Rad protection unit 1

Exposure

*Number of ionizations (radiation) interacting with air

*Used to measure radiation exposure or intensity to a specific area; such as the human body

*Tube output and leakage radiation from tube

*Applies to only x-ray and gamma rays

Exposure unit

coulombs/kilogram

C/kGg

Air Kerma (AK)

*How energy is transferred from beam of radiation to air

*replacing exposure

*x-ray tube input and output to IR

*Dose to be delivered to pt

Kinetic Energy Released in Air, Material, per unit Mass

Air Kerma (AK) unit

mGy or mGy/min

Absorbed Dose

*Absorbed dose in patient tissue

*Amount of energy (radiation) passing through and object and absorbed per unit mass (patient tissue) and stays in it

*the cause of biological damage in exposed tissue

Absorbed Dose unit

Gy or mGy

Equivalent Dose (EqD)

*Absorbed Dose x radiation weighing factor (WR)

1sV = 1000 mSv

1sV = 100 rems

*Occupational Exposure

*Badge reports

EqD = D (dose) x WR

Equivalent Dose (EqD) unit

Sievert (sV) or mSv

Effective Dose (EfD)

*Overall risk of exposure to patient from ionizing radiation

the type of radiation and the sensitivity of the organ

*Dose x radiation weighing factor (WR) x tissue weighing factor (WT)

EfD = D (dose) x WR x WT

Effective Dose (EfD) unit

Sievert (sV) or mSv

Dose Area Product (DAP)

•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 entrance skin dose and the area of tissue exposed

•Radiation dose to air, times the area of the x-ray field

•Gives better indication of overall harm

AK = 20mGy; area exposed 100 cm2

20mGy x 100 cm2 = 2000 mGy-cm2

Dose Area Product (DAP) Unit

mGy-cm2

Collective Effective Dose (ColEfD) or (S)

*Cumulative dose to a population or group exposed to a given radiation source or group of sources - could be internal or external sources

*Calculated by average EfD x the # of persons exposed

Example:

200 people receive 0.25 Sv

200 x 0.25= 50 person-sievert

Collective Effective Dose (ColEfD) or (S) Unit

person-sievert

Average Effective Dose (Eexp)

*Average dose to individual in a group exposed to a specific source EXCLUDING those NOT exposed from that source

*Calculated by dividing (S) of exposed by # of exposed

• Excludes individuals not exposed from the specific source

Example: dose to an individual in the group during Chernobyl

Average Effective Dose (Eexp) Unit

Sievert (sV) or mSv

Effective Dose per Individual in US (EUS)

*Effective dose per individual in US population whether exposed to source or not

*Calculated by dividing total (S) by total number of individuals in US population

Example: Television exposure of all / # of individuals

Effective Dose per Individual in US (EUS)

Sievert (sV) or mSv

oRadiation

the transfer of energy from one location to another

ionizing radiation

X-rays are classified as because

•When passing through normal matter,
x-rays were found to produce electrically charged particles: (+) and (-)

•Altered atoms or molecules making up these particles are called ‘ions’

Classified as ionizing radiation

oInvisible

oCan have varying degrees of penetration in normal tissue depending on energy

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

oHave a wide range of energies within the x-ray beam; typically heterogenous, not monoenergetic

Effective measures to safeguard from unnecessary exposures from ionizing radiation

Patients

Personnel

General Public

biological effects

Living tissue can be damaged by exposure to ionizing radiation

what may cause injury in normal biologic tissues

The production of ions during ionizing radiation and the ejected electrons

SAFELY CONTROL RADIATION

Safe operation of x-ray equipment

Follow protocols and procedures

Setting correct techniques for patients and limit exposure

Using shielding when appropriate

HOW TO MINIMIZE EXPOSURES: 

•Proper techniques (appropriate kVp/ mAs)

Technique books

Proper measuring of body part

•Procedural factors

Immobilizations

Proper image receptor

Positioning around the patient’s limitations

•Human determinants

Pathological conditions

Body habitus

Movement

UNNECESSARY EXPOSURE DEFINITION

•Exposure that does not benefit a person in terms of:

Diagnostic information

Enhancing the quality of the study 

VOLUNTARY ASSUMPTIONS OF RISKS

•Weigh the positive vs negative

•Good voluntary risk is imaging for

Screening purposes:

Mammogram (most effective tool for breast cancer diagnosis)

Injury

Illness

DIAGNOSTIC EFFICACY

•Provides the basis for the justification of procedures

•The degree to which a study reveals the presence or absence of a disease while following radiation safety guidelines

