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Similar to Sutton Leiden Presentation Dec 2008 Ds4
Sutton Leiden Presentation Dec 2008 Ds4
- 1. Development of DRLsin the UK David Sutton Ninewells Hospital & Medical School Dundee, UK
- 2. Why have DiagnosticReference Levels ? Radiation is harmful Diagnosis is beneficial Need to use the smallest amount of radiation which will result in the correct diagnosis.
- 3. Perceived image qualityis task and reader dependent.
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- 5. What dose isjust low enough & what image quality is just good enough to achieve the required diagnosis? Why have Diagnostic Reference Levels ?
- 6. It’s easier todecide that if the majority of radiologists agree that a particular dose range results in images that are diagnostic then they probably are. Why have Diagnostic Reference Levels ?
- 7. What is aDiagnostic 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.
- 8. What is aDiagnostic Reference Level ? A level set using an arbitrary (i.e. not scientific) threshold in a distribution A trigger for the first step in the optimisation process ‘
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- 10. Historical Perspective –What is diagnostic? UK Survey of Patient Dose 1983-5 20 Hospitals 5 37 Pelvis AP 8 88 Abdomen AP 11 71 L Spine AP 4 43 T Spine AP 11 48 Chest PA 5 19 Skull AP Room Ratio Patient Ratio Examination
- 11. UK Survey ofPatient Dose 1983-5
- 12. RCR “Patient DoseReduction 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%”
- 13. ICRP 60 1991Consideration should be given to the use of dose constraints or investigation levels selected by the appropriate professional or regulatory agency for application in some common diagnostic procedures.
- 14. 1992 – UKNational Protocol Practical guidance on comparing local performance with National Practice Local performance to be assessed in terms of mean dose in a representative sample of standard sized patients. Not a legal requirement.
- 15. Doses to patientsfrom medical x-ray examinations in the UK – 1995 review 50 000 patient dose measurements 375 UK hospitals Average 30% reduction in mean doses for common x-ray exams since 1984
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- 18. NRPB 2000 Reviewof Patient Doses
- 19. NRPB 2000 Reviewof Patient Doses
- 20. Revised EU MedicalExposures Directive (97/43/Euratom) : MED Article 4(2) “Members shall promote the establishment and use of diagnostic reference levels for diagnostic examinations in radiology and nuclear medicine and the availability of guidance for this purpose (having regard to European diagnostic reference levels where available)”
- 21. MED in UKLaw (1) - Revised EU Medical Exposures Directive (97/43/Euratom): UK Ionising Radiations Regulations 1999 - Suitable quality assurance programmes for medical imaging equipment should be implemented and should include measurements at suitable intervals to enable the assessment of representative patient doses
- 22. MED in UKLaw (2) Revised EU Medical Exposures Directive (97/43/Euratom) : Ionising Radiation(Medical Exposure)Regulations 2000 Hospital needs to establish DRLs and Undertake appropriate reviews when DRLs are consistently exceeded and Ensure that corrective action is taken where appropriate.
- 23. MED in UKLaw (3) UK Department of Health : Hospitals can adopt national DRLs for use locally or establish their own based on local practice, if sufficient local data are available Quite clear that local DRLs can be established
- 24. 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 .
- 25. Most easily understoodat National i.e. – very large sample – level 75 th percentile chosen as the ‘indistinct border” – No real scientific basis National Diagnostic Reference Levels
- 26. Skull Chest TSpine L spine Abdomen Pelvis Bitewing L Ob Breast UK National Diagnostic Reference Levels 2007 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)
- 27. Variation of NationalDRL with time - Ba Enema : 75 th percentile threshold 1984 -2005 1984 2005
- 28. DoH Guidance April2007 “An employer may decide to adopt National DRLs or to set higher OR lower DRLs depending on the imaging equipment available to them or the patient case mix of the healthcare establishment. Local DRLs higher than those set nationally would need to be justified”
- 29. Local Diagnostic ReferenceLevels DoH Guidance April 2007 By taking responsibility for establishing and setting their own DRLs, hospitals (or groups of hospitals) should have the ability to adapt local practice and more effectively optimise exposures.
- 30. DRLs The firststep You must have a dose monitoring programme in place Your dose monitoring programme needn’t just measure dosimetric quantities such as esd, dlp or kap – although preferable. Example : screening time during pacemaker insertion.
- 31. (The second step)IPEM Report 88 : Guidance on the establishment and use of Diagnostic Reference Levels for Medical X-Ray Examinations.
- 32. Setting Local DRLs -or- Choosing DRLs to set locally The establishment of Local DRLs is NOT a precise science. You need simple and practical methods to set them. You need simple and practical methods to audit them. And you don’t need to measure everything! – Typical or representative examinations.
- 33. Skull Chest TSpine L spine Abdomen Pelvis Bitewing L Ob Breast UK National Diagnostic Reference Levels 2007 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)
- 34. How do youset Local DRLs Adopt recognised reference / published levels Adapt the actual values (potentially downwards) to your own practice .
- 35. NDRL/ : LDRLA guide to the rather indistinct borderline between ‘good and normal practice’ and ‘bad and abnormal practice’ Local DRL NDRL
- 36. Or use yourown data to set Local DRLs One way of doing this is to set a Local DRL as the mean of the distribution of mean room doses that you measure. This is OK even if you only have one room. In this case you are monitoring the variation of mean room dose with time.
- 37. Criteria for inclusion(1) Examinations must be performed reasonably frequently in the hospital / department Data collection must be feasible
- 38. Criteria for inclusion(2) Ideally include at least one examination performed on each item of equipment that makes a significant contribution to the workload of the department
- 39. Criteria for inclusion(3) Ideally cover the work of all groups of operators carrying out radiological procedures, e.g. - Radiographers / technologists radiologists non-radiological clinicians
- 40. Choose examinations thattypify the work of the hospital Don’t include more than you have to Setting DRLs in your hospital Don’t forget to audit & review them (i.e.close the audit loop)
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- 42. How do youaudit against DRLs
- 43. How do youaudit against DRLs If a DRL is consistently exceeded, you need to investigate why that is. What is meant by “consistently”. One way assumes that a set of measured patient doses would be considered to be consistently above a DRL if their average was greater than the DRL. Then the problem becomes one of defining what is meant by ‘greater’.
- 44. What do wemean by “greater than” If the mean dose exceeds the local DRL by more than a defined proportion (e.g. 20%) and by at least 2 times the standard error of the mean of the local measurement then an investigation is required as to why the DRL has been exceeded.
- 45. What if yourdoses exceed the drl? ? The outcome of an investigation will be to identify why the DRL has been exceeded. Remedial measures should be identified and, where possible, acted upon prior to recommencing the dose audit cycle.
- 46. What are themost likely factors to consider if a DRL is consistently exceeded? Measurement Methodology Case Mix Equipment Technique
- 47. Outcome of investigationIdentify why DRL exceeded Identify remedial measures Investigate ways of reducing doses Equipment factors Technique change Act, prior to recommencing audit cycle.
- 48. What does aDRL do? DRL only triggers the first step in the optimisation process. But it is a trigger that may tell you where to look and where to prioritise your effort.
- 49. Balancing patient doseand image quality Which examinations should form the focus of the optimisation effort?. How do we prioritise ?
- 50. And Finally DiagnosticImage quality is the main concern Don’t reduce dose so much that the images become non diagnostic – dose reduction is NOT a holy grail Many dose savings can be made without affecting the image at all
- 51. THANK YOU FORYOUR ATTENTION Ninewells Hospital & Medical School