorescent material, was lying several feet from the tube. No light escaped the Crookes tube, but the fluorescent material glowed, with the intensity increasing as the plate was brought closer to the tube. This glow was termed fluorescence.

    • Experimental Investigation: Investigated this "X-light" by placing various materials between the tube and the fluorescent plate, including wood, aluminum, and his hand.

    • First Published Medical Radiograph: Produced and published a medical x-ray image in early 1896 showing his wife's hand.

    • Historical Significance: Characterized by accidental discovery, unrecognized prior observations by contemporaries, and Roentgen's vigorous investigation which allowed him to describe almost all properties of x-rays recognized today within less than a month.

  • Early American Radiography and Initial Radiation Hazards:

    • First US Radiographic Examination: Conducted around February 1896 in the physics laboratory at Dartmouth College on Eddie McCarthy, who broke his wrist while skating.

    • Development of Fluoroscopy and Early Radiation Injuries:

    • Thomas Edison developed the fluoroscope in 1898 and investigated several fluorescent screens.

    • Edison discontinued his experiments when his assistant and longtime friend, Clarence Dally, experienced severe x-ray burns that caused his arm to be amputated.

    • Clarence Dally died in 1904, which is counted as the first x-ray fatality in the United States.

Comprehensive Historical Timeline of Radiology and Diagnostic Imaging

  • 1895: Roentgen discovers x-rays.

  • 1896: First medical applications of x-rays in diagnosis and therapy are made.

  • 1900: The American Roentgen Society, the first American radiology organization, is founded.

  • 1901: Roentgen receives the first Nobel Prize in Physics.

  • 1905: Einstein introduces his theory of relativity and the equation E=mc2E = mc^2.

  • 1907: The Snook interrupterless transformer is introduced.

  • 1913: Bohr theorizes his model of the atom, featuring a nucleus and planetary electrons.

  • 1913: The Coolidge hot-filament x-ray tube is developed.

  • 1917: The cellulose nitrate film base is widely adopted.

  • 1920: Several investigators demonstrate the use of soluble iodine compounds as contrast media.

  • 1920: The American Society of Radiologic Technologists (ASRT) is founded.

  • 1921: The Potter-Bucky grid is introduced.

  • 1922: Compton describes the scattering of x-rays.

  • 1923: Cellulose acetate "safety" x-ray film is introduced (Eastman Kodak).

  • 1925: The First International Congress of Radiology is convened in London.

  • 1928: The roentgen is defined as the unit of x-ray intensity.

  • 1929: Forssmann demonstrates cardiac catheterization on himself.

  • 1929: The rotating anode x-ray tube is introduced.

  • 1930: Tomographic devices are shown by several independent investigators.

  • 1932: Blue tint is added to x-ray film (DuPont).

  • 1932: The U.S. Committee on X-ray and Radium Protection (now the NCRP) issues the first dose limits.

  • 1942: Morgan exhibits an electronic photo-timing device.

  • 1942: The first automatic film processor (Pako) is introduced.

  • 1948: Coltman develops the first fluoroscopic image intensifier.

  • 1951: Multidirectional tomography (polytomography) is introduced.

  • 1953: The rad is officially adopted as the unit of absorbed dose.

  • 1956: Xeroradiography is demonstrated.

  • 1956: First automatic roller transport film processing (Eastman Kodak) is introduced.

  • 1960: Polyester base film is introduced (DuPont).

  • 1963: Kuhl and Edwards demonstrate single-photon emission computed tomography (SPECT).

  • 1965: Ninety-second rapid processor is introduced (Eastman Kodak).

  • 1966: Diagnostic ultrasonography enters routine use.

  • 1972: Single-emulsion film and one-screen mammography become available (DuPont).

  • 1972: Damadian and Lauterbur produce the first magnetic resonance image (MRI).

  • 1973: Hounsfield completes development of first computed tomography (CT) imaging system (EMI).

  • 1974: Rare earth radiographic intensifying screens are introduced.

  • 1977: Mistretta demonstrates digital subtraction fluoroscopy.

  • 1979: The Nobel Prize in Physiology or Medicine is awarded to Allan Cormack and Godfrey Hounsfield for CT.

  • 1980: The first commercial superconducting MRI system is introduced.

  • 1981: Slot scan chest radiography is demonstrated by Barnes.

