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Physics Ch. 7,8,9
chanpter 7,8,9 (bushong)
| Question | Answer |
|---|---|
| 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
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