1. Dose Surveys in Radiography David Sutton / Colin Martin Kampala IAEA/RCA Kampala

2. Dose survey without a dosemeter Ask hospitals to collect patient data for a given procedure Use published tables of X-ray output Calculate IAK using the patient factors Calculate ESAK, using BSF

3. Room A, Hospital Z Patient name kVmAsFSD (mm) 1.7050780 2.7460750 3.7255760 4.Etc.

4. Standard X-ray outputs kVpµGy/mAs at 1 m 6030 7040 8050 9060 10070 These are not true values – just indicative

5. Calculating patient ESAKs Patient 1 70 kV Output is 40 µGy/mAs at 1 m Patient mAs is 50 Distance is 0.78 m IAK = 40x50x(1/0.78) 2 ~ 3300µG (3.3 mGy) ESAK = 3.3 x 1.35= 4.4 mGy

6. Calculating patient ESAKs Patient 2 74 kV

7. Tube output Is proportional to mAs Is proportional to kV 2 So overall, output is proportional to mAs x kV 2 Output is proportional to mAs x kV 2 Kampala

8. Calculating patient ESAKs Patient 2 74 kV Output is proportional to kV 2 Output is 40 µGy/mAs x (74/70) 2 at 1 m = 44.7 µGy/mAs Output at 1m is 44.7 x 60 = 2682µGy Correct for distance and mulitply by BSF

9. DRLs National DRLs –Based national dose survey (3 rd quartile) –boundary between good and normal practice and bad and abnormal practice Dose survey required to compare against or set DRLs Kampala

10. Dose Audit – What to think about What should be audited –Examinations –Equipment –Patients Data collection Data analysis Reporting Investigating Kampala

11. Phantoms TRS 457 “Dose assessments with phantoms cannot provide a direct estimate of the average dose for a given patient population … it is important therefore that any measurements with phantoms are supplemented by measurements made on patients“ (CoP, Appendix VII) Comment: need not be measurements on patients, any method to derive patient dose data is o.k. (actually, calculation of K i from patient exposure data would be preferred) Only exemption: mammography, here MGD determined with a phantom is advised

12. Dose Surveys Measure doses to patients (or phantoms) Compare measured doses to standards Decide if action is required Begin again

13. Surveys: Planning Identify rooms to be audited Identify procedures carried out in those rooms that you wish to audit Decide how to obtain Dose information Identify suitable reference values

14. Planning a dose survey in radiography Examinations What examinations are you going to audit? Kampala

15. 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

16. 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

17. 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

18. Choosing Exams to survey Choose examinations that typify the work of the hospital Don’t include more than you have to Don’t forget to audit & review them (i.e. close the audit loop)

19. UK – “Simple Examinations” Kampala

20. UK – “Simple Examinations” Kampala

21. Cross Section of Patients Examinations with UK NDRL –Chest –Abdomen –Pelvis –Spine Thoracic Lumbar Clinical context –Trauma –Acute admissions –Out patient clinics –GP referrals –In patients Kampala

22. Dose Survey – What to think about What should be audited –Examinations –Equipment –Patients Data collection Data analysis Reporting Investigating Kampala

23. Planning a dose survey in radiography How are you going to collect the dose data ? 1) Physics Kampala

24. Detector Considerations Accuracy & Precision Sensitivity Energy Response Linearity Dose rate dependence Kampala

25. Detector Considerations Robustness Is it going to be visible on the patient? CALIBRATION –Traceable? –Feasible? Kampala

26. Detector Considerations Ionisation Chambers –Instrument of choice for a long time –Ideal for output mGy/mAs –Good energy response –Not good for real patient measurements though – WHY??? Kampala

27. Detector Considerations Solid State Detectors –Good sensitivity –Modern equipment has good energy response at diagnostic energies –Lead back limits ability to measure ESD –But there are new transparent detectors –Similar pros and cons to ion chambers Kampala

28. Detector Considerations TLD –Small –Transparent –TLD-100 MDD ~ 50 µGy –TLD -100H MDD ~ 1 to 2 µGy –Calibration and read out issues –Logistical issues – what might they be? Kampala

29. Detector Considerations -KAP KAP Kampala Transmission ionization chamber

30. Kampala Kerma-Area Product: KAP This is the dose related quantity measured and displayed on all modern X-ray equipment excluding CT (in Europe). Stored on DICOM Header in DR Can be transcribed to RIS / PACS system KAP meter

31. Planning a dose survey in radiography How are you going to collect the dose data ? 1) Physics 2) Logistics –Is it better to audit one exam at a time ? Kampala

32. Data Collection – How many patients? It is important that the size of a sample of patients is sufficiently large as to avoid large statistical variations of the mean value of the measured quantity. Care has to be paid also to the selection of patients according to their anatomical parameters (e.g. weight). A range of 10–50 patients for the sample size is suggested. 32

