1. 28/10/20151 First FRCR Examination in Clinical Radiology Diagnostic Radiology & Radionuclide Radiology (4b) Patient Dosimetry John Saunderson Radiation Protection Adviser

2. 28/10/20152 RCR Syllabus Methods Diagnostic reference levels (including high dose techniques) Magnitude and measurements.

3. 28/10/20153 Methods General radiology Fluoroscopy Computed Tomography Nuclear Medicine.

4. 28/10/20154 General radiology ESD –Thermoluminescent dosemeter (TLD) –exposure factors Dose-Area Product (DAP) Effective dose.

5. 28/10/20155 T.L.D. Crystals, e.g. lithium fluoride Radiation causes electrons to be caught in “traps” At lab. TLDs heated to 240 o C Electrons released, light emitted Amount of light emitted proportional to dose.

6. 28/10/20156 T.L.D.s+/- +Small +Tissue equivalent +Read 1  Gy +Easy for radiographer -No direct readout -Sensitive to heat, UV, dirt -Tricky to calibrate -Easy to loose -Special ones needed for low dose (e.g. chest).

7. 28/10/20157 Using exposure factors kV, mAs, field size, FSD If D = dose at 100 cm for 80 kV, 100 mAs then ESD = D x kV 2 /80 2 x mAs/100 x 100 2 /FSD 2 x BSF BSF = backscatter factor, depends on HVL and field size.

8. 28/10/20158 E.g. What is ESD for 100 kV, 50mAs, 15 x 15 cm field, 75 cm FSD for Room 3? From annual survey –@ 80 kV, D = 9.1 mGy/100mAs @ 1 m –HVL for 100kV was 3 mmAl From tables –BSF for 3mmAl, 15 x 15 field = 1.33 Therefore, entrance surface dose =9.1mGy x 100 2 /80 2 x 50/100 x 100 2 /75 2 x 1.33 = 0.17 mGy.

9. 28/10/20159 Using exposure factors+/- +No fiddly TLD for radiographers! +No fiddly TLDs for physicist! +Radiographers can calculate ESDs +No minimum dose -No direct readout -Exposure parameters must be recorded -Assumes tube output not changed from last survey.

10. 28/10/201510 Dose Area Product Because dose falls with 1/d 2 and area increases with d 2, DAP is independent of distance.

11. 28/10/201511 DAP+/- +No fiddly TLD for radiographers! +Only one number to record +Instant answer -Doesn’t take into account backscatter -Initial cost (several thousand £) -Units sometimes cause confusion (cGy.cm 2, or Gy.cm 2,  Gy.m 2 ).

12. 28/10/201512 Effective dose Complicated to calculate from ESD or DAP Can use computer models which make assumptions on –field size –patient size –field position

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18. 28/10/201518 Fluoroscopy Dose-Area Product (DAP) Exposure factors Effective dose.

19. 28/10/201519 DAP +/- for fluoroscopy +Instant answer, etc. +DAP moves with the tube +Gives good indication of relative risks of inducing cancer -Not directly linked to erythema risk.

20. 28/10/201520 Exposure factors Based on assumed FSDs, etc.

21. 28/10/201521 Effective dose Can be “fudged” using radiograph software.

22. 28/10/201522 GAFCHROMIC film

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25. 25 GAFCHROMIC film optical density is proportional to the absorbed dose 0.01 Gy to 50 Gy Energy independent from 30 keV to 30 MeV £20 per 14” x 17” sheet

26. 28/10/201526 Computed Tomography CT Dose Index (CTDI) Dose-Width Product (DWP) Effective dose

27. 28/10/201527 CT Dose Index (CTDI) Applies to a single slice Can be used to compare –different slice widths –different physical filter –different scanners –etc.

28. 28/10/201528 Dose-Length Product (DLP) DWP = CTDI x n x T Gives an idea of relative dose for a whole scan Can be used to compare effect of pitch, etc.

29. 28/10/201529 Effective dose NRPB program similar to radiography one

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31. 28/10/201531 CT dose/risk calculation e.g. wrong patient referred for CT scan (laryngectomy)

32. 28/10/201532 Nuclear Medicine MIRD Add up dose to each organ from the dose irradiating from each organ.

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34. 28/10/201534 Diagnostic Reference Levels Early 80’s survey DRLs today IRMER

35. 28/10/201535 Mid-80’s survey Method Survey of twenty UK hospitals 13 most common views For each 10-20 patients (60-80kg) at DAP or ESD by TLD measured.

36. 28/10/201536 Mid-80’s survey Results E.g. Chest PA –Median ESD = 0.18 mGy –Minimum ESD = 0.03 mGy –Maximum ESD = 1.43 mGy –Max / min = 48 !!.

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38. 28/10/201538 Mid-80’s survey Recommendation Use 75 th percentile as reference value i.e. carry out local surveys and take action if average dose is greater than ¾ of national survey doses e.g. for chest PA reference = 0.3mGy ESD Send results to NRPB to review national reference doses every 5 years.

39. 28/10/201539 DRLs today A DRL is essentially a guide to the rather indistinct border between “good and normal practice” and “bad and abnormal practice”.

40. 28/10/201540 IRMER National DRLs –set as 3rd quartile –average from survey of “standard patients” –should be below DRL Local DRLs –?Average for Trust? –Most should be below average

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47. 28/10/201547 Staff and Environmental Monitoring Devices –TLD –OSLD –Film –Electronic Body Extremity Environment

48. 28/10/201548 Relevant measurement techniques

49. 28/10/201549 Measuring Dose Luxel dose badges TLD finger rings –Can be cold sterilized –Heat sensitive

50. 28/10/201550 Luxel badges Wear underneath lead rubber apron Assume dose to badge = effective dose Can be worn for 2 weeks to 3 months (usually 1 month) Must be returned promptly.

