Term
| What are the 5 radioopacities? |
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Definition
| gas, fat, fluid/soft tissue, bone/mineral, metal |
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Term
| What are the 4 things that determine X-ray attenuation? |
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Definition
1. Thickness
2. Atomic number
3. Physical density (ie water vs. ice)
4. X-ray energy |
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Term
| What is in the radio cassette that makes the image on the film? |
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Definition
| A phosphorescent screen that illuminates when X-rays hit it. Crystals in the screen glow in proportion to the X-ray energy that hits it. It's the light that exposes the silver on the film by ionizing it. |
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Term
| What's the relationship between "speed" of screen and resolution? |
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Definition
| The larger the crystals (and thicker the screen), the more light they produce, so the faster they produce an image (reducing the exposure time required). However, the larger crystals mean lower resolution. |
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Term
| What has to match between screens and film? |
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Definition
| Color sensitivity (e.g. often blue or green). |
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Term
| What is bremsstrahlung? Where does it come from? |
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Definition
| "Braking radiation." What generates X-rays in an X-ray tube. Electrons are "boiled off" a cathode and voltage applied btw. the cathode and an anode sends them flying toward the anode. They "brake" around tungsten nuclei. |
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Term
| What is the primary product of bremsstrahlung? |
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Definition
| HEAT. (plus a few X-rays) |
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Term
| What are the speed and number of electrons "boiled off" the cathode related to? |
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Definition
Speed depends on the voltage difference between the cathode and anode (kilovolts)
Number of electrons depends on the amperage (milliamperage). |
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Term
| What are the 3 knobs on an X-ray machine? |
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Definition
| kVp (voltage), mA (amperage), and time. |
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Term
| What 2 settings are sometimes combined? |
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Definition
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Term
| What is the combination of settings (3 knobs) referred to? |
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Definition
| A radiographic technique. |
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Term
| What are the standard ranges of kVp, mA, and time? |
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Definition
kVp = 60-120 kVp.
mA = 100-400mA
time = 1/120 - 1/20sec |
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Term
| How do kVp/mA have to change in relation to each other to maintain technique? |
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Definition
| For ever 7-10% change in kVp, mA must change by 2x. When kVp goes up, mA must go down, and vice versa. |
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Term
| Define radiopaque and radiolucent. |
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Definition
Radiopaque: white
Radiolucent: black |
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Term
| How can you improve contrast? |
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Definition
Use low kVp technique
Collimate
Grids (decrease scatter, increase patient dose) |
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Term
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Definition
| When part being X-rayed is >10cm. |
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Term
| What is a Bucky exposure? |
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Definition
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Term
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Definition
1. Reduce patient-film distance
2. Increase tube-film distance |
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Term
| Is the lateral view named for the side towards the tube or cassette? |
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Definition
| The side touching the cassette. |
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Term
| How do you hang radiographs? |
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Definition
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Term
| How much radiation does the average person receive each year? |
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Definition
| 3.6mSv. 3 from natural sources, .6 from manmade ones. Smokers get much more. |
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Term
| What is the maximum permissible dose for people with occupational exposure? |
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Definition
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Term
| How much radiation do vets get? What increased risk of cancer does this correspond to? |
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Definition
| About 4.6 mSv per year (i.e. 1 mSv/year more than average). Increases cancer risk by 0.37%. |
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Term
| What is the ALARA principle? |
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Definition
| Make radiation exposure As Low As Reasonably Possible. |
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Term
| Who should wear a badge to measure radiation exposure? |
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Definition
| Anyone likely to receive >10% of MPD. |
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Term
| Where should badge(s) be worn? |
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Definition
| Outside gown at neck level (to check thyroid exposure) and inside gown at waist level. |
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Term
| How does radiation dose relate to distance from the beam? |
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Definition
| Inversely related to the square of the distance. |
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Term
| Does the lead gown protect a technician from the primary beam? |
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Definition
| NO! Only from scatter radiation. |
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