target-film distance

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Related to target-film distance: penumbra

tar·get-film dis·tance

(TFD) (tahrgĕt-film distăns)
The space measured from the focal point of an x-ray tube to the film.
Synonym(s): source-film distance.


1. an object or area toward which something is directed, e.g. target animal, population, level or nucleotide sequence.
2. the area of the anode of an x-ray tube where the electron beam collides causing the emission of x-rays.
3. a cell or organ that is affected by a particular agent, e.g. a hormone or drug.

target cell
see target cell.
target-film distance
the distance from the target of the x-ray tube and the plane of the x-ray film.
target lesion
skin lesion consisting of annular or arciform areas of erythema with central pigmentation. Associated with bacterial hypersensitivity and seborrheic dermatitis. Called also bull's eye lesion.
performance target
in herd health programs target performances are set up in a number of production and health functions in order to provide an incentive and give some measure of performance other than an absolute one. This enables farmers to be rated on their effective performance in spite of the great variations that can occur between them in basic resources.
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