Rad Bio

Question 1

x-rays, gamma rays are what kind of radiation (charged/particulate)?
neutron?
alpha/beta/proton?

Answer 1

uncharged, non-particulate

uncharged, particulate

charged, particulate

Question 2

Five radiation characteristics that effects ionization in living tissues

Answer 2

1. charge (Q)
2. energy (E)
3. mass (M)
4. velocity (V)
5. linear energy transfer (LET)

Question 3

Greater charge effect on tissue?

Answer 3

Greater ionization

Question 4

Greater Energy effect on tissue?

Answer 4

greater cell death, greater ionization

Question 5

Mass of ionizing particle effect on tissue?

Answer 5

Lighter - sparse ionization, follow indirect path

Heavy - Densely ionizing, direct path

Question 6

Velocity of ionizing particle effect on tissue

Answer 6

Increase velocity = decrease ionizations

Question 7

Why does increasing velocity of a particle decrease ionization?

Answer 7

slower particle has greater chance of coming close to orbital electron

Question 8

Linear energy transfer (LET) definition?

Answer 8

avg energy released on ionization per length (keV/um)

Question 9

High LET particles? Low?

Answer 9

High: alpha, proton, neutron

Low: x-rays, y-rays

Question 10

LET vs charge? velocity?

Answer 10

LET directly proportional to square of charge

LET inversely proportional to square of velocity

LET proportional to Q^2/v^2

Question 11

Primary target for cell damage from ionizing rad?

Answer 11

DNA

Question 12

Double strand DNA break leads to (3)

Answer 12

Cell death
genetic mutations
carcinogenesis

Question 13

Direct effect of ionizing damage? How much biological damage caused this way?

Answer 13

Direct ionization of macromolecule (DNA); 1/3rd

Question 14

Indirect effect of ionization damage? How much bio dmg caused this way?

Answer 14

1. ionize water to free radical OH and H (and an aqueous electron)
2. free radical interacts with DNA

2/3

Question 15

How fast does damage happen from these mechanisms?

Answer 15

10e-5 seconds

Question 16

Relation between LET and effect type? Low vs High LET?

Answer 16

Low LET - mostly indirect effect

High LET - mostly direct effect

Question 17

What is deterministic effect of radiation injury caused by?

Is there a threshold dose?

Severity of effects vs dose?

Probability of having effects?

Answer 17

killing large # cells

YES

Proportional to dose

Will definitely happen

Question 18

What is stochastic effect of radiation injury caused by?

Is there a threshold dose?

Severity of effects vs dose?

Probability of having effects?

Answer 18

sublethal damage leading to carcinogenesis or heritable mutation

NO, happens at random

Independent of dose

Greater dose = greater chance

Question 19

Host factors influencing how much damage radiation causes? (7)

Answer 19

Volume of tissue
Radiosensitivity of cells/tissue
Stage in cell cycle
Reproductive capability
Age
Oxygen
Temp

Question 20

O2 and Temp vs damage

Answer 20

more O2 and higher temp = more damage

Question 21

Stage in cell cycle with most/least damage?

Answer 21

M - most

S - least

Question 22

Most radiosensitive cells are (3)

Answer 22

undifferentiated, rapidly dividing, many future divisions

Question 23

Most sensitive tissue

Least sensitive tissue

Answer 23

Most: bone marrow, intestines, oral mucous membrane, spermatogenic cells

Least: Muscle, brain/spinal chord, erythrocytes (RBCs)

Question 24

Exceptions to law of Bergonie and Tribondeau

Answer 24

oocytes and small lymphocytes are mature yet still sensitive

Question 25

Deterministic effects on fetus (4)

Answer 25

Teratogenic effects 1. intrauterine death in 1st week 2. intra-auterine growth retardation 3. congenital malformations 4. developmental abnormalities

Question 26

Stochastic effects on fetus

Answer 26

childhood cancer

Question 27

Radiogenic effects in stages of gestation: Preimplantation? Organogenesis? Fetal?

Answer 27

Preimplantation: all or none Organogenesis: congenital abnormalities, growth retardation Fetal: growth retardation, microcephaly, mental retardation

Question 28

Fetal dose from dental xray vs dose threshold for birth defects?

Answer 28

Dental xray:

Question 29

Why do we hold back on dental x-rays then?

Answer 29

to reduce risk of stochastic effects

Question 30

Acute radiation syndromes chart

Answer 30

yeah the chart

Question 31

4 Possible therapies for hematopoietic syndrome?

Answer 31

Blood transfusion Bone marrow transplant Abx Isolated environment

Question 32

oral radiotherapy dose and duration

Answer 32

64-70 Gy in 6-7 weeks

Question 33

Radiation effect on oral mucosa?

Answer 33

Desquamation Inflammation/pain white/yellow pseudomembrane secondary fungal infection

Question 34

Long term radio effects on oral mucosa? Heals when?

Answer 34

atrophic thin avascular mucosa heals after 2 mo

Question 35

Radiation effect on taste buds? Heals?

Answer 35

lower taste acuity, heals 2-4 mo

Question 36

Radiation effect on teeth: prior to calcification? post-calcification? Erupted teeth?

Answer 36

pre-calcification: tooth bud destroyed post-calcification: malformations and arrested growth erupted: radioresistant

Question 37

Radiation effect on salivary glands?

Answer 37

reduced secretion/xerostomia | pH altered --> decalcification and radiation caries

Question 38

radiation effects on bone

Answer 38

damage to vasculature of periosteum and cortical bone | kills osteoblasts :(