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