Xray Emission Spectrum Flashcards
Types of spectrum
Discrete
Continuous
Contains only specific values
Discrete spectrum
All possible values
Continuous spectrum
Have a range of energies and form a continuous emission spectrum
Bremsstrahlung X-rays
Precisely fixed energies and form the discrete emission spectrum
Characteristic X-rays
Adding up the total number of x-rays over the entire spectrum emitted
Integration
Characterized by quantity and quality
X-ray beam
Number of X-rays in the beam
Quantity
Penetrability of the beam
Quality
Intensity of the beam is measured in
Roentgens (R)
milliroentgens (mR)
mGya
Intensity of the X-ray beam
X-ray quantity
Amount of X-rays
Quantity of X-rays
Measure of the number of ion pairs produced in air by quantity of xrays
Roentgen (mGya)
Ionization of air increases
Number of X-rays on the beam increases
Exposure rate is expressed in
mR/s
mR/min
mR/mAs
Larger the area under the curve
Higher is the X-ray intensity or quantity
Factors affecting X-ray quantity
mA or mAs
kVp
Filtration
Voltage waveform
Doubling the mA or mAs will produce
Twice as many X-ray at every energy
Change in mA or mAs results in
Proportional change in the amplitude of the X-ray emission spectrum
Change in kVp affects
Both the amplitude and position of the X-ray emission spectrum
Area under the curve and the output intensity is
Proportional to the square of the ratio of the kVp change
15% increase in the kVp
Equivalent to doubling the mAs
Metal filters ranges from
1 to 5 mm of Aluminum
Purpose of filtration
Reduce the number of low energy X-rays
Adding filtration to the useful beam
Reduces patient dose
Reduced X-ray beam intensity
Added filtration
Absorbs low energy X-rays
Added filtration
Hardens the beam because of its relative increase in average energy
Added filtration
Produce the lowest voltage ripple
High frequency generators
Regular variation in a direct current voltage
Voltage ripple
Quantity of X-rays is
Much greater at peak voltages than at lower voltages
Energy of the beam increases
Penetrability also increase
Ability of X-rays to penetrate deeper in the tissue
Penetrability
Penetrability of X-ray beam
X-ray quality
Process of removing low energy X-rays
Filtration
Filtered X-ray beam
Monoenergetic (reduced patient dose)
Improve contrast means
To remove X-rays with energies above certain levels
Removal of regions of an X-ray beam
Not normally possible
Efficient in removing low energy X-rays through photoelectric effect
Aluminum
Aluminum is
Readily available
Inexpensive
Easily shaped
Types of filtration
Inherent
Added
Glass or metal enclosure
Inherent filtration
Window provides
A low inherent filtration
Inherent filtration is approx.
0.5mm Al equivalent
X-ray tube used in mammography have
Very thin X-ray tube window (equivalent of 0.1mm Al filtration)
Thin sheet of aluminum positioned bet the protective housing and X-ray beam collimator
Added filtration
Range of values of any quantity such as X-rays
Spectrum
