Quality Control VOCAB

quality assurance

on-going performance improvement activities that provide confidence that high quality images and services are provided

quality control

monitors technical equipment to ensure it is operating within established tolerances

linearity

(aka reciprocity) changes in mA should produce proportional changes in exposure with all other factors being equal

(ex: if mAs is doubled, exposure should double within 10%)

___ measures the rate of electrical flow across the x-ray tube

mA

factors that can influence flow include:

variations in generator, electrical demands within the building causing electrical fluctuations, aging of x-ray equipment

low of reciprocity

any combination of mA and time that equals the same mAs should produce the same exposure

exposure reproducability

the same set of exposure factors should always produce the same exposure intensity without varying more than 5% (same exposure multiple times)

half value layer (HVL)

a direct indication of the penetration power of the x-ray beam (the higher the HVL, the more penetrating the beam)

when the measured HVL falls below minimum requirements, either ___ or ___

either the kVp calibration is off or there is insufficient filtration

back up timer

should terminate exposure within 6 seconds or 600 mAs (whichever occurs first)

acceptance testing

done at the time of equipment installation to confirm it is operating within set parameters and to establish baseline for follow-up QA testing

luminance

emission of light; ability to display different shades of brightness; measured in lumens (Lm)

lumen

power of light flow through space

illuminance

rate of light striking the surface

ambient light

light already present in an area before additional lighting added (natural light from windows or artificial room lighting)

primary monitor

high resolution monitor used by the radiologist for diagnostic purposes

must be a minimum of 2048 × 2560 to be used for interpretation

secondary monitor

is used by technologists and does not offer the same high resolution as the radiologist’s reading station

must be at least 1024 × 1280 and is not to be used for interpretation purposes

dark noise

term used to describe the noise seen on a digital image receptor that is processed without first making an exposure (dark noise degrades images)

ghost images (DR)

residual image occurs when the DEL value does not return to 0 after an exposure (can occur after an excessively high exposure has been made)

can also be caused by off-focus/STEM radiation

veiling glare

caused by light that scatters within monitor

brightness uniformity

should not vary more than 10% between monitors in the same reading area (brightness between center and 4 corners of monitor should not vary more than 20-30% of their average)

blooming

occurs when there is an unwanted change in the actual focal spot size during a change in exposure (low tube current - less expansion) (high tube current - more expansion)