focal spot (redirected from fine focal spot)

focal spot,

the area on the anode of an x-ray tube or the target of an accelerator that is struck by electrons and from which the resulting x-rays are emitted. The shape and size of a focal spot influence the resolution of a radiographic image. An increase in focal spot size, which may accompany deterioration of the x-ray tube, reduces the ability to define small structures. Also called actual focal spot.

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focal spot,

n See spot, focal.

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focal spot

the area on the target of the x-ray tube which the electron stream strikes and from which x-rays are emitted. Called also focus. The larger the area of the focal spot, the poorer is the detail in the x-ray image.

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actual focal spot

the actual area of the focal spot on the radiographic target as viewed at right angles to the plane of the target.

broad focal spot

a relative term which refers to the effective dimension of the x-ray focal spot usually greater than 1 mm². See also fine focal spot (below).

effective focal spot

the face of the anode that carries the target in an x-ray tube is slanted from the vertical to increase the volume of the target but to reduce the size of the origin of the x-ray beam.

focal spot-film distance

see focal-film distance.

fine focal spot

a focal spot of less than 1 mm² which is used in radiography studies where high detail is required.

focal spot-skin distance

distance from the film spot to the skin of a patient receiving radiation therapy.