biological effects of rad

Question 1

Modulator

LET =

Answer 1

linear energy transfer = dE/dl… energy deposited per unit length
high LET = lots of concentrated damage
low results in scattered damage

Question 2

Modulator

RBE= ?

Answer 2

radiological biological effectiveness
have same biological endpoint- comparison of source to reference
RBE = D ref/ D test
RBE ~ QF ~ Wr

Question 3

modulator

mitotic cell cycle

Answer 3

most sensitive M and G2

least in late S phase

Question 4

linear and quadratic effects are equal at…

Answer 4

D = alpha/beta

Question 5

Modulator

Fractionated Radiation

Answer 5

Repair of normal tissue
reassortment
but, could have repopulation if interval too long

Question 6

Modulator

Dose Rate

Answer 6

low dose…a little over time

high dose causes more damage more quickly

Question 7

Modulator

Oxygen effect

Answer 7

low LET radiation have higher effect

presence of oxygen sets the damage

Question 8

Radiation carcinogenesis

Answer 8

it is, esp. at high doses and high dose rates.
good epidemological evidence for acute exposures above 0.2 to 5 Gy
Inversely correlated to age at exposure
females more sensitive
minimum latency…
~ 3 yrs leukemia, 4 yrs bone, 5 yrs thyroid, 10 yrs solid
Mean latency about 20-30 yrs

Question 9

reports

Answer 9

icrp 99
BIER VII
icrp 103. Tissue weighting factors update
preston, et. al….good report on organs

Question 10

heritable effects?

Answer 10

not detectable

Question 11

In Utero

Answer 11

sources… lou wagner wrote the book, or Brent
most risk…1 st trimester
No malformations 100-1000 mGy 3rd trimester
Termination of pregnancy at

Question 12

cataracts

Answer 12

operative cataract odds ratio of 1.4 at 1 Gy
dose threshold seen at 0.1 Gy- upper bound of 0.8 Gy

ICRP 2011 statement on tissue reaction says lens of eye threshold to be 0.5 GY ( limit to 20 mSv/yr averaged over 5 yrs. No single year > 50 mSv)

Question 13

cardiovascular

Answer 13

RT patients effects 1-2 Gy show risk 10-20 yrs later

circulatory disease threshold is now 0.5 Gy to heart or brain per ICRP 2011 statement on tissue reactions

Question 14

Tissue and organ sensitivities

Answer 14

no functional impairment…

Question 15

Background rad in us

Answer 15

~ 6.3 mSv/y with med component

~ 2 mrem/ day

Question 16

Typical general radiology doses

dental

Answer 16

dental...  0.05 mSv
Chest... 0.1 mSv
Head... 0.1 mSv
Mammography...0.7
abdomen...1.2 mSv
pET CT ( CT only)...0.72 mSv
head CT... 2 mSv
chest...7 mSv
abdomen or pelvis...10 mSv
CT angiograpy...13 mSv

Question 17

typical nuclear med

Answer 17

f-18…9 mSv
i-131… 1 mCi 7.5 mSv
tc-99…5 mSv
i-131 therapy…270 mSv

Question 18

Low dose

Answer 18

10 cGy..

below a different group of genes repair damage than the group that repairs higher dose damage

Question 19

expanded paradigm

Answer 19

production of damage is linear

Response to damage is not- different sets of genes

Question 20

Risk

Answer 20

whole population… 5.5% per Sv
adult…4.1% per Sv

Less than ~0.2 Sv… no evidence of any effects

Not for individuals
Aapm PP-25a less than 50mSv don’t use

Question 21

Effective dose- can you use for an individual?

Additional problem with literature…

Answer 21

NO!… it is from average man/woman values to phantoms

When you see effective dose, there is no mention of which icrp report they used…26, 60, or 103… weighting factors change

Question 22

effective dose calcs- how accurate?

Answer 22

order of magnitude!

don’t use decimals…no meaning as accuracy is not good…
Can use to see if doses go up or down.

Question 23

if effective dose cannot be used to assess risk, what can?

Answer 23

effects at low doses require hugh cohorts to assess effects…bomb survivors not that numerous.
had some rad workers that meet numbers…not suitable via BEIR. Bottom line…lots of uncertainty- giving a number is silly.

Question 24

LNT- 2006 French Academy of Sciences

Answer 24

LNT relationship is inconsistent with radiation biologic and experimental data

Damage is linear, but biological response is not

Question 25

Hall

Answer 25

Below 100 mSv, it has not been proven there is any risk.
LNT is used to estimate risk for occupational purposes.
Cannot predict from the data