As a technologist, you must take responsibility for the welfare of your patients

•Quality patient care

•Quality images

TECHNOLOGIST’S JOB

•Code of Ethics (ASRT) #5 and #7

•Legally part of the Standard of Practice for the profession

TECHNOLOGIST’S RESPONSIBILITY

•Keep radiation level at lowest level

•Techniques- use smallest amount of exposure to produce a good, diagnostic image

•ALARA

•Minimize repeats- optimal image the 1^st time

•Repeats cause increased exposures to patient and technologist

•Proper shielding (if utilized)

•Reduces exposures

•50% for females

•90-95% for males

•Be aware of rules of your department- follow protocols

•Be educated in safe operations

RADIOLOGIST/PHYSICIAN RESPONSIBILITIES

•Consulting

•Do not order unnecessary exams

•Radiologists- utilize same safe practices as the technologist when performing studies

EMPLOYER RESPONSIBILITIES

•Implement and maintain a radiation safety program

•Supply the necessary resources

•Written policy describing ALARA and the commitment of managing it

Exposure audit

ALARA

•Keep radiation “as low as reasonably achievable” for patients and personnel (1954 NCRP)

ORP

•optimization for radiation protection (ICRP)

CARDINAL RULES

Time

Distance

Shielding

Alliance for Radiation Safety in Pediatric Imaging (2007)

•Partnership with overall purpose to reduce dose to pediatrics

•Raise awareness among non radiology users

Image Gently Campaign

•2008, alliance initiated this campaign

•Dissemination of pediatric CT dose reduction

•CT can save children's lives, but dose should be lowered by ‘child sizing’

“Pause and Pulse” Image Gently in Fluoroscopy Campaign – most recent

Image Wisely

•2009 ACR and RSNA formed Joint Task Force on Adult Radiation protection about large increase in general public to ionizing radiation

•Lower amount of radiation used in medically necessary imaging studies and eliminating unnecessary procedures

PATIENT EDUCATION

Explain procedure and what cooperation is needed

Explain any follow up

Make them feel like an active participant

Answer questions

BERT (background equivalent radiation time) 

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

•

•Can be referenced to explain

exposure levels to patients

•Helps educate and

 reduces anxiety

BERT continued 

•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

•BERT is NOT a radiation quantity; it is a method

Radiographic Dose Documentation

•Dictating dose exposures and/or fluoro time into radiology reports

RADIATION

•The emission of energy in the form of electromagnetic waves or as moving subatomic particles passing through space from one location to another

§Protons, neutrons, beta particles, etc.

•Types (Box 2.1 in text)

§Mechanical vibration- which causes sound (Ultrasound)

§Electromagnetic wave-radio, microwaves, visible light, x-rays

ELECTROMAGNETIC SPECTRUM

•The full range of Frequencies and wavelengths of electromagnetic waves

•Divided into 2 parts for radiation protection purposes:

Ionizing

Xrays

Gamma rays

UV >10 eV

Nonionizing

UV <10 eV

Visible light

Infrared rays

Microwaves

Radiowaves

Ionizing

X-rays and gamma rays

UV rays with energy GREATER than 10 eV

High energy, high frequency, short wavelength that transfers energy that can remove an electron from an atom that it was attached to

Foundation of x-rays and human tissue interactions

Valuable to produce images, but has potential to produce biological damage

Nonionizing

Infrared rays, microwaves, radio waves

Ultraviolet radiation LESS than 10 eV, visible light

Lower energy, lower frequency, longer wavelength

Does not have enough kinetic energy to eject electrons from an atom

SOURCES OF RADIATION

•Natural

(background)

•Human-made
(man-made, artificial)

NATURAL RADIATION OR BACKGROUND ~50%

•Have always been a part of the environment due to planets geology and relative location to sun and solar system.

•Dose approx: 3.1mSv

•3 components:

Terrestrial

Cosmic

Internal

TERRESTRIAL RADIATION

•From radioactive material in the crust of the earth

•Levels depend on the composition of the soil or rocks (mountainous areas are higher)

•Examples

Uranium

Radium

Thorium

Radon/Thoron

2.3mSv of natural

Free agent floating around in soil

Most significant contributor

RADON

•Highest contributor of natural background radiation

•Colorless, odorless, radioactive gas that is always present in some degree in the air

•Higher levels in soil that contains granite, shale, phosphate, and pitchblende

•Enters buildings through cracks or holes in the framework

•Present in building materials like bricks, concrete and gypsum wallboard

•Usually higher in the cooler months

RADON

•High concentrations have potential to cause serious health hazards

Emits alpha radiation

•2^nd leading cause of lung cancer per EPA (Environmental Protection Agency)

