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Title: Radiation Occupational exposures and protection


1
Radiation Occupational exposures and protection
  • A. H. Mehrparvar, MD
  • Occupational Medicine department
  • Yazd University of Medical Sciences

2
history
  • 1896 - Henri Becquerel discovers radioactivity
    and nuclear medicine is born.1901 W.C.
    Roentgen receives the Nobel in Physics for the
    discovery of x-rays.1905 - The first English
    book on Chest Radiography is published.

3
  • 1913 Coolidge hot cathode tube is introduced,
    simplifying the work of technicians and allowing
    more uniform results.1914 M. von Laue
    receives the Nobel in Physics for x-ray
    diffraction from crystals.1915 W.H. Bragg and
    W. L. Bragg receives the Nobel in Physics for
    crystal structure derived from x-ray diffraction.

4
  • 1918 Eastman introduces film. Until then,
    radiographs were made onto glass photographic
    plates.1920 - Society of Radiographers
    forms.1924 K.M.G. Siegbahn receives the Nobel
    in Physics for x-ray spectroscopy.1927 A. H.
    Compton receives the Nobel in Physics for
    scattering of x-rays by electrons.

5
  • 1930s From this point, doctors are appointed
    with specific interests in diagnosis or
    therapy.1931 - Ernerst 0. Lawrence developes
    the cyclotron and paves the way for major
    experiments later conducted at the Radium
    Institute in Paris.1936 P. Debye receives the
    Nobel in Chemistry for diffraction of x-rays and
    electrons in gases.1937 -The first clinical use
    of "artificial radioactivity" is carried out for
    the treatment of a patient with leukemia at the
    University of California at Berkeley.

6
  • 1946 -A landmark nuclear medicine advance. A
    thyroid cancer patient's treatment with
    radioactive iodine causes the complete
    disappearance of the spread of the patient's
    cancer. This is considered by some as the true
    beginning of nuclear medicine. Wide-spread
    clinical use of nuclear medicine does not start
    until the early 1950s.1950s - Development of
    the image intensifier and X-ray television.1955
    - First use of a radioactive tracer in the lungs
    with the introduction of inhaled xenon-133 and
    external counting.

7
  • 1956 - The medical use of Ultrasound starts in
    Glasgow. Professor Ian Donald M.D. and his
    colleagues, working at the University of
    Glasgows Department of Midwifery are the first
    to apply ultrasound as a diagnostic modality in
    the fields of obstetrics and gynaecology.1962 -
    M. Perutz and J. Kendrew receive the Nobel in
    Chemistry for the structure of hemoglobin. J.
    Watson, M. Wilkins, and F. Crick receive the
    Nobel in Medicine for the structure of DNA.1967
    - The first clinical use of MRI takes place in
    Nottingham University Hospital.1972 - CT is
    invented by British engineer Godfrey Hounsfield
    of EMI Laboratories in England.

8
  • 1970s - Visualization of most organs of the body
    with nuclear medicine, including liver and spleen
    scanning, brain tumor localization, and studies
    of the gastrointestinal track.1979 A. McLeod
    Comack and G. Newbold Hounsfield receive the
    Nobel in Medicine for computed axial
    tomography.1980s - Begin the use of
    radiopharmaceuticals for such critical diagnoses
    as heart disease and the development of
    cutting-edge nuclear medicine cameras and
    computers. The use of computers, laser printers
    and software transforms Nuclear Medicine.1981
    K. M. Siegbahn receives the Nobel in Physics for
    high resolution electron spectroscopy.1985 H.
    Hauptman and J. Karle receive the Nobel in
    Chemistry for direct methods to determine x-ray
    structures.1988 J. Deisenhofer, R. Huber, and
    H. Michel receive the Nobel in Chemistry for the
    structures of proteins that are crucial to
    photosynthesis.

9
Types of radiation
  • Ionizing
  • Electromagnetic energy
  • X-ray
  • Gamma ray
  • Subatomic particles
  • Electron
  • Proton
  • Neutron
  • ? particle
  • Non-ionizing

10
  • Definition energy in the form of particles or
    waves
  • Types of radiation
  • Ionizing removes electrons from atoms
  • Particulate (alphas and betas)
  • Waves (gamma and X-rays)
  • Non-ionizing (electromagnetic) can't remove
    electrons from atoms
  • infrared, visible, microwaves, radar, radio
    waves, lasers

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12
Why is radiation harmful
  • Radiation deposits small amounts of energy, or
    "heat" in matter
  • Alters atoms
  • Damage to cells DNA causes mutations and cancer
  • Similar effects may occur from chemicals
  • Much of the resulting damage is from the
    production of ions

13
Acute exposure
  • Large doses received in a short time period
  • accidents
  • nuclear war
  • cancer therapy
  • Short term effects (acute radiation syndrome 150
    to 350 rad whole body)
  • Anorexia Nausea
  • Fatigue Vomiting
  • Epilation Diarrhea
  • Hemorrhage Mortality

14
Acute whole body exposure
15
Chronic exposure
  • Doses received over long periods
  • Background radiation exposure
  • Occupational radiation exposure
  • 50 rem acute vs 50 rem chronic
  • acute no time for cell repair
  • chronic time for cell repair
  • Average US will receive 20 - 30 rems lifetime
  • Long term effects
  • Increased risk of cancer, genetic defects
  • 0.07 per rem lifetime exposure
  • Normal risk 25 (cancer incidence

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  • Non radioactive workers must receive less than
    100 mrems / year
  • Average annual background exposure for U.S.
    population 360 mrem / year
  • State and federal exposure limits for radiation
    workers 5000 mrem / year
  • Anticipated exposures Less than the minimum
    detectable dose for film badges (likely less than
    10 mrem / month) - essentially zero

18
Radiation Protection Basics
  • Time minimize the time that you are in contact
    with radioactive material to reduce exposure
  • Distance keep your distance. If you double the
    distance the exposure rate drops by factor of 4
  • Shielding
  • Lead, water, or concrete for gamma X-ray
  • Thick plastic (lucite) for betas
  • Protective clothing protects against
    contamination only - keeps radioactive material
    off skin and clothes

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20
  • uRadiation Energy (electromagnetic waves
  • or particulates)
  • uIonization The removal of electrons from
  • an atom
  • uIonizing Radiation Particles or rays with
  • sufficient energy to remove electrons from
  • atoms

