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# Xray Emission

### Bushong (9th; Ch 9)

A measure of the number of ion pairs produced in air by a quantity of x-rays roentgen (R) or milliGray [subscript a] (mGya)
the number of x-rays in the useful beam x-ray quantity
X-ray intensity of most general purpose radiographic tubes, when operated at approx. 70 kVp 5 mR/mAs (50 μGya) at 100cm SID
Units of x-ray intensity roentgens (R), mGya, mR/s, mR/min, or mR/mAs
X-ray quantity or intensity; measured in roentgens (R) radiation exposure
radiation ________ = x-ray _________ = _____ quantity exposure; intensity; x-ray
x-ray ________ is ________ proportional to the mAs quantity; directly
a measure of the total number of electrons that travel from cathode to anode to produce x-rays milliampere seconds (mAs)
a measure of the electrostatic charges; 6.25 x 10¹⁸ electrons Coulomb (C)
Formula for x-ray quantity & mAs I₁/I₂ = mAs₁/mAs₂
Formula for x-ray quality & kVp I₁/I₂ = (kVp₁/kVp₂)²
X-ray ________ is ____________ to the kVp² quantity; proportional
mC = ___ mAs
For optical density to remain constant, if kVp is increased by ___ then mAs should be _______ by ½ 15%; reduced
X-ray quantity is _________ proportional to the square of the ________ from the ______ inversely; distance; source
X-ray intensity varies _________ with the ______ of the ________ from the x-ray tube ______ inversely; square; distance; target
Formula for x-ray quantity & distance I₁/I₂ = (d₂/d₁)²
Square Law mAs₁/mAs₂ = (SID₁)²/(SID₂)²
When SID is increased, ___ must be increased by ____ to maintain constant exposure to the IR mAs; SID²
Purpose of filters reduce number of low-energy x-rays
Commonly used metal filter 1-5mm Al
Adding __________ to the useful x-ray beam reduces _______ ____. filtration; patient dose
Disadvantage of ↑ kVp & ↓ mAs for OD to remain constant ↓ image contrast
Disadvantage of added filtration ↓ image contrast
increases the number of high energy x-rays in the beam by removing the lower-energy nonpenetrating x-rays beam hardening
one description of the ability of x-rays to penetrate deeper in tissue penetrability
the penetrability of an x-ray beam x-ray quality
X-rays of any given energy are more penetrating in material of ____ atomic number than in material of ____ atomic number low; high
the reduction in x-ray intensity that results from absorption & scattering attenuation
the thickness of absorbing material necessary to ↓ reduce the x-ray intensity to ½ of its original value Half-value layer (HVL) of an x-ray beam
HVL of diagnostic x-ray beam 3-5mm Al, or 3-6cm soft tissue
the best method for specifying x-ray quality HVL
X-ray beam quality can be identified by _______ or __________, but ___ is most appropriate voltage; filtration; HVL
Atomic number of aluminum (AL) 13
Atomic number of gadolinium 64
Atomic number of holmium 67
Atomic number of copper (Cu) 29
Atomic number of tin 50
Increasing the ___ peak _________ the quality of an x-ray beam kVp; increases
Amount of total filtration 2.5mm Al
Increasing filtration increases the _______ of an x-ray beam quality
Atomic number of Beryllium 4
↑ filtration = ↑ beam _______ = ↓ beam ________ quality; quantity
part of the glass or metal enclosure of an x-ray tube through which x-rays are emitted window
reason why window is thin provides for low inherent filtration
type of filtration provided by the glass or metal enclosure of an x-ray tube; filters emitted x-ray beam inherent filtration
inherent filtration of a general purpose x-ray tube 0.5mm Al equivalent
type of special purpose tube with very thin window mammography
inherent filtration of mammography unit 0.1mm Al; sometimes made of Beryllium rather than glass
Added filtration results in ↑ ___ HVL
Added filtration resulting from the silver surface of the mirror in the collimator 1mm Al equivalent
material inserted between an x-ray source & a patient to shape the intensity of the x-ray beam; an x-ray beam filter designed to make the remnant beam more uniform in intensity compensating filter
special filters used with CT imaging systems to compensate for the shape of the head or body "bow-tie"-shaped filters
type of filter sometimes used in chest radiography; thin region over mediastinum & thick portions lateral over lung fields bilateral wedge filter; trough filter
type of filter applicable to digital fluoroscopy, where the IR, the image intensifier tube, is round; can be concave or convex conic filters
type of filter that compensates for OD variation of body parts that vary considerably in thickness wedge filter
type of filter used in special procedures involving long sections of anatomy on 2 or 3 separate IRs step-wedge filter