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Rad Protection in Fluoro & INTRO RHB regs

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Rad Protection in Fluoro & INTRO RHB regs

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  1. Rad Protection in Fluoro & INTRO RHB regs RT 244 - 2008 Week 1,2 Wed

  2. Regulatory Requirements 1. Regarding the operation of fluoroscopy units 2. Regarding personnel protection 3. Regarding patient protection

  3. Fluoroscopic Positioning Previewing • Radiographers are trained in positioning • Unnecessary radiation exposure to patient is unethical • Fluoroscopic equipment should not be used to preview patient’s position

  4. Patient Protection • Tabletop exposure rate • Maximum 10 R/min • Typically 1 – 3 R/min • Some books ave is 4 R/min **

  5. Patient Protection • Minimum source-to-skin distance • 12” for mobile equipment • 15” for stationary systems • Audible alarm at 5 mins. • Same rules for collimation

  6. Patient Protection • Typical exposure rates • Cinefluorography • 7.2 R/min • Cassettes • 30 mR/exposure • 105 mm film • 10 mR/exposure

  7. Protection of Radiographer and Radiologist • Lead apron • 0.25 mm Pb/eq • Highest energy scatter • 90o angle to the incident beam • Same level as radiographer /radiologist’s gonads

  8. Protection of Radiographer and Radiologist • Single step away from the table decreases exposure exponentially • Bucky slot cover • Lead rubber drape • Radiologist as shielding

  9. ISOEXPOSURE CURVES

  10. Protection of Others • Radiographer’s responsibility to inform others in the room to wear lead apron • Do not initiate fluoroscopy until all persons have complied

  11. PUBLIC EXPOSURE • 10 % OF OCCUPATIONAL • NON MEDICAL EXPOSURE • .5 RAD OR 500 MRAD • UNDER AGE 18 AND STUDENT • .1 rem 1 mSv

  12. COLLIMATION(for X-ray TUBE Collimator) • The PATIENT’S SKIN SURFACE • SHOULD NOT BE CLOSER THAN • ___________ CM BELOW THE COLLIMATOR? • ____________ INCHES? 15 cm / 6.5 inches

  13. The Patient & Scatter

  14. Radiation Protection (recap) • Tube in never closer to the patient than 15” in stationary tubes and 12” with a C arm • As II moves away from the patient the tube is being brought closer • Bucky tray is connected to a lead shield called the Bucky slot cover. It must be 0.25 mm Pb • There should be a protective apron of at least 0.25 mm Pb that hangs down from the II • Every machine is required to have an audible timer that signals 5 minutes of fluoroscopy time • Exposure switch must be a “dead man” type

  15. Regulations about the operation • Fluoroscopic tubes operate at currents that range from0.5 to 5 mA with 3 the most common • AEC rate controls: equipment built after 1974 with AEC shall not expose in excess of 10 R/min; equipment after 1974 without AEC shall not expose in excess of 5 R/min

  16. Other regulations • Must have a dead man switch • Must have audible 5 min. exposure timer • Must have an interlock to prevent exposure without II in place • Tube potential must be tested (monitored)weekly • Brightness/contrast must be tested annually • Beam alignment and resolution must be tested monthly • Leakage cannot exceed 100mR/hr/meter

  17. Fluoroscopy exposure rate • For radiation protection purposes the fluroscopic table top exposure rate must not exceed 10 mR/min. • The table top intensity should not exceed 2.2 R/min for each mA of current at 80 kVp

  18. Patient Protection • A 2 minute UGI results in an exposure of approximately 5 R!! • After 5 minutes of fluoro time the exposure is 10-30 R • Use of pulsed fluoro is best (means no matter how long you are on pedal there is only a short burst of radiation) • ESE must not be more than 5 rads/min

  19. Rad Protection • Always keep the II as close to the patient as possible to decrease dose • Highest patient exposure happens from the photoelectric effect (absorption) • Boost control increases tube current and tube potential above normal limits • Must have continuous audible warning • Must have continuous manual activation

  20. ESE FOR FLUORO • TLD PLACED AT SKIN ENTRACE POINT • 1 – 5 R/MINUTE AVE IS 4 R/MIN • INTERGRAL DOSE – • 100 ERGS OF TISSUE = 1 RAD EXPOSURE • OR 1 GM RAD = 100 ERGS

