Rad Bio Chap 1-3 Review

Benefit Vs Risko Benefits of exposure outweigh risk for radiogenic malignancy or defects

Diagnostic efficacy- degree to which study accurately revels presence or absence of diseaseo Provides basis for determining if study is justified

Referring Physicians should justify need for each study o Radiographers accept responsibility for protecting patients

Radiation Protectiono ALARA-as low as reasonably achievableo Cardinal Rules- Time, Distance, Shielding

Biologic Damage- ionizing Radiation passes through matter it produces positive & negative charged particles(Ion Pairs) May or may not produce Damage

BERT-Background Equivalent Radiation Time o Compares radiation received during a study to amount received in nature

Types Radiationo 1.Ultrasound-mechanical vibrations=soundo 2.Electromagnetic Waves-(X-Rays) electric and magnetic fields fluctuate

Characterized Wavelength & Frequency Wave Particle Duality-travel in waves act like particles

o 3. Particulate Radiation- Alpha-Large Mass ,less penetrating, long wavelength, Beta-Small Mass, more penetrating, requires 1mm of lead to be absorbed Protons-positive, # of protons in nucleus=Zeff Neutrons- Neutral,

Ionizing Vs Non-ionizingo Ionizing-X-rays & Gamma Rays

Sufficient energy to eject electrons from the atomo Non-Ionizing- UV Rays, Radio, Light

Equivalent Dose- radiation Quantity used for radiation protection purposes when a person receives exposure from various types of ionizing radiation

Effective Dose-takes into account the dose for all types of ionizing radiation & weighting factor of those body parts for the development of radiation induced malignancy or risk of genetic damage.

o Measured in Sieverts Sources of Radiation:

o Natural(2.95mSv) Terrestrial-present in earths crust

Radon-55% of Terrestrial Cosmic-Sun, Stars Internal-.67mSv per year ingested or inhaled

o Manmade(3.6mSv) X-Ray, Nuc Med, Consumer Products, CT(1.5mSv)

o Annual Effective Dose 6.25 mSv per year o NCRP-National Council on Radiation Protection –issues report

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kVp-highest energy level of photons; Quality mAs- mA X Time how much radiation directed at pt.; Quantity Ionization-addition or subtraction of electrons causing an unstable atom Absorption-transfer of electromagnetic energy from x-rays to pts biologic material

o Absorbed Dose-amt of energy absorbed per unit of masso More Energy-greater chance for damage

Primary Radiation-Emerging x-ray photon beam o Energy of average photon in beam is 1/3 of kVp

Secondary Radiation-any radiation resulting from interactions with patiento Scatter Radiation- photons emitted in a direction different than primary beamo Stray Radiation- Leakage from tube housing

Attenuation-reduction in the number of primary photons in the x-ray beam due to absorption or scatter

Direct Transmission-X-ray photons traverse the pt without interactingo Reach the IR o Show up Black on Film

Indirect Transmission- X-ray photons undergo interactions and are scattered or deflectedo May still Traverse and Reach IR

Photonso Primary-photons that have left x-ray housing but no yet interacted with tissueo Exit(Image Formation)-photons that emerge from tissue and strike IRo Attenuated-photons either scattered away for IR or give up energy and cease to exist. o Small-Angle Scatter- bending of a Exit Photon that leads to blur on the film.

Photon Interaction With Mattero 1.Coherent Scattering (classical,elastic,unmodified)

No Loss of Energy Low Energy Photons Slight Change in Direction 20O

Rayleigh & Thompson Not important to Diagnostic Imaging

o 2.Compton Scattering (incoherent,inelastic,modified) Photon interacts with Outer Shell electron & ejects the electron

Ejected Electron-Compton Electron –Can Ionize other atoms, Loses its energy and recombines to another atom.

Incoming Photon changes direction with less energy Leave an unwanted fog on film.

o 3.Photoelectric Absorption Photon interacts with inner shell electron and surrenders all its energy Photoelectron –ejected orbital electron

Increase pt dose & contributes to tissue damage Outer Shell Electrons fill Inner shell causing emission of- Characteristic photon-

low energy, locally absorbed Auger Electrons-2nd option when inner shell vacancy is filled energy is liberated

to another electron of atom thereby ejecting it Probability of PE

Energy photon Atomic number(Z) higher number more absorbed Body part thickness

o 4.Pair Production Not use in diagnostic xray Photon Energy must be 1.022 MeV Photon Interacts with Nucleus Produces Positron & Negatron

Positron reacts with electron Annihilate each other resulting in 2 photons.

o 5.Photodisintegration 10MeV or greater Therapy Interaction occurs in Nucleus Energy absorbed by nucleus releasing an Neutron

Or proton/neutron(deuteron) Alpha Particle

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X-Rays Discovered Nov 8,1895 by Roentgen First American Fatality – Clarence Dally October 1904 Cancer Deaths reported as early as 1910

o Radiodermatitiso Blood Disorders -aplastic anemia, leukemia

1921 British X-Ray and Radium Protection Committee was Created-accomplished nothing 1900-1930 way of measuring Radiation Exposure Skin Erythema Dose Short Term Somatic Effects

o Acute-minutes, hours, days or weeks of exposure

o Nausea, fatigue, redness of skin, loss of hair, fever, shedding of skin, Blood disorders Tolerance Level-dose a worker could be subjected to without any apparent acute effects.

o 1931- 0.2 Roentgen per day o 1936-0.1 Roentgen per day

Roentgen (R) is measurement of exposure to x-radiation Rem-Radiation Equivalent Man Rad- Radiation Affective Dose Exposure(X) total electrical charge of one sign per unit mass that x-ray photons generate in dry

air at standard temp. and pressure. o Coulomb---Roentgen

Absorbed Dose(D)-amount of energy per unit mass absorbed by an irradiated object o Rad---Grays

Equivalent Dose (EqD)-specifies how biologic damage from different types and does of radiation will be equivalent if correct weighting factors are included (Types & Energies)

o EqD=D X WR

o Rems---Sieverts Effective Dose (EfD) – describes the way the same effective amount of damage can be attained

by giving different equivalent doses to different organs. (Type & Part ) o EfD=D X WR X WT

o Rems--- Sieverts Collective Effective Dose-used to describe radiation exposure of a population or group from low

doses of different sources of ionizing radiation. o Person-Sievert.

Quality Factor – adjustment multiplier used in calculation of dose equivalence to specify the ability of a dose of any radiation to cause biologic damage.

o 1-small and fasto 20-large and slow

Units o 100 Rad= 1 Grayo 100 Rem= 1 Sievert o 1 Rad = 1 Rem o Rad-Gray move 2 places lefto Gray-Rad move 2 places to righto Rems- mSv move 1 place righto mSv-Rems move 1 place left o King Philip Died By Drinking Chocolate Milk