Radiation Safety Considerations for PET/CT

1. Radiation Safety Considerations for PET/CT Robert E. Reiman, MD, ABNM Radiation Safety / OESO Duke University Medical Center

2. Radiation Safety? Who Cares!

3. Why We Have Radiation Protection Programs • December 1895: Roentgen discovers x-rays. • 1/1896 – 12/1896: 23 cases of radiation dermatitis documented. • 1911 –1914: 252 radiation-induced cancer cases with 54 fatalities.

4. “I’m From the Government, and I’m Here to Help You...”

5. Why We’re Regulated In the early years of the Twentieth Century, radium was widely promoted as a cure for practically everything, from cancer to baldness. Radium was added to hundreds of “over-the-counter” commercial “beauty” and “health” products.

6. Why We’re Regulated Eben Byers, socialite and U.S. Open champion, drank three bottles of “Radithor” a day for three years. He died a painful death from radionecrosis of the jaw and skull in 1932. After a Congressional inquiry, the FDA seized oversight of radium-containing products.

7. PET/CT Regulations • “10 CFR 20” – Title 10 (Energy), Code of Federal Regulations, Part 20 • “10 CFR 35” – Title 10, Code of Federal Regulations, Part 35 • 10 CFR 20 addresses general standards for radiation protection. • 10 CFR 35 addresses use of “by-product” materials in medicine.

8. PET/CT Regulators • NRC directly oversees 17 states. • 33 “Agreement States” implement NRC regulations...and then some. • FDA regulates production of PET radiopharmaceuticals, and manufacture and sale of CT scanners. • Individual states regulate operation of CT scanners.

9. Helpful Organizations • International Commission on Radiological Protection (ICRP) • National Council on Radiation Protection and Measurements (NCRP) • Nuclear Regulatory Commission (NRC) • “Agreement State” Radiation Protection Agencies

10. Principle of “ALARA” As Low As Reasonably Achievable

11. Annual Radiation Dose Limits

12. Radiation Warning Signs PET/CT Scanner Cyclotron “Hot” Lab

13. Record Retention • Shipping and Receiving (3 years) • Area Surveys and Trash Surveys (3 years) • Public Dose Limit Compliance (3 years) • Personnel Dosimetry (lifetime)

14. Criteria for Personnel Monitoring • 10 CFR 20: Personnel monitoring occupational dose is required if the sum of external and internal EDE could be expected to exceed 10 % of the annual whole-body occupational limit. • Licensees can monitor at lower exposure levels as part of an ALARA program.

15. Survey Meter Quality Assurance • Meters OFF when not in use • Operation check with each use • Regular battery and high-voltage checks • Annual calibration

16. Hands in the Beam? • NO hands in the useful (primary) beam unless protected by 0.5 mm lead or equivalent shielding. • Mechanical patient restraint should be used whenever practical in lieu of human holders. Health Physics, Aug 2003

17. Medical Events: Administrative Criteria • Administered to wrongpatientorresearchsubject. • Wrongradiopharmaceutical administered. • Wrongroute of administration. • Administered activity differs from that in the written directive by more than 20 percent.

18. Medical Events: Dose Criteria • Effective Dose Equivalent > 5 rem (0.05 Sv). • Single organ / tissue dose > 50 rem (0.5 Sv).

19. Reporting Medical Events • Must notify NRC / Agreement State agency within one calendar day after discovery. • Must follow up with a written report within 15 days after discovery. • Must notify referring physician within 24 hours. • Must notify patient or guardian unless contraindicated by referring physician.

20. I Already Know All This Stuff...Why Is PET/CT Different?

21. PET = Nuclear Medicine on Steroids

22. PET + = TWICE the Headaches CT

23. Why is PET Different? • PET radionuclides have higher Exposure Rate Constants than “traditional” nuclear medicine radionuclides. • Photon energies are higher. • Half-lives are shorter.

24. Higher Exposure Rate Constants

25. Higher Dose Rate From Patients

26. PET Shielding: Tenth Value Layers * TVL = thickness of material required to absorb 90% of photons

27. Shorter Physical Half-Life

28. Shorter Half-Life >> Lower Dose* *Dose received by a bystander at 1 meter during 5 half-lives or more

29. How Can I Minimize My Staff’s Exposure?

30. PET/CT: Sources of Exposure to Staff • Cyclotron (?) • Radiopharmaceutical Production (?) • Dose Dispensing / Calibration • Dose Administration • Patients • X-rays From CT

31. What Doses Do People Get? Ref: Beyer T, Mueller SP, Brix G et al. Radiation exposure during combined whole-body FGD-PET/CT imaging. 51st Annual Meeting, Society of Nuclear Medicine, June 22, 2004. Abstract 1331.

32. Measures to Reduce Personnel Dose • Time, Distance and Shielding • Laboratory Technique • Administrative and Procedural Controls

33. Good Hot Lab Technique • Cover work surfaces • Protective gloves • Wash hands frequently

34. Things NOT To Do in the Hot Lab • Don’t Drink • Don’t Eat • Don’t Smoke • No cosmetics

35. Minimize Time and Maximize Distance! Technologists should minimize the time spent in close proximity (less than two meters) from the patient.

36. Maximize Distance! • Inverse Square Law ( 1/r2 ) • Dramatic reductions in exposure • Simulations of PET technologist’s interactions with patients show that 75% of dose is accumulated during time tech is within 2 meters of patient.

37. I’m Outta Here... I Got 8 mrem! I Got 2 mrem! I Got 0.1 mrem! I Got 0.5 mrem!

38. Utilize Shielding Positrons can be stopped by 2 - 5 mm Lucite. Gammas require a high-Z material. Neutrons require high hydrogen content (paraffin or the “waters of hydration” in concrete).

39. PET Barrier Materials

40. Typical Hot Lab “Shadow” Shield

41. Other Shielding Methods Syringe Shields (Tungsten and Lead Glass) Unit Dose Stations

42. Shielding: If you can’t be in the shielded booth...

43. ...then stand behind the doc.

44. X-Ray Protective Equipment

45. X-ray Aprons -- No Protection at 511 KeV The “lead” aprons used in diagnostic radiology have about 0.5 mm lead equivalent. These afford significant protection at energies under 120 KeV, but are nearly useless against annihilation photons. 100 KeV: Transmission = 4.3 % 511 KeV: Transmission = 91.0 %

46. Measures to Reduce Dose: Other Techniques Tongs to Maximize Distance Syringe Shields (Tungsten and Lead Glass) Mobile Shields

47. Measures to Reduce Dose: Procedural Controls • Automated dose dispensing and Calibration (“Unit” Dose) • Elimination or automation of “flush” during patient administration • Rotation of personnel

48. How Do I Minimize Radiation Exposure to My Patients?

49. Reducing PET/CT Patient Dose • Optimize administered radioactivity. • Reduce CT mAs. • Increase “pitch”. • Technique charts to minimize CT exposure to pediatric patients and small adults.

50. Reducing PET/CT Patient Dose Ref: Beyer T, Mueller SP, Brix G et al. Radiation exposure during combined whole-body FGD-PET/CT imaging. 51st Annual Meeting, Society of Nuclear Medicine, June 22, 2004. Abstract 1331.