Oral Rad Unit 5 Test

the study of the effects of ionizing radiation on living tissue, to understand the harmful effects of x-radiation

radiation biology

produced through the photoelectric effect or Compton scatter and results in the formation of a positive atom and a dislodged negative electron

ionization

x-radiation causes cell damage primarily through the formation of ___?

free radicals

occurs when an x-ray photon ionizes water

free radical

primary component of living cells

water

an uncharged atom or molecule that exists with a single, unpaired electron in its outermost shell

free radical

what is the lifetime of a free radical

10 ^ -10 seconds

how do free radicals achieve stability

• recombine without causing changes in molecule

• combine w/ other free radical and causes changes

• combine w/ ordinary molecules to form a toxin peroxide capable of producing widespread cellular change

what are the 2 theories used to describe how radiation damages biological tissue

1. direct theory

2. indirect theory

suggests that cell damage results when ionizing radiation directly hits critical areas, or targets within the cell

direct theory

suggests that x-ray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell

indirect theory

an ___ injury occurs when free radicals combine and form toxins, not because of a direct hit of x-ray photons

indirect

why are the chances of free radical formation and indirect injury great

because cells are 70-80% water

used to correlate the “response” or damage, of tissue with the “dose” or amount of radiation received

dose-response curve

when dose and damage are plotted on a graph a _____ is seen

linear, non-threshold relationship

what does a linear relationship indicate

response of tissue is directly proportional to the dose

what does a non threshold relationship indicate

threshold dose level for damage does not exist

suggests that no matter how small the amount of radiation received, some biological damage does occur

non-threshold dose-response curve

threshold curve

linear curve

essentially the same as the linear curve

linear non-threshold curve

the deleterious effects of ionizing radiation on human tissue can be divided into two types. what are they?

• stochastic

• non stochastic

occur as a direct function of dose

stochastic effects

do not have a dose threshold

stochastic effects

occur as a result of the effect of ionizing radiation on chromosomes that result in genetic mutations

stochastic effects

ex of stochastic effects

induction of leukemia and other cancers

have a threshold and increase in severity with increased absorbed dose

non stochastic effects

occur only after a threshold of exposure has been exceeded

nonstochastic effects

what are non stochastic effects caused by

significant cell damage or cell death

ex. of non stochastic effects

• skin erythema

• loss of hair

• cataract formation

• decreased fertility

• radiation sickness

• teratogenesis

• fetal death

“deterministic effects”

non stochastic effects

requires larger radiation dose to cause serious impairment of health

nonstochastic

defined as the time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs

latent period

the more radiation received and the faster the dose rate, the ___ the latent period

shorter

after the latent period, a ____ occurs

period of injury

a variety of cellular injuries may result, including cell death, changes in cell function, breaking or clumping of chromosomes, formation of giant cells, cessation of mitotic activity, and abnormal mitotic activity

period of injury

what is the last event in the sequence of radiation injury

recovery period

with each radiation exposure, cellular damage is followed by ___?

repair

the ____ of repeated radiation exposure can lead to health problems

cumulative effects

factors used to determine the degree of radiation injury

• total dose

• dose rate

quantity of radiation received, or the total amount of radiation energy absorbed

total dose

rate at which exposure to radiation occurs and absorption takes place

dose rate

true or false:

children are more susceptible to radiation damage than are adults

true

more damage occurs to cells that are most sensitive to radiation, such as ___?

rapidly dividing cells

young cells

extensive radiation injury occurs when large areas of the body are exposed because of the damage to the ______?

blood-forming tissues

after the latent period, effects that are seen within minutes, days, or weeks are termed as __?