21
  • Activity units
  • 1 Curie (Ci) 3.7x1010 disintegrations/s
  • 1 Bequerel (Bq) 1 disintegration/s
  • Dosimetric units Radiation interacts with
    matter by ionizing or exciting the atoms and
    molecules making up the material.
  • Measure of the quantity of ionization
  • or
  • Measure of the amount of energy deposited

22
  • Dosimetric units
  • 1 Roentgen ( R ) the quantity of x-rays or
    gamma-rays producing an ionization of
  • 2.58x10-4 Coul/kg in air at STP
  • Exposure Rate G.A/d2
  • A is the activity
  • d is the distance from the source
  • G is an exposure rate constant (R.cm2/hr.mCi)
  • G is dependent on the decay scheme, energy,
    absorption coefficient in air and the specific
    ionization of electrons

23
  • Dosimetric units Total energy absorbed per unit
    mass is more relevant Absorbed Dose (D)
  • D gives no indication of rate of irradiation
  • no information on type of radiation
  • Both of these are important for biological
    effects!
  • 1 Gray (Gy) 1 Joule/kg
  • Old unit. 1 rad 100 erg/g0.01 Gy

24
  • For biological effectsabsorbed dose is not
    enoughyou need to know what type of radiation.
    Ex Alphastransfer more energy than
    g-rays..weighting factor or a quality factor
  • Dose equivalent
  • H Q.D
  • Q is the quality factor (depends on energy, type)
  • D is the absorbed dose

25
  • LET AMOUNT OF ENERGY DEPOSITED BY RADIATION PER
    UNIT LENGTH OF TISSUE TRAVERSED calloway
  • RBE- QUANTITATIVE MEASUREMENT OF BIOLOGIC EFFECT
  • QF NUMERIC UNIT GIVEN TO RADIATION BASED ON RBE
    TO DETERMINE REM

26
  • LET - SPARSELY IONIZING RADIATION
  • GAMMA AND X-RAY
  • LOW LET OF 3 KEV OR LESS
  • ARE PENETRATING
  • INTERACT RANDOMLY ALONG ITS TRACK (STOCHASTIC)
  • AS LET INCREASES SO DOES RBE
  • HIGH LET
  • LOW PENETRATION
  • SLOW MOVING
  • Direct Effect

27
  • Wr -Radiation weighting factor
  • number assigned to different types of ionizing
    radiation. Dependent of the LET of particular
    radiation
  • Wt Tissue weighting factor
  • Tissue radiosensitivity of irradiated material

28
  • REM IS CALCULATED BY MULTIPLYING THE QF OF A
    PARTICULAR TYPE OF RADIATION X RAD
  • QF FOR X-RAYS IS 1
  • THEREFORE ONE RAD OF EXPOSURE TO X-RAY ONE REM
  • QF FOR ALPA IS 20
  • HIGH LET
  • SLOW MOVING
  • LOW PENETRATION
  • THEREFORE ONE RAD OF EXPOSURE TO ALPHA 20 REMS

29
SOMATIC
  • Short Term
  • ARS
  • Hemopoietic (BONE MARROW SYNDROME) 100-1000 RAD
  • 25 RADS CAN DEPRESS BLOOD COUNT
  • Gastointestinal (600-1000 RADS)
  • CNS (5000 RADS
  • Locally
  • Erythema 300-1000 RADS
  • Epilation
  • Delay/suppress menstruation 10 RADS
  • Temporary sterility (both sexes 200 RADS
  • LONG TERM
  • THOSE EFFECTS THAT CAN BE DIRECTLY RELATED TO
    HIGH DOSE OF RADIATION ARE CLASSIFIED AS
    NONSTOCHASTIC
  • Cataract
  • Reduced fertility
  • Fibrosis
  • Organ atrophy
  • Sterility
  • LONG TERM STOCHASTIC
  • CANCER
  • EMBRYOLOGIC EFFECTS

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31
Background radiation
  • The average person in the United States receives
    about 360 mrem/yr (whole body equivalent dose)
  • This dose is mostly from natural sources of
    radiation

32
Typical Annual Radiation Exposures to a Resident
of the U.S.
Source mrem
Inhaled (radon its progeny 200
Other internal (K-40) 39
Terrestrial 28
Cosmic 27
Cosmogenic 1
Medical X-ray 60
Total 360

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34
  • Radiation Bioeffects
  • There are two types of radiation bioeffects -
    deterministic and stochastic.
  • Deterministic
  • Severity increases with radiation dose
  • Threshold 50-100 rem
  • Dose and dose rate dependent
  • Examples
  • Cataract induction
  • Epilation (hair loss)
  • Erythema (skin reddening)
  • Blood changes

35
Radiation Bioeffects
  • Stochastic
  • Probability of occurrence increases with
    radiation dose
  • Threshold 10 rem, but regulatory models assume
    no threshold (ALARA!)
  • Examples
  • Cancer induction
  • Genetic mutations
  • Developmental abnormalities

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37
  • Stochastic Radiation Effects
  • Cancer
  • incidence begins to increase in populations
    acutely exposed to more than 10 rem
  • continues to increase with increasing dose
  • nominal risk 0.0001/rem for high dose and dose
    rate
  • Genetic Effects
  • more than 100 rem of low-dose rate, low LET
    radiation needed to double the incidence of
    genetic defects in humans
  • no human hereditary effects seen at gonadal doses
    less than 50 rem
  • In Utero Irradiation
  • developmental and other effects begin to increase
    at 10 rem
  • Conclusion
  • assessment of radiation risk should be limited to
    dose estimates near and above 10 rem (10,000
    mrem)

38
  • Occupational Exposure Limits
  • The amount of radiation dose a worker can receive
    in one year is limited by Federal Law (Title 10,
    Code of Federal Regulations, Part 20)
  • You are entitled to regular reports of your
    occupational exposure at University of Arkansas

39
  •                         
  • Annual Occupational Dose Limits - 10 CFR 20
  • Total effective dose equivalent to whole body  5
    rem (5,000 millirem)
  • Lens of eye 15 rem (15,000 mrem)
  • Sum of deep-dose and committed dose equivalents
    to all other tissues and extremities 50 rem
    (50,000 mrem)

40
ALARA Principle
  • UA radiation safety activities strive to keep all
    radiation doses associated with University
    activities well below the regulatory limits and
    As Low As Reasonable Achievable (ALARA)
  • ALARA (as low as reasonable achievable) limits
    are 10 of these  500 mrem deep, 1500 mrem eye
    and 5000 mrem shallow extremity

