central ray


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central ray (CR)

the portion of an x-ray beam that is directed toward the center of the film or of the object being radiographed.

central ray

The theoretical center of an x-ray beam. The term designates the direction of the x-ray photons as projected from the focal spot of the x-ray tube to the radiographical film.
See also: ray

central ray

the center of the area of radiation created as the x-ray beam diverges. The further from the center of the ray one is, the more distortion there is and, if the beam is not correctly centered over the part to be viewed, there will be more distortion still. The central point is the point of minimum distortion.
References in periodicals archive ?
Central Ray 3 The correct central ray for the chosen projection was identified.
The central ray should be directed from the lateral to the medial aspect, centered midway between the superior and inferior portions of the breast.
The mammographer directs the central ray from the anterior to the posterior aspect of the patient at a 90 [degrees] angle, perpendicular to the ribs.
All patient dose calculations, including back scatter, were made in the central ray at 23 cm above the Bucky/tabletop surface.
While RPH is an off-axis aberration, SA is on-axis, whereby light rays entering more peripherally through the pupil are focussed more myopically or hyperopically than the central rays which are focussed at the fovea.
Then the intersections with the target of the central rays of ray tubes are also evaluated via ray tracing, and the fields of them are determined by the theory of geometrical optics (GO).
Secondly, the eye's crystalline lens has a varying refractive index and curvature; the central nucleus has a higher refractive index than the cortex so that the central rays are refracted more (Figure 2).

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