Minimizing Patient Exposure Flashcards
What combination of kV and mAs is recommended to decrease patient exposure?
Low mAs with high kV
List at least three types of patient shields
Flat contact shields, shaped contact shields, shadow shields, and breast shields
What is the single most important way to reduce patient exposure?
Restriction of the useful beam
List three type of beam restrictions
Collimators, cones, and aperture diaphragms
The X-ray tube glass envelop and its insulating oil function as what kind of filtration?
Inherent filtration
How much total filtration is required for equipment operating above 70 kV?
2.5 mm aluminum eqivalent
What is the primary purpose of filtration of the useful x-ray beam?
To reduce patient skin dose
How does added filtration affect the average energy of the x-ray beam?
The average energy is increased
How does added filtration affect the minimum wavelength of the x-ray?
Added filtration has no effect on the minimum wavelength of the x-ray beam
What are the two ways used to express x-ray beam quality?
kV and HVL (half value layer)
Because the primary x-ray beam is polyenertgetic, the entrance dose is often significantly __ than the exit dose
greater
To reduce exposure to the lens, the reproductive organs, and the breasts, it is helpful to perform theses examinations in what position
PA
What is the concept employed everyday, with every examination, in order to achieve optimal radiation protection?
ALARA (as low as reasonably achieveable)
What is the feature of most x-ray imaging systems that terminates the x-ray exposure once adequate exposure reaches the image receptor?
Automatic exposure control (AEC)
How is imaging system speed related to patient exposure?
Faster-speed systems reduce required exposure
Changing from non grid to grid procedure will require a/an __ in patient exposure
increase
A/an ___ technique can function similar to, or in place of, a low ratio grid when distance is introduced between the patient/part and the image receptor
air gap
When used correctly, digital imaging can significantly __ patient dose
reduce
What is the principal reason that fluoroscopy potentially delivers a significantly higher patient dose than general radiography?
Because the source of x-ray photons is much closer to the patient in fluoroscopy
Grids improve the radiographic image by reducing the amount of scattered radiation fog, but necessitate a/an __ in exposure
increase
During C-arm fluoroscopy procedures. the patient-to-image intensifier distance should be as __ as possible to reduce patient entrance dose
short
How dose fluoroscopic magnification mode affect patient dose?
Magnification mode increases patient dose
According to CFR, Title 21, for continued awareness od patient exposure during fluoroscopic procedures, cumulative air karma is displayed in what unit of measure?
mGya (milligray in air)
What are tow features of digital fluoroscopy that function to reduce patient dose?
pulsed fluoroscopy and last image hold
The exposure switch on mobile x-ray equipment must allow the operator to be at least what distance from the X-ray tube during the exposure?
2m/6 ft
The SSD in mobile fluoroscopy must be at least
30 cm/12 in
The SSD in stationary fluoroscopy must be at least
38 cm/ 15 in
In what type of mobile x-ray equipment dose the kV decrease during the exposure?
Capacitor/condenser discharge mobile units
How is patient entrance exposure (ESE) effected as fluoroscopic SSD is decreased?
Patient ESE increases as SSD is decreased
What must be the lead equivalent of the fluoroscopic image receptor assembly?
2.0 mm Pb equiv
Fluoroscopic total filtration must be at least
2.5 mm AL equiv
The fluoroscopy timber must provide signal after how much fluoroscopic time has elapsed?
5 mins
Fluoroscopic tabletop intensity should not exceed __ per mA operated 80 kV
21 mGya/min (2.1 R/min)
High level control fluoroscopy tabletop exposure must not exceed __
200 mGya/min (20 R/min)
Automatic adjustment of the kV and/or mAs for adequate visualization during fluoroscopic examinations.according to part thickness, s termed __
automatic brightness control (ABC)