41
Radiation signage
42
  •                  
  • Types of Radiation Exposure
  • External - from gamma photons, x-rays or
    high-energy beta particles emitted from a source
    outside the body
  • Internal - from sources inside the body, which
    presumably came to be there following ingestion
    or inhalation of contamination

43
  •                  
  • Protection Against Internal Exposure
  • Pathways of contamination
  • Inhalation, ingestion, wound, through skin
  • Minimization
  • awareness of the hazard
  • good laboratory technique
  • use of personal protective equipment (ppe) such
    as gloves, lab coats and fume hoods
  • proper and timely performance of surveys for
    radioactive contamination

44
Personal Protective Equipment            
                                 
    Fume Hood          
Lab Coat
Protective Gloves
45
  •              
  • Protection Against External Exposure
  • The three important factors in protecting against
    external exposure are
  • time,
  • distance and
  • shielding. 
  • Judicious use of a combination of these factors
    can minimize radiation exposure. 
  •  

46
  • Dosimetry Badges
  • Personnel dosimeters (film badges) are issued by
    the Radiation Safety Division to document your
    occupational exposure.  Depending on what you
    work with, you may or may not need one.
  • Labs using H-3, C-14, P-33, S-35 and/or Ca-45 
    no monitoring required
  • Labs using P-32  a finger ring dosimeter is
    required
  • Labs using Cr-51, I-125, I-131, other gamma
    emitters and/or analytical x-ray equipment 
    whole body dosimeter is required

47
                     How to Correctly Wear Your
Badge Whole body badges should be worn between
the neck and the waist. Ring badges can be worn
on any finger.  The badge should be on the inside
of your palm, facing the radioactive work.    
48
Radiation Detection Instruments A radiation
field or contamination can be detected by a
number of instruments. Geiger Counter ("GM
detector")  very sensitive instrument used to
detect surface contamination Ionization
Chamber  used to measure higher-exposure fields
(milliroentgens per hour and above).  Can be used
as fixed-position "area monitors", or portable
survey instruments.
49
  • Spills of Radioactive Material
  • Notify other persons in the area of the spill.
  • Evacuate if spill is of a volatile material.
  • Immediately remove contaminated shoes or
    clothing.
  • Mark the spill area and limit access to avoid
    the inadvertent spread of contamination.
  • Flush contaminated skin thoroughly with water.
  • Notify the Radiation Safety Division.

50
SPILLS
51
  •                     
  • Some "Don'ts" for Avoiding Internal Exposure
  • Radionuclides that represent trivial external
    hazards, such as carbon-14 or tritium, can become
    significant internal hazards if ingested. 
  • Do Not Ever
  • pipette radioactive materials by mouth suction
  • smoke in the labs
  • eat or drink in the labs
  • apply cosmetics in the labs
  • leave radioactive materials unattended
  • In general, keep your hands away from your mouth,
    eyes and other mucosal surfaces.

52
CARCINOGENESIS
  • The cancer that can be ALMOST classified as
    radiounique is leukemia
  • Has a short latency period
  • Has a linear nonthreshold dose response curve
  • Epidemiologic studies indicate a higher
    incidences in leukemia after large exposures
  • Radium watch dial workers bone ca
  • Uranium miners lung ca
  • Early medical radiation workers leukemia
  • Thymus gland treatment thyroid ca
  • Children of Marshal Island thyroid ca
  • Atomic bomb survivors leukemia/breast, lung and
    bone

53
  • Spontaneous abortions during first 2 weeks of
    pregnancy-- 25 RAD or higher
  • 2nd week to 10th week major organogenesis IF
    radiation is high enough can cause congenital
    abnormalities
  • Principle response after that may be malignant
    disease in childhood

54
The pregnant radiographer
  • WHICH OF THE FOLLOWING IS (ARE) TRUE?
  • 5 mSv for the period of pregnancy
  • 500 mrem for the period of pregnancy
  • 0.5 mSv per month
  • 0.05 mrem per month
  • Two badges
  • TRUE
  • TRUE
  • TRUE
  • TRUE

55
MINIMIZING PATIENT EXPOSUER
  • SHIELDING
  • Gonadal shielding females reduces gonad dose by
    50
  • Gonadal shielding males reduces gonad dose by 95
  • Flat, shadow shields
  • COLLIMATION
  • DID YOU KNOW THAT THERE ARE A HIGHER SET OF LEAD
    SHUTTERS PLACED NEAR THE X-RAY TUBE WINDOW TO
    ABSORB OFF-FOCUS RADIATION?

56
  • FILTRATION
  • INCREASED FILTRATION (HVL) INCREASES THE AVERAGE
    BEAM ENERGY
  • No filtration on a 70 kVp tube (0-70) would
    produce an average energy of 35 kVp
  • However, if you filter out the lower energies
    (30-70 kVp) is 50 kVp
  • Inherent
  • Added
  • _________is required for machines operating at 70
    kVp

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PERSONNEL PROTECTION
  • Lets keep safe!

59
THE ENVIRONMENT
  • CONTROLLED AREA
  • OCCUPANCY FACTOR
  • UNCONTROLLED AREA
  • USE FACTOR
  • WORKLOAD
  • Badged personnel
  • Who,what is where
  • Everyone else!
  • of time primary beam is directed at a
    particular wall
  • of x-ray exams per week

60
  • Primary barrier
  • 7 feet, 1/16 inch of lead
  • Secondary barrier
  • Extend to ceiling
  • 1/32 inch of lead

61
  • One standard design practice is to measure the
    halving thickness of a material, the thickness
    that reduces gamma or x-ray radiation by half.
    When multiple thicknesses are built, the
    shielding multiplies. For example, a practical
    shield in a fallout shelter is ten
    halving-thicknesses of packed dirt. This reduces
    gamma rays by a factor of 1/1,024, which is 1/2
    multiplied by itself ten times. This multiplies
    out to 90 cm (3 ft) of dirt. Shields that reduce
    gamma ray intensity by 50 (1/2) include (see
    Kearney, ref)
  • 9 cm (3.6 inches) of packed soil or
  • 6 cm (2.4 inches) of concrete,
  • 1 cm (0.4 inches) of lead,
  • 0.2 cm (0.08 inches) of depleted uranium,
  • 150 m (500 ft) of air.

