Diagnostic Reference Levels

1. IAEA DRLs KAMPALA Diagnostic Reference Levels David Sutton / Colin Martin Dundee & Glasgow Kampla

2. ICRP 73 1996 First introduced the idea of a ‘diagnostic reference level’ Simple test for identifying situations where levels of patient dose are unusually high Kampla

3. Application of DRLs • Values of measured quantities above which some specified action or decision should be taken •  Values must be specified and • Action must be specified • DRLs will be intended for use as a convenient test for identifying situations where the levels of patient dose are unusually high. Kampla

4. What is a Diagnostic Reference Level ? . • A dose level for typical examinations for groups of standard-sized patients or standard phantoms and for broadly defined types of equipment • A guide to the – indistinct – border between good / normal practice and bad / abnormal practice Kampla

5. What is a Diagnostic Reference Level ? ‘ • Something set using an arbitrary (i.e. not scientific) threshold in a distribution • A trigger for the first step in the optimisation process • A tool that serves as a means to identify situations where patient doses are unusually high Kampla

6. What are they NOT? • Static : DRLs require continuous updating • DRLs are not limiting (maximum) values; the application of dose limits is not appropriate in diagnostic radiology • A carte blanche that • image quality is appropriate • the examination is performed at an optimized dose level • Surrogates for individual dose estimation Kampla

7. Diagnostic Reference Levels –Why? Radiation is harmful Diagnosis is beneficial Need to use the smallest amount of radiation which will result in the correct diagnosis. OPTIMISATION Kampla

8. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

9. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

10. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

11. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

12. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

13. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

14. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

15. Diagnostic Reference Levels –Why? • Identify which dose is just low enough & what image quality is just good enough to achieve the required diagnosis. Kampla

16. Perceived image quality is task and reader dependent. Kampla

17. Radiologist A Radiologist B Kampla

18. 50 mA 100 mA 20 mA 150 mA 200 mA Kampla

19. Diagnostic Reference Levels –Why? • What dose is just low enough & what image quality is just good enough to achieve the required diagnosis? • Very Difficult to do!!! Kampla

20. Diagnostic Reference Levels –Why? • So lets just decide that if the majority of radiologists agree that a particular dose produces an image that’s diagnostic then it probably is. - A guide to the – indistinct – border between good / normal practice and bad / abnormal practice. Kampla

21. Diagnostic Reference Levels –Why? (Another possible reason) • Regulatory Compliance • Required under some National legislation; Required by new BSS (John will talk about the BSS) Kampla

22. Diagnostic Reference Levels • A guide to the – indistinct – border between good / normal practice and bad / abnormal practice. • Based on the premise that images are diagnostic in the first place . • A step on the road to optimisation Kampla

23. Historical Perspective– What is diagnostic ? :UK Survey of Patient Dose 1984 -20 Hospitals Kampla

24. UK Survey of Patient Dose 1984 Kampla

25. RCR “Patient Dose Reduction in Diagnostic Radiology 1990” “Some 1300 man Sv could be saved by persuading the 25% of hospitals with the higher doses for the six exams to change their technique to fall in line with the remaining 75%” Kampla

26. DRLS are OFTEN defined by the 75th percentile WHAT IS A PERCENTILE ?

29. Third Quartile Median

30. Third Quartile

31. Different Data

33. Some Data Third Quartile Median

34. Third Quartile

35. Third Quartile Median

36. Third Quartile

37. Diagnostic Reference Levels (A guide to the – indistinct – border between good / normal practice and bad / abnormal practice.) Most easily understood at National i.e. – very large sample – level 75th percentile chosen as the ‘indistinct border” – No real scientific basis Kampla

38. National DRLs Usually set at 3rd quartile value from distribution of hospital mean doses Excludes high dose ‘tail’ of distribution Expected to come down as equipment & optimisation improve Kampla

39. Achievable Dose By definition, most centres will be below the DRL. The median (50th percentile) of the distribution used to set the DRL is called the Achievable Dose. Achievable dose is a reasonable goal with standard techniques and technologies. Kampla

40. UK Survey 2010 January to December 2010 165,000 ESD measurements for radiographs 185,000 KAP measurements for radiographs 22,000 KAP measurements for Fluoroscopy Kampla

41. UK Survey 2010 Kampla

42. UK 75th percentiles : Radiography Kampla

43. UK 75th percentiles : Fluoroscopy Kampla

44. Why do you think that doses have come down Since 1985? Quick Think Kampla

45. How do you audit against DRLs in your Hospital? Remember - A DRL is a dose level for typical examinations for groups of standard-sized patients or standard phantoms and for broadly defined types of equipment So decide which examinations you are going to audit and in which faciility !!!! . Kampla

46. Some UK National Diagnostic Reference Levels Skull Chest T Spine L spine Abdomen Pelvis Bitewing L Ob Breast Ba Swallow Ba Meal Ba Enema IVU MCU Pyelography Coronary Angio Venography etc CT Head CT Chest CT Abdomen CT CA ChestAbdoPelvis (Paediatric CT and complete exams) Kampla

47. Do you have to audit against all the National DRLs locally? ‘…NO’ It depends on what you do Kampla

48. Criteria for inclusion (1) • Examinations must be performed reasonably frequently in your hospital / department and should be representatve of all equipment. • Data collection must be feasible Kampla

49. Criteria for inclusion (2) You should ideally include at least one examination performed on each item of equipment that makes a significant contribution to the workload of the department Kampla

50. Criteria for inclusion (3) • Examinations should be inclusive with regard to staff • Examinations should ideally cover the work of all groups of operators carrying out procedures in the department, i.e. - • radiographers • radiologists • non-radiological clinicians • others Kampla