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Exposure and Effects
H H Exposure and Effects
| Question | Answer |
|---|---|
| Dose limit for radiologic personnel | 5 rem/yr |
| Rem = ?Rad = ?Roentgen | Rad = Rem = Roentgen for x-ray radiation |
| 3 ways to estimate patient dose | 1. Entrance skin exposure 2. Gonadal dose 3. Mean marrow dose |
| Cardinal Principles of Radiation Protection | 1. Minimize time 2. Maximize distance 3. Maximize shielding |
| High level radiation exposure leading to death within days or weeks | Acute Radiation Syndrome |
| 4 Period of Acute Radiation Syndrome | 1. Prodromal 2. Latent 3. Manifest 4. Recovery or Death |
| decreased WBCs, decreased RBCs, and decreased platelets | Hematologic syndrome |
| nausea, vomiting, diarrhea | Gastrointestinal syndrome |
| first nausea and vomiting, then extremely nervous, confused, loss of normal senses, seizures, ataxia, lethargy | CNS syndrome |
| the most radiosensitive macromolecule | DNA |
| more sensitive to radiation when irradiated in an oxygenated state | Tissue |
| the rate at which energy is transferred from ionizing radiation to soft tissue | Linear Energy Transfer (LET) |
| RBE for x-ray | 1 |
| LET increases the biologic damage increases | Relative Biological Effectiveness (RBE) |
| Radiosensitivity varies with maturation and metabolism | Law of Bergonie and Tribondeau |
| high sensitivity to radiation | young tissue |
| High metabolic rate tissues | more radiosensitive |
| Tissue with a high proliferation rate | more radiosensitive |
| Stem cells | radiosensitive – more mature cells are less sensitive |
| Late effects (delayed) presents at 6 months or more | Leukemia, Malignancies, Local Tissue Damage, Shortening of lifespan and Genetic Damage |
| concerns imaging instrumentation and equipment maintenance | Quality Control |
| Make sure the film is not outdated | Quality Control |
| Screens are cleaned | 4x/year |
| concerns patient care and image quality | Quality assurance |
| How many retakes were taken | Quality assurance |
| Is the patient getting the right study for the problem | Quality assurance |
| mAs controls | radiation quantity, film optical density, and patient dose |
| A short exposure time reduces | motion blur |
| KVp controls | radiographic contrast |
| Increasing filtration causes | a reduction of the quantity of x-ray photons but increases the quality of the radiation |
| Increasing the voltage ripple causes | a decrease in both the quality and quantity of the x-ray radiation |
| Increasing the focal film distance | decreases the quantity of radiation at the film but results in no change in the quality of the radiation |
| Increasing mAs or s causes | an increase in the quantity of radiation but no change in the quality of the radiation |
| Increasing kVp causes | an increase in both the quality and quantity of x-ray radiation |
| If x-ray too light need to | increase mAs |
| unequal magnification | Distortion |
| the ability of an image receptor to respond to a low x-ray exposure | Speed |
| wide latitude | Long gray scale |
| describes the amount of the shades of gray | Latitude |
| narrow latitude | Short gray scale |
| equal to the slope of the straight line portion of the characteristic curve | Radiographic contrast |
| determined by the size, shape, and x-ray attenuating characteristics of the subject and the energy (kVp) of the beam | Subject contrast |
| contrast – inherent in the film | Image receptor |
| Latitude and contrast are | inversely proportional |
| Use a long source to image distance (focal film distance) | minimize magnification |
| Use a short object to image distance (object film distance) | minimize magnification |
| image size/object size | Magnification factor (MF) |
| optical density due to development of silver grains that contain no useful information | Fog density |
| optical density on unexposed film – due to composition of the film and the dye that is added to the base | Base density |
| relationship between intensity of exposure and blackness of the film after processing | Sensitometry |
| due to the random nature of x-ray photons | Quantum mottle |
| due to phosphor size on the screens | Structure mottle |
| due to the distribution and size of the silver halide crystals | Film Graininess |
| Scale of contrast | # of shades of gray |
| known as an H and D curve | characteristic curve |
| a graph of optical density and how it relates to exposure | characteristic curve |
| Parts of characteristic curve | toe, straight line, shoulder |
| If the slope is steep | it will show white and black and no grayness |
| more horizontal the slope | tells us how much grayness it has |
| straight line tells us | about the contrast |
| the most important component of characteristic curve | the straight line |
Created by:
hakrrins
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