X-radiations is a form electromagnetic radiation having a wave length ranging from 0.01 to 10 nanometers, frequency ranging between 30 petahertz to 30 exahertz,and energies ranges between 100eV to 100KeV respectively .The wave length of X-Rays are shorter than those of Ultraviolet rays and longer than that of gamma rays.
Emission of X – Rays
X-Ray are emitted by electron and gamma rays are emitted by the nucleus, another way to differentiate the two is on the basis of wave length gamma rays are of shorter wavelength as compared to X-ray emitted from the X-rays tube is of longer wave length. Minimum amount of photon energy is emitted by electron/nucleus which is sufficient enough to ionize the atom. The ionizing radiation which is released by the nucleus/electron is harmful to the living tissues.
Penetration of X- Rays
The depth of penetration depends upon the magnitude over the X-Ray spectrum. The photons energy is adjusted in accordance to the application so that sufficient transmission can produce good contrast image. In malignacy high radiation doses are required for treatment due to this advantage the risk of harmful effects of radiations can be outweighed.
Types of X – Rays
- Hard X-rays: The photon energies above 5-10 keV and wave length between 9 -0.2-0.1nm wavelength) are called hard X-Rays. It has deep penetration power due to which it is used in diagnosing and treating different diseases in medicines and inspecting the luggage of passenger by Airport Security Personnel. In crystallography hard X-Ray can be used to determine the structure of crystal
- Soft X-Rays. The photons energies below 5 keV Soft X-ray can are absorbed in air.
Generation of X-Rays.
X-rays are emitted by electron and they are generated by X-Ray tube ,a vacuum tube that uses high voltage to accelerate the electron released by the cathode plate .The high velocity electron collide with the anode and result in generation of X-Rays. In Medicine the target used in X-Ray tube is usually tungsten or more crack resistant alloy of 5% rhenium and 95% tungsten and some time metal molybendium for more specialized application in mammography. In crystallography, a copper target is the most commonly used.
X-Ray Fluorescence
The inner electron are knocked down from inner electron shell results in production of X-rays photon ,this process produce an emission of spectrum of X-Rays of different frequencies results in spectral line generation and depends upon the targets (anode) element used and thus are called characteristic line ,the transition from upper shell ( K shell )are K Line and L shell are L line.
Voltage in Diagnostic X-Ray Tubes.
Voltage in X – Ray Tube ranges from20 to 150 KV and highest energies ranges from roughly 20vto 150 keV. Most of the electric power produce by the tube is dissipated as waste heat.
Uses of X – Rays in Diagnosis and Treatment
- Projection (Plain) Radiography
Plain radiology was the only imaging modality which was used for diagnostic purpose in radiology for a period of 50 years of radiology. It is still presently used in evaluation of lungs, heart and skeleton, due speed and relatively of low cost it is commonly used. X-Ray tube generate a bean which is transmitted through a patient strike the underdeveloped film held tight to the screen of light emitting phosphors in a light –tight cassette. The film is then developed chemically and an image appears on the film. Now film screen radiography has been replaced by Digital Radiography, in which the signals are generated into digital information system and an image on the computer screen.
- Fluoroscopy and Angiography
Fluoroscopy and angiography are special applications of X-Ray imaging ,in which a fluorescent screen and image intensifier tube connected to close circuit television system. This allow real-time imaging of structures in motion or augmented with radio contrast agent .Radio contrast agents are administered , often swallowed or injected into the body of the patient ,to delineate anatomy and functioning of blood vessels, the genitourinary system or gastrointestinal tract. Two radio contrasts are presently in use. Barium (as BaSO4) may be given orally or rectally for evaluation of GI tract. Iodine, in multiple proprietary forms, may be given orally, rectal, intra-arterial or intravenous routes. These radio contrast agents strongly absorb or scattered X-Ray radiation, in conjunction with the real time imaging allow demonstration of dynamic processes, such as peristalsis in the digestive tract or blood flow in the arteries of veins. Iodine contrast may also be used as contrast agent in venous system; in these cases the contrast agent attenuates the X-ray radiation less than surrounding tissues.
