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Rad Imag. 2
Ch 8-11
| Question | Answer |
|---|---|
| Xrays in air are measured in | grays |
| The number of xrays in the useful beam define xray | quanitity, exposure, intensity |
| Xray quantity increases in direct proportion to increases in | mAs |
| If SID is reduced by one half the intensity of the image intensity increases | 4 times |
| If filter thickness is increased then xray intensity is | reduced |
| If filter thickness is decreased then xray intensity is | increased |
| Which has the greater effect on increasing density, a 10% increase in kVp or a 10% increase in mAs? | kVp |
| If xray quantity is doubled, the optical density on the finished radiograph will be increased by a factor of | doubled |
| A change from 200 mAs to 400 mAs will cause intensity to ___ and optical density to ___ | double; double |
| An increase of 15% in kVp is equivalent to increasing mAs | 100% |
| The penetrability of an xray beam is called xray | quality |
| An xray that could pass through thick tissue would have high | penetrability and quality |
| Beam quality is affected by | kVp and filtration |
| Image contrast is affected by beam | quality and kVp |
| Xray beam quality is increased by increasing | filtration |
| A compensating filter is used to create | uniform optical density |
| The two primary forms of xray interaction in diagnostic range are | Compton scattering and photoelectric absorption |
| An xray interacts with an atom without ionization during | coherent interaction |
| An outer shell electron is ejected and the atom ionized during | Compton interation |
| Photoelectric absorption involves the ejection of | K shell electrons |
| Compton scatter is directed at ___ angle from the incident beam | any |
| There is compete absorption of the incident xray photon on | photoelectric interaction |
| Only at energies above 10MeV can | photodisintegration take place |
| K shell binding energy increases with increasing | atomic number |
| Bone has greater mass density than | fat, soft tissue, or air |
| Because of differential absorption about __% of incident beam contributes to the image | .5 |
| Differential absorption depends on the | kVp of exposure, atomic number of absorber, and mass density of absorber |
| Attenuation is caused by | absorption and scatter |
| Barium is a good contrast agent because of its | high atomic number |
| A negative contrast agent is | air |
| ____ kVp techniques reduce patient dose | high |
| If 5% of the incident beam are not attenuated then 95% were | absorbed or scattered |
| A high quality radiograph should always demonstrate | structures and tissues |
| Spatial resolution improves with decreased | screen, motion, and geometric blur |
| The ability to image two separate objects and visually detect one from the other is called | resolution |
| High speed IR generally produce images with | increased noise |
| The slope of the straight line portion of the characteristic curve shows the film | contrast |
| A transmission of 10% incident light corresponds to an optical density of | 1 |
| An IR with wide latitude can be used over a great range of | exposures |
| The three primary geometric factors affecting quality are | magnification, distortion, and focal spot blur |
| Way to minimize magnification | long SID and small OID |
| Focal spot blur can be reduced by using a | small focal spot, long SID, and small OID |
| Subject contrast is affected by | patient thickness, atomic number, density, and kVp selection |
| The chest has high subject contrast because of the wide differences in ____ and ____ tissue mass density between air and bone. | atomic number; greatest |
| Radiographic image quality is improved when source image distance is | increased |
| The primary control of radiographic contrast is by varying | kVp |
| Optical density is primarily controlled by | changing mAs |
| Image forming xray are those which have been transmitted without | interaction or absorbed or scattered through compton interaction |
| The % of Compton interaction increases as kVp | increases |
| Approximately ___ % of incident beam is transmitted through the patient. | 0-9 |
| Compton scatter contributes only to image | noise |
| Decreasing kVp will _____ patient dose | increase |
| Photoelectric interaction increases when kVp is | decreased |
| Scatter radiation increase as field size | increase |
| The most common beam restricting device Is the | variable collimator |
| Compression devices will | increase contrast |
| The use of collimation | improves contrast and reduces patient dose |
| Beam restriction with an aperture diaphragm is only accurate at a | fixed distance |
| You can improve image contrast with heavy patients without increasing patient dose by using | tight collimation |
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