X rays, history and properties of x rays

X rays

The spectrum composing electromagnetic radiation include rays which are
Gamma rays
UV rays
electric waves
X-rays are a part of this gamma-ray spectrum emitted by the cosmic system.

these rays which are used for diagnostic purposes are not emitted by any radio-active material instead they are produced by heating molybdenum and tungsten cathode in a vacuum tube at high temperatures.


x ray
When these cathodes are heated electrons having a short wavelength emits radiation from the surface of these materials. The radiations are then raced toward tungsten anode by a strong electrical current which results in abrupt stopping and change in direction of rays beam thereby focusing the rays on to the part of the body under examination.

On penetrating the body they cast an impression on the plate kept under the area of the study.
The plate is then processed and an image is generated for medical evaluation.

these rays are invisible to human eyes because they have a short wavelength. these rays are composed of photons which have no mass and charge and travel at the speed of light. These photons are called X-ray photons.

History of X-rays

It was discovered accidentally in 1895 by Cornard Roentgen.
Roentgen was a  German physicist from the  University of Wurzburg. He was engaged in studying an electron beam as it passed through the vacuum tube to strike a tungsten filament.

He observed that in addition to electrons, unknown rays were also produced which could penetrate the glass envelope of his apparatus and produce a glow on a distant fluorescent screen.

He was able to photograph the bone of the hand of his wife by placing it over a photographic plate and then shining the ray on it.
Since no name had given to this radiation the name X-ray was given by him.

For this amazing discovery, Roentgen was awarded the Nobel Prize in physics in the year 1901.

Medical Uses

these rays discovery provided a new dimension to the advancement of medical and other sciences.
The medical use of it is for both diagnostic and therapeutic purposes.

The technique of using these rays for imaging body parts is called radiography. The use of X-rays for diagnosis is known is radio-diagnosis and the use of these rays for treatment is known is radiotherapy.

As diagnostic tool radiography has proved of immense value in the detection of diseases, fractures and many other problems.
Therapeutically, X-rays are used in the treatment of many types of cancer because they can destroy the cancer cell, though the adjacent normal cells also get affected.

Properties of X-rays

a. Penetrating power

The wavelength of X-rays is 0.01 to 10 nm. It is this property of a short wavelength which gives them the power of penetration through different materials.
When X-rays passed through material they are absorbed to various extent and it depends on the density of the matter.
Dense tissues such as bones can absorb X-rays readily and this cast a white shadow on the plate as no X-rays can reach the plate.

b. Photographic effect

When these rays photons strike a photosensitive film, the image of the object under examination gets imprinted on the film. When such a film is developed and fixed chemically, a radiography image becomes visible.
The X-ray films have a base made up of cellulose acetate which is coated on either side with silver bromide emulsion.
An X-ray image is called Skiagram.

c. Florescent effect

When X-rays strike certain metallic salts the rays cause them to light up, that is, light rays are produced and the image of the object becomes visible to the naked eye during the period of exposures.
This property is utilized in
bowel loops
blood vessels
spinal cord.

d. Biological effect

X-rays can destroy both normal and abnormal cells. Hence these rays are potentially dangerous.
On repeated exposures, it can cause
hair loss
brittle nails
development of cancer
Genetic mutation.

preventive measures

Wherever and whenever possible these rays should be avoided particularly in children, young people, and pregnant women.
However, should the need arise, they must be used with adequate precautions to reduce morbidity and mortality?

What is projectional radiography?

The practice of producing two-dimensional images using X-rays us known as projectional radiography. This radiography practice is helpful in the detection of pathology of the skeletal system and also for disease process in the soft tissues.

Examples of projectional radiograph

Chest X-ray that can be used to identify lung diseases such as
1.  Pneumonia
2.  Lung cancer
3.  Pulmonary edema

An abdominal x-ray can detect
1. Bowel obstruction
2.  Free air
3.   Free fluid

To generate the image of the circulatory system an initial image is taken at the region of interest and then another image is taken after an iodinated contrast agent is added to the blood vessels. The two images taken are then digitally subtracted leaving the image of iodinated contrast outlining the blood vessels.

What is Computed tomography?

Computed tomography also is known as a CT scan is an imaging technique where images or slices of an area of the body are obtained from a series of two-dimensional x rays taken in a different direction. First, the cross-sectional images have obtained. these images are then combined to produce a three-dimensional image of the inside of the body. Computed tomography is used for diagnostic and therapeutic purposes in various medical cases.

What is fluoroscopy?

It is an imaging technique in which moving images of the inner structures of the patient are obtained with the help of a fluoroscope. A fluoroscope consists of two components that are x rays source and a fluorescent screen. The patient is placed between the x rays sources and a fluorescent screen. In modern fluoroscopic ray image intensifier and a CCD camera is coupled to the screen. The CCD camera record images and played it on a monitor.

Cardiac catheterization
Barium swallow

Dental radiography

Dental radiography is used to diagnose oral problems such as cavities.

In medical low energy x rays are useless because they are absorbed by the body due to which radiation dose increases without contributing to the image. To solve this problem thin metal sheet called an x-ray filter is placed over the window of the x-ray tube that absorbs low energy x rays. The process of absorbing low energy x rays from a spectrum is known as the hardening of the beam.