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PROPERTIES OF X-RAYS

Presented by:Sharanya MajumdarFinal BDSBapuji Dental College & Hospital

History of dental radiography Highlights in the history of dental radiographyElectro magnetic Spectrum Introduction Properties of electromagnetic radiationProperties of X-raysDefinition Physical properties Effect of interaction of x-rays with Matter Chemical properties Biological properties Physiochemical properties Contents:

Nothing materializes as if magic by overnight. Even Roentgens discovery depended upon the development and application of three converging thoughts; Electricity, Vacuum and Magnetism Prologue to discovery

Sir William Morgan unknowingly was the first man to produce x-rays while conducting one of his experiments.

History of Dental Radiography

Professor Wilhelm Conrad Roentgen made the most important discovery striking and outstanding property of cathode ray.Dr. C. Edmund Kells (1880) known as the Father of Dental Radiography, was the first dentist to practice radiography in root canal therapy on May10,1899.

Introduction Electromagnetic radiation can be defined as the propagation of wave like energy (without mass) through space or matter.Electromagnetic radiations are arranged according to their energies in what is termed Electromagnetic spectrum

Electromagnetic spectrum

They travel through space in a wave motion along a straight line. They travel at the speed of light in vacuum, i.e. 3x10 m/sec or 186,000 miles/second. As they travel through space they give off an electric field at right angles to the path of propagation and a magnetic field at right angles to both. Properties of Electromagnetic Waves 8

In passing through matter the intensity of radiation is reduced both because energy is taken up by the material and some energy is deflected from its original path to travel in a new direction.

Definition: X-rays are defined as weightless packages of pure energy that are without electrical charge and that travel in waves along a straight line with a specific frequency and speed. The properties of X-rays may be classified as:Physical Chemical Biological Physiochemical Properties of X-rays

X-rays belong to a family of electromagnetic radiations having a wavelength between 10 and 0.01.

They travel with the same speed as that of visible light (i.e. 1,86,000 miles per second)

They are invisible to the eye and cannot be seen; heard or smelt (they remain undetected by the human senses)

Physical Properties of X-rays

They cannot be reflected, refracted or deflected by a magnet or electric field as they do not possess any charge.

X-rays are pure energy, no mass and they transfer energy from place to place in the form of quanta (photons).

Physical Properties (Contd.)

X-rays are produced by the collision of electrons with tungsten atoms. The collisions which occur are of two types, thus giving rise to two types of spectra: Continuous spectra (General radiation, Bremsstrahlung radiation or braking radiation) Characteristic spectrum or line spectrum

X-rays can penetrate various objects and the degree of penetration depends upon the quality of the X-ray beam, and also on the intensity and wavelength of the X-ray beam.

In the case of diagnostic X-ray beam there are three X-ray mechanisms by which these processes take place:Coherent Scattering Photoelectric ScatteringCompton Scattering Effect of Interaction of X-rays with Matter

HeatHeatIonizationRecombinationX-rays BremsstrahlungScatteredRadiationCharacteristicRadiationPhotoelectric effect Pair productionAnnihilationradiation

Photoelectric absorption

X-rays induce colour changes of several substances:Methylene blue gets bleached Sodium platinocyanide, which is apple green in colour turns darker green then to light brown and finally to dark brownX-rays bring about chemical changes in solutions which are otherwise completely stableX-rays cause destruction of fermenting power of enzymes Chemical properties

When x-rays are incident on a atom, one of the reaction it produces is excitation.These state of excitation in biological materials enable it to take part in a chemical process into which in the normal state it would not enter.This is an important cause of biological damage produced by radiation. Biological effect of X-rays may be classified into two types Somatic effect Genetic effect Biological properties

The photographic paper or film when exposed to X-ray radiation and then developed will be found blackened. This blackening is known as film density & the degree of blackening depends upon:Amount of radiation Quality of radiation Characteristic of a film Concentration and age of developing solution Length of developing time Use of intensifying screens

Physiochemical Properties

X-rays travel in straight line.X-rays can penetrate liquids, solids & gases. The composition of the substance determines whether the X-rays penetrate or are absorbed. X-rays are absorbed by matter, the absorption depends on the atomic structure of the matter & the wavelength of the X-ray. X-rays interact with materials they penetrate and cause ionization, dissociate silver ions in film emulsions.

Conclusion

X-rays can cause substances to fluorescence or emit light radiation in longer wavelengths.X-rays can produce an image on a photographic film.X-rays cause biological changes in living things. Conclusion ( Contd.)

Essentials of Oral and Maxillofacial Radiology by Freny R. Karjodkar

Oral Radiology-Principles & Interpretation (6th Edition) by White & Pharoah References