Unit 6/7

radiation

emission of energy as electromagnetic waves

ionizing radiation

radiation that removes an orbital electron

direct effect

radiation hits radiosensitive molecule directly causing cell damage or death

indirect effect

radiation hits water or other molecule producing free radicals that can poison the cell

free radicals

energetic unchanged molecules with a single unpaired electron in the outer shell

air kerma

amount of energy deposited in a unit of mass of air

absorbed dose

measure transfer of radiation energy into matter, absorbed per unit mass

effective dose

sum of equivalent doses in all specified tissues and organs health risk

dose equivalent

measure of the biological damage to living tissue due to radiation exposure

photon

bundle of energy

various forms of radiation protection (6)

exposure factor, collimation, distance, filtration, shielding, personnel protection

natural environmental radiation (4)

cosmic rays, terrestrial radiation, internally deposited radionucleus, radon

man made radiation (5)

diagnostic radiation, nuclear fuel, research application, industrial sources, consumer items

photoelectric effect

primary xray beam interaction with inner shell electrons in the patient, gives us images

compton effect

the primary beam interaction with the outshell electrons producing scatter and reduced energy

coherent scatter

low energy photons interacting with matter

pair production

interacts with nuclear fields greater than 1.02 MeV

photo disintegration

interaction with energies over 10 MeV, emits a nucleon, destroys nucleus

Bone Z#

13.8

Soft tissue Z#

7.4

Lung Z#

7.4

Fat Z#

6.3

Air Z#

7.6

Lead Z#

82

particulate radiation

uses alpha and beta particles

electromagnetic radiation

uses gamma rays and x rays

5 Radiologic Measurement Units and SI units

-Exposure (GYa)

-Absorbed Dose (Gyt)

-Effective dose/dose equivalent (Sv)

-Radioactivity (Bq)

importance of radiation weighing factors

effectiveness of radiation that can do damage

purpose of dose limit and where are they specified for

the amount of exposure allowed to receive annually on in a life time (whole/partial body, patient, general population, natural source)

dose limits recommended by the NCRP

annual body (5 rem), cumulative body (1 rem x age), annual eye (150 rem), annual thyroid (50 rem), embryo/fetus (0.5 rem), annual 18 under/ public (0.1 rem)

radiation biology

concerned with effects of ionizing radiaztion on living systems

radiosensitive

susceptibilitiy of cells tissues and organs to ionizing radiation

linear energy transfer

rate of energy transfer from ionizing radiation to soft tissue

relative biologic effectiveness

ratio if biological effectiveness of one type of ionizing radiation relative to another

protraction

radiation dose delivered continuously at lower dose rate

fractionation

radiation dose delivered in equal portions at regular intervals

radiosensitizers

sensitizing agents enhance the effect of radiation

radioprotectors

compounds that protect from radiation

short term effects

effects that increase in severity with an increase in dose

long term effects

malignancy and genetic effects due to low doses delivered over a long period

somatic effects

in general body cells, cancer, cataracts, life span shortening

genetic effects

in germ cells, miscarriages birth defects metabolic or biologic changes premature death

long term/stochastic effects examples (2)

leukemia, cancers

short term/deterministric effects (2)

epilation, acute radiation syndrome

nonstochastic effect

LD 50/60

dose to whole body causing 50% of irritated subjects to die in 60 days

how did we learn about radiation biology

physical factors that affect radiosensitivity

linear engery transfer, relative biologic effectiveness, protraction, fractionation

biological factors affecting radiosensitivity

oxygen effect, age, recovery, chemical agents, hormesis

how can radiation effect macromolecules

mainchain scission, cross linking, point lessions

main chain scission

back bone of long chain macromolecules is severed

cross linking

side spurs created by irritation and attach to other segments of the same molecule

pint lesions

disruption of single chemical bonds in a macromolecule

how is DNA directly affected by radiation

cell death, abnormal metabolic activity, damage to future generations

law of bregonie and tribondeau

sensitivity is proportional to metabolic activity of the cell and inversely to their degree of differentiation

factors influencing radiation effects

cell, tissue type, species variation, individual sensitivity, exposure rate, tissue volume

cell type radiosensitivities (high)

lymphocytes, spermatogonia, erythroblasts, intestinal crypt cells

cell type radiosensitivities (intermediate )

endothelial cells, osteoblasts, spermatids, fibroblasts

cell type radiosensitivities (low)

muscle cells, nerve cells

tissue type radiosensitivities (high)

lymphoid tissue, bone marrow, gonads

tissue type radiosensitivities (intermediate)

skin, gastrointestinal tract, cornea, growing bone, kidney, liver, thyroid

tissue type radiosensitivies (low)

muscle, brain, spinal cord

short term effects definition

biologic effects that appear in minutes hours day or weeks after exposure

long term effects on body

biologic effects that appear months or years after exposure

somatic effect on body

genetic effect on body

somatic effects examples

genetic effect examples

stochastic effects (3)

deterministic effects (3)

embryological effects (3)

when is the most critical embryological effect period

how much radiation is required for temporary infertility and sterility

acute radiation syndrome

4 stages of acute radiation syndrome

different acute radiation syndrome

hematologic signs and symptoms (3)

gastrointestinal signs and symptoms (3)

central nervous system signs and symptoms (3)

doses for recovery or death of acute radiation syndrome