PURPOSE:Tomography is a technique used to produce sharp image of a plane or section between the patient. This allows the clinician to identify the anatomy of this section of tissue without the distraction of super imposed shadow. The principal advantage of tomography is improved contrast resolution.
PRINCIPLES:
In linear tomography the x ray tube and the film holder are linked by a rod mechanism. During the exposure the tube moves in one direction and the film holder moves in the opposite direction. As these shifts occur, the X-ray tube continues to emit radiation so that most structures in the part of the body under examination are blurred by motion. Only those objects lying in a plane coinciding with the pivot point of a line.
Linear tomography,
Object lying outside the plane of the fulcrum will exhibit increasing motion blur with increasing distance from the object plane. The thickness of tissue that will be imaged is called the tomographic section, and its thickness is controlled by the tomography angle.
Equipment
Most features of tomography x-ray imaging system appear similar to those of conventional radio graph system. In the tomography system, you will find the vertical rod that connects the x-ray tube above the table with the image receptor below the patient to enable both to move in reciprocal fashion about the fulcrum. This feature is unique to tomography.
As the top of the rod moves in one direction, the bottom of the rod moves in the opposite direction. At one point no movement is occurring in either direction. This is the fulcrum; all images at the level of the fulcrum are stationary, thus appearing with less blur and high contrast
APPLICATION
Tomography is commonly used for improved radiographic contrast by blurring structures on either side of the plane. the radiographic contrast of the tissue of interest is enhanced by blurring of the anatomical structures above and below that tissue.
