Rad protection- CPE study

x-rays are classified as ______ due to the electrical charge effect

ionizing radiation

fundamental properties of x-rays

• can have varying degrees of penetration in normal tissue depending on energy

• travel in straight lines at the speed of light until they interact with atoms

• have wide range of energies within the x-ray bean; heterogenous, not monoenergetic

cardinal rules- these principles can be applied to patient and technologist

• time

• distance

• shielding

  • can reduce exposure to both patient and radiography

image gently campaign

• 2008, alliance initiated campaign dissemination of pediatric CT dose reduction

• pause and pulse: image gently in fluoroscopy campaign- initiated to reduce dose in fluoroscopy procedures; using low dose pulsed fluoro

image wisely

• 2009, ACR and RSNA formed Joint Task Force on Adult Radiation Protection to address concerns about increases of public exposure to ionizing radiation

• objective of lowering the amount of radiation used in medically necessary imaging studies and eliminating unnecessary procedures

BERT- background equivalent radiation time

• compares the amount of radiation received during a specific procedure to the amount of natural background radiation over a certain period of time

• helps explains exposures to patients

• educates and reduces anxiety

• does not imply radiation risk; it is a means for comparison

• emphasizes to patient that radiation is an innate part of the environment

• provides a more comprehendible answer to patient

• is NOT a radiation quantity; it is a method

ionizing radiation

• examples: x-rays and gamma rays

• UV rays with GREATER energy than 10eV

nonionizing radiation

• examples: infrared rays, microwaves, radiowaves

• UV rays LESS than 10eV

radon definition

highest contributor of natural background radiation- colorless, odorless, radioactive gas present in the air

radon

• 2nd leading cause of lung cancer per EPA

• EPA recommendations: homes to have annual levels no greater than 4 pico curies per liter of air 4pCi/L

human-made radiation (50%)

• consumer product examples: early TVs, airport surveillance, ionizing smoke detectors, some timepieces with luminous dials, video display terminals, shoe fitting fluoroscopes, dentures

• air travel

• nuclear fuel- for generation power

• atmosphere fallout- from weapon testing

• nuclear accidents

Chernobyl (1986)

• thyroid cancer in adolescents and children

• increase in breast cancer

• leukemia

most recent Nuclear plant accident

Fukushima (2011)

X-rays were invented

• date: november 8, 1895

• by: wilhelm c. roentgen

first clinical x-ray in US

• date: February 1896

• by: Dr. Gilman frost and professor Edwin frost

• image was of: a boy’s broken wrist

first radiation induced death in US

• year: 1904

• who: clarence madison dally

what did edison invent?

fluoroscope

air kerma (Gya)

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

• standard or free air ionization chamber is device to calibrate and measure

• measured in: SI unit: gray

• metric/traditional: joules/kg

acronym KERMA

kinetic energy released in matter, air/material/ unit mass

absorbed dose (D)

• measures the absorbed patient dose

• ionizing radiation passing through object and stays in it

• the higher the atomic number the higher the absorbed dose

• responsible for biologic damage to the tissue exposure

• measured in Gray (Gy) or mGy

equivalent dose (EqD)

• product of average dose in human tissue or organs and it’s radiation weighting factor (Wr)

• measures the quantity of radiation received by radiation workers

• measurements:

  • SI unit- Sv or mSv

  • Traditional- rem

• radiation badge reports measured in rem

• conversion:

  • 1SV= 100 rems

  • 1SV= 1000 mSv

• EqD = D x Wr

ExCAGES

exposure → coulomb- absorbed dose → gray- equivalent dose → sievert

effective dose (EfD)

• measures overall risk of exposure to the patient from ionizing radiation

• takes into consideration type of radiation and radiosensitivity of the tissue

• uses tissue weighting factor Wr

• Measured in: SI or mSv

• can be used to compare the average amount of radiation received by the entire body from specific radiology exam with that from natural background radiation

collective effective dose (ColEfD) or (S)

• cumulative dose to a population or group exposed to a given radiation source or group of sources

• measured in person-sievert

DAP- dose area product

• a measure of the amount of radiant energy that has been delivered into a portion of the patient’s body surface

• takes into consideration the dose and the tissue exposed

• radiation dose to air x the area of x-ray field

• better indication of overall harm

Average effective dose (Eexp)

• effective dose to those exposed

• measured in millisievert

• calculated by dividing cumulative dose (S) of the individual by the total number of individuals exposed

  • excludes individuals NOT exposed from the specific source

effective dose per individual in US (Eus)

• dose per individual in the US population whether exposed to the source or not

  • measured in millisievert

• calculated by dividing cumulative dose (S) by the total number of individuals in US population

Somatic effect of radiation

• short term effect examples:

  • erythema, decrease in blood cells, CNS failure, disruption in GI structures and function

• long term/ late effect examples:

  • cancer, cataracts, shortening life expand, embryologic effects during 1st trimester

what is the unit for exposure?

coulombs/kilogram

• C/kGg

• C/kg

what is the unit for air kerma?

mGy or mGy/min

what is the unit for absorbed dose

Gy or mGy

what is the unit for equivalent dose?

sievert (sV) or msv

what is the unit for collective effective dose (ColEfD) or (S)

person-sievert

What badge is reusable?

TLD

What badges are not affected by temp & humidity?