33. Patient weights National Protocol (IPSM 1992) –Mean weight = 70 ± 5 kg –Weight range 50 to 90 kg (60 to 80 kg for common examinations) Kampala

34. Patient selection Select examination of interest Define weight range (typically 60-80 kg) Make measurements / collect data for at least 10 patients – 20 preferable Kampala

35. Data Collection Will depend on the method you are using to determine the patient dose. But you’re probably going to try and get as much as you can Ideally you would probably like : Kampala

36. Per Exam Patient Height and Weight ( Who says the weight?) kV mAs FFD Patient thickness (if you’re calculating) KAP (if you are using it) You will be very lucky to get all of this data Kampala

37. & If you’re using TLDS The TLDs inside pre numbered plastic bags Unused TLDs in one box Used TLDs stored somewhere else. And none of them in the x-ray room! Bitter experience leads to the above!! Kampala

38. Data Collection –Paper –RIS – bigger samples possible –PACS – bigger samples possible –Calculation from Factors ( is probably a paper collection) Kampala

39. Data Collection –Paper Data tailored to needs Prospective ? Accuracy of data entry –RIS Retrospective Patient numbers Multiple views (Radiography) ?? Patient weight, kV/mAs DDI ? Accuracy and consistency of data entry (units) –PACS EI in DICOM header Not CR or film ? Accessibility of data Kampala

40. Paper Entry – Get the design right! Kampala

41. Good Fortune Required It will very likely that you will have transcription errors So some sanity checking will be needed –EG plot of dose against kV 2 x mAs –Plot of dose and weight –See later Kampala

42. Dose Surveys – What to think about What should be audited –Examinations –Equipment –Patients Data collection Data analysis Reporting Investigating Kampala

43. Data Analysis What tools are you going to use to analyse your data? What are you going to extract from your data? What are you going to do with what you extract? Kampala

44. Data Analysis What tools are you going to use to analyse your data? –A spreadsheet program (or a calculator) –Graphs of the data –Statistics Mean, SD, sem. Percentiles Kampala

45. First steps It will very likely that you will have transcription errors So some sanity checking will be needed –EG plot of dose against kV 2 x mAs –Plot of dose and weight Kampala

46. AP Lumbar Spine Survey Kampala

47. Chest Note Units Poor data recording Kampala

48. Cleaned Up Chest Kampala

49. AP Pelvis – Arbroath 31 patients Kampala Event DateExaminationProjectionRoomDosageDosage typkVpmAsAge At Event 01/09/2011XPELVAPA244KAP6315.772 01/09/2011XPELVAPA2145KAP752351 01/09/2011XPELVAPA2131KAP7719.172 01/09/2011XPELVAPA2225KAP733670 01/09/2011XPELVAPA2134KAP7519.171 01/09/2011XPELVAPA2177KAP7524.978 01/09/2011XPELVAPA2396KAP7555.677 02/09/2011XPELVAPA2213KAP7333.262 02/09/2011XPELVAPA2436KAP8154.268 02/09/2011XPELVAPA2106KAP7314.280 05/09/2011XPELVAPA235KAP735.5489 05/09/2011XPELVAPA237KAP735.7389 05/09/2011XPELVAPA2122KAP7318.789 06/09/2011XPELVAPA2280KAP754080 07/09/2011XPELVAPA242KAP6617.356 07/09/2011XPELVAPA228KAP6611.356 07/09/2011XPELVAPA271KAP731156 08/09/2011XPELVAPA268KAP7310.987 08/09/2011XPELVAPA280KAP7312.250 08/09/2011XPELVAPA2458KAP7367.949 13/09/2011XPELVAPA280KAP7313.584 13/09/2011XPELVAPA2224KAP7337.380 13/09/2011XPELVAPA2369KAP7556.843 13/09/2011XPELVAPA2353KAP755433 13/09/2011XPELVAPA2477KAP7571.467 13/09/2011XPELVAPA294KAP751463 13/09/2011XPELVAPA255KAP738.4570 13/09/2011XPELVAPA2309KAP7544.630 13/09/2011XPELVAPA2294KAP7542.152 14/09/2011XPELVAPA2131KAP732154 14/09/2011XPELVAPA2280KAP7344.665

