Taking Radiographs

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Taking Radiographs

Technical exposure factors:
Milliamperage (mA) – measure of the electrical current passing through the x-ray tube; controls the amount of radiation produced by the x-ray tube; controls quantity of the x-ray photons produced.

Kilovoltage (kVp) – measure of electrical “pressure” forcing the current through a tube; control penetrating ability of the beam – affects both the quantity and quality of x-ray photons produced.

Source-to-image distance (SID) (focal film distance) – distance between point of emission in the x-ray tube and the image receptor; affects intensity of the radiation as it reaches the film

Collimation – controls size and shape of x-ray field coming out of tube

Film speed –

Exposure time – increased exposure time increase the amount of electrons emitted, increasing image density

For standard foot x-ray of average sized patient – mA=200; kVp=54 (for AP) or 63 (for lateral); exposure = 0.033sec

Geometric Qualities:
Motion – motion is most common cause of ‘unsharpness’

Focal spot size – smaller the focal spot, the better the imag

Source-to-image distance –

Size distortion –

Shape distortion

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