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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 • 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
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 • 2.5 mm @70 kVp • 1.5 mm between 50-70 kVp • .5 mm below 50 kVp (mammo)
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
Intensity (R ) should not exceed 2.1 R per minute for each mA at 80 kVp 10R/min (100mGya/min) fluoro OR 20R/min (200mGya/min) high level fluoro DAP (for both fluoro and rad imaging systems DOSE RESPONSE PRODUCT DOSE AND VOLUME OF TISSUE IRRADIATED DAP INCREASES WITH INCREASING FIELD SIZE DAP Meter imbedded in collimator FLUOROSCOPY
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