Radiation Shielding Information and Guidance

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Radiation Shielding Information and Guidance

• Don Parry, Health Physicist
• Michigan Department of Consumer Industry
  Services
• Radiation Safety Section
• dparry_at_michigan.gov

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Radiation Shielding Information

• Plan Reviews
• Plans should be submitted prior to construction!
• Rule 331(2) of the Ionizing Radiation Rules
  states that shielding is subject to design
  approval by the department
• Most medical x-ray rooms should normally be
  provided with 1/8 inch thick lead for primary
  barriers (including floors) and 1/16 inch thick
  lead for secondary barriers (including doors)
• Construction of an x-ray room without an approved
  plan may cause shielding modifications to be done
  after the room is constructed

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Radiation Shielding Information

• Form BHS/HFS 852 Information Required for a
  Radiation Shielding Plan Review
• Available on Web site
• Be sure to include all requested information
  including
• Plans or blueprints of rooms and adjacent areas
  to scale with compass directions. (1/4 1 foot
  preferred)
• Location of x-ray equipment, x-ray table,wall
  bucky, exposure switch, viewing window and
  control panel
• Description of occupancy of adjoining areas
  including above or below
• Description of floor and ceiling construction
  including minimum concrete thickness and density.

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Radiation Shielding Information

• Form BHS/HFS 852 (Continued)
• Be sure to include all requested information
  including
• Location,type, thickness and height of proposed
  shielding
• Indicate thickness and density of concrete and
  masonry materials
• Limits of travel of table, tube and image
  receptor
• Maximum kVp, mA and estimated workload in
  mAmin/wk
• For CT scanners, include a copy of the
  iso-exposure curves normally provided by the
  manufacturer
• Name and address of facility
• Name and address to send response letter

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Radiation Shielding Information

• Shielding Guidance
• Barriers should be designed for weekly radiation
  dose limits of 10 millirem per week for
  controlled area and 0.5 millirem per week for
  uncontrolled areas
• Vertical barriers must extend from the floor to a
  minimum height of 7 feet.
• If it is necessary to add additional shielding to
  the ceiling of the room, then the shielding in
  the walls must be extended above the 7-foot
  height to overlap the ceiling shielding.

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Radiation Shielding Information

• Shielding Guidance
• If there are multi story buildings in close
  proximity of the x-ray room, which have occupied
  spaces that could be exposed to scatter radiation
  that is not attenuated by the 7-foot high wall
  shielding, additional shielding may be necessary
  to protect those areas
• Outside walls and, particularly, windows may
  require shielding to protect distant areas even
  if the nearest occupied area is not immediately
  adjacent

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Radiation Shielding Information

• Operator Booth Shielding Guidance
• The lead glass viewing window should have an area
  of at least 1 square foot
• At least 1 square foot of the viewing window
  should be centered no less than 2 feet from the
  open edge of the booth and be centered 5 feet
  from the floor.
• The operator should be allotted not less than 7.5
  square feet of unobstructed floor space in the
  booth

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Radiation Shielding Information

• Operator Booth Shielding Guidance
• The operators booth should have no dimension
  less than 2 feet.
• The exposure switch needs to be permanently
  fastened behind the operators barrier so that
  the operator is protected from primary,
  first-scattered, and leakage radiation, even at
  arms length from the switch.
• The booth shall be located or constructed such
  that unattenuated direct scatter radiation
  originating on the examination table or at the
  wall-mounted image receptor will not reach the
  operator's position in the booth.
• Additional guidance available on web site

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Radiation Shielding Information

• Certificate of Need
• Equipment that requires a CON will not be
  registered until plans have been reviewed by the
  Radiation Safety Section.
• At least 1/16 inch lead normally is required for
  the walls of a CT room. CT rooms with high
  workloads and adjacent uncontrolled occupied
  areas may need shielding that is thicker than
  1/16 inch lead.
• Facilities with CT x-ray equipment may want to
  enlist the services of a qualified medical
  physicist for shielding advice. Plans would
  still need to be submitted to RSS for review.

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Radiation Shielding Information

• Dental Cephalometric and Tomographic Equipment.
• Dental cephalometric equipment requires shielding
  of the primary beam with 1/16 inch thick lead
• Dental Tomographic equipment requires primary
  beam shielding along with a fixed operators
  barrier with an exposure switch in a location at
  least arms length from the line of scatter.
• Dental extra oral facilities should submit plans
  for review and approval to the RSS

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Radiation Shielding Information

• Floors
• Need to use minimum thickness of concrete floor
  in shielding calculations
• Need to know density of concrete (147 lbs/ft3
  standard)

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Radiation Shielding Information

• Examples
• No Occupancy above or below
• On Slab
• Shielding should be floor to 7
• 1/16 inch thick secondary, 1/8 inch thick primary

1/8 inch lead (blue)
Leakage
Scatter
1/16 inch lead (red)
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Radiation Shielding Information

• Examples
• Occupied space below
• Need 1/16 inch thick lead on floor with 1/8 thick
  lead under table
• Floor shielding should overlap wall shielding

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Radiation Shielding Information

• Examples
• Crawl space
• Occupied space above
• Need lead in floor under table to prevent scatter
  under vertical barriers

Wall shielding needs to overlap ceiling shielding
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Radiation Shielding Information

• Examples
• CT with adjacent Multi Story Building
• May need additional shielding on outside wall

Occupied uncontrolled space in adjacent building
Adjacent Multi Story Building
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Radiation Shielding Information

• Examples
• Exposure switch location

Switch needs to be arms length from first
scattered and leakage radiation
Switch Location
Adjacent Multi Story Building
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Radiation Shielding Information

• Summary
• Submit shielding plans to the Radiation Safety
  Section for design approval prior to
  construction!
• Dental extraoral equipment such as cephalometric
  and tomographic units should also have shielding
  plans approved.
• Include all information requested on form BHS/HFS
  852.
• Equipment that requires a Certificate of Need
  will not be registered until a plan is reviewed
• Most rooms will be adequately shielded with 1/8
  inch thick lead for primary barriers and 1/16
  inch thick lead for secondary barriers.
• Be sure to consider areas above and below the
  x-ray room when designing shielding.

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Contact Information

• HeadquartersRadiation Safety SectionMichigan
  Department of Consumer Industry ServicesP.O.
  Box 30664Lansing, Michigan 48909 Phone (517)
  241-1989Fax [phone]
• Visitor/delivery address5th Floor, G. Mennen
  Williams Building525 W. Ottawa StreetLansing,
  Michigan 48933
• District OfficeOur district office, formerly in
  Pontiac, has moved to Radiation Safety
  SectionMichigan Department of Consumer
  Industry Services38600 Van Dyke, Suite
  375Sterling Heights, Michigan 48312
• Phone [phone]Fax [phone]