week 7 deterministic effects

what is a deterministic effect

a biologic response whose severity increases with radiation dose and usually has a dose threshold

what is stochastic effect

a radiation effect with no threshold dose where probability increases with dose

what is the main cause of deterministic effects

cell death or loss of normal cell reproduction/function

give examples of deterministic effects

cataracts, sterility, epilation, erythema, acute radiation syndromes, death

what is bystander effect

irradiated cells send signals that alter behaviour of nearby non-irradiated cells

what is genomic instability

genetic mutations and chromosomal damage occuring many cell generations after irradiation

what is adaptive response (hormesis)

low doses of radiation may reduce the effects of a later higher dose

define early effect

radiation response occuring within minutes of days after exposure

define late effect

radiation response not observed until 6 months or more after exposure

what is acute radiation syndrome

a high radiation dose delivered in a short time causing extensive cell death and organ damage

what is chronic radiation syndrome

low doses over long periods causing delayed effects such as cancer or skin changes

what is somatic effects

an effect occuring in the exposed individual during their lifetime

what is genetic effect

damage to reproductive cells that may appear in offspring

what factors affect threshold dose

tissue type, state of health, dose rate, delivery mode/fractionation

what is the haematopoietic syndrome dose range

approx 0.5-10 Gy whole-body exposure

what syndrome occurs at 10-100 Gy

Gastrointestinal (GI) syndrome

what syndrome occurs above 50 Gy

central nervous system (CNS)/ cerebrovascular syndrome

what is LD50/30

dose causing death of 50% of an exposed population within 30 days without medical treatment

what is the estimated human LD50/30

approx 3-5 Gy (about 3.5)

which deterministic syndrome is always fatal and affects intestinal stem cells

gastrointestinal syndrome

how long until death in GI. syndrome

3-10 days ( up to 2 weeks with care)

how long until death in CNS syndrome

1-3 days

what is the threshold dose for cataract formation

>0.15 Sv to the lens of the eye