Radiation Protection Final

Film Badges range from ?

10 mrem to 500 rem

1 sievert (Sv) = ____ rem

100

1 Gray (Gy)=

100 Rad

Advantages and disadvantages of pocket dosimeter ?

Advantage: VERY sensitive Disadvantage: Most expensive Not used for radiography personnel•Most likely used by a visitor to a Nuclear Power plant

Absorbed dose is?

Measurement used to determine the amount of radiation a patient receives during a diagnostic procedure.

primary function of beam filtration?

patient skin dose (exposure) by absorbing low energy, long photons that would be absorbed by the patient's skin and not contribute to the film•Increases overall energy of beam•"Harder beam"

ALARA

"As Low As Reasonably Achievable" Beneficial for everyone: the Patient, Tech, Radiologist and family

Range for OSL ?

1 mRem to 1000 Rem range

Sensing material for OSL ?

Al Oxide

All EMR travel

At the speed of light 3 x 108 meters per second 3 x 1010 centimeters per second 186,000 miles per second

Personnel Monitoring Report displays only

Beta, X-ray & Gamma; not Alpha

Coherent scatter is also known as ?

Classical

Atom releases (photon) energy equal to that of the original photon is what kind of scatter?

Coherent

Which scatter is more likely to occur at higher kVp values in diagnostic x-ray

Compton Scatter

Responsible for most occupational dose?

Compton scatter

What contributes no useful information?

Compton scatter

What is responsible for scatter (film fog)?

Compton scatter

___________ are shipped with our personnel monitoring devices so that the manufacture can subtract background radiation readings.

Control Badges

Range for pocket dosimeter

Diagnostic range = 0 to 200 mR (very accurate)

Occupational dose is Expressed in ?

Dose Equivalent

What incorporates the type of radiation & the sensitivity of the part (organ/tissue) in question

Effective Dose (E)

•D x WRx WT =

Effective Dose (E)

Defined in NCRP report #116 as "the sum of the weighted equivalent doses for all irradiated tissues or organs"

Effective Dose (E) (EfD)

D x WR =

EqD

Badge reading of "M" indicates

Exposure below films sensitivity level.

How do you measure TLD ?

It is heated in total darkness & light emitted is measured We view it as a "glow curve" and when translated, we have the amount of radiation exposure the crystals absorbed

The newest most widespread personnel monitoring system for RTs

Optically Stimulated Dosimeter (OSL)

Which dosimeter is relatively unaffected by temperature and humidity and can be worn a year ?

Optically Stimulated Dosimeter (OSL)

When is the Incident photon interacts with an inner (K) shell electron & is totally absorbed (disappears) Photoelectron is (produced) ejected & atom is ionized•Photoelectron leaves a vacancy or hole in the "K" shell

Photoelectric effect

wear a second badge at waist level under the apron when ?

Pregnant

Radiation of varying energies that is emitted from the tube is the ?

Primary Beam

Traditional unit is the?

Rad

What is Exposure?

Radiation Quantity for determining intensity based on ionization of air. •Roentgen (R) is the standard unit for exposure in the air •1 Roentgen (R) = 2.58 x 10-4 C/kg •It expresses the amount of radiation output from an x-ray machine that strikes a ionization chamber for calibrating new/updated machines

Collimation does what?

Reduces scatter and Increases contrast because it reduces the volume of tissue being exposed•In terms of Rad Protection, it reduces overall patient dose by limiting the area (volume) of the tissue being irradiated

What emerges from the patient and strikes the film?

Remnant (exit) radiation a.k.a image forming radiation

includes primary photons that are not absorbed in the body or stopped by the grid

Remnant radiation

"All or nothing" effect (in regards to severity)

Stochastic (Probabilistic) Effects

Effects of radiation that are mutational, non-threshold or randomly occurring biologic somatic changes, independent of dose

Stochastic (Probabilistic) Effects

Rad x WR =

Sv/mSv

What replaced film badges?

Thermoluminescense Dosimeter (TLD)

3 Cardinal Principles of Radiation

Time Distance Sheilding

Total filtration is

Total = must be 2.5 mm Al equivalent for machines operated at 70 kVp or above•Increasing Total filtration will decrease skin entrance dose

Energy transfered to pt is ?

absorption

Personnel monitoring devices do not measure ?

alpha levels

The Rad is equivalent to?

an energy transfer of 100 ergs per gram of irradiated object.

