# b413s5a -answers f07 - Not for hand-in BME-413 Biomedical...

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Not for hand-in BME-413 Biomedical Instrumentation Study Questions Set #2a Fall 2007 1. If a physician wears a lead apron having an equivalent of 1 mm lead thickness, by what factor would the x-rays be attenuated if he stood in a 60 KeV beam (assume attenuation coefficient of μ~ 60.0/cm). If the x-ray dose rate was 0.01 Gray per minute on the apron, what dose would he receive during a 1 minute fluoroscopy? How does this compare to a chest x-ray? I=Io exp –ux So I/Io = exp (-60)(0.1) = 0.002 403 times reduction So since QF for x-rays=1 and for 1 minute then the dose is 0.01/403 = 24 microGrays/min x 1min x 1 (QF) =240 microSiemens A chest x-ray is about 200 microSiemens . The physician wouldn’t want to stand in the beam this long. 2. Define the x-ray terms: angiography, fluoroscopy, Gray, RAD. REM. use of contrast agents to show up arteries (angiography) an x-ray moving picture a unit of ionizing radiation absorbed dose Gray and RAD a unit of radiation equivalent exposure REM=RAD * QF 3.

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