  21. SSD – TUBE TO SKIN DISTANCE • FIXED UNITS • 18” PREFERRED • 15 “ MINIMUM MOBILE UNITS ( C-ARMS) • 12’ MINIMUM

  22. PATIENT PROTECTION • LIMIT SIZE OF BEAM • BEAM ON TIME • DISTANCE OF SOURCE TO SKIN • PBL • FILTRATION (2.5 mm Al eq) @ 70 • SHEILDING • SCREEN/FILM COMBO

  23. GONAD SHIELDING • MUST BE . 5 MM OF LEAD • MUST BE USED WHEN GONADS WILL LIE WITHING 5 CM OF THE COLLIMATED AREA (RHB) • KUB. Lumbar Spine Pelvis • male vs female shielding

  24. Gonad shielding & dose • ♀ receive 3x more dose than • ♂ for pelvic x-rays • 1 mm lead will reduce exposure (primary) by about 50% ♀ • by about 90 – 95 % ♂

  25. KEEP I.I. CLOSE TO PATIENT

  26. Over vs under the table fluoro tubes

  27. PATIENT EXPOSURE • REDUCE DISTANCE OF IMAGE INTESIFIER • INCREASE DISTANCE FROM THE TUBE

  28. Patient entrance skin exposure (ESE) is higher when the fluoroscopic x-ray tube is too close to the tabletop.

  29. PATIENT EXPOSURE • REDUCE SIZE OF COLLIMATED BEAM WHEN POSSIBLE

  30. Framing and patient dosesyll = Pg 31 • The use of the available film area to control the image as seen from the output phosphor. • Underframing • Exact Framing, (58 % lost film surface) • Overframing,(part of image is lost) • Total overframing

  31. EXPOSURE RATES FLUORO • MA IS 0.5 MA TO 5 MA PER MIN • AVE DOSE IS 4 R / MIN • IF MACHINE OUTPUT IS 2 R/MA/MIN = WHAT IS PT DOSE AT 1.5 MA FOR 5 MIN STUDY? • 15R

  32. EXPOSURE RATES FOR FLUORO • CURRENT STANDARD • 10 R/MIN (INTENSIFIED UNITS) • HLC: BOOST MODE 20 R/MIN • OLD (1974) NO ABC NON IMAGE INTES • 5 R/MIN

  33. DOSE REGULATIONS • BEFORE 1974 - AT TABLETOP • 5R/MIN (WITHOUT AEC) • 5R/MIN (WITHOUT AEC) – BOOST MODE • After 1974 with AEC • 10 R/MIN 20R/MIN BOOST

  34. RADIATION PROTECTIONThe Patient is the largest scattering object • Lower at a 90 DEGREE ANGLE from the patient + PRIMARY BEAM AT 1 METER DISTANCE - • 1/1000 OF INTENSITY PRIMARY XRAY or 0.1%

  35. BUCKY SLOT COVER .25 MM LEAD

  36. Bucky Slot Cover

  37. ISOEXPOSURE CURVES

  38. SCATTER FROM THE PATIENT TABLE TOP, COLLIMATOR, TUBE HOUSING, BUCKY STRAY RADIATION – LEAKAGE OR SCATTER RADIATION PERSONNEL PROTECTION

  39. TOWER CURTAIN .25 MM LEAD EQ

  40. Lead curtain & dose reduction

  41. Pulsed Fluoro • Some fluoroscopic equipment is designed for pulsed-mode operation. With the pulsed mode, it can be set to produce less than the conventional 25 or 30 images per second. This reduces the exposure rate. • Collimation of the X ray beam to the smallest practical size and keeping the distance between the patient and image receptor as short as possible contribute to good exposure management.

  42. PERSONNEL PROTECTION • STANDING BEHIND A PROTECTIVE PRIMARY (1/16TH pb) BARRIER: • PRIMARY RADIATION EXPOSURE – 99.87% REDUCED • PORTABLE BARRIER = 99 % REDUCTION

  43. PERSONNEL PROTECTION • PROTECTIVE APRONS – • 0.25 PB = 97% ↓ TO SCATTER • 0.5 PB = 99.9% ↓ TO SCATTER • THYROID SHEILDS (0.25 & 0.5) • GLOVES (0.25 & 0.5)