Transcript DESIGNING FOR RADIATION PROTECTION

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
 kVp, mA or mAs
 Visible or audible signal of exposure
SID
 Tape measure or laser lights indicate the
distance
 Must be accurate with 2% of the
indicated SID
COLLIMATION
PBL
BEAM 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
 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)
 Reproducibility
 Linearity
 Operator shield
MOBILE RADIOGRAPHY
 Lead apron assigned to portable
 Exposure switch should allow operator to
be 2 meter from tube (6+)feet
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
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
FLUOROSCOPY
 Intensity (R ) should not exceed 2.1 R
per minute for each mA at 80 kVp
 DAP

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DOSE RESPONSE PRODUCT
DOSE AND VOLUME OF TISSUE
IRRADIATED
DAP INCREASES WITH INCREASING
FIELD SIZE
PROTECTIVE BARRIERS
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
 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 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
 Distance
 Occupancy-levels
 Control vs uncontrolled
 workload
 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
 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
 Mounted of fixed to control panel
 No long cords
TLD, OSL