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Physical Property
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Radiation
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Technical Factors
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WHITE and BLACK terminology *
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Best Uses
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Limitations
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Radiography
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Tissue density
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YES, generally low
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Projection, orthogonal views, inverted image
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White= density, opacity
Black= lucency, low density
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Surveys of large areas, such as chest, abdomen, bones, acute problems like trauma, portable studies
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Lots of overlap, not good for complex shapes, does not discriminate soft tissues, not good for central nervous system
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Contrast Studies
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Tissue density
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YES, moderate to high
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Fluoroscopy, barium vs iodine, digital subtraction
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White= density, opacity
Black= lucency, low density
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Real-time view to assess motion, contrast can be injected into vessels or other body regions
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Still has overlap, not good for central nervous system, invasive, limited in patients with renal failure if using iodine-based contrast
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CT Scans
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Tissue density
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YES, moderate
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Imaging planes, CT windows, oral and IV contrast
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White= density, high attenuation
Black= lucency, low attenuation
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Lungs, lymph nodes, GI tract and abdominal organs, quick survey of central nervous system, acute processes, details of bones
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Limited visibility of detailed structure of central nervous system, uterus, many soft tissues, breast, prostate
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MR Scans
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Tissue magnetic/ chemical properties
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NO
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T1 vs T2-weighted imaging, fat saturation
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White= high signal, bright
Black= low signal
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Detailed examination of central nervous system, uterus, soft tissues around joints, breast, prostate
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Limited visibiliy of lungs, not good detail of bones, not good for GI tract due to motion, not good for acute processes due to long imaging time
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US Scans
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Tissue reflection of sound waves
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NO
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Imaging plane, small field of view, limited depth
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White= echogenic, high echos
Black= anechoic, echo lucent, low echos
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Superficial structures like thyroid, breast, testis, uterus ovaries, some tendons, quantify flow, abdominal organs, portable studies, biopsies
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Blocked by air and bone, so not good for lungs, pancreas if GI gas is present deep bones, limited in patients who are obese
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Nuclear Medicine
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Tissue uptake of radioactive tracer
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YES, moderate
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Position of camera, types of tracers
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White= high uptake, high activity, hot
Black=low uptake, low activity, cold
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Imaging and quantification of normal and abnormal body processes for which a tracer exists
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Images do not show much anatomic detail, not good for trauma or very acute conditions as studies take time
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