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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

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DESIGNING FOR RADIATION PROTECTION

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  1. DESIGNING FOR RADIATION PROTECTION

  2. 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

  3. Control panel should indicate • Condition of exposure • When x-ray tube is being energized • kVp, mA or mAs • Visible or audible signal of exposure

  4. SID • Tape measure or laser lights indicate the distance • Must be accurate with 2% of the indicated SID

  5. 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)

  6. 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)

  7. Reproducibility • Linearity • Operator shield

  8. MOBILE RADIOGRAPHY • Lead apron assigned to portable • Exposure switch should allow operator to be 2 meter from tube (6+)feet

  9. 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

  10. 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

  11. 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

  12. PROTECTIVE BARRIERS

  13. 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

  14. 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

  15. 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

  16. Factors that affect thickness of barrier • Distance • Occupancy-levels • Control vs uncontrolled • workload • Use factor

  17. 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

  18. 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

  19. Exposure switch • Mounted of fixed to control panel • No long cords

  20. TLD, OSL

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