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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