Loss of intensity as it passes thru the patient•Absorption + scatter is?

attenuation Does not reach the film

During routine diagnostic procedures, when a protective apron is not used, dosimeters (on a single badge system) should be worn ?

b/w the shoulders and waist (front of the body) to approximate the location of maximal radiation dose to the Whole Body

Coherent scatter is most likely to occur at ?

below 10 keV

Disadvantages of film badges are ?

can't wear for long periods (limited to one month). Heat, water, humidity and other environmental factors can easily affect (fog) it.•Exp. <10 mrem not measured (M)

what material is the most commonly used material in radiographic table construction

carbon fiber

What reduces compton interaction thus reducing scatter

collimation

As energy (kVp)level increases, probability decreases for ?

compton scatter

Radioactivity is measured in?

curie (traditional unit) & becquerel (primarily used in nuclear medicine)

What is Radiation Protection?

effective measures employed by radiation workers to safeguard patients, personnel, and the general public from unnecessary exposure to ionizing radiation

Compton Scatter is ? (Modified)

incident photon interacts with an outer shell (loosely bound) electron & ejects it •Partial transfer of energy

Advantages of film badges are ?

inexpensive & permanent physical record

Leaded glass envelope with the window acting as a filter along with the insulating oil•Anything that acts as a filter in the machine•Includes mirror

inherent filtration

Sensing material found in TLD's

lithium fluoride (LiF)

When a protective apron is worn (e.g. Fluoroscopy), dosimeter should be worn ?

outside of apron at collar level on the anterior surface of the body.

Outer shell electrons drop down to fill inner shells, thus emitting characteristic x-rays (cascade) also known as fluorescentradiation

photoelectric effect

An ion chamber (filled w/air) that form ions in the gas when radiated

pocket Dosimeter

Fastest means of determining radiation exposure

pocket dosimeter

Personnel Monitoring required when ?

potential to receive 10% of the annual occupational effective dose limit in one year (.5 rem/50mSv)

Increase kVp and decrease mAs will

reduce pt exposure

NCRP Report #116 outlines ?

safe dose limits for the occupational and non-occupational population

Stochastic (Probabilistic) Effects

•"Russian Roulette" or Lottery Ticket •Usually manifests as a Late effect •Greater dose, greater chance a specific late effect will be seen, but severity will NOT increase •CA or genetic alterations

Nonstochastic (Deterministic) Effects

•"Sunburn Effect" •Manifest after a Threshold dose is reached•Severity of biological damage increases with increasing dose •Diagnostic exams do not cause these effects-Long fluoro cases can cause early effects in extreme case

The primary beam is made up of ?

•10-30% characteristic •70-90% Brems's (at 70 kVp)

Pregnancy DL

•5 mSv (.5 rem) for entire gestation •not more than .5 mSv (.05 rem) /month

What is EMR?

•All wavelike forms of electromagnetic energy are photons traveling in a straight line as a sine wave

•Particulate Radiation (posses mass)

•Alpha •Beta •Protons •Neutrons

Non-Occupational DL

•Annual DL = 5 mSv (.5 rem) (infrequent) •Continuous exposure = 1 mSv (.1 rem) (frequent)

Occupational DL

•Annual DL = 50 mSv (5 rem) (5000 mRem) (S) •Cumulative DL = 10 mSv (1 rem) x age in years (S)•Lens of eye = 150 mSv (15 rem) (N) •All other organs (thyroid, skin & extremeties) = 500mSv (50 rem) (N) •Students under the age of 18 = 1 mSv (.1 rem)

Disadvantage of TLD

•Can only be analyzed once •Being replaced by OSL •Mainly used as ring badges for nuclear med

Five Interactions with Matter

•Coherent •Compton •Photoelectric •Pair Production •Photodisintegration

Optically Stimulated Dosimeter (OSL) measurement process ?

•During processing, laser light stimulates these electrons to emit visible light (also viewed as a glow curve) •Can be reanalyzed multiple times (for accuracy)

Three parts of EMR (does NOT posses mass)

•Gamma Rays •X-Rays •High Energy Ultraviolet Radiation (over 10 eV)

Advantages of the TLD dosimeter

•More accurate and sensitive than Film Badge•not affected by humidity and temp.•Reusable after reading•Can wear up to 3 months