62
electron knocked out
The ionized atom causes changes which MAY damage
cells, which MAY cause health effects
63
  • Ionizing radiation

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ALPHA RADIATION
  • Alpha radiation consists of helium nuclei which
    consist of two protons and two neutrons. These
    four particles are bound together so tightly that
    the alpha particle behaves in many situations as
    if it were a fundamental particle. An alpha
    particle has a mass of 4u and carries two units
    of positive charge.
  • Alpha particles are very easily absorbed. A thin
    sheet of paper is usually sufficient to stop
    alpha particles. These particles will thus be
    shielded by your skin and do not constitute an
    external radiation hazard. Care should however be
    taken when working with alpha radiation as it can
    cause great damage to the mucous membrane when
    ingested or inhaled. Do not take alpha radiation
    lightly!

66
alpha
  • Two neutrons and two protons
  • Charge of 2
  • Emitted from nucleus of radioactive atoms
  • Transfer energy in very short distances (10 cm in
    air)
  • Shielded by paper or layer of skin
  • Primary hazard from internal exposure
  • Alpha emitters can accumulate in tissue (bone,
    kidney, liver, lung, spleen) causing local damage

67
BETA RADIATION
  • Beta radiation consists of high speed electrons
    which originate in the nucleus. These "nuclear
    electrons" have identical properties to the
    atomic electrons, that is they have a mass of
    1/1840u and carry one unit of negative charge.
    Another type of beta radiation, positron
    radiation, consists of particles of the same mass
    as the electron, but carry one unit of positive
    charge.
  • Beta radiation is more penetrating that alpha
    radiation. It requires shielding of up to 10 mm
    of perspex for complete absorption. One important
    problem encountered when shielding against beta
    radiation concerns the emission of secondary
    X-rays, which result from the rapid slowing down
    of the beta particles. This X-radiation is called
    Bremmstrahlung. Beta particles must thus always
    be shielded with low atomic number elements such
    as aluminium and perspex. When beta particles are
    shielded with lead, they slow down so rapidly
    that bremmstrahlung occurs. Never use lead when
    shielding against beta radiation!

68
beta
  • Small electrically charged particles similar to
    electrons
  • Charge of -1
  • Ejected from nuclei of radioactive atoms
  • Emitted with various kinetic energies
  • Shielded by wood, body penetration 0.2 to 1.3 cm
    depending on energy
  • Can cause skin burns or be an internal hazard of
    ingested

69
gama
  • Electromagnetic photons or radiation (identical
    to x-rays except for source)
  • Emitted from nucleus of radioactive atoms
    spontaneous emission
  • Emitted with kinetic energy related to
    radioactive source
  • Highly penetrating extensive shielding required
  • Serious external radiation hazard

70
X
  • Overlap with gamma-rays
  • Electromagnetic photons or radiation
  • Produced from orbiting electrons or free
    electrons usually machine produced
  • Produced when electrons strike a target material
    inside and x-ray tube
  • Emitted with various energies wavelengths
  • Highly penetrating extensive shielding required
  • External radiation hazard
  • Discovered in 1895 by Roentgen

71
Tissue sensitivity
Very High White blood cells (bone marrow) Intestinal epithelium Reproductive cells
High Optic lens epithelium Esophageal epithelium Mucous membranes
Medium Brain Glial cells Lung, kidney, liver, thyroid, pancreatic epithelium
Low Mature red blood cells Muscle cells Mature bone and cartilage
72
GAMMA RADIATION
  • Gamma radiation belongs to a class known as
    electromagnetic radiation. This type of radiation
    consists of quanta or packets of energy
    transmitted in the form of a wave motion.
  • Gamma radiation is highly penetrative according
    to its energy. It is shielded with lead.

73
X-RAYS
  • X-radiation is also a class of electromagnetic
    radiation and is identical to gamma radiation in
    most respects. The essential difference between
    the two types of radiation lies in their origin.
    Whereas gamma rays result from changes in the
    nucleus, X-rays are emitted when atomic electrons
    undergo a change in orbit.
  • X-rays are always shielded with lead.

74
NEUTRONS
  • There are radioactive sources that emit neutrons.
    The method of shielding is complicated by the
    very wide range of energies encountered.
  • Should you require more information regarding
    neutron sources and the shielding of these
    sources, please contact the radiation protection
    officer.

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Atoms and radioactivity
  • Most atoms are stable, but some may emit
  • excess energy (radiation) and are called
  • radioactive.

78
RADIATION WORKERS
  • Any person working with radioactive substances is
    classed as a radiation worker. Personnel of the
    University of Pretoria may not work with
    radioactivity before they are registered as
    radiation workers. Registration is handled by the
    radiation protection officer.
  • Internationally we distinguish between two groups
    of radiation workers, those who undergo routine
    medical examinations and have personal monitoring
    devices and those who do not. The possible
    radiation dosage, that a radiation worker can
    receive, determines the group to which he
    belongs.
  • Working condition A (according to IAEA an ICRP)
  • Working conditions are of such a nature that the
    possibility exists that a radiation worker can
    receive more than 30 of the annual dose
    equivalent limit. These workers are classified as
    type A radiation workers and have to undergo
    routine medical examinations and must have
    TLD-meters.
  • Working condition B (according to IAEA and ICRP)
  • Working conditions are of such a nature that it
    is highly unlikely that a radiation worker will
    receive more than 30 of the annual dose
    equivalent limit. These workers are classified as
    type B radiation workers and do not undergo
    medical examinations or have to carry TLD-meters.

79
MEDICAL EXAMINATIONS
  • Type A radiation workers must undergo a medical
    examination before they can commence work with
    radioactivity. He/she can then be examined every
    twelve to fourteen months or longer depending on
    the radiation levels and exposure possibilities.
    This routine examination is no longer enforced by
    the Hazardous Substances Act and can be done on a
    voluntary basis.
  • The examination is handled by a physician
    appointed by the University of Pretoria and
    includes the following
  • A complete examination of the blood.
  • A complete examination of the urine.
  • A complete examination of the hands, eyes and
    fields of vision.
  • Female radiation workers must inform the
    radiation protection officer immediately if they
    should fall pregnant. Her working conditions will
    then be discussed with the appointed physician
    and he will decide whether it's safe for her to
    continue working with radioactivity for the
    duration of her pregnancy.

