Exposure Factors or Prime Factors PRIME FACTORS What is “technique” How does

Exposure Factors or Prime Factors  PRIME FACTORS What is “technique”  How does www.phwiki.com

Exposure Factors or Prime Factors PRIME FACTORS What is “technique” How does

Koerner, Brendan, Contributing Editor has reference to this Academic Journal, PHwiki organized this Journal Exposure Factors or Prime Factors PRIME FACTORS What is “technique” How does it affect the “image” Exposure Factors – 3 or 4 The four prime exposure factors are: Voltage = kVp Current = mA Exposure time = seconds or fractions of a sec Source-to-image distance = SID

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PRIME FACTORS KVP MAS DISTANCE kVp Kilovolts controls how fast the electrons are sent across the tube Controls, quality, penetrability & contrast Increasing kVp also increases scattered photons reducing image quality Does kVp influence OD “SHORT” VS “LONG” SCALE

kVp Low kVp (50 – 60) Short scale High contrast “Bone work” kVp High kVp (90 – 120) Long scale Low contrast “Chest images”

mA Determines the number of photons, radiation quantity, OD & patient dose Changing mA does not change the kinetic energy of e- Available mA stations are usually 50, 100, 200, 300, 400 & 600 Exposure Time Should be kept as short as possible, as long as most examinations. To minimize the risk of patient motion mA X s = mAs mAs controls OD mAs determines the number of photons in the primary beam

Distance Affects exposure of the IR because of the Inverse Square Law SID largely determines the intensity of photons at the IR Distance has no effect on radiation quality INTENSITY IS SPREAD OUT Inverse Square Law Formula Intensity 1 Intensity 2 Distance 2 – Squared Distance 1 – Squared

SID Changes Direct Square Law New mAs = New distance 2 Old mAs Old distance 2 Focal-Spot Changes

Producing optimal radiographs key as long as diagnosing disease How much of the radiation received by the patient Actually reaches the IR About 1%

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Creating the IMAGE When x-rays pass through a patient’s body, three things can happen: (1) the x-ray photon is transmitted, passing through the body, interacting with the film, in addition to producing a dark area on the film; (2) the x-ray photon is absorbed in an area of greater tissue density, producing lighter areas on the film; in addition to (3) the x-ray photon is scattered in addition to reaches the film causing an overall gray fog. IMAGES DENSITY = THE AMOUNT OF BLACKENING “DARKNESS” ON THE RADIOGRAPH CONTRAST – THE DIFFERENCES BETWEEN THE BLACKS TO THE WHITES

mAs Changes at least 20 – 30 % mas change needed to see a visible change in density mAs DOUBLED = DENSITY DOUBLED + 25% + 50 % mas

Technique selection – Fixed kVp For each anatomic part there is an optimum kVp mAs is varied based on part thickness or pathological condition

Koerner, Brendan Contributing Editor

Koerner, Brendan is from United States and they belong to Wired Magazine and they are from  San Francisco, United States got related to this Particular Journal. and Koerner, Brendan deal with the subjects like Computers; Information Technology Industry

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