  • 1981: The International System of Units (SI) is adopted by the International Commission on Radiation Units and Measurements (ICRU).

  • 1982: Picture archiving and communications system (PACS) becomes available.

  • 1983: First tabular grain film emulsion (Eastman Kodak) is developed.

  • 1984: Laser-stimulable phosphors for computed radiography appear (Fuji).

  • 1988: A superconducting quantum interference device (SQUID) for magnetoencephalography (MEG) is first used.

  • 1989: The SI is adopted by the NCRP and most scientific and medical societies.

  • 1990: The last xeromammography system is produced.

  • 1990: Helical CT is introduced (Toshiba).

  • 1991: Twin-slice CT is developed (Elscint).

  • 1992: The Mammography Quality Standard Acts (MQSA) is passed.

  • 1996: Digital radiography that uses thin-film transistors (TFTs) is developed.

  • 1997: Charge-coupled device (CCD) digital radiography is introduced by Swissray.

  • 1997: Amorphous selenium flat panel image receptor is demonstrated by Rowlands.

  • 1998: Multislice CT is introduced (General Electric).

  • 1998: Amorphous silicon-CsI image receptor is demonstrated for digital radiography.

  • 2000: The first direct digital mammographic imaging system is made available (General Electric).

  • 2002: Sixteen-slice helical CT is introduced.

  • 2002: Positron emission tomography (PET) is placed into routine clinical service.

  • 2003: The Nobel Prize in Physiology or Medicine is awarded to Paul Lauterbur and Sir Peter Mansfield for MRI.

  • 2003: Digital radiographic tomosynthesis is demonstrated.

  • 2004: Sixty-four-slice helical CT is introduced.

  • 2005: Dual-source CT is announced (Siemens).

  • 2007: The 320-slice helical CT is introduced (Toshiba).

  • 2009: NCRP Report No. 160, Ionizing radiation exposure of the population of the United States: 2006, is published.

  • 2011: Digital mammographic tomosynthesis is clinically approved.

  • 2012: Discovery of the Higgs boson at the CERN Large Hadron Collider, Switzerland.

Diagnostic Imaging Modalities and Medical Applications of Radiation

  • X-Ray Diagnostic Imaging Modalities:

    • Radiography:

    • Uses film or a solid-state image receptor.

    • Features an x-ray tube usually mounted from the ceiling on a track that allows movement in any direction.

    • Provides fixed images for diagnostic evaluation.

    • Fluoroscopy:

    • Usually conducted with an x-ray tube located under the examination table.

    • Provides moving images on a television monitor or flat panel display.

    • Computed Tomography (CT):

    • Uses a rotating x-ray source and detector array.

    • Acquires a volume of data, enabling fixed images to be reconstructed in any anatomical plane: coronal, sagittal, transverse, or oblique.

  • Radioactivity and Nuclear Radiology:

    • Definition of Radioactivity: The property of certain elements to emit rays or subatomic particles spontaneously from matter.

    • Nobel Prize in Physics Recognition: Awarded to Pierre Curie, Marie Curie, and Henri Becquerel for their pioneering work in radioactivity.

    • Discovery of Medical Utility:

    • Pierre Curie experimented with radium on animals and observed that radium killed diseased cells, presenting the first suggestion of radioactivity's medical utility.

    • Marie Curie refined the knowledge of radioactivity and purified radium metal.

    • Marie Curie's continuous study of radioactivity led to a severe illness requiring a kidney operation.

    • Nuclear Radiology Defined: The branch of radiology using radioactive materials for medical diagnosis and treatment.

    • Technical Milestones in Nuclear Physics:

    • Ernest Lawrence (1932): Invented the cyclotron, a chamber used to accelerate particles to high speeds for use as projectiles; first made radioisotopes available in large quantities.

    • Enrico Fermi: Demonstrated a successful chain reaction in a Uranium pile, which was later developed into nuclear weapons used to bomb Nagasaki and Hiroshima in Japan.

    • Weapons research became the foundation for highly beneficial medical applications of radioisotopes.

  • Evolving Imaging Specialties:

    • Technical advances since 1895 have created an extensive array of diagnostic modalities in modern imaging departments:

    • Computed tomography

    • Magnetic resonance imaging

    • Nuclear medicine

    • Radiation therapy

    • Ultrasonography

    • Interventional radiology