25: Basics of Radiation Physics

Basics of Radiation Physics

Pioneers in Dental Radiology

Wilhelm Conrad Röentgen (1845–1923)

Wilhelm Röentgen, the physicist from Germany is considered the father of diagnostic radiology. Röentgen discovered X-rays in 1895.

Personal life and early years

Wilhelm was born to a German father Friedrich Conrad Röentgen and Dutch mother Charlotte Constanze on March 27th, 1845 in the small town of Lennep in Rhineland. When Röentgen was 16 years old he enrolled in Utrecht Technical School, Netherlands. In 1868, he obtained a diploma in mechanical engineering from the Polytechnic School in Zurich. Under the tutelage of AEE Kundt, Wilhelm studied the properties of gases and obtained a doctoral degree in 1869. After obtaining his PhD, he worked as Kundt’s assistant at the University of Würzburg and later elevated to the post of an associate professor in theoretical physics. Wilhelm married Anna Ludwig in 1872. She was the daughter of an inn-keeper and 6 years elder to him. His wife died in 1919, following a prolonged illness and Wilhelm died due to intestinal cancer at the age of 73 years on February 10th, 1923. They were buried in Giessen.

William Herbert Rollins (1852–1929)

William Herbert Rollins was an American scientist and dentist. He was a pioneer in radiation protection and is known as the father of radiation protection. It is believed that he had published over 200 scientific articles regarding the hazards of radiation. Rollins, although a practicing dentist, also had a medical degree from Harvard Medical School. He called X-rays ‘X-light’ and documented them extensively in 1904. He is called the ‘Forgotten Man’ of dentistry. William Rollins proposed the use of filters to remove the low energy X-rays from the primary beam and introduced collimation. He recommended a long targetfilm distance to improve image quality. He pioneered the sandwiching of the X-ray film between two intensifying screens to increase the film speed. Dr Rollins advocated the need to determine a safe and harmless dose of radiation. In 1901, he advocated the use of leaded glasses for radiation personnel and a lead shield to cover all areas on the patient’s body that were not being imaged. Rollins also felt the need to construct a lead hood that would cover the X-ray tube head.

Edmund C Kells (1856–1928)

Edmund Kells was born in New Orleans, Louisiana, to a dentist Charles E Kells. He became a dentist, researcher, and inventor. His experiments caused the loss of most of his left arm. In 1899, he set up the first X-ray laboratory (The New Orleans X-Ray Laboratory) for radiographs and fluoroscopic examinations. He demonstrated the radiograph of chest and hip, a bullet in the head and the measurement of a root canal. He hired the first acknowledged dental assistant—Malvina Cuera, before which, his wife used to help him to mix materials and take the X-rays. In 1986, Edmund Kells and Brown Ayres devised a technique for radiographing the teeth and jaws. Dr Kells, in Dental Cosmos, mentioned the importance of keeping the film and object at right angles to the source using a film holder. In 1903, he introduced processing tanks and time-temperature processing. In 1909, Kells cut, wrapped and used rolltype photographic film.

Franklin W McCormack

Franklin McCormack, an American medical X-ray technician, employed paralleling technique principles in intraoral radiography. He wrapped the film with a black paper and used a flat metal plate to make the film packet rigid. He was also known for using bite blocks and hemostat as film holders to stabilize the film in the mouth.

Readers are encouraged to visit the website of the roentgen museum for more information on the chronology of events in origin of radiology (www.roentgenmuseum.de).

Films and Processing of Films

1896: The exposure time varied between 5 and 15 minutes and the processing time varied between 30 and 60 minutes
1913: Hand-wrapped, moisture-proof, dental packet containing two films
1919: First machine-wrapped dental X-ray film packet called Regular film (Kodak) with emulsion on only one side
1920: Film hangers were introduced
Early 1920s: Cellulose nitrate as base, emitted poisonous gases on burning
1924: Radia-tized film (Kodak) with double side emulsion
1924: Non-flammable cellulose triacetate film base
1940: Ultra speed (improved Radia-tized film) doubled the film speed of the 1924 film
Early 1960s: Polyester film base
1980s: Ektaspeed film introduced by Kodak

Fundamentals of Radiation Physics

Electromagnetic Radiation

There are two concepts to understand electromagnetic radiation, namely, classical theory and modern quantum theory. According to the classical theory, the flow of energy at the universal speed of light through free space or through a material medium is in the form of the electric and magnetic fields that make up electromagnetic waves such as radio waves, visible light, and gamma rays. In such a wave, time-varying electric and magnetic fields are mutually linked with each other at right angles and perpendicular to the direction of motion (Figure 1).

In terms of the modern quantum theory, electromagnetic radiation is the flow of photons (also called light quanta) through space. Photons are packets of energy (hν) that always move with the universal speed of light. The symbol h is Planck’s constant, while the value of ν is the same as that of the frequency of the electromagnetic wave of classical theory. The spectrum of frequencies of electromagnetic radiation extends from very low values over the range of radio waves, television waves, and microwaves to visible light and beyond to the substantially higher values of ultraviolet light, X-rays, and gamma rays.

Jan 12, 2015 | Posted by in Oral and Maxillofacial Radiology | Comments Off on 25: Basics of Radiation Physics
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