80
DOSIMETRY
  • Type A radiation workers must all have personal
    monitoring devices. These must be worn at all
    times when working with radioactivity or when
    working in a room where radioactivity is stored.
  • TLD-meters are obtained from the SABS. These are
    worn for a period of 28 days and are then sent
    back to the SABS for measurement. The reports
    must be sent to the radiation protection officer
    who keeps records of the occupational exposure of
    all type A radiation workers.
  • In some cases, type B radiation workers will be
    asked to get personal monitoring devices or
    TLDs. These reports must also be forwarded to
    the radiation protection officer.

81
ISOTOPE LABORATORIES
  • The use of unsealed radioactive materials
    requires special laboratory facilities to limit
    the intake of these materials by radiation
    workers and to prevent unnecessary exposure to
    radiation from these substances.
  • The Department of Health controls the use of
    radioactive isotopes and divides radioisotope
    laboratories into three categories, A, B and C
    according to specifications laid down by the
    IAEA.
  • The University of Pretoria only has B- and
    C-category laboratories.

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C-category laboratory
  • The floors, walls and working surfaces must be
    completely washable. The floors must be sealed,
    even where it comes into contact with the walls.
    Corners, cracks and uneven working surfaces must
    be avoided. Anything that can become a dust trap
    must be avoided, as these laboratories must be
    cleaned quickly and efficiently when a spillage
    occurs.
  • The laboratory must preferably have two basins.
    One, clearly demarcated for this purpose, must be
    used as the active basin. In other words,
    anything that might be contaminated with a
    radioactive substance, must be washed in this
    basin. The other basin is used exclusively by
    radiation workers to wash their hands. The basins
    must be equipped with foot-, elbow-, or
    knee-controlled taps.
  • The ventilation of the laboratory must not be
    coupled to a central ventilation system, it must
    be independent. The system must be able to
    replace the volume of air in the laboratory
    approximately 8 times per hour and the outlet
    must be directly to the outside.
  • All furnishings in the laboratory must be
    completely washable and must be kept to a
    minimum.
  • All entrances to the laboratory must be clearly
    marked with radiation warning signs, emergency
    numbers and notices that prohibit eating,
    drinking, smoking and the application of
    cosmetics inside the laboratory.
  • Waste containers, lined with plastic bags and
    equipped with foot-controlled lids are necessary
    in the laboratory. They should be clearly marked
    as radioactive waste bins.

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B-category laboratory
  • All the specifications mentioned for B-category
    laboratories are applicable to B-category
    laboratories too.
  • The ventilation system must be able to replace
    the volume of air in the laboratory 12 times per
    hour.
  • A radiation monitor must be at hand for the
    routine monitoring of working surfaces. Radiation
    workers must also monitor their hands and feet
    before leaving the laboratory.

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RULES AND REGULATIONS
  • No food may be eaten or stored in the laboratory.
  • No liquids may be consumed or stored. Drinking
    water at the basins is not allowed.
  • Smoking is prohibited.
  • Cosmetics may not be applied in the laboratory.
  • The pipetting by mouth of any liquid containing a
    radioactive substance is strictly forbidden.
  • All wounds and abrasions must be covered by a
    waterproof plaster before entering the
    laboratory.
  • Female radiation workers must inform the
    radiation protection officer when they fall
    pregnant.
  • All spillage or suspected spillage must be
    reported to the radiation protection officer.
  • Radioactive waste must only be placed in the
    specified containers.
  • New workers must be registered as radiation
    workers before they commence work with radiation.
  • Personal dosimeters must be worn at all times
    where specified.

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RADIATION PROTECTION PROGRAM
  • The radiation protection program of the
    University of Pretoria is divided into the
    following six sections
  • A Organisation and Management committed to
    safety and the ALARA (As Low As is Reasonably
    Achievable) principle.
  • B Successful personnel selection and training.
  • C Effective occupational radiation protection.
  • D Effective public radiation protection.
  • E Effective emergency planning and preparedness.
  • F Implemented quality assurance.

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Key Scientific Organizations
  • International Commission on Radiological
    Protection (ICRP)
  • International Atomic Energy Agency (IAEA)
  • International Commission on Radiological Units
    and Measurements (ICRU)
  • National Council on Radiation Protection and
    Measurements (NCRP)

89
The Philosophy of Radiation Protection
  • Justification
  • Optimization
  • Dose limitation

90
External Dose
91
Dose Equivalent (H)
  • Biological response varies by radiations
  • Radiation weighting factors used to provide a
    common scale
  • DT,R is absorbed dose
  • T is tissue (organ)
  • R is radiation type R
  • WR is radiation weighting factor

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Effective Dose Equivalent (HE)
  • Different tissues respond differently to same
    radiation dose
  • Tissue weighting factors used to provide a common
    scale
  • HE is the effective dose equivalent
  • WT is the tissue weighting factor

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Effective Dose Equivalent, continued
  • Take dose equivalent for each organ
  • Multiply by radiation risk factor, WT
  • Sum to get effective dose equivalent for the
    entire body
  • Where HT is the tissue (organ) dose equivalent

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Tissue Weighting Factors WT
Tissue or Organ Tissue Weighting Factor, WT
Gonads 0.25
Bone Marrow (red) 0.12
Lung 0.12
Breast 0.15
Thyroid 0.03
Bone Surface 0.03
Remainder 0.30
From ICRP 20, ICRP-60 values and tissues are
different
95
Occupational Exposure Limits
  • To prevent nonstochastic effects
  • 0.15 Sv (15 rem) lens of the eye
  • 0.5 Sv (50 rems) all other tissues
  • To limit stochastic effects
  • Dose-equivalent limit from uniform whole body
    irradiation is 50 mSv (5 rem) in 1 year
  • Effective dose-equivalent from nonuniform
    irradiation 50 mSv (5 rem) in 1 year

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Exposure of General Public
  • For routine releases from sites
  • 1 mSv (100 mrem) per year
  • Occasional 5 mSv (500 mrem) per year if average lt
    1 mSv
  • Remediated sites
  • 0.15 mSv (15 mrem) per year
  • e.g., Decommissioned reactors, waste sites etc.
  • Air emissions
  • 0.1msv (10 mrem)

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Aim of Radiation Protection
  • To ensure that radiation doses received by the
    public, patients and staff are as low as
    reasonably achievable
  • ALARA principle