51. 28/10/201551 Electronic Dosemeters Used by Radiation Physics staff to test x-ray unit and measure environmental doses

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53. 28/10/201553 Absent Badges Participant Name, Number Begin wear date End wear date Dosimeter Location Body Dose (mSv) Extremity Dose (mSv) Body Dose YTD Exremity Dose YTD NotesDerived FALSE ARCHER, MS G,0017601/09/201330/09/2013Chest0.1 1.27 MEASURED FALSE ARCHER, MS G,0017601/09/201330/09/2013Right Finger 0.2 1.2 MEASURED FALSE ATKINSON,A,0030801/09/201330/09/2013Chest0.03 0.18 MEASURED FALSE AVERY, DR G,0029801/09/201330/09/2013Chest0.04 0.24 MEASURED FALSE AVERY, DR G,0029801/09/201330/09/2013Left Finger 0.2 9.6 MEASURED FALSE AVERY, DR G,0029801/09/201330/09/2013Right Finger 0.2 23.7 MEASURED FALSE AZOR, B,0058701/09/201330/09/2013Chest0.02 0.1 MEASURED FALSE BAJALAN, L,0032501/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BARLOW, NICHOLAS,0005301/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BEADLE, MRS E,0060901/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BEADLE, MRS E,0060901/09/201330/09/2013Right Finger 0.2 1.2 MEASURED FALSE BOTTOMLY, JAYNE,0069401/09/201330/09/2013Chest Component Note: H-UnusedMEASURED 1 BOWERING, SUE,0027901/09/201330/09/2013Chest ABSENT FALSE BRAMALL, M,0058801/09/201330/09/2013Chest0.01 0.03 MEASURED FALSE BROWN, SUSAN,0032601/09/201330/09/2013Chest0.03 0.07 MEASURED FALSE BYASS, DR O,0038401/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BYASS, DR O,0038401/09/201330/09/2013Left Finger 0.2 13.3 MEASURED FALSE BYASS, DR O,0038401/09/201330/09/2013Right Finger 0.2 14.9 MEASURED FALSE CAST, DR J,0037601/09/201330/09/2013Chest0.01 0.99 MEASURED FALSE CAST, DR J,0037601/09/201330/09/2013Waist0.48 4.13 overapronMEASURED FALSE CAST, DR J,0037601/09/201330/09/2013Right Finger 1.1 14.8 MEASURED YTD = year to date Luxel badge results (Sept 2013, CHH Radiology)

54. 28/10/201554 Absent Badges Participant Name, Number Begin wear date End wear date Dosimeter Location Body Dose (mSv) Extremity Dose (mSv) Body Dose YTD Exremity Dose YTD NotesDerived FALSE ARCHER, MS G,0017601/09/201330/09/2013Chest0.1 1.27 MEASURED FALSE ARCHER, MS G,0017601/09/201330/09/2013Right Finger 0.2 1.2 MEASURED FALSE ATKINSON,A,0030801/09/201330/09/2013Chest0.03 0.18 MEASURED FALSE AVERY, DR G,0029801/09/201330/09/2013Chest0.04 0.24 MEASURED FALSE AVERY, DR G,0029801/09/201330/09/2013Left Finger 0.2 9.6 MEASURED FALSE AVERY, DR G,0029801/09/201330/09/2013Right Finger 0.2 23.7 MEASURED FALSE AZOR, B,0058701/09/201330/09/2013Chest0.02 0.1 MEASURED FALSE BAJALAN, L,0032501/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BARLOW, NICHOLAS,0005301/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BEADLE, MRS E,0060901/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BEADLE, MRS E,0060901/09/201330/09/2013Right Finger 0.2 1.2 MEASURED FALSE BOTTOMLY, JAYNE,0069401/09/201330/09/2013Chest Component Note: H-UnusedMEASURED 1 BOWERING, SUE,00279 01/09/2 013 30/09/2 013Chest ABSEN T FALSE BRAMALL, M,0058801/09/201330/09/2013Chest0.01 0.03 MEASURED FALSE BROWN, SUSAN,0032601/09/201330/09/2013Chest0.03 0.07 MEASURED FALSE BYASS, DR O,0038401/09/201330/09/2013Chest Component Note: H-UnusedMEASURED FALSE BYASS, DR O,0038401/09/201330/09/2013Left Finger 0.2 13.3 MEASURED FALSE BYASS, DR O,0038401/09/201330/09/2013Right Finger 0.2 14.9 MEASURED FALSE CAST, DR J,0037601/09/201330/09/2013Chest0.01 0.99 MEASURED FALSE CAST, DR J,0037601/09/201330/09/2013Waist0.48 4.13 overapronMEASURED FALSE CAST, DR J,0037601/09/201330/09/2013Right Finger 1.1 14.8 MEASURED Luxel badge results

55. Absent Badges Participant Name, Number Begin wear date End wear date Dosimeter Location Body Dose (mSv) Extremit y Dose (mSv) Body Dose YTD Extremity Dose YTD NotesDerived FALSE C##T, DR J,00376 01/09/201330/09/2013 Chest0.01 0.99 MEASURED FALSE C##T, DR J,00376 01/09/201330/09/2013 Waist0.48 4.13 overapron MEASURED FALSE C##T, DR J,00376 01/09/201330/09/2013 Right Finger 1.1 14.8 MEASURED Luxel badge results Effective dose assumed to be underapron dose. 0.99mSv to end Sept, so predicted annual dose = 12/9 x 0.99 = 1.32mSv for year Finger dose, 4.13 to end Sept, so predicted annual dose = 12/9 x 14.8 = 19.73 mSv for year

56. 28/10/201556 f i n