• TLD & OSL

What badges provides immeadiate readout?

• pocket dosimeter & DIS

What badge is self contained?

OSL

What badge is $150/unit?

• pocket dosimeter

What is the most common badge?

OSL

What is the most sensitive badge?

• pocket dosimeter

What badge has 2 electrodes (1 positive & 1 negative)?

• pocket dosimeter

What badge has a 1-year use?

OSL

What badge has a 3 month use?

TLD

What badge is affected by humidity & is only a 1-month use?

• film badge

What badge can determine primary and scatter radiation?

Film badge

What badge is made of lithium fluoride?

TLD

What badge is made of aluminum oxide?

OSL

What badge has a crystal lattice?

TLD

What badge has complete reanalysis?

OSL

What badge resembles a fountain pen?

• pocket dosimeter

When are monitor badges required?

When an individual will receive more than 10% of the recommended anual dose of 50 msg

Control badge

• used to calculate monthly occupational doses

• Badge is kept in a distant room & the reading is SUBTRACTED from your total reading to give you your monthly occupational dose

How to get monthly occupational dose

• subtract the reading (that consists of background radiation) from the total reading

ALARA I (calendar quarter) Deep dose

Every 6 months

• 125 mrem deep dose

ALARA I - shallow dose

1250mrem

ALARA I- lens of eye dose

• 1125 mrem

ALARA I- limb dose

• 3750 mrem

ALARA II deep dose

6 months

• 375 mrem

ALARA II- shallow dose

3750 mrem

ALARA II- lens of eye dose

1125 mrem

ALARA II- limb dose

3750 mrem

Film badge has what material

• aluminum & copper

What functions as the sensing material for TLDs

Lithium fluoride

How is the energy stored in a TLD?

Trapping electrons in crystal lattice

When the crystals are heated in a TLD what happens?

They are released by the lattice into the conduction band & return to normal state

In what form is energy released from a TLD?

Visible light that is measured by a TLD analyzer

What is the most common type of device used to monitor occupational exposure?

OSL/ OSLD

What monitor has the best features of all dosimeters?

OSL/OSLD

OSL/ OSLD contains what

Aluminum oxide

3 filters within an OSL/ OSLD

1. Aluminum (least absorption, shallow)

2. Tin (eye)

3. Copper (most absorption, deep)

Of the 3 layers of an OSL/ OSLD, which has the least absorption?

Aluminum layer

Of the 3 layers of the OSL/OSLD, which is the most absorption

• copper

How does an OSL/ OSLD work?

• electrons are trapped in the detector & read out when the dosimeter is struck by a laser light

  • Releases energy in a form of a light

What is the most sensitive and uncommon monitoring badge?

• pocket ionization chamber

What monitor resembles a fountain pen?

• pocket ionization chamber

What does a pocket ionization chamber contain?

• 2 electrodes

  • 1 positive

  • 1 negative charged

Pocket ionization chamber advantages

• immediate read out

How to do a DIS read out

• connect to a computer

  • Activates the vendor’s software for reading

Deep dose equivalent- DDE

• 1 cm depth in soft tissue

• Absorbed dose

Shallow dose equivalent- SDE

• 0.007cm depth in soft tissue

• Dose to external skin

Eye or lens dose equivalent- EDE/ LDE

• 0.3cm depth in the eye

• Exposure to the lens

CDE purpose

• Total dose received over a period of time, usually during a 50-year period from an inhaled or ingested radioactive material

  • Specific to a single organ or tissue

Annual dose limit to single organs

500 msg

CEDE purpose

• applies to long term radiation of individual organs or tissue resulting from inhalation or ingestion of long-lived radioactive material Specific to

  • Long decay life

How is a CEDE delivered?

• slowly over a long period of time from an inhaled or ingested material

How to calculate CEDE

Sum of all organs (CDE) x weighting factor for important (tissue weighting factors)

How is TEDE calculated

• sum of deep dose equivalent for external radiation & the committed dose equivalent

  • DDE+CDE=TEDE

Annual dose limit for WHOLE BODY to limit the risk of cancer, genetic effects, cataracts, skin damage, & sterility

50 msg

Collimation accuracy %

2%

SID indication percent

• 2%

Types of beam limiting devices

• aperture diaphragm

• Cones

• Collimators

Aperture diaphragm

• flat lead w/ a hole cut in it & placed below the windows

  • Most common is RECTANGULAR

    • Square

    • Round

  • Reduces scatter

Cones

• circular metal cylinders that connect to front of the use & limits the size of the beam

• Can be flared or straight

• Can be telescoped 10-12 inches to make field size smaller (extensive cylinder)

Cones have been replaced by ___

Collimators

Near (upper)

• near x-ray production

  • Reduces exposure from off focus radiation!!!!

Far (lower)

• located close to light source

  • Confines beam to area of interest

Total filtration in the housing is ___ mm Aluminum (Al) equivalent for units that operate above 70 kVp

2.5

Inherent filtration

• 0.5 mm Al equivalent

  • Made up of glass envelope, insulating oil, & glass window

Added filtration

• 2.0mm Al equivalent Made up

  • Sheets of Al added outside the glass window above the collimator

  • Can be accessed by service person

  • Can be changed as tube ages

Mobile & fluoro require ___ mm Al filtration

2.5