Radiation Biology and Safety

Question 1

discuss tissue sensitivity

Answer 1

high sensitivity: in rapidly dividing tissues such as lymphoid organs, bone marrow, gonads, alimentary tract mucosa, skin and other organs with epithelial linings (eye lens)

intermediate: in growing cartilage/bones, also in vessels

low: in established tissues such as mature bone/cartilage, muscle, and the nervous system

Question 2

describe the 2 effects of radiation in the organism

Answer 2

1. stochastic (random): severity is independent of dose but the probability of the occurrence increases with dose; there is no dose threshold (all or non phenomenon); assumes that any amount of radiation has a detrimental effect (there is no safe dose), examples include cause cancer and hereditary effects (if radiation effects gonads)
2. deterministic: a certain minimum dose must be exceeded before the effect occurs; severity increases with dose so there is a practical dose threshold; examples include cause cataracts and skin damage

Question 3

describe ALARA

Answer 3

As Low As Reasonably Achievable

making every effort to maintain exposures to ionizing radiation as far below the dose limits as practical; takes into effect: time, distance, and shielding

time: decrease length of exposure: reduce exposure as much as you can, plan ahead to avoid retakes, and limit people in the room during exposure (and rotate staff)

distance: increase distance from source (and patient): use the inverse square law where the intensity of the radiation decreases in proportion to the square of the change in distance; stay at least 6 feet from source and patient, so use chemical restraint and positioning aids to make this possible

shielding: lead clothing protects from scatter radiation but NOT from the primary beam! so collimate the shit out of everything you can! when possible use standalone body shields or be out of the x-ray room; DO NOT FOLD lead clothing; hang it up to prevent cracks

Question 4

describe personnel monitoring

Answer 4

a legal requirement that applies to all personnel working with any apparatus capable of producing or emitting ionizing radiation and that all personnel must wear dosimeters to measure external radiation exposure to provide a permanent legal record of an individual’s exposure to radiation

Question 5

describe dose limits

Answer 5

1. individuals under 18 years old are not allowed in the radiology suite
2. pregnant women should not be allowed in the radiology suite and OCCUPATIONAL EXPOSURE can only be exposed to up to 5mSv/year; must declare pregnancy and wear a fetal dosimeter as well
3. non-occupational (public) individuals under 18 years old may only be exposed to up to 1 mSv/year
4. occupational individuals may only be exposed to up to 50 mSv/year

these rules can fluctuate based on institution so don’t memorize numbers, just trends!!

Question 6

describe radiation safety faults

Answer 6

1. standing behind/holding cassette = exposed to primary beam radiation and NO distance from primary beam
2. forgoing protective gear
3. placing unprotected hands in primary beam path while holding body part to be x-rayed
4. improper collimation (too big for body part to be x-rayed)