quiz 1 - diagnostic imaging
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35 Terms
what does frequency mean in terms of radiology?
the number of waves passing a given point per unit of time
what does wavelength mean in terms of diagnostic imaging?
the total distance from crest to crest or trough to trough.
what is a crest on a timeline?
the peak at the top of a wave
what is a trough on a timeline?
the bottom point of a wave.
what is amplitude?
it is the height of the wave
what two types of energy is used to produce x-rays?
Electromagnetic and electrical.
what is the central ray?
it is the x-ray produced off the central point of the focal spot of the anode and directed 90 degrees to the image receptor.
what is the ROI?
it is the region of interest. it’s the area of the patient through which the central ray must pass to obtain the correct radiograph.
what does collimate mean?
it means decrease the field size of where the x-ray beams will hit.
what does the receptor do?
the receptor receives the x-rays and produces the actual image.
what is the intrinsic conversion efficiency?
it is the speed at which x-rays are converted to light
what is the percentage of heat vs x-rays that are produced?
99% heat, 1% x-ray
what must electricity have in order to move?
a closed circuit
what is the abbreviation for high voltage?
kV
what is current mA?
milliamperes: the number of electrons used to produce x-ray photons
what controls the penetration of the x-ray beam and regulates photon frequency and energy?
voltage kVp (kiloVolts potential)
what should the mAs be set to on our x-ray machine?
5
what does a filament transformer do?
it reduces the current and voltage to the correct amount to heat the cathode filament and produce the electron cloud
what are rectifiers?
they keep the electricity flowing in one direction like a direct current
where are x-rays produced?
in the x-ray tubewha
what type of emission are electrons “boiled off”?
a thermionic one
why use tungsten wire?
because there are a lot of electrons (74) and they are far from the nucleus
which side of the beam is the intensity of radiation greater?
the cathode side
which side of the animal should be placed on the cathode side to take advantage of greater amount of radiation?
the cathode side because the beam will be able to pentrate the animal better
what determines the direction of the beam of radiation?
the angled bevel on the outer edge of the anode
what angle should the bevel be?
less than 15 degrees
what is known as the focal spot bloom?
the spot that gets heated around the focal spot from multiple exposure
what is the ideal distance from patient when getting an x-ray on a patient with a portable unit?
30 inches
how many stages are there to an exposure switch?
two
what is the first stage of the exposure switch?
it activates the rotating anodewha
what is stage two of the exposure switch?
it activated the exposure, producing x-rays.
why are bones white on x-rays?
because they are denser
what things are radiolucent on an x-ray?
fat and air
what is radiation dose measured by?
a dosimeter
what are the three cardinal rules for reducing x-ray exposure?
decrease time of exposure, increase the distance between source and subject, shielding between the operator and the source