103
Why use LEAD (Pb)?
  • Lead is used as a radiation shielding material as
    it has a high atomic number (i.e. 82)
  • atomic number of an element is the number of
    protons in the nucleus (which is equal to the
    number of electrons around the nucleus)
  • for the photoelectric process, the mass
    absorption coefficient increases with the cube of
    the atomic number (z3)
  • Revise your knowledge of absorption and
    scattering processes by CONSULTING any good
    quality radiation physics text book

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Lead Equivalent
  • Lead can be moulded into shapes to form
    protective barriers
  • It can also be incorporated into other materials
    such as rubber for use in aprons or gloves or in
    glass for viewing windows. In these cases it is
    the lead atoms present which ( because of their
    high atomic number) are still responsible for the
    majority of the absorption provided for low and
    medium energy (up to 300 kVp) radiation

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  • Dose Units are known as the rad and rem
  • rad the amount of energy absorbed in tissue
  • rem relates the amount of ionization in air (R)
    or the amount of
  • absorbed energy (rad) to the degree of biological
    damage

106
Sources
  • Natural (79)
  • Cosmic rays (outer space)
  • Terrestrial radiation (earths crust)
  • Radium, radon (the most common, indoor air
    pollution)
  • Internal radiation
  • K-40, C-14
  • Artificial (21)
  • Medical radiation
  • Diagnostic
  • Therapeutic
  • Industrial
  • Consumer products

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Biological effects
  • F. Biological Effects of Radiation
  • Cell sensitivity to radiation is determined by
    two primary factors
  • Level of cell activity resulting in increased
    rates of chemical diffusion across the nuclear
    membrane.
  • Rate of cell division resulting in more time
    spent with the protective nuclear membrane
    dissolved.
  • Other factors apply but will be discussed later.

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  • These criteria can be used to list the body's
    cells and organs in approximate order from most
    to least radiosensitive
  • Fetal tissue
  • Reproductive cells (for long term genetic
    reasons).
  • Red and white blood forming cells primarily
    located in the bone marrow.
  • Lens of eye.
  • Most internal organs such as the lung and lower
    intestine.
  • Skin of the whole body, thyroid, nerve, etc.
  • Extremities such as hands and feet.
  • In order to put the rem into its proper
    biological perspective, it is useful to compare
    it to the effects of large acute exposures which
    are received in 24 hours or less.

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  • CAUTION The exact boundary of each exposure
    range depends on
  • individual health and the availability of
    medical treatment after exposure.
  • rem Immediate Effects
  • 0 - 25 None
  • 25 - 100 Small measurable changes in white
    blood cell count.
  • 100 - 200 Possible symptoms of radiation
    sickness
  • Blood changes including a white blood cell
    decrease
  • leading to decreased disease resistance, a red
    blood
  • cell decrease leading to fatigue, and a blood
    platelet decrease leading to a decreased
    ability of blood to clot
  • over wounds. Intestinal wall damage leading
    to nausea,
  • vomiting, and diarrhea.

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  • Note The severity of symptoms increases with
    increasing exposure until the following
    approximate exposures are reached
  • 500 Lethal Dose to 50 if those exposed within
    30 days (LD50/30) along with epilation (loss
    of hair) within two
  • weeks.
  • 1000 Additional symptoms include convulsions due
    to Central
  • Nervous System damage.
  • The American Cancer Society states that 25 of
    the 20 to 65 year old age group develops cancer
    from sources such as errors in gene duplication,
    smoking, air pollution, food, and natural
    background radiation. An increased exposure of 1
    rem would increase the risk of cancer from about
    25 to about 25.03.

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Radiation Dosimetry
General Public Dose Limit 100
mrem/yr Occupational Dose Limit 5,000 mrem/yr
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Loss of Life Expectancy
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Sources
  • Tobacco smoke
  • Smoke detectors
  • Consumer Products
  • Security Devices and Processes
  • Airport luggage x-ray machines
  • Construction Materials
  • concrete, cinder blocks, bricks, and granite
  • Food and Food Containers
  • potassium in foods, such as bananas, are the
    radionuclide, potassium-40
  • Pottery glazes

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Medical sources
  • Most man-made exposure in Canada is from medical
    x-rays or the medical use of radioactive
    material. Nuclear fallout and nuclear power
    contribute very little to British Colombians
    radiation exposure. Medical exposure is
    increasing partly due to the increased use on
    Computed Tomography (CT) and the increase dose
    associated with current procedures. Currently
    over 40 of patient x-ray dose come from CT
    procedures. Medical x-ray diagnosis is only
    carried out when the patient-benefit from the
    procedure outweighs the harm from the exposure.

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Assessing risk
  • risk of exposure-the way that radioactive
    materials move through the environment and the
    potential for human contact
  • risks from exposure-how radiation affects human
    health.
  • Activities
  • monitor the environment for above-normal
    background levels of radiation
  • use data from studies of effects from exposing
    human cells
  • develop mathematical models to estimate the
    effects of potential exposures from existing
    exposure data.

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EPA's Radiation Protection Program Strategic Goals
  • Goal 1. Prepare for and respond to radiation
    emergencies.
  • Goal 2. Reduce exposures through sound
    environmental radiation regulations.
  • Goal 3. Provide scientific and technical
    expertise for management of radioactive waste and
    contaminated media.
  • Goal 4. Develop and provide credible information
    to make effective risk-management decisions about
    radiation.
  • Goal 5. Promote responsible management of natural
    and man-made radiation sources and materials and
    encourage safer alternatives.
  • Goal 6. Foster a workforce that meets current and
    future challenges of radiation protection.

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  • Protection

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  • Monitoring and surveillance
  • Radiological hazard assessment and work control
  • Radiological incident emergency management
  • External, extremity, and special area dose
    monitoring
  • Radiological sample and in-vivo and in-vitro
    bioassay analyses and services
  • Radiation monitoring instrument maintenance,
    repair, and calibration
  • Radiological engineering
  • Radiological dose assessment
  • Technical consulting and subject matter expertise
    in all of the above areas

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WHY RADIATION PROTECTION?
  • The Hazardous Substances Act of 1973, (Act No. 15
    of 1973), states that every organisation that has
    an authority to use radioactive substances, must
    appoint a radiation protection officer.
  • The radiation protection officer, according to
    the above mentioned law, should be placed in
    control of all activities that pertain to the
    authorities that the organisation holds and of
    all actions and operations which are carried out
    or performed in terms of such authorities by any
    radiation worker or other employee in the employ
    of such organisation.

