Chapter 10 Notes Flashcards
primary protective barriers are designed to
protect against direct exposure to primary x-ray beam
secondary protective barriers are designed to
protect against exposure from scatter and leakage radiation
current recommendation by the NCRP that equivalent dose limit for embryo-fetus not exceed
0.05 rem (0.5 mSv) in any month, once the pregnancy becomes known
NCRP collects, analyzes, develops, and disseminates information on
radiation protection, radiation measurements, quantities, and units
regulatory agencies
NRC and FDA
stochastic effects
no threshold; random in nature; regardless of amount of dose, some will experience effect
with stochastic effects, as dose increases
chance of occurrence increases
deterministic effects
threshold; once threshold is surpassed, increase in dose will increase severity of response
dose limits for general public
5 mSv (0.5 rem) for infrequent exposure; 1 mSv (0.1 rem) for continuous exposure
cardinal rules of radiation protection
minimize time, maximize distance, and shielding
what is your last line of defense
sheilding
field size should never be larger than
IR
collimation does what
reduces patient dose and improves image quality
technique selection
high kVp/low mAs
filtration removes what photons
low-energy
most common filter material
aluminum
2.5-mm aluminum equivalent (Al/eq) filtration required when operating at or above _____
70 kVp
patient dose is still reduced with greater filtration by
reducing patient skin exposure when removing low-energy photons
use _____ possible grid ratio to effectively remove scatter, without jeopardizing image quality
lowest
gonadal shielding should be used any time gonads lie within _____ of primary beam
5 cm
three types of gonadal shielding
flat contact, shaped contact, and shadow shields
IR speed
fastest possible IR system will minimize patient dose
patient exposure estimates
should be developed and available for routine procedures on average patients
equipment should be surveyed annually by
radiologic medical physicist
BEIR V report states that the fetus is particularly radiosensitive from _____ weeks gestation
8-15
monthly equivalent dose limit for fetus
0.5 mSv (0.05 rem) per month once pregnancy is declared
risk at _____ negligible compared to other risks
5 rad
risk of malformation significant at
15 rad
dose equivalent _____ to declared pregnant woman for entire pregnancy
5 mSv (0.5 rem)
pregnancy declaration according to NRC must be
in writing, dated, include estimated date of conception
assignment of pregnant workers to areas of lower exposure violates
application of ALARA for other workers
