History of radiology

1831 Mischael Faraday described electromagnetic induction.

1861 Leonard proposed inverse square law pertaining to the cathode rays.

1895 On November 8, Wilhelm Roentgen discovered X-ray.

1896 William T.G. Morton, a dentist, announced that it is possible to take

radiograph of the teeth.

1896 Frank Harrison, an English dentist made dental radiographs with 10

minutes of exposure time. His images could differentiate the tooth

structure and pulp chamber. He also reports the harmful effects of

radiation.

1896 Dr. Edmund C. Kells discovered his own X- ray apparatus and

described a technique for radiographing the teeth and the jaw. He also

proposed the principle of keeping the film and object at right angles to the

source of the X-ray.

1904 Weston A. Price a Cleveland dentist described paralleling technique

and bisecting-angle technique.

1918 Eastman Kodak Company developed a darkroom with processing

tanks.

1925 Raper proposed bite-wing technique for the detection of interproximal

caries.

1960 Panoramic X-ray machines were marked.

1980Kinos L.T. ET all developed a portable radiographic X-ray camera

made of tantalum and aluminum.

Matter: is any thing that occupies space and has mass.

Radiation: is a form of energy transmits through space and matter. It may

occur in two forms: stream of particles and electromagnetic waves.

Radiology: is the medical science that deals with the study of radiation and its

use, radioactive substances and other forms of radiation energy in the

diagnosis and treatment of diseases.

Radiograph: is an image on a film which is visible when viewed under

transillumination, produced by the passage of X-ray through an object or body.

Radiography: is the art and science of making radiographs by the exposure of

films to X-rays.

Dental radiology: is that area of dentistry which is concerned with the study of

radiation and its use; for the evaluation of teeth, their associated structures,

and facial and cranial bones.

Dental radiograph: is an image on a film showing teeth and associated

structures when viewed under transillumination.

Atomic structure

atomic number

atomic weight

This binding energy

is measured in

electron-volts (eV)

or kilo-electron-volts

(keV).

Ionization: is the process of converting an atom to ion. An ion pair is formed

when an electron is removed from an atom in the ionization process and

become positive ion. This ion pair tries to attain electrically stable state by

reacting with other ion.

Radioactivity: is the process by which certain unstable atoms or elements

undergo spontaneous disintegration or decay.

Ionizing radiation is radiation that is capable of producing ions by removing or

adding electron to an atom.

Particulate radiation

Electromagnetic radiation.

There are three types of particles:

Alpha particles are emitted from the nucleus of heavy metals and exist as

two proton and neutrons, without any electrons. Accordingly, they quickly give

up their energy and penetrate only a few microns of body tissue.

Beta particles are fast-moving electrons emitted from the nucleus of

radioactive atoms. High-speed beta particles are able to penetrate matter to a

greater depth than alpha particle, to a maximum of 1.5cm in tissue. This

deeper penetration occurs because beta particles are smaller and lighter and

carry a single negative charge; therefore they have a much lower probability of

interacting with matter than do alpha particles. Beta particles are used in

radiation therapy for treatment of skin lesions.

Cathode rays are high-speed electrons originating in manufactured devices

e.g. X-ray tube.

Electromagnetic radiation

It is the propagation of wave-like energy through space or matter.

Electromagnetic radiations are either artificial or natural which are the cosmic

rays, gamma rays, X-rays, ultraviolet rays, visible light, infrared light, radar

waves, microwaves, and radiowaves.

The effect of electromagnetic radiation on human tissues as follow:

Television and radiowaves: No effect on human tissues.

Microwaves (low energy radiation): May produce heat within organic tissue.

Low energy radiation capable of causing less ionization: As these have low

ionization effects on living tissues, which used in magnetic resonance imaging.

Gamma rays and X-rays: these rays are capable of causing ionization.

X-radiation: is a high-energy ionizing radiation produced by the collision of a

beam of electrons with a metal target in an X-ray tube as electromagnetic

radiation.

X-ray: is a beam of energy that has the power to penetrate substances and

record the resultant image on radiographic film. X-rays have properties of both

waves and particles.

X-rays have smaller wavelengths and therefore higher energy than ultraviolet

waves.

Properties of X-rays

X-rays are invisible and cannot be detected by any of human senses.

X-rays have no mass or weight.

X-rays have no charge.

X-rays travel in the same speed as light.

X-rays travel as waves and have short wavelength.

X-rays have a high frequency.

X-rays travel in straight lines and can be deflected or scattered.

X-rays diverge from the source.

X-rays cannot be focused to a point.

X-rays have penetrating power.

X-rays are absorbed by matter. The absorption depends on the

atomic structure of matter and the wavelength of the X-rays.

X-rays cause ionization of matter.

X-rays can cause certain substances to fluoresce or emit radiation in

longer wavelength.

X-rays can produce image on photographic film.

X-rays can cause biologic changes in living cells.

An electrical and magnetic fields fluctuate perpendicular to the

direction of X-rays and at right angles to each other.

Medical uses of X-ray

The two types of X-rays used in health sciences can be classified as:

Diagnostic X-rays are used to make the shadow pictures of teeth,

face, and jaws, which helps us to look at calcified structures and

evaluate their insides.

Therapeutic X-rays are usually very powerful radiation beams

coming from radioactive nuclides, cyclotrons or linear accelerators,

which help us to literally burn away the malignancies of the jaws.

The branch of oncology which deals with the use of therapeutic

radiation is called radiotherapy.