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Diagnostic X-ray Facility Protection
  • The purpose of diagnostic x-ray facility
    protection is to establish and promote quality
    diagnostic imaging at the x-ray facility while
    providing protection for workers and lowering
    patient doses as far as practicable.

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Optimization of Protection in Occupational
Exposure
  • Medical and supporting staff whose work involves
    medical x-rays can reduce their occupational
    exposures through adequate shielding of the x-ray
    facility and proper functioning of x-ray
    equipment (See Diagnostic X-ray Facility
    Protection), and by following radiation safety
    procedures during day-to-day operations.
  • The three fundamental principles of radiation
    protection from ICRP 60 are (1) the practice
    involving exposure to radiation is justified by
    the benefit obtained from the practice (2) all
    exposures should be kept As Low As Reasonably
    Achievable (ALARA), economic and social factors
    being taken into account and (3) dose limits
    should be applied to provide an adequate standard
    of protection even for the most highly exposed
    individuals.

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Dose limits of workers
  • Occupational exposures to medical x-rays in
    British Columbia are regulated provincially by
    WorkSafeBC(WCB) and federally by Health Canada.
    Based on WCBs Occupational Health and Safety
    Regulations, the dose limits for workers are
  • an annual effective dose of 20 mSv (whole-body
    dose)
  • an annual equivalent dose of
  • 150 mSv to the lens of the eye
  • 500 mSv to the skin, averaged over any 1 cm2
    regardless of the area exposed, and
  • 500 mSv to the hands and feet

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  • In addition to these dose limits, the WCB has
    also defined an Action Level of 1.0 mSv/y. If the
    exposure of the worker exceeds or may exceed an
    annual dose of 1.0 mSv, employers must
  • provide and ensure the proper use by workers of
    an acceptable dosimeter or radiation badge.
  • perform radiation surveys to measure radiation
    levels in work areas
  • provide written instructions on safe and proper
    procedures and practices related to the use of
    the radiation-emitting device.

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Dose Limits for the Pregnant Worker
  • Special limits are imposed for pregnant workers
    as an additional control to enhance the
    protection of the unborn child. ICRP guidance for
    pregnant workers can be found in Pregnancy and
    Medical Radiation (ICRP 84) or as a PowerPoint
    presentation in http//www.icrp.org/docs/ICRP_84_P
    regnancy_s.pps. The worker should inform his or
    her supervisor once she knows of her pregnancy.
    Once the worker has declared her pregnancy the
    special limits for the pregnant worker for the
    remainder of her pregnancy in WCBs Occupational
    Health and Safety Regulations is the lesser of
  • effective dose of 4 mSv
  • dose limit specified for pregnant workers under
    the Nuclear Safety and Control Act or any
    successor legislation, and the regulations under
    that Act.

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Protective Items (Lead Aprons)
  • The basic steps to reduce exposure to radiation
    are
  • minimize time exposed to the radiation-emitting
    device or source to as short as possible
  • increase distance from the radiation-emitting
    device or source to as far as practicable
  • wear protective items that provide effective
    shielding such as lead aprons, thyroid collars,
    and gauntlets

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Guidelines (general)
  • The current/future x-ray workload (i.e. number of
    films exposed) does not exceed 960 (on average)
    in a 40-hour work week schedule. Two workload
    ranges are provided to select from.
  • The x-ray unit is normally operated at up to
    125 kVp, with a maximum film (cassette) size of
    35cm x 43cm (14 x 17). An upright bucky is
    provided which receives up to 20 of the
    radiographic workload and up to 5 of
    radiographic exposures are taken cross-table,
    with the remaining workload directed downwards to
    the floor (see over for locations).
  • The room containing the unit has dimensions no
    smaller than 3m x 4m.
  • Unexposed x-ray film is stored in a film bin,
    lined with at least 0.8mm (2 lb/ft²) lead.

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  • Shielding is required to provide protection
    outside the room (a) for workers to meet the
    Action Level of 1mSv/year, as specified in the
    WCB Occupational Health and Safety Regulation
    (see WCB website http//www.worksafebc.com/policy
    /regs) and (b) for members of the public not to
    exceed the recommended public dose limit of 1
    mSv/year.
  • For workers directly involved in the taking of
    x-rays, this guideline provides an option for
    shielding the control booth to either 20 mSv/year
    (the maximum permissible dose) or to 1 mSv/year
    (the Action Level referred to above). Note that
    the control booth shielding is based on providing
    protection against secondary radiation (i.e.
    leakage and scatter) only, but not the primary
    beam.

131
  • Occupancy behind barriers the shielding
    assessment (over) has taken into account the
    amount of time (occupancy) spent by persons
    outside the barriers (i.e. walls/doors)
  • ?? Full occupancy applies to areas occupied by
    workers or other persons for a total of more than
    30 minutes per day, and applies to adjacent rooms
    and tenanted facilities.
  • ?? Partial occupancy applies to areas occupied by
    workers and other persons for a total of no more
    than 30 minutes per day, and applies to areas
    such as adjacent stairwells, parkades and parking
    lots, lanes, gardens and infrequently used rooms
    (storage). Areas that can be converted from
    Partial Occupancy to Full Occupancy (e.g. from
    storage to office) should be considered as Full
    Occupancy for shielding requirements.
  • If the facility has accessible areas (e.g.
    rooms) above and/or below the x-ray room,
    protection for these areas must be provided in
    the intervening floors (see over). For
    confirmation of construction material
    requirements for the intervening floor, above
    and/or below the x-ray room, please refer to the
    current BC Building Code.

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Room layout (general)
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Guideline (mamography)
  • The x-ray unit is operated at up to 35 kVp.
  • The room containing the unit has dimensions of
    at least 3m x 3m
  • The x-ray workload (number of film exposures)
    per 40 hour workweek does not exceed 1200.
  • Shielding is required to provide protection
    outside the room, a) for workers to meet the
    Action Level of 1mSv/year, as specified in the
    WCB Occupational Health and Safety Regulation
    (see WCB website http//www.worksafebc.com/policy
    /regs) and b) for members of the public, to not
    exceed the recommended public dose limit of 1
    mSv/year.

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  • Operator protection is required to ensure that
    the maximum permissible dose of 20 mSv/year is
    not exceeded and that doses are kept as low as
    reasonably achievable. The shielding specified
    for the operator protective shield (see over)
    will ensure the operator does not exceed the WCB
    1 mSv/year Action Level, keeping exposures well
    below the dose limit.

