RAD-101 Ch 9 Basic Radiation Protection and Radiobiology

radiation has sufficient energy to cause what

ejection of electrons from atoms

what does loss of electrons result in

ionization of atoms

ionization can have what kind of effect

biological

what are the sources of ionizing radiation

natural

manmade

what makes up the largest portion of manmade radiation exposure

medical and dental x-ray examinations

what are the conditions necessary for x-ray production

source of electrons

means for setting them in high-speed motion

mechanism for decelerating them abruptly

factors of x-ray production

source of electron

high-speed motion

deceleration

cathode filament

potential difference

target

what is the source of electron knows as

thermionic emission

how does deceleration occur

electrons strike anode surface

what does cathode filament produce

milliamperage (mA) from negative tube

what causes potential difference

kilovoltage peak (kVp)

x-ray tube design

diode tube

glass envelope maintains a vacuum

x-ray bream produced is what

heterogeneous

what does heterogenous x-ray beam mean

it’s composed of wide spectrum of energies

possible paths x-ray beam can undergo

total absorption

pass through with no loss of energy

undergo scattering and secondary interactions with some energy loss

how is energy of beam expressed

in kiloelectron volts (keV)

what is primary beam

x-ray beam leaving x-ray tube towards patients

methods of x-ray interaction with matter

classic coherent scattering

photoelectric interactions

compton scattering

pair production

photodisintegration

what methods of x-ray interactions with matter are important in radiography

photoelectric interactions

compton scattering

classic coherent scattering involves what type of x-rays

low energy

how does x-ray interact with atom in classic coherent scattering

as a whole

what happens to atom in classic coherent scattering

becomes excited and emits x-ray with same energy

does ionization occur in classic coherent scattering

no

what happens to incoming x-ray photon in photoelectric effect

completely absorbed by collision with inner-shell electron

what x-ray interaction methods is responsible for largest patient exposure

photoelectric effect

what happens to electron in photoelectric effect

electron leaves atom, creating an ion pair

free electron unites with other matter

how is secondary radiation created in photoelectric effect

result of electron cascade from outer shell to inner shell

what happens to incoming photon in compton scattering

collides with outer-shell electron, creating a free compton electron and ion pair

looses some energy

scatters in random direction

undergoes other interactions until its energy is totally absorbed

how quickly is electron vacancy filled in compton scattering

nearly instantly

what is the source of most occupational exposure

compton scatter

when were SI units officially adopted

1985

what is SI unit of exposure (x)

coulombs per kilogram (C/kg)

what is SI unit of air kerma and absorbed dose (D) (eEd)

gray (Gy)

what is SI unit of effective dose (EfD) and dose equivalent (EqD)

sievert (Sv)

what is SI unit of radioactivity

becquerel

what does exposure measure

exposure in air, not to individual

what is air kerma

total kinetic energy released in a unit mass (kg) of air

what does air kerma measure

transfer of kinetic energy to tissue or air

air kerma is measured in

joules per kilogram (J/kg)

what is absorbed dose

radiation energy per unit mass of absorbing medium

how is absorbed dose expressed

gray (Gy)

units of Joules/kg

gray (Gy) and sievert (Sv) is how many times larger than rad

100 times

1 Gy = 100 rad

1 Sv = 100 rem

absorbed dose depends upon

type of absorbing tissue

what does absorbed dose measure

amount of energy absorbed in any tissue

air (Gy_a)

tissue (Gy_t)

unit of dose equivalence accounts for

overall risk of exposure

effective is a product of

absorbed dose (Gy) x QF

what does effective dose account for

different types of radiation and biologic effects

• alpha, beta, x-ray, gamma

• referred to as quality factor (QF)

• QF of x-ray is 1

radioactivity (Bq) measures

activity of radioactive material

• rate of radioactive decay

  • radionuclide

radioactivity is used in

nuclear medicine and radiation therapy

what is becquerel (Bq)