•

•Radon causes 20,000 cancer deaths per year in the US

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

•1 in 15 homes in US is above limits

COSMIC RADIATION

•Nuclear interactions caused by the:

•Sun (solar)

•Beyond solar system (galactic)

•

Greatest intensity (exposures) occurs at high altitudes

Lowest intensity (exposures) occurs at sea level

**Average US exposure is 0.3 mSv per person

INTERNAL RADIATION

•Part of the human metabolism

•Radioactive atoms that make up small percentage of the body tissue

Ingested

Inhaled

oVarious foods, particles of air, dust

- Ionizing radiation released: alpha, beta particles, gamma rays

Exists in small quantities within the body:

   Potassium-40, Carbon-14, Hydrogen-3,and Strontium-90

oRadionuclides also exist in soil and air

HUMAN-MADE (ARTIFICIAL) RADIATION ~50%

•Consumer products

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

•Atmospheric fallout from weapon testing

•Nuclear power plant accidents

Three Mile Island Unit 2 (TMI-2)- 1979

Chernobyl- 1986

oMain effect is thyroid cancer of children and adolescents

oIncrease seen in breast cancer

Fukushima- 2011

•Medical radiation

§Diagnostic machines

§Radiopharmaceuticals/ radioisotopes

Which of the following is not a source of background radiation?

1.Radioisotopes used in Nuclear Medicine

What percentage of annual exposure is from Human-made radiation?

50%

What type of radiation is x-ray?

Ionizing

What term is a synonym of ALARA?

ORP

What is the 2^nd leading cause of lung cancer?

Radon

November 8, 1895

Wilhelm Conrad Roentgen

“On a New Kind of Ray a Preliminary Communication

First Clinical Radiograph in US

•February 1896- Hanover physician Dr. Gilman Frost and Dartmouth College physics professor Edwin Frost took the first known clinical radiograph

•It was a boy’s broken wrist and the exposure took 20 minutes

Clarence Madison Dally -

•First radiation fatality;

oradiation induced cancer at 39 y/o

•First cancer related death to a physician due to occupational exposure

1910

radiation exposure received to those performing professional responsibilities

Radiologists and dentists

•Radiodermatitis

oReddening of the skin from radiation exposure

oResulted in cancer

•Aplastic anemia

oA blood disorder

oBone marrow failure

•Leukemia

oAbnormal overproduction of WBC

Early dose measurements

Skin erythema dose

Tolerance Dose

Maximum Permissible Dose (MPD)

replaced the “tolerance dose” in 1950s

   - permitting the largest dose of ionizing radiation that an
     occupationally exposed person was allowed within a certain period

 

   - noted that some small risk of damage could still exist

   - originally expressed in the unit rem
     (radiation equivalent man, previously Roentgen equivalent man);
 

    - replaced with SI unit SIEVERT now

•Replacement of tolerance dose essentially meant that ‘no amount of radiation is considered safe’

- Probability of long-term harm (cancer) was expected to decrease as
  dose is decrease, but never to ‘zero’

Due to ‘no amount of radiation exposure being safe’ and no
  environment could be built with ‘zero’ tolerance, how would it be
  determined the maximum allowed occupational exposure?

o Compare rates of death and accident among various occupations

o

 Examples of very hazardous/hazardous occupations

deep sea diving

professional mountaineering

REM

•remains as a traditional unit for radiation quantity Equivalent Dose
  (EqD); specifically for radiation dosimetry reports for occupationally
  exposed personnel

• Sv replaced rem for radiation protection purposes

•1 Sv

= 1000 mSv

EXPOSURE

COULOMB/ KILOGRAM

ABSORBED DOSE

GRAY

EQUIVALENT DOSE

SIEVERT

Radioactivity (A)

•Measures the quantity of radioactive material

•Not used in diagnostic x-ray

Radioactivity (A) measured in

oSI: Becquerel (Bq)- named after a French engineer and scientist (Antione Henri Becquerel)

oTraditional: Curie (Ci)- named after Pierre and Marie Curie

oIn 1903 the Curies and Mr. Becquerel won the Nobel Prize for work with radioactivity

Somatic effects

•Effects that are seen in the individual who received the exposure

•Short term (acute or early)

o Erythema

o Decrease in blood cells

o Disruption of GI structures and function

o CNS failure

•Late effects

o Cancer

o Cataracts

o Shortening of life span

o Embryologic effects during 1^st trimester

Genetic effects

•Damage to the cell’s genetic code/DNA molecule

•Seen in offspring of the individual who received the
 exposure

•Exposure is received pre-conception (in sperm and ova)

oExcessive mutations

How do you convert sievert to millisievert?

Multiple by 1000