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Guideline (fluoroscopy)
  • The current/future x-ray workload in the room
    does not exceed 50 fluoroscopic (radioscopic)
    procedures average fluoroscopy (radioscopy) time
    is 5 minutes per patient and 300 radiographic
    film in a 40 hour workweek schedule.
  • The x-ray unit is normally operated in the
    range 70-100 kVp, and occasionally at up to 125
    kVp. The maximum film (cassette) size is 35cm x
    43cm (14 x 17) and maximum image intensifier
    size is 41cm (16). An upright bucky is provided
    which receives up to 20 of the radiographic
    workload (i.e. 60 radiographs/week). Up to 5 of
    the radiographic workload (i.e. is
    radiographs/week) can be taken cross-table (see
    over for locations).
  • The room containing the unit has dimensions no
    smaller than 3m x 4.5m.

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  • Unexposed x-ray film is stored in a film bin,
    lined with at least 0.8mm (2 lb/ft²) lead.
  • Shielding is required to provide protection
    outside the room, a) for workers, to meet the
    Action Level of 1mSv/year, as specified in the
    WCB Occupational Health and Safety Regulation
    (see WCB website http//www.worksafebc.com/policy
    /regs), and b) for the general public, to not
    exceed the recommended public dose limit of 1
    mSv/year.
  • For workers directly involved in the taking of
    x-rays, this guideline provides an option for
    shielding the control booth to either 20 mSv/year
    (the maximum permissible dose) or to 1 mSv/year
    (the Action Level referred to above). Note that
    the control booth shielding is based on providing
    protection against secondary radiation (i.e.
    leakage and scatter) only.

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  • Occupancy outside barriers the shielding
    required (over) takes into account the amount of
    time (occupancy) spent by persons outside the
    barriers (i.e. walls/doors)
  • ?? Full occupancy applies to areas occupied by
    workers or other persons for a total of more than
    30 minutes per day, and applies to adjacent rooms
    and tenanted facilities.
  • ?? Partial occupancy applies to areas occupied by
    workers and other persons for a total of no more
    than 30 minutes per day, and applies to areas
    such as adjacent stairwells, parkades and parking
    lots, lanes, gardens and infrequently used rooms
    (storage). Areas that can be converted from
    Partial Occupancy to Full Occupancy (e.g. from
    storage to office) should be considered as Full
    Occupancy for shielding requirements.

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Guideline (CT)
  • The current/future x-ray workload does not exceed
    200 patients/week per 40 hour work week schedule.
  • The CT unit is operated at up to 150 kVp.
  • The room containing the unit has dimensions no
    smaller than 3.5m x 6m (see over).
  • Shielding is required to provide protection
    outside the room, a) for workers, to meet the
    Action Level of 1mSv/year, as specified in the
    WCB Occupational Health and Safety Regulation
    (see WCB website http//www.worksafebc.com/policy
    /regs), and b) for members of the public, to not
    exceed the recommended public dose limit of 1
    mSv/year.

141
  • For workers directly involved in the taking of
    x-rays, this guideline provides an option for
    shielding the control booth to either 20 mSv/year
    (the maximum permissible dose) or to 1 mSv/year
    (the Action Level referred to above). Note that
    the control booth shielding is based on providing
    protection against secondary radiation (i.e.
    leakage and scatter) only.
  • No person other than the patient shall be
    inside the room during diagnostic exposures
    except when required to assist the patient, when
    protective lead aprons shall be worn.

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  • Occupancy outside barriers the shielding options
    (see over) allow for consideration of the amount
    of time (occupancy) spent by persons outside each
    of the barriers(i.e. walls/doors)
  • ?? Full occupancy applies to areas occupied by
    workers or other persons for a total of more than
    30 minutes per day, and applies to adjacent rooms
    and tenanted facilities.
  • ?? Partial occupancy applies to areas occupied by
    workers and other persons for a total of no more
    than 30 minutes per day, and applies to areas
    such as adjacent stairwells, parkades and parking
    lots, lanes, gardens and infrequently used rooms
    (storage). Areas that can be converted from
    Partial Occupancy to Full Occupancy (e.g. from
    storage to office) should be considered as Full
    Occupancy for shielding requirements.
  • If the facility has accessible areas (e.g.
    rooms) above and/or below the CT room, protection
    for these areas must be provided in the
    intervening floors (see over). For confirmation
    of construction material requirements for the
    intervening floor, above and/or below the CT
    room, please refer to the current BC Building
    Code.

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  • Non-ionizing radiation

145
  • Sources
  • Ultraviolet light
  • Visible light
  • Infrared radiation
  • Microwaves
  • Radio TV
  • Power transmission

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  • Ultraviolet Black light induce fluorescence
    in some materials
  • Vision very small portion that animals use to
    process visual information
  • Heat infrared a little beyond the red
    spectrum
  • Radio waves beyond infrared
  • Micro waves
  • Electrical power transmission 60 cycles per
    second with a wave length of 1 to 2 million
    meters.

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UV
  • Sun light
  • Most harmful UV is absorbed by the atmosphere
    depends on altitude
  • Fluorescent lamps
  • Electric arc welding
  • Can damage the eye (cornea)
  • Germicidal lamps
  • Eye damage from sun light
  • Skin cancer

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UV effects
  • High ultraviolet kills bacterial and other
    infectious agents
  • High dose causes - sun burn increased risk of
    skin cancer
  • Pigmentation that results in suntan
  • Suntan lotions contain chemicals that absorb UV
    radiation
  • Reaction in the skin to produce Vitamin D that
    prevents rickets
  • Strongly absorbed by air thus the danger of
    hole in the atmosphere

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Visible light
  • Energy between 400 and 750 nm
  • High energy bright light produces of number of
    adaptive responses
  • Standards are set for the intensity of light in
    the work place (measured in candles or lumens)

150
IR
  • Energy between 750 nm to 0.3 cm
  • The energy of heat Heat is the transfer of
    energy
  • Can damage cornea, iris, retina and lens of the
    eye (glass workers glass blowers cataract)

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Microwave and radio wave
  • Energy between 0.1 cm to 1 kilometer
  • Varity of industrial and home uses for heating
    and information transfer (radio, TV, mobile
    phones)
  • Produced by molecular vibration in solid bodies
    or crystals
  • Health effects heating, cataracts
  • Long-term effects being studied

152
Laser
  • That depends
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