1What is the law of Bergonie and Tribondeau
Radiosensitivity of tissue varies with maturation and metabolism
2Stems cells are__? Maturation cells are__?
Radiosensitive; radioresistant
3high metabolic rate is __?
radiosensitive
4low metabolic rate is __?
radioresistant
5young tissue is more__ than older tissue
radiosensitive
6what makes a cell more radiosensitive
increased proliferation and growth rate
7What is L.E.T (linear energy transfer)
rate of which energy is transformed from ionizing radiation to soft tissue per unit length of track
8what is LET measured in?
keV/ um
9Why is LET useful
describes the quality of radiation
10What is low LET
Causes dmg through indirect action and production of free radicals (x-ray; gamma rays) Single strand breaks in DNA
11What is High LET
radiation with substantial mass and charge (alpha particles) ; Double Strand DNA breaks
12What is Relative Biologic effectiveness
capability of radiation with varying LET to produce a biologic response
13What is LET relation to RBE
as LET increases so does RBE (direct correlation)
14What is the equation for RBE
diagnostic x-rays = RBE of 1
15what is protraction and fractionation used for
allows for intracellular repair, tissue recovery and higher total doses; useful for radiation therapy
16what is protraction
dose delivered continuously but at a lower rate and over a longer period of time
17what is fractionation
dose delivered in cycles at equal portions and regular intervals
18what are the biologic factors that affect radiosensitivity
oxygen effect
age
recovery
chemical agents
hormesis
19what is oxygen effect
tissues high in oxygen are more sensitive to radiation (diagnostic x-ray = 3.0 OER
20what happens when dose is large enough to kill cell before division?
interphase death
21Can cells recover from rad dmg after interphase death
no
22what is equation for recovery
interacellular repair + repopulation
23what is a radiosensitizer
increase the effects of radiation (halogenated pyrimidines)
24what is radioprotectors
decrease effect of radiation (cysteine)
25what is hormesis
possible beneficial effect of small amounts of radiation
26what does hormesis do
stimulates hormonal and immune responses and extends life span
27what is radiation dose-response relationships
the relationship between radiation dose levels and the response observed
28what is linear radiation dose- response relationship
directly proportional to dose; dose doubled = response doubles
29what is non-threshold radiation dose - response relationships
regardless of size of dose, a response is expected to be produced
30what follows linear non threshold relationships
radiation induced genetic damage and late effects
31why the linear, nonthreshold dose-response relationship is used as a model for diagnostic imaging radiation management
results can be extrapolated to estimate low dose response from high dose results
32when are threshold radiation dose- radiation relationships used
when dose is larger than 0 and the level below which there is no response
33when is sigmoid curve used
in radiation therapy to show high dose cellular response
34how many rads in 1 Gy
100 rads
35how many rads in 1dGy
10 rads
36how many rads in 1 cGy
1 rad
37how many rads in 1mGy
.1 rad
38what is REM
radiation equivalent man
39what is Sievert
SI unit of equivalent dose
401 Sv equals how many rems
100 REM
411 dSv = how many rem
10 rem
421 cSv = how many rem
1 rem
431 mSv = how many rem
.1 rem
44what are coulombs per kilo or air kerma
SI unit of ionizing radiation exposure
45how many Roentgen in 1 Gya
100 R
46how many R in 1 dGya
10 R
47how many R in 1cGya
1 R
48how many R in 1 mGya
.1 R
49what is numerical value of OER
diagnostic x-ray = OER of 3
50what is numerical value of RBE
diagnostic x-ray = RBE 1