MI 240 Unit 1

Radiation biology is the study of….

the effects of ionizing radiation on biological tissue

records of storage and disposal of residual and contaminated items must be kept for…

inspectors

atom is ionized =

deposit of energy in tissue

• biological effects begin here

radiation interacts at the _____ level

atomic

x-ray energy deposited in the atom and ionization can affect the ____ holding atoms together causing the molecule to _____

bonds, break apart

cause of cancer or genetic mutations

cells begin to function improperly/ serious impairment

cause of radiation sickness

cells can cease to function/ cell death

cells respond differently depending on dose…

• radiation is more liekly to kill a cell outright than to turn it into cancer cell

• high but non-lethal doses of radiation to specific tissues can cause changes which can lead to certain types of cancer

when do early tissue interactions typically occur?

• minutes

• hours

• days

• weeks

examples of early tissues interactions

• nausea

• fatigue

• diffuse redness of skin (erythema)

• hair loss (epilation)

• intestinal disorders

• fever

• blood disorders

• shedding of outer layer of skin

early effects of radiation cause

• vary depending on duration of exposure time to ionizing radiation

• typically from high doses given acutely

  • acute radiation syndrome (radiation sickness) will most likely take place

early tissue interaction whole body exposure

• hemopoietic (hematologic) syndrome

• GI syndrome

• CNS syndrome

early tissue interaction local tissue damage

• skin

• gonads

when do late tissue interactions occur?

• months or years after exposure (down the line)

examples of late tissue interactions

• cataracts

• fibrosis

• organ atrophy

• loss of parenchymal cells

• reduce fertility

• sterility

late effects of radiation is caused by

lower doses given over long periods of time, but can also occur from higher acute exposures

late tissue effects local tissue damage

• skin

• cataracts

fetal effects of radiation is caused by

embryo/fetus exposed in utero to low or high levels of radiation

types of fetal effects of radiation

• prenatal death

• neonatal death

• congenital malformation

• childhood malingnancy

• diminished growth and development

human populations in which radiation effects have been observed

• early radiologist

• radium watch dial painters, radium craze

• Thorotrast contrast studies

• certain conditions treated with radiation

• uranium miners

• atomic bomb survivors

• Marshall islanders- bomb testing

• radiation accident victims- Chernobyl, TMI, Fukushima

• radiation therapy patients

what does coulomb/kg measure

exposure to ionizing radiation in air; electrical charge

• measures the output of imaging systems and radiation monitors used to calibrate machines

• amount of radiation that may strike an object when in the vicinity of a radiation source

  • applies only to x-rays and gamma rays

Air KERMA stands for

Air- Kinetic energy released in matter

Air kerma is measures in

gray (gy)

Air Kerma is

• kinetic energy transferred from photons to electrons during ionizations/ excitiation

• SI unit that can express how energy transfers from the beam to air

Air Kerma is mainly used in

• fluoro (if shown ‘per min’ it is showing from fluoro)

• OR

absorbed dose in air =

what is delivered to the patient

Air Kerma expresses

the radiation concentration delivered to a point, such as the entrance surface of a patient’s body

DAP meter stands for

dose area product

what does the DAP meter measure

• measures the amount of energy delivered to the patient by the x-ray beam

  • total sum of air kerma over exposed area of patient’s surface

where is the DAP meter located

located between the collimator and patient (beyond the collimator)

equation for DAP meter

mGy x cm²

absorbed dose is measured/ expressed in

• gray (gy)

• cGy, mGy, uGy

absorbed dose is responsible for

biologic damage to the tissue that is exposed

Absorbed dose measures what

the quantity that express the concentration of radiation energy absorbed at a specific point within the body tissue

• indicates the energy that the patient actually receives from an exposure to ionizing radiation

what unit is used to measure the biologic effects of radiation?

sievert

the concept of radiation weighting factor is used to do what?

takes into account the radiation type and energy range that may cause biologic damage

equivalent dose (sv) measures what

• average dose in a tissue or organ in the human body and its associated radiation weighting factor

weighting factor (Wr) is what

takes into consideration that some radiation types may cause more biologic damage than other types depending on the dose

1 mGy =

1 mSv

equation for equivalent dose

EqD = D x Wr

equivalent dose is used to

compare biologic damage from different types of radiation

quantity of radiation recieved by radiation workers

the concept of tissue weighting factor is used to do what?

