8: Radiation Safety - Mahoney

Question 1

stochastic effects

Answer 1

responses where probability of occurrence increases with dose

• the higher the dose, the greater chance of effects

Question 2

deterministic/nonstochastic effects

Answer 2

severity of response increases with does

-higher the dose, the more severe the response

Question 3

do not have a threshold dose and are observed for months or years

Answer 3

stochastic effects

Question 4

result from low radiation doses over along time

Answer 4

stochastic effects

Question 5

leukemia, bone, breast and lung CA

cataracts and radiodermatitis

Answer 5

stochastic effects

Question 6

have threshold dose which needs to be exceeded before response is seen and severity of response proportional to dose

Answer 6

deterministic effects

Question 7

occur early within min or days

Answer 7

deterministic effects

Question 8

radiation sickness
skin desquamation
congenital malformations

Answer 8

deterministic effect

Question 9

most sensitive tissues

Answer 9

bone marrow > lymphocytes > GI

Question 10

most resistant tissue

Answer 10

CNS

Question 11

law of bergonie and tribondeau

Answer 11

sensitivity of tissues depends upon proliferative capacity

rapidly dividing cells are more sensitive than slow

fully differentiated cells are less sensitive

Question 12

4 physical factors affecting radiosensitivity

Answer 12

• LET linear energy transfer (measure of amount of energy transferred along path of radation) (xrays low; alpha particles high)
• relative biological effectiveness (one form of radiation compared to another)
• protraction ( dose to neoplasm delivered continuously but at lower dose rate)
• fractionation (same dose to neoplasm delivered in equal fractions separated by time)

Question 13

*** biologic factors affecting radiosensitivity

Answer 13

• more sensitive in oxygenated state
• utero and old age most sensitive
• males more sensitive
• can recover if not killed before next division
• sulfhydryl groups are radioprotective
• vit K, methotrexate, actinomycin D are radiosensitizers

Question 14

linear

nonlinear

Answer 14

response directly proportional to dose

response not directly proportional

Question 15

threshold

nonthreshold

Answer 15

no response produced at a dose below the threshold dose

any size dose is expected to produce a response

Question 16

direct v. indirect

Answer 16

interacts directly with a molecule like DNA

caused by free radicals formed from ionizing radiation interacting with body

Question 17

*** estimated avg annual whole body dose of ionizing radiation from natural sources is…

Answer 17

300 mrem or 3 mSv

Question 18

estimated avg annual whole body dose of ionizing radion from man-made sources is

Answer 18

630 mrem or 6.3mSv

Question 19

cumulative annual dose for an adult is …

Answer 19

1/10 of age in yrs X 1 rem

ex: 40 yo — 4 rem or 4000 mrem

Question 20

for pregnancy…

Answer 20

use high kVp technique and precise collimation of beam

Question 21

entrance dose of foot xray =

Answer 21

less than 1 rad (1mGy)

[therapeutic abortion not indicated if fetal dose is less than 10 rad (10mGy)

Question 22

effects of more than 10 rad radiation to fetus

Answer 22

2wks - spontaneous abortion or no effect

2nd-8th wk - congenital abnormalities of skeleton or nerves

2nd-3rd trimester - leukemia could occur in childhood

Question 23

define dose limit

Answer 23

amount of radiation that if received annually runs the risk of death to 1 in 10,000

Question 24

cumulative annual whole body occupational exposure

Answer 24

age (yrs) x 1 rem

Question 25

*** Limits for occupationally exposed to radiation
annual effective =
cumulative annual effective =
equivalen annual dose fo rskin, hands, feet =
equivalent annual dose for lens of eye =
pregnant =

Answer 25

50 mSv or 5 rem

10 mSv or 1 rem x age

500 mSv

150 mSv or 15 rem

5 mSv (.5 rem for the 9 mo of preggers)

Question 26

limit for children less than 18

Answer 26

1 mSv (100 mrem) for annual exposure

Question 27

limits for adult public

Answer 27

1/10- that of radiation workers

Question 28

typical exposure rate at the xray beam entrance into pt with fluoroscopy

Answer 28

2R/min

limit is 10R/min (why 5 min bell)

Question 29

an operator position 3 ft from the xray beam entrance area will receive ___ of the pts ESE

Answer 29

0.1%

standing one step further away from the pt can cut the physician’s exposure rate by a factor of 4

dose rates reduced by factor of 5 when physician stands on image recepotr side of table during a lateral projection

Question 30

who is required to wear lead aprons?

Answer 30

everyone in room or w/i 2 m if using a mobile c-arm