50. AP Pelvis – Arbroath 31 patients Kampala Event DateExaminationProjectionRoomDosageDosage typkVpmAsAge At Event 01/09/2011XPELVAPA244KAP6315.772 01/09/2011XPELVAPA2145KAP752351 01/09/2011XPELVAPA2131KAP7719.172 01/09/2011XPELVAPA2225KAP733670 01/09/2011XPELVAPA2134KAP7519.171 01/09/2011XPELVAPA2177KAP7524.978 01/09/2011XPELVAPA2396KAP7555.677 02/09/2011XPELVAPA2213KAP7333.262 02/09/2011XPELVAPA2436KAP8154.268 02/09/2011XPELVAPA2106KAP7314.280 05/09/2011XPELVAPA235KAP735.5489 05/09/2011XPELVAPA237KAP735.7389 05/09/2011XPELVAPA2122KAP7318.789 06/09/2011XPELVAPA2280KAP754080 07/09/2011XPELVAPA242KAP6617.356 07/09/2011XPELVAPA228KAP6611.356 07/09/2011XPELVAPA271KAP731156 08/09/2011XPELVAPA268KAP7310.987 08/09/2011XPELVAPA280KAP7312.250 08/09/2011XPELVAPA2458KAP7367.949 13/09/2011XPELVAPA280KAP7313.584 13/09/2011XPELVAPA2224KAP7337.380 13/09/2011XPELVAPA2369KAP7556.843 13/09/2011XPELVAPA2353KAP755433 13/09/2011XPELVAPA2477KAP7571.467 13/09/2011XPELVAPA294KAP751463 13/09/2011XPELVAPA255KAP738.4570 13/09/2011XPELVAPA2309KAP7544.630 13/09/2011XPELVAPA2294KAP7542.152 14/09/2011XPELVAPA2131KAP732154 14/09/2011XPELVAPA2280KAP7344.665 Event DateExaminationProjectionRoomDosageDosage typkVpmAsAge At EventCheck 01/09/2011XPELVAPA244KAP6315.77262313 01/09/2011XPELVAPA2145KAP752351129375 01/09/2011XPELVAPA2131KAP7719.172113244 01/09/2011XPELVAPA2225KAP733670191844 01/09/2011XPELVAPA2134KAP7519.171107438 01/09/2011XPELVAPA2177KAP7524.978140063 01/09/2011XPELVAPA2396KAP7555.677312750 02/09/2011XPELVAPA2213KAP7333.262176923 02/09/2011XPELVAPA2436KAP8154.268355606 02/09/2011XPELVAPA2106KAP7314.28075672 05/09/2011XPELVAPA235KAP735.548929523 05/09/2011XPELVAPA237KAP735.738930535 05/09/2011XPELVAPA2122KAP7318.78999652 06/09/2011XPELVAPA2280KAP754080225000 07/09/2011XPELVAPA242KAP6617.35675359 07/09/2011XPELVAPA228KAP6611.35649223 07/09/2011XPELVAPA271KAP73115658619 08/09/2011XPELVAPA268KAP7310.98758086 08/09/2011XPELVAPA280KAP7312.25065014 08/09/2011XPELVAPA2458KAP7367.949361839 13/09/2011XPELVAPA280KAP7313.58471942 13/09/2011XPELVAPA2224KAP7337.380198772 13/09/2011XPELVAPA2369KAP7556.843319500 13/09/2011XPELVAPA2353KAP755433303750 13/09/2011XPELVAPA2477KAP7571.467401625 13/09/2011XPELVAPA294KAP75146378750 13/09/2011XPELVAPA255KAP738.457045030 13/09/2011XPELVAPA2309KAP7544.630250875 13/09/2011XPELVAPA2294KAP7542.152236813 14/09/2011XPELVAPA2131KAP732154111909 14/09/2011XPELVAPA2280KAP7344.665237673

51. AP Pelvis – Arbroath 31 patients Kampala

52. AP Pelvis – Arbroath 31 patients Kampala

53. AP Pelvis – Arbroath 31 patients Mean 191 cGycm 2 Sample size : 31 Next slide – effect of increasing sample size to 360 Kampala

54. AP Pelvis – Arbroath 361 patients Kampala

55. Dose Surveys – What to think about What should be audited –Examinations –Equipment –Patients Data collection Data analysis Reporting Investigating Kampala

56. Dose Survey - Reporting What is your report for? What does it contain? Who do you send it to? How will you ensure that recommendations are acted upon? Kampala

60. Dose Survey – What to think about What should be audited –Examinations –Equipment –Patients Data collection Data analysis Reporting Investigating Kampala

61. Dose Survey- Investigating What is your report for? What does it contain? Who do you send it to? How will you ensure that recommendations are acted upon? Kampala

62. What are the most likely factors to consider if a DRL is exceeded? Measurement Methodology Equipment Case Mix Technique

63. Summary Dose survey required: –To set DRLs and test compliance –Optimise new equipment/ protocols Choice of examinations and equipment Patient selection and sample size Data collection: paper or RIS Survey by protocol Need for dose audit for children Kampala