Rad Bio Flashcards
x-rays, gamma rays are what kind of radiation (charged/particulate)?
neutron?
alpha/beta/proton?
uncharged, non-particulate
uncharged, particulate
charged, particulate
Five radiation characteristics that effects ionization in living tissues
- charge (Q)
- energy (E)
- mass (M)
- velocity (V)
- linear energy transfer (LET)
Greater charge effect on tissue?
Greater ionization
Greater Energy effect on tissue?
greater cell death, greater ionization
Mass of ionizing particle effect on tissue?
Lighter - sparse ionization, follow indirect path
Heavy - Densely ionizing, direct path
Velocity of ionizing particle effect on tissue
Increase velocity = decrease ionizations
Why does increasing velocity of a particle decrease ionization?
slower particle has greater chance of coming close to orbital electron
Linear energy transfer (LET) definition?
avg energy released on ionization per length (keV/um)
High LET particles? Low?
High: alpha, proton, neutron
Low: x-rays, y-rays
LET vs charge? velocity?
LET directly proportional to square of charge
LET inversely proportional to square of velocity
LET proportional to Q^2/v^2
Primary target for cell damage from ionizing rad?
DNA
Double strand DNA break leads to (3)
Cell death
genetic mutations
carcinogenesis
Direct effect of ionizing damage? How much biological damage caused this way?
Direct ionization of macromolecule (DNA); 1/3rd
Indirect effect of ionization damage? How much bio dmg caused this way?
- ionize water to free radical OH and H (and an aqueous electron)
- free radical interacts with DNA
2/3
How fast does damage happen from these mechanisms?
10e-5 seconds
Relation between LET and effect type? Low vs High LET?
Low LET - mostly indirect effect
High LET - mostly direct effect
What is deterministic effect of radiation injury caused by?
Is there a threshold dose?
Severity of effects vs dose?
Probability of having effects?
killing large # cells
YES
Proportional to dose
Will definitely happen
What is stochastic effect of radiation injury caused by?
Is there a threshold dose?
Severity of effects vs dose?
Probability of having effects?
sublethal damage leading to carcinogenesis or heritable mutation
NO, happens at random
Independent of dose
Greater dose = greater chance
Host factors influencing how much damage radiation causes? (7)
Volume of tissue Radiosensitivity of cells/tissue Stage in cell cycle Reproductive capability Age Oxygen Temp
O2 and Temp vs damage
more O2 and higher temp = more damage
Stage in cell cycle with most/least damage?
M - most
S - least
Most radiosensitive cells are (3)
undifferentiated, rapidly dividing, many future divisions
Most sensitive tissue
Least sensitive tissue
Most: bone marrow, intestines, oral mucous membrane, spermatogenic cells
Least: Muscle, brain/spinal chord, erythrocytes (RBCs)
Exceptions to law of Bergonie and Tribondeau
oocytes and small lymphocytes are mature yet still sensitive
Deterministic effects on fetus (4)
Teratogenic effects
- intrauterine death in 1st week
- intra-auterine growth retardation
- congenital malformations
- developmental abnormalities
Stochastic effects on fetus
childhood cancer
Radiogenic effects in stages of gestation:
Preimplantation?
Organogenesis?
Fetal?
Preimplantation: all or none
Organogenesis: congenital abnormalities, growth retardation
Fetal: growth retardation, microcephaly, mental retardation
Fetal dose from dental xray vs dose threshold for birth defects?
Dental xray:
Why do we hold back on dental x-rays then?
to reduce risk of stochastic effects
Acute radiation syndromes chart
yeah the chart
4 Possible therapies for hematopoietic syndrome?
Blood transfusion
Bone marrow transplant
Abx
Isolated environment
oral radiotherapy dose and duration
64-70 Gy in 6-7 weeks
Radiation effect on oral mucosa?
Desquamation
Inflammation/pain
white/yellow pseudomembrane
secondary fungal infection
Long term radio effects on oral mucosa? Heals when?
atrophic thin avascular mucosa
heals after 2 mo
Radiation effect on taste buds? Heals?
lower taste acuity, heals 2-4 mo
Radiation effect on teeth:
prior to calcification?
post-calcification?
Erupted teeth?
pre-calcification: tooth bud destroyed
post-calcification: malformations and arrested growth
erupted: radioresistant
Radiation effect on salivary glands?
reduced secretion/xerostomia
pH altered –> decalcification and radiation caries
radiation effects on bone
damage to vasculature of periosteum and cortical bone
kills osteoblasts :(