Shielding design for interventinal procedure, by Gary ...

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Shielding design for interventinal procedure, by Gary ...

  1. 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. 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. 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. 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. 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. 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. 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. 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. 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. 10. Available Shields Shields commonly available are very awkward to position where they will be most effective. Tricky to maintain the sterile field.
  11. 11. Composite protective shields Do Recently introduced Composite protective shields provide shielding from scatter radiation while maintaining the integrity of the sterile field?
  12. 12. Composite Shields
  13. 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. 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. 15. Experimental Setup
  16. 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. 17. Sterile Composite Shield
  18. 18. Side of Table Pad Covered with additional protective shield
  19. 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. 20. Sterile Shield and Skirt
  21. 21. Exposure Rate (uR/min) @ 0° Level without shield Sterile shield % reduction Sterile and Table skirt % reduction Eye Level 756 180 76.2% 132 83% Chest level 1140 492 56.8% 180 84% Waist level 1278 900 29.6% 186 85% Knee level 1332 1266 5.0% 174 87%
  22. 22. Exposure Rate (uR/min) @ 15° Level without shield Sterile shield % reduction Sterile and Table skirt % reduction Eye Level 936 354 62% 126 87% Chest level 1200 414 66% 174 86% Waist level 1584 714 55% 186 88% Knee level 1812 1596 12% 174 90%
  23. 23. Exposure Rate (uR/min) @ 30° Level without shield Sterile shield % reduction Sterile and Table skirt % reduction Eye Level 786 234 70% 210 73% Chest level 1164 654 44% 162 86% Waist level 1008 714 58% 156 88% Knee level 798 1596 20% 138 83%
  24. 24. Exposure Rate (uR/min) @ 45° Level without shield Sterile shield % reduction Sterile and Table skirt % reduction Eye Level 1014 384 62% 156 85% Chest level 1602 486 70% 204 87% Waist level 1008 882 53% 216 88% Knee level 2004 1584 21% 246 88%
  25. 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. 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. 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. 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. 29. Thank you for your attention

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