short-term effects

associated with large amounts of radiation absorbed in a short time

short-term effects

a short term effect that causes nausea, vomiting, diarrhea, hair loss, and hemorrhage

acute radiation syndrome

effects that appear years, decades, or generations

long term effects

associated with small amounts of radiation absorbed repeatedly over a long period

long term effects

linked to the induction of cancer, birth abnormalities, and genetic factors

repeated low levels of radiation

all the cells in the body can be classified as either ____ or ___

somatic or genetic

all the cells in the body except for the reproductive cells

somatic cells

the reproductive cells are termed _____

genetic cells

depending on the type of cell injured by radiation, the biologic effects of radiation can be classified as or

somatic or genetic

seen in a person who has be irradiated

somatic effects

are somatic effects transmitted to future generations

no

major somatic effects of radiation exposure include ___

induction of cataracts and cancer including leukemia

are not seen in the irradiated person but are passed on to future generations

genetic effects

radiation injures that produces changes in genetic cells ____ affect the health of the exposed individual

do not

cannot be repaired

genetic damage

basic structural unit of all living organisms

cellw

what is a cell composed of

central nucleus and surrounding cytoplasm

the cell ___ is more sensitive to radiation than is the ____

nucleus; cytoplasm

damage to the nucleus affects the what?

chromosomes containing DNA and results in disruption of cell division

a cell that is sensitive to radiation

radiosensitive

a cell that is resistant to radiation

radioresistant

the response of a cell to radiation exposure is determined by what?

• mitotic activity

• cell differentiation

• cell metabolism ells

cells that have higher ____ are more sensitive to radiation

metabolism

what are some cells that are radiosensitive

• blood cells

• immature reproductive cells

• young bone cells

cell that is most sensitive to radiation

small lymphocyte

what are some cells that are radioresistant

• bone

• muscle

• nerve

radiosensitive organs

• lymphoid tissues

• bone marrow

• testes

• intestines

radio resistant organs

• salivary glands

• kidney

• liver

an organ, that if damaged, diminishes the quality of a persons life

critical organ

critical organs

• thyroid gland

• bone marrow

• skin

• lens of the eye

units are used to describe 3 quantities of radiation, what are they?

• exposure

• dose

• dose equivalent

2 systems are used to define radiation measurements, what are they?

1. traditional system (standard system)

2. SI system (international system of units)

the traditional units of radiation measurement include: ?

• roentgen(R)

• radiation absorbed dose(rad)

• roentgen equivalent (in) man (rem)

the SI units of radiation measurement include: ?

• coulombs/kilogram (C/kg)

• gray (Gy)

• sievert (Sv)

refer to the measurement of ionization in air produced by x-rays

exposure

what is the traditional unit of exposure for x-rays

roentgen (R)

The quantity of x-radiation or gamma radiation that produces and electrial charge of 2.58 × 10 ^ -4 coulombs in a kilogram of air at a standard temperature and pressure conditions

roentgen (R)

one roentgen is equal to the amount of radiation that produces approximately _______?

2 billion, or 2.08 × 10 ^ 9 ion pairs in one cubic centimeter of air

limited to measurements in air only

roentgen (R)

only used for x-rays and gamma rays

roentgen (R)

exposure is stated in ___

coulombs per kilograms

unit of electrical charge

coulombs

measures the number of electrical charges or the number of ion pairs in 1 kg of air

C/kg

conversions for roentgen and coulombs per kilogram

• 1 R = 2.58 × 10 ^ -4 C/kg

• 1 C/kg = 3.88 ×10 ^ 3 R

defined as the amount of energy absorbed by a tusk

dose

traditional unit of dose

rad

can be applied to ALL forms of radiation

rad

measures radiation absorbed by the body but does not take into account the radiosensitvity of different tissues

rad

a special unit of absorbed dose that is equal to the deposition of 100 ergs of energy per gram of tissue

rad

using SI units, 1 rad is equivalent to _____ joule per kilogram

0.01

the SI unit equivalent unit to the rad is the ___

Gy or 1 J/kg

conversions for rad and Gy

• 1 rad = 0.01 Gy

• 1 Gy = 100 rad

used to compare biologic effects of different types of radiation

dose equivalent