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RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology. RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY. Part 16.2: Optimization of protection in fluoroscopy Practical exercise. Overview / Objectives.

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RADIATION PROTECTION IN DIAGNOSTIC AND INTERVENTIONAL RADIOLOGY

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  1. IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology RADIATION PROTECTION INDIAGNOSTIC ANDINTERVENTIONAL RADIOLOGY Part 16.2: Optimization of protection in fluoroscopy Practical exercise

  2. Overview / Objectives • To become familiar with quality control tests in fluoroscopy • To measure the maximum dose rate to the patient 16.2: Optimization of protection in fluoroscopy

  3. IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology Part 16.2: Optimization of protection in fluoroscopy Maximum dose rate

  4. Fluoroscopy - Maximum Dose Rate Purpose : • to know the maximum dose rate to the patient Method : • place ~2mm lead over the image intensifier • place a dosimeter ~ 30 cm from the intensifier • operate unit at maximum kVp and mA • measure dose rate • X ray tube below the patient table 16.2: Optimization of protection in fluoroscopy

  5. Set-up for measurement of maximum dose rate. 16.2: Optimization of protection in fluoroscopy

  6. The ionization chamber should be protected to avoid pressure and possible malfunctioning. It should be in contact with the acrylic to measure also backscattering. 16.2: Optimization of protection in fluoroscopy

  7. The intensifier should be as far as possible from the table with the x-ray tube as close as possible to the patient position. These are the worst conditions in terms of maximum radiation dose tothe skin patient 16.2: Optimization of protection in fluoroscopy

  8. Note:the X-ray tube is placed very close to the table. 16.2: Optimization of protection in fluoroscopy

  9. A radio-opaque marker (a key) can be used to center the chamber in the image field 16.2: Optimization of protection in fluoroscopy

  10. The key shows the motion of the C-arm or the table. 16.2: Optimization of protection in fluoroscopy

  11. The key should be removed after having centred the chamber. 16.2: Optimization of protection in fluoroscopy

  12. A folded lead apron is used to measure the maximum dose rate (use enough layers to approximate 2 mm of lead). The lead apron is placed over the protected chamber. 16.2: Optimization of protection in fluoroscopy

  13. Note:This geometry is the worst in terms of patient radiation dose— the tube close to the table and the intensifier far from the patient. It also increases the scattered radiation dose to the physician and staff. 16.2: Optimization of protection in fluoroscopy

  14. The dose rate is79.5 mGy/minfor this situation 16.2: Optimization of protection in fluoroscopy

  15. The image quality is poor. The chamber edge is hardly visible. 16.2: Optimization of protection in fluoroscopy

  16. The generator selects the maximum possible kV (110 kV for this equipment) and 3.6 mA. 16.2: Optimization of protection in fluoroscopy

  17. In the high contrast mode with the same geometry, the maximum of 110 kV and 7.34 mA is selected by the generator. 16.2: Optimization of protection in fluoroscopy

  18. The image quality is still poor although slightly improved. 16.2: Optimization of protection in fluoroscopy

  19. In thehigh contrast modethe maximum dose rate is186.7 mGy/min. 16.2: Optimization of protection in fluoroscopy

  20. Fluoroscopy - Maximum Dose Rate Analysis : • FDA limits: • normal-dose fluoroscopy: maximum air-kerma rate 88 mGy/min (30 cm from the image receptor) • High-dose-rate fluoroscopy: maximum air-kerma rate 176 mGy/min (30 cm from image receptor) Frequency : • acceptance, 6-monthly • tube change, generator repair 16.2: Optimization of protection in fluoroscopy

  21. Importance of quality assurance (QA) • It is very important to have a QA programmes established in your practice and not to base dose controls on specification provided by the manufacturer or on the additional checks performed by the manufacturer. 16.2: Optimization of protection in fluoroscopy

  22. Where to Get More Information Quality Control in Diagnostic Imaging, Gray JE, Winkler NT, Stears J, Frank ED. Available at no cost. http://www.diquad.com/QC%20Book.html 15.3: Optimization of protection in radiography

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