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CA Fluoro test
| Question | Answer |
|---|---|
| Maximum intensity (current) for fluoro? | 2.2 rads/min |
| Dose rate should not exceed... | 5rads/min |
| Three elements which increase in scattered radiation | • High kVp • Large field size • Thick body part |
| What is a rad | absorbed dose of patient |
| What is Gray? | SI unit equivalent (1 rad = 100ergs/gram = 0.01 joule/kg = 0.01 Gray) |
| What is REM and what is the max dose? | occupational dose (max = 5 REM/year); absorbed dose equivalent; |
| What is Seivert? | SI unit equivalent (1 rem = 0.01 Sv = 10mSv) |
| What is a half value layer? | thickness of specified substance that reduces exposure rate of 1’ beam by 1/2 |
| 5 elements to reduce patient exposure | Collimate Time, distance, shielding Use “Last frame hold” Short patient-to-detector dist, long source to patient dist High kVp (quality) and low mA (quantity) |
| 5 elements to reduce patient exposure | Pulsed fluoro (lower frame rates) Largest image intensifier mode (non-mag) Video disc recording Avoid grids Use spot film camera / digital photospot |
| Cathode is the ...? | source |
| Anode is the ...? | target |
| Why is Output phosphor is 1000x brighter than input? (4) | because of flux gain, minification, smaller size and additional energy when e- accelerated through |
| What is Compton scattering ? | recoil e- produced and photon energy < incident photon |
| Primary protective barrier | Should intercept the ENTIRE useful bean and the beam generator should not function in its absence |
| Measuring compliance | How ooutput from the XR tube should be calculated |
| XR activation of the tube must be controlled with a device requiring constant pressure, formally called? | Dead-man's switch |
| Fluoro timer, what is it and how long? | Cumuative time in use of XR tube, not to exceed 5 min |
| Minimum source to skin distance? | II fluoro may be 20 cm minimum for specific procedures, otherwise 30cm on portable and 38 on stationary |
| Maximum intensity (current) for fluoro | 2.2 rads/min |
| max Dose rate for fluoro | 5rads/min |
| What is Visual acuity ? | ability to perceive detail |
| what is Integration? | ablility to form object, average for human eye 0.2 sec |
| What is Vignetting? | loss of peripheral image 2/2 image intensity greater at center and less at edges |
| What kind of vision are cones responsible for? | photopic vision, located in fovea centralis (“cones are for color”) |
| CA rads control regs require that protective aprons used during fluoro shall be at least how thick? | 0.25mm lead for body, 0.5mm for gonads |
| The normal viewing distance for binocular vision is: | 10-15 inches |
| the grainy effect is due to photon starvation (low photons), therefore low res and contrast | quantum mottle |
| image intensifier tube lag | image will blur If the XR tube is moved rapidly |
| what is the function of an ABC mechanism of an image intensifier fluoro system ? | Maintain a fixed dose rate to the patient |
| what does ABC stand for | Automatic Brightness Stabilization System |
| Safety features of "boost" (2) | 1. continuous manual activation is required 2. continuous audible signal is required |
| What does "boost" or high control level do? | increases tube current and potential above normal limits |
| When do you use a shaddow shield? | in sterile field or use with incapacitated patients, attached to XR tube housing |
| Minimum distance for target to table top mobile | 12 inches |
| Minimum distance for target to table top standard | 18 inches |
| roentgen (R) | unit of exposure (measures x-ray beam intensity) |
| rad | unit of absorbed dose (measures patient dose) |
| rem | unit of dose equivalent (measures occupational exposure) |
| gray (Gy) | SI unit of absorbed dose (rad) |
| seivert (Sv) | SI unit of dose equivalent (rem) |
| 1 rad = ? rem | 1 |
| 1 rad= ? Gy | 0.01 |
| 1 rem = ? Sv | 0.01 |
| 1 rad = ? erg / gram | 100erg / 1gram |
| 1 roentgen (R) = ? rad | 0.877 rad |
Created by:
katvo
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