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rad imaging/safety
dangers of radiation and methos to avoid radiation injury.
| Question | Answer |
|---|---|
| Three things are used to determine the diagnostic quality of an image. | Density, contrast, detail |
| What is Density? | degree of blackness on a radiograph. Increasing the mA, increases the blackness of the film, mA=quantity of x-rays produced. |
| What is Contrast? | the number of shades of gray on a radiograph inversely controlled by the kVp. Increasing the kVP decreases the contrast of the film. Decreasing Kvp increases the constrast of the film. kVp=the force/speed of the x-rays |
| evaluation of technique: Exposure | radiograph underexposed (white) = too bright Increase kVp or Mas Radiograph overexposed (black) = too dark Decrease kVpor mAs |
| What is Detail? | radiographic detail is necessary when trying to note the interfaces between various tissues and organs. Can be affected by patient motion, penumbra effect, distortion, scatter radiation. |
| Penumbra effect | loss of detail resulting from x-rays originating different spots on the anode. x-rays than take different angles to hit the same point on the detector. |
| Reducing Penumbra effect | increasing the source image receptor distance (SID), decreasees the penumbra effect. Object image distance (OID): distance from the object being imaged to the film or image receptor. Penumbra is decreased by keeping the OID as short as possible. |
| Distortion | occurs when the subject is not parallel to the image receptor. Preventing distortion: decrease object image receptor distance (OID) as much as possible, keep object parallel, keep x-ray beam perpendicular, take multiple images of the area of interest. |
| types of distortion | magnification: object is not as close to the image receptor making it looks larger than its actual size. Elongation: image appears longer than the actual size of the image. Foreshortening: image appears shorter than the actual size of the image. |
| Scatter radiation | decreasing scatter radiation decreased the "fogging" of the film |
| Protection Practices | Collimate to the area of interest 2.5mm aluminum fiber should be used on exposure coming from the tube. Use correct setting to decrease exposures. Do not allow any operator body parts to encounter the primary beam Wear proper PPE. |
| Protection Practices pt.2 | Use correct accessory equipment (cassette holders, restraint equipment) Anesthetize or sedate pt if possible. Only required personnel should be in the x-ray room. Pregnant women and those under 18yrs old should not be in the room. |
| Protection Practices pt.3 | Keep as much distance from the primary beam as possible and look away from the beam. Calibrate and maintain x-ray machine on a regular basis. Follow radiation safety codes. |
| Radiation Safety | Absorption of radiation above a certain amount change or alters the tissues. |
| Tissues most susceptible to radiation | - skin - lymphatic tissue hematopoietic - leukopoietic tissue - breast tissue - thyroid bone - germinal tissue/gonads - radiodermatitis/ |
| Radiation Damage | Stochastic effect: radiation damage over time, examples: malignancy, sterility, anemias, cataracts. Genetic effects: radiation damage to the DNA of the recipients reproductive cells Seen in future generations. |
| Primary Beam | Radiation direct from the x-ray tube. Higher energy x-ray beam. |
| Scatter Radiation | radiation produced from the primary beam hitting and bouncing in all directions. Main cause of radiation exposure. |
| Leakage Radiation | Radiation leaking from the x-ray machine. Rarely occurs due to the newer machines providing adequate filtration. |
| Absorbed dose | how much radiation the pt is absorbing. Gray(Gy) Radiation Absorbed Dose (RAD) 1 Gy = 100 rad |
| Dose Equivalent | How much radiation the operator is receiving. Sievert (Sv) Roentgen equivalent in man/mammal (REM) 1 Sv = 100 REM Roesntegen |
| Measured Radiation | Measures the radiation in the air, leakage from the machine, etc. airKerma (Gy), Coulomb/kg (C/kg) |
| Maximum Permissible Dose (MPD) | the maximum does of radiation a person is allowed to receive during occupational exposure over a specified time. If one exceeds their MPD they are likely to experience physical effects from radiation exposure. |
| NCRP | The National Council on Radiation Protection and Measurements sets levels for exposure and has developed ALARA (as Low as Reasonably Achievable) Occupational person MPD = 0.05 Sv/year Non-Occupational person MPD = 0.005 Sv/year |
| Dosimeters | measurement of personal radiation exposure. they are sensitive so they should be stored well when not in use. Used for a set time then mailed back to the company to be measured. Reports are returned indicating how much was received. |
| PPE | Types: - lead gowns - lead gloves - thyroid shield - lead based glasses - All PPE should be >0.5mm thick - Lead gloves must be >0.25mm thick |
Created by:
user-2018406