• takes into account the radiosensitivity of the organ or tissue irradiated (specific organ)

effective dose (sv) is what

the sum of the weighted equivalent doses for all irradiated tissues or organs

equation for effective dose

EfD = dose x Wr x Wt

if more than one area of the body is exposed the effective dose is just the ….

sun of the effective doses for each area exposed

effective dose takes into account-

the effect of the type of radiation used and the radiosensitivity of the organ or tissue irradiated

• best measure to overall risk of exposure to humans from ionizing radiation

conversion help

• 1 Gy = 1 Sv

• 1000 mGy = 1 Gy

• 1 Gy = 1000 mGy

cumulative lifetime limit x age

10 mSv x age or 0.01 Sv x age

annual limit

50 mSv or 0.05 Sv

lens of the eye

150 mSv or 0.15 Sv

skin, extremities

500 mSv or 0.5 Sv

embyro/fetus dose total gestation period

5 mSv or 0.005 Sv

embyro/fetus dose 1 month

0.5 mSv or 0.0005 Sv

general public annual limit- continuous

1 mSv or 0.001 Sv

general public annual limit - infrequent

5 mSv or 0.005 Sv

lens of eye for public

50 mSv or 0.05 Sv

skin, extremities for public

50 mSv or 0.05 Sv

an atom is comprised of

• nucleus

• electron shells

what is the nucleus

center of an atom

what is the nucleus composed of

• protons

• neutrons

where are the electron shells

they orbit the nucleus

what are the electron shells occupied by

electrons

what is the maximum number of electrons per shell

2n²

closer an e- shell is to the nucleus, the ____ the binding energy

higher

arrangement of shells determine what

how an atom reacts chemically

the outer shell can have a maximum number of how many electrons

8 electrons (octet rule)

valence electrons are what

• electrons in the outmost shell of an atom

• atoms tend to gain, lose, or share valence electrons to achieve filled outer shell

what is the octet rule?

electrons in outermost shell can have no more than 8 electrons

an atom in the neutral state is

• electrically neutral, balanced

• # of electrons in shells is equal to # of protons in nucleus

ionization is what?

the adding or removing of an orbital electron from an atom

the larger to atom the ___ energy is needed to ionize

more

compton interaction ionizes an _____ electron

outer shell

photoelectric interaction ionizes an _____ electron

inner shell

ion pairs are…

the fundamental result of ionizing radiation interacting with matter

the first step in how x-rays create images or damage cells is what

ion pairs

how to make an ion pair

1. the atom is neutral

2. an x-ray photon strikes the atom with enough energy to knwock an electron out of its orbit

3. result in ion pair

   1. anion

   2. cation

a negative electron (anion) is

a newly freed, negatively charged electron (sometimes called a photoelectron)

a positive ion (cation) is

the rest of the atom, which lost a negative electron and is now positively charged

molecules are made up of

two or more atoms bonded together

molecules are formed by

ionic and covalent bonding

what is an ionic bond

it is the attraction between positively charged ions and negatively charged ions that forms after electrons are transferred from one atom to another

• giving/ tranferring

what is a covalent bond

when two atoms share one or more pairs of electrons so that both atoms can fill their outer (valence) shells

• stays connected/ ‘holding hands’

mass number (A) is

the number of protons plus the number of neutrons in a nuclide

atomic number (Z)

the number of protons in a nuclide

isotopes are

• atoms with the same number of protons and electrons

• but have a DIFFERENT number of neutrons

  • mass changes but the element stays the same

how many protons does barium have

56

the most abundant atom of barium has an atomic mass of

138

what is this an image of

ionic bond

what is this an image of

covalent bond

another name for coherent scattering

classical scattering

coherent (classical) scattering is what

• x-ray interact with an atom and excited it

• x-ray scatters in different direction when it is released

• no change in energy or wavelength

• no energy transfer, no ionization

this is an example of

coherent (classical) scattering

coherent scattering happens at

below 10 kVp

compton scattering is

• ionization of out shell electrons

• out shell electron ejected

• incident photon will scatter in a different direction

• compoton or scattered photon

the scattered photon in compton scattering has

• less energy

• longer wavelength

• lower frequency

what is this an example of

compton scatter

compton scatter mainly affects

• the technologists (us)

• can increase occupation dose

compton scatter occurs at

higher kVp

Compton scatter produces large amount of scatter in the ____

patient

the process of photoelectric absorption is an interaction between

• x-ray photon

• inner shell electron