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DESIGNING FOR RADIATION PROTECTION. TUBE HOUSING. REDUCES LEAKAGE TO LESS THAN 100 mR PER HOUR AT A DISTANCE OF ONE METER FROM HOUSING One meter is 3.3 feet Body parts should not rest on tube housing. Control panel should indicate. Condition of exposure When x-ray tube is being energized

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tube housing
TUBE HOUSING
  • REDUCES LEAKAGE TO LESS THAN 100 mR PER HOUR AT A DISTANCE OF ONE METER FROM HOUSING
  • One meter is 3.3 feet
  • Body parts should not rest on tube housing
control panel should indicate
Control panel should indicate
  • Condition of exposure
  • When x-ray tube is being energized
  • kVp, mA or mAs
  • Visible or audible signal of exposure
slide4
SID
  • Tape measure or laser lights indicate the distance
  • Must be accurate with 2% of the indicated SID
collimation pbl beam alignment
COLLIMATIONPBLBEAM ALIGNMENT
  • X-ray beam and light should be within 2% of SID
  • PBL not required anymore
  • Beam should line up with image receptor
  • Proper alignment of beam to film (indicator light)
filtration
FILTRATION
  • 2.5 mm @70 kVp
  • 1.5 mm between 50-70 kVp
  • .5 mm below 50 kVp (mammo)
  • See question on page 569 (refer to chart 31-3 on page 461)
slide7
Reproducibility
  • Linearity
  • Operator shield
mobile radiography
MOBILE RADIOGRAPHY
  • Lead apron assigned to portable
  • Exposure switch should allow operator to be 2 meter from tube (6+)feet
fluoroscopy
FLUOROSCOPY
  • Source to skin distance – 38 cm
  • Mobile SSD – 30 cm
  • When intensifier is in parked position—no fluoro
  • Intensifier serves as a primary protective barrier and must be 2 mm Pb equivalent.
  • Filtration should be at least 2.5 mm Al equivalent—Tabletop, patient cradle or other material factored in for total filtration
  • Collimation—unexposed border should be visible on TV monitor
fluoroscopy1
FLUOROSCOPY
  • Dead man type exposure switch
  • Bucky opening covered automatically by .25 mm lead
  • Protective curtain -- .25 mm Pb equivalent
  • Timer (audible) when fluoro time has exceeded 5 minutes
fluoroscopy2
Intensity (R ) should not exceed 2.1 R per minute for each mA at 80 kVp

DAP

DOSE RESPONSE PRODUCT

DOSE AND VOLUME OF TISSUE IRRADIATED

DAP INCREASES WITH INCREASING FIELD SIZE

FLUOROSCOPY
design criteria
DESIGN CRITERIA
  • Location of x-ray table
  • Where is the primary beam directed?
  • Surrounding environment (controlled area vs. uncontrolled area)
  • RF room
  • Dedicated room
  • Use factor
  • # of exams in a room
primary protective barrier
Primary Protective Barrier
  • Anywhere the primary beam is directed ( dedicated chest rooms)
  • Lead bonded to sheet rock of wood paneling
  • Concrete, concrete block, brick
  • 4 inches of masonry = 1/16 inch of lead
  • Image intensifier considered a primary protective barrier
secondary barriers
SECONDARY BARRIERS
  • Secondary radiation (scatter, leakage)
  • Patient is source of scatter
  • Barrier does not have to be leaded
  • gypsum board 4 thicknesses of 5/8th inch drywall
  • glass ½ to 1 inch thickness
  • lead acrylic
  • Control booth
  • Lead aprons (5mm of lead attenuates____%_at _____kVp
factors that affect thickness of barrier
Factors that affect thickness of barrier
  • Distance
  • Occupancy-levels
  • Control vs uncontrolled
  • workload
  • Use factor
use factor
USE FACTOR
  • Amount of time x-ray beam is directed at wall/floor
  • Wall given a use factor of ¼
  • Floor given a factor of 1
  • Secondary barrier use factor of 1
  • Dedicated chest room-use factor of 1
finally
FINALLY
  • Barriers are designed with 75-100 kVp usage in mind so most barriers are thicker than needed
  • Exposure to outside of room is calculated to result in a DL of 100mrem per week but do not factor in patient and image receptor interception. DL is actually 1/10th of the recommended DL
exposure switch
Exposure switch
  • Mounted of fixed to control panel
  • No long cords
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