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Kilovoltage(kV)
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Milliamperage(mA)
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Chapter two final
| Question | Answer |
|---|---|
| Kilovoltage(kV) | controls the energy(penetrating power) of the x-ray beam |
| Milliamperage(mA) | controls the quantity or number of x-ray produced |
| Exposure time (ms) | controls duration of the exposure usually expressed in milliseconds |
| Image quality factors for radiograph images | Density, Contrast, Resolution and Distortion |
| Density | amount of "blackness" on the produced radiograph |
| Controlling Factors of Density | mA's are main and SID is second |
| Adjusting Film density | mA's of 25% to 30% to make visual change |
| Anode Heel affect | cathode end to thicker part of patient except in chest xrays |
| Contrast | the difference in density between adjacent areas of radio graphic image |
| Controlling Factors of Contrast | kV higher kV produces lower contrast (less shades of grey) 15% increase in kV will increase film density similar to doubling mA's |
| Grids | used for body parts 10 com or more |
| off center grid | the CR is not centered along the center of the axis of the grid |
| Off level grid | CR and grid are not in equal angles |
| off focus grid | must be used a certain SID to prevent grid cut off |
| Up side down grid | grid put in up side down |
| Resolution | recorded sharpness on the image |
| Controlling Factors | focal spot size, SID and object image receptor distance |
| Distortion | misrepresentation of object size or shape |
| Controlling Factors for distortion | SID,OID object image receptor alignment and Central ray alignment |
| Digital Imaging | a numeric representation of the x-ray intensities that are transmitted to the patient |
| Exposure Factors for Digital Imaging | mA's, kV's |
| Image Quality Factors for Digital | Brightness, Contrast, Resolution, Distortion,Exposure index, Noise |
| Brightness | the intensity of a light that represents the individual images on a monitor =(similar to density) |
| Contrast in DI | the difference in brightness light and dark areas of an image |
| Contrast Resolution | ability of an imaging system to distinguish between similar tissue |
| Controlling Factors for Brightness | the screen |
| pixels | a single shade of grey |
| bit depth | the greater the contrast resolution the greater the bit depth |
| Pixel size | acquisition pixel size-minimum size (important one) display pixel size-minimum that can be displayed on monitor |
| Resolution in DI | the recorded sharpness or details of a structure |
| Controlling Factors of Resolution in DI | display matrix, pixel size |
| Distortion | misrepresentation of object size or shape as projected onto radiographic recording media |
| Exposure index | a numeric value that is Representative of the exposure that the IR has received |
| "s" number | inversely proportional to radiation that strikes the IR |
| exposure index | is directly proportional to the radiation that strikes the IR |
| Noise | a random disturbance that obscures or reduces clarity |
| SNR | Signal-to-noise ratio high good low bad |
| Computed Radiology | similar to conventional film screen but using digital |
| Collimation | used to reduce patient dose and scatter |
| 30% Rule | at least 30% of IR must be exposed |
| PACS | picture archiving communication systems |
| DICOM | Digital imaging Communication in Medicine |
| ALARA | As low as reasonably achievable |
| Roentgen (R) | radiation exposure in the air measured on rem( radiation protection) rads (patient dose) |
| Rads | patient dose of radiation |
| occupational recommendations | 5 rem (50 mSv) of whole body effective dose per year |
| general public | *frequent exposure*.1 ren (1 mSv) per year not frequent .5 rem (5mSv) |
| Pregnant technologist | .05 rem (.5 mSv) per month .5 rem (5 mSv) for gestation period |
| ALARA principles | Always wear protection, restraining devices, collimation, proper technique *time distance and shielding* |
| SEE | Skin entrance exposure |
| Effective dose high | male-AP unshielded hip Female-AP thoracic spin w/o breast shields |
| Floro limit | 10 R/min |
| Accurate Collimation | limiting the size and shape of the x-ray beam to only clinical intrest |
Created by:
kelmccauley
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