Rectification Constant - A value of the heat unit formula that varies depending on the generator
used.
Generators used in Radiography - single phase generator delivers pulsating x-ray beam (1), Three
phase generator = 3 phase 6 pulse machine (1.35) , High frequency generator = 3 phase 12 pulse
...
LXMO Exam
Rectification Constant - A value of the heat unit formula that varies depending on the generator
used.
Generators used in Radiography - single phase generator delivers pulsating x-ray beam (1), Three
phase generator = 3 phase 6 pulse machine (1.35) , High frequency generator = 3 phase 12 pulse
machine (1.41)
Rectification - The rectifier of the x-ray tube changes alternating current (AC) to direct current
(DC). This process ensures that the x-ray production flows in the right direction; from the filament to the
target.
Heat Unit (HUs) Formula - KVP x MA x Time x (rectification constant) = HUs
Cumulative MPD - Cumulative Maximum Permissible Dose is the total amount of radiation that an
x-ray worker could have been exposed to since the age of 18 according to NCRP (National Council on
Radiation protection.)
Cumulative MPD Formula - CMPD = 5 (N-18) The "N" in the equation refers to the current age of
the worker, always subtract 18 from the current age before multiplying by 5. 5 refers to the number of
REMS per year that is max for worker.
Inverse square law - The closer you are to the source of radiation, the more exposure you will
receive and vice-versa. As distance increases, exposure decreases; as distance decreases, exposure
increases.
Inverse square law formula - i1/ i2 = (D2)2 / (D1)2 i2 will be the unknown (x). To make it easier to
solve, square the values first the cross multiply and divide.
Ampere "A" - Unit used to measure the rate, or volume, of current flow in the circuit. X-ray circuit
contains 0.3 A
, Potential Difference - Is the force or speed of the electron flow in the current. The volt "V" is used
to measure the potential difference. x-ray circuit contains 120,000V
Diode - Allows electrons to flow only in one direction.
Transformer - Increases or decreases voltage by fixed amount (AC only)
Sine wave - Energy expressed in a recurring wave-form.
Wavelength - The distance from crest to crest in a sine wave
Frequency - The number of times per second that a crest passes a given point.
Kilovoltage (Kvp) - Voltage is measured at the peak of the electric cycle. Kvp controls the energy
(wavelengths) or penetrating power of x-ray beam. X-rays with shorter wavelengths have more power.
Anode Heel effect - Uneven distribution of radiation intensity in the x-ray beam. X rays that are
directed away from the cathode are more likely to be absorbed than those directed toward it.
Actual focal spot - Area on the target surface that is struck by the electron steam.
Effective focal spot - Refers to the vertical projection (which will vary based on degree of
angulation) of the actual focal spot onto the patient and image receptor. The size of the effective focal
spot influences the resolution in the image.
Focal Spot - Precise area on the target
Bremsstrahlung radiation - "brems" braking or slowing Interactions that occur within the anode
which result in production of photons. Below 70 kvP, 100% of photons in x-ray beam are from brems.
Above 70 kvP, about 85% of the beam is brems.
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