Wilhelm Conrad Roentgen, a physics professor at the University of Wurzburg in Barvaria, discovered x-rays in November of 1895, while experimenting with Crooke electrical tubes.  He worked for several weeks in seclusion to prove his findings were valid before announcing his discovery.

The new rays were called "x-rays" because x was the mathematical symbol for an unknown quantity.  X-rays interact with atoms in the material being exposed.  Some electrons are knocked off, leaving atoms that have an electrical charge (ions).  Because x-rays create ions, they are called ionizing radiation.

The first radiograph was produced when Bertha Roentgen, his wife, placed her hand on a photographic plate in the direct radiation beam for fifteen minutes.  The photo-radiograph showed the bones in her hand along with her rings.  Professor Roentgen presented his findings at the Wurzburg Physico-Medical Society and continued to study the production and effects of the rays.  Professor Roentgen became a member of the Physical Society of Stockholm and received the first Noble Prize in Physics (1901).

In the United States, Michael Pupin, a professor at Columbia University, produced radiographs about two weeks after Roentgen.  Another US researcher, Thomas Edison, worked to improve radiography with fluoroscopy (x-rays in motion) until his assistant died of severe radiation exposure.

Pierre and Marie Curie, along with Henri Becquerel, were awarded the 1903 Nobel Prize for physics because of their work with radioactivity.  Marie Curie purified radium metal and in 1911 received the Nobel Prize for chemistry.  During World War I, she developed radiography equipment and trained French and American soldiers to produce radiographs.

Ernest Lawrence (1932) invented the cyclotron that allowed particles to be accelerated to such a fast speed that it was possible to make materials radioactive upon collision.  Enrico Fermi's work with nuclear chain reactions at the University of Chicago led to atomic weapons, first tested in 1945.  The research leading to the development of the atomic bomb contributed to the development of radioactive materials for medical, scientific, and industrial use.

Innovations in imaging technology include the development of screens that reduce the amount of ionizing radiation necessary to produce a radiograph; more reliable x-ray-producing tubes; and the application of computer and information transfer technology to imaging systems (e.g., computed tomography and digital imaging).  Ionizing radiation is not used in two of the newest imaging methods:  ultrasound and magnetic resonance imaging.

The discovery of ionizing radiation in 1895 has led to the rapid development of the radiation sciences.  Through research of naturally occurring radiation in the environment, man made applications have emerged.  Medical use of radiation science occurs in several forms, including diagnostic x-rays, body scans utilizing radioactive materials, therapeutic doses of ionizing radiation to tumors, ultrasound scans, and magnetic resonance images.  Professionals in the field serve a variety of roles and make valuable contributions to the many applications of the radiation sciences.