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Physics Ch. 7,8,9

chanpter 7,8,9 (bushong)

How are useful characteristic xrays produced in tungsten? by removal of a k-shell electron
What is produced when the projectile electron excites an outer shell electron? heat
When are xrays produced? projectile electrons interact with target atoms
Bremsstrahlung radiation is produced by? conversion of projectile electron kinetic energy to electromagnetic energy
In bremsstrahlung xray production the projectile electron is from what? cathode
What projectile electron-target interaction results in xray emission? removal of inner shell electron
The area under the curve of the xray emission spectrum represents what? the total number of xrays
Normally the xray emission spectrum contains what? both characteristic and bremsstralung xrays
The characteristic xray emission spectrum principally depends on which of the following? target material
The continuous xray emission spectrum principally depends on what? projectile electron energy
The xray emission spectrum represents what? xrays emitted from the xray tube
The xray emission spectrum is a plot if what? the number of xrays versus energy
To construct an xray emission spectrum, one most know what? the number of xrays at each energy interval
What characteristic is reduced as xray energy increases? xray wavelength
When the mAs is increased, xray quantity does what? increases proportionately
When distance is increased, xray quantity at that distance does what? Decreases in proportion to the distance squared
When xray tube filtration is increased, xray quantity does what? decreases
In general, xray quantity will increase with what? Increase in kVp
Another meaning of "xray quantity" is xray: intensity
Which of the following does not affect xray quantity? Radioactivity
To maintain a constant optical density, what percentage increase in kVp should be accompanied by a reduction of one half in mAs? 15%
Which of the following is the most appropriate measure of xray beam quality? HVL (half value layer)
The quality of an xray beam is pricipally a function of what? kVp
The HVL (half value layer) is affected principally by a change in what? kVp
When filtration is added to an xray tube, what increases? Radiation quality
As filtration is added to an xray beam, what happens? low energy xrays are removed more readily than high energy xrays
An increase in mAs will increase what? xray quantity
It is often stated that mAs controls quantity and kVp controls what? quality
What will enhance xray beam quality? filtration
What is attenuation? the reduction in xray beam intensity resulting from photoelectric absorption and compton scattering of xrays
The inherent filtration in a general purpose radiographic xray tube is usually equivalent to what? 0.5mm Al
The purpose of a wedge filter in diagnostic radiology is to produce what? a uniform xray beam intensity at the image receptor
Coherent Scattering 1.very low energy keV levels 2.10 keV and lower 3.little importance in diagnostic radiology
Compton's Effect 1.occurs between moderate energy xrays and outer shell e's 2.photons can be deflected in any direction 3.produces unwanted densisties in the form of fog 4.cause of most rad dose to tech during fluoro
Photoelectric effect 1.occurs in the diagnostic range when an incident photon is totally absorbed during ionization of an inner shell e 2.incident photon disappears, and k shell e, now called photoelectron, is ejected from atom 3.produces characteristic radiation
Pair Production 1.occurs when an incoming photon having a minimum 1.02 meV energy, comes close enough to the nucleus force field 2.Is actual proof of Einstein's equation E=mc2
Photodisintegration 1.high energy xray photons, above 10meV 2.absorbed directly by the nucleus 3.emits a nucleon or other nuclear fragments
Anatomic structures that readily transmit xrays are called: radiolucent
Cascading Effect when there is a k shell vacancy and then the L shell fills it, and then the M shell fills the L shell vacancy and so on.
Which interactions are important in the diagnostic area? compton effect and photoelectric
What are most of the xray's energy levels going to be at? most of the xrays are going to be at 1/3 of the energy set
Xray emission spectrum Is a graph of the xray tube output demonstrating the # of xrays vs. the energy of the xrays
Brems form what kind of emission spectrum? continous
Characteristic xrays form what kind of emission spectrum? discrete
What factors can cause a shift or change in the position of the emission spectrum? 1.increasing kV(quality and quantity increase) 2.increasing mA(quantity changes) 3.increase in filtration(quality and quantity increase) 4.target with higher atomic #(only time characteristc line chance,shifts right) 5.change from 1 phase to 3 phase
What does adding filtration do to the beam? it hardens the beam
What filtration is required for a diagnostic unit that operates up to 150 kV? a HVL of 2.5mm Al total filtration is required
Added filtration = what? increased HVL
What are the 3 types of filtration? 1.Inherent: glass,oil (built into tube), 0.5mm Al 2.Added: aluminum sheets, 2.0mm Al 3.Compensating: provide variation in intensity across the xray beam
Differential absorption and attenuation of the beam depend on what factors? 1.atomic # 2.mass density 3.xray energy
Differential absorption? varying degrees of xray absorption in tissues, also determines the contrast of image
List human tissue from lowest to highest effective atomic number? 1.fat 2.soft tissue 3.lung 4.bone
List contrast media from lowest to highest effective atomic number? 1.air 2.iodine 3.barium
List other materials from lowest to highest effective atomic number? 1.concrete 2.molybdenum 3.tungsten 4.lead
What are the xrays called that pass thru the body, unaffected, to the IR? remnant or exit, if interact with IR than image forming
When higher energy exposures are made which interaction decreases? Compton effect
Which interaction produces scatter radiation? Compton effect
Which interaction produces secondary radiation? Photoelectric effect
Which interaction gives image contrast? Photoelectric effect
Which interaction is important to the tech in terms of dose received? Compton effect
Which interaction proves Einstein's equation E=mc2? Pair Production
Anode heat production? most energy of projectile e's are converted into heat, 99%
How are Brems radiation produced? interactions near the nuclei of the atom
How are Characteristic radiation produced? interactions with e's in the inner shell of an atom
Created by: Chrslarsen