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Shielding design for interventinal procedure, by Gary ...

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  • 1. The Value of Composite Protective Shields in Exposure Reduction During Interventional Procedure Gary D. Hartwell, David J. Spinosa*, Allen R. Goode, John F. Angle, Alan H. Matsumoto Divisions of Medical Physics and Interventional Radiology University of Virginia Health System, Charlottesville, VA * Inova Fairfax Hospital Falls Church, Va.
  • 2. Background
    • Many fluoroscopically guided interventional procedures require high exposure.
    • Benefits to patients far outweigh the risks.
    • Patients are often large.
    • Require long fluoroscopic times.
  • 3. Physician Corollary
    • Can result in potentially serious long term consequences for the physicians who perform them.
    • Over a career the risks to the physician not mitigated by a corresponding benefit.
  • 4. Dosimeter Locations
    • OUTSIDE LEAD:
    • Left and Right Locations -> Collar, Waist and Knee (Total 6 DMs)
    • INSIDE LEAD: 0.5 mm equivalent
    • Left and Right Locations -> Waist
    • Control:
    • 1 DM was placed outside the angiographic suite.
  • 5. Procedures Types and Physician Position
    • IRs performed 176 Diagnostic and Interventional Procedures over a 7 Month Period:
        • 105 arterial
        • 43 venous
        • 28 GU/biliary including TIPS
    • Procedures Performed by side of Table ->
    • Left (54)
    • Right (97)
    • Both (25)
  • 6. Median Exposure per Procedure
      • Median (25,75 percentile)
    • Rt Col: 1.5 (0.4, 3.2) Lt Col: 1.9 (0.55, 5.25)
    • Rt W: 4.20 (1.0, 9.9) Lt W: 4.50 (0.80, 17.0)
    • Rt K: 5.10 (0.80, 12.8) Lt K: 4.20 (1.20, 18.4)
    • Rt W (I): 0.10 (0.00, 0.2) Lt W (I): 0.10 (0.0, 0.3)
    • Control: 0, 0, 0
  • 7. Interesting Results
    • The Median Radiation Exposure to the Waist and Collar Locations ->
    • Significant Difference
    • (Rt, p<0.0001; Lt, p<0.0001)
    • Lead Apron ->
    • Reduced Radiation Exposure at the Waist Location by 97.7% (p<0.0001)
  • 8. Maximun Exposure (mR) per Procedure by Location
    • Rt Col: 131 Lt Col: 245
    • Rt W: 3037 Lt W: 1795
    • Rt K: 1218 Lt K: 1174
    • Rt W (I): 93 Lt W (I): 20
  • 9. Fluoroscopic Entrance Skin Exposure (ESE)
    • 1995 median patient thickness 21.5 cM
    • 1995 median ESE 1250 mR min -1
    • 2005 median patient thickness 23.5 cM
    • 2005 median ESE 750 mR min -1
  • 10. Available Shields
    • Shields commonly available are very awkward to position where they will be most effective.
    • Tricky to maintain the sterile field.
  • 11. Composite protective shields
    • Do Recently introduced Composite protective shields provide shielding from scatter radiation while maintaining the integrity of the sterile field?
  • 12. Composite Shields
  • 13. Study Objectives
    • Evaluate how effectively these shields reduce exposure to the physician.
    • Ease of use while maintaining sterile field.
    • Ease of deployment for different procedure conditions
  • 14. Methods
    • Angiographic table was located 110 cm above the floor.
    • X-ray tube under the table.
    • Dosimeter was fixed at different heights on a tripod 1 meter from the point where the beam intersected the phantom.
    • Exposure measurements were made and recorded without and with combinations of the composite shields in place.
  • 15. Experimental Setup
  • 16. Exposure Measurement Heights
    • Eye level 170 cm above the floor.
    • Chest level 145 cm above the floor.
    • Waist level 105 cm above the floor
    • Knee level 75 cm above the floor
  • 17. Sterile Composite Shield
  • 18. Side of Table Pad Covered with additional protective shield
  • 19. Exposure Measurement Angles
    • C-arm at 0 degrees oblique.
    • C-arm at 15 degrees oblique.
    • C-arm at 30 degrees oblique.
    • C-arm at 45 degrees oblique.
    • Tube always on the side of the operator.
  • 20. Sterile Shield and Skirt
  • 21. Exposure Rate (uR/min) @ 0°
  • 22. Exposure Rate (uR/min) @ 15°
  • 23. Exposure Rate (uR/min) @ 30°
  • 24. Exposure Rate (uR/min) @ 45°
  • 25. Maximum Exposure Rate
    • Radiation Measurements while operating at the maximum exposure rate were also made at the 0 degrees position in order to:
    • Confirm performance of the shields at the high exposure rates and increased scatter radiation that would be expected from large patients.
    • Evaluate how well the composite shields performed at the higher beam energy.
  • 26. Maximum Exposure Results
    • 125 kvp.
    • 9.7 R per minute exposure rate.
    • Exposure at chest height without shields 12 mR per minute.
    • Exposure at chest height with shields 1.9 mR per minute.
    • More than 6 times average patient rate
    • Greater when HLC used.
  • 27. Relevant Question
    • Is there a size patient who should be be denied an elective procedure because of poor image quality and excessive dose to the physician?
  • 28. CONCLUSIONS
    • Shields can be very effective >80%
    • Composite shields were equally effective at all diagnostic energies
    • Shields must be used in combination
    • Must be placed in the optimum location.
  • 29. Thank you for your attention