1. Radiation Protection of Patients Unit
National DRL Programmes Regional Meeting on the Establishment and Utilization of Diagnostic Reference Levels Kampala, Uganda, February, 2013
John Le Heron
Radiation Protection of Patients Unit
Radiation Safety and Monitoring Section
Division for Radiation, Transport and Waste Safety

2. Outline
Experiences and approaches of 2 countries UK
Australia

3. UK approach – radiography & fluoroscopy
Reference:
HPA – CRCE – 034 Doses to patients from radiographic and fluoroscopic x-ray imaging procedures in the UK – 2010 review
CT is handled separately

4. UK – Obtaining the data UK has a National Patient Dose Database – NPDD
Set up in 1992 by NRPB (now HPA)
A 5 year review cycle
Data collection over a 5 year period
Supplied from hospitals
Medical physicists mainly
Also radiographers and radiologists

5. UK – What data are collected?
Standard forms used:
Dose per radiograph
Dose per examination
Data on dose, patient, location, imaging equipment, and technique
Some fields mandatory
Many optional fields

6. UK – More detail on data collected
The submission of optional data was quite generally poor
Factor
% of dose measurements
Patient height 44
Patient age 38
Patient gender 34
Radiographic kV 98
AEC used or not 2
Filtration 8
Image receptor used – FS, CR, DR 94

7. UK – Submitting the data
Data were accepted in any format – paper and computer files
Most were ed
Using a spreadsheet for the data

8. UK – Quality assurance of submitted data
One person entered the data into NPDD
A second person checked
Statistical analysis for each set of data
Key parameters – dose, age, patient weight, kVp, filtration, mAs
Mean, standard deviation, sample size, and min and max were calculated
Outliers were investigated

9. UK – Selection of data for analysis
For a given room and procedure
At least 10 patients
Patient size
Adults
National protocol
Sample mean weight in range 65 to 75 kg
Patients in range 50 to 90 kg
Children - UK paediatric data in NPDD about 3%
Large variation in size between new born & 15 y
Adjusting doses to 5 standard-sized children
0, 1, 5, years
Based on thickness of body part being x-rayed

10. UK – Deriving national DRLs
Derived for those exams and procedures where dose measurements on adult patients are available from a sufficiently large sample size to be representative of national practice
At least:
10 hospitals;
20 rooms; and
100 patients
DRL values are based on rounded 3rd quartile values for the distributions of room mean doses for a given exam or procedure

11. UK – last cycle, Jan 2006 to Dec 2010
320 Hospitals
~ ¼ of hospitals and clinic with X-ray facilities
Dose data
For single radiographs
ESAK values
KAP values
For complete examinations
KAP values
fluoroscopy times
No. of radiograph data increased significantly over previous cycle
About 96% of ESAK values were calculated,
4% using TLD

12. UK – numbers of data used in updating the DRLs
ESD data per radiograph:
Projection
No. Hospitals
No. Rooms
No. Patients
Abdomen AP 70
167
12 000
Chest PA 95
285
43 500
Lumbar Spine AP 80
192
5 300
Pelvis AP 84
204
9000
KAP data per radiograph:
Projection
No. Hospitals
No. Rooms
No. Patients
Abdomen AP 78
188
17 800
Chest PA
162
433
Lumbar Spine AP
101
206
5 500
Pelvis AP
144
305
19 000

13. UK – national DRLs 38 diagnostic X-ray exams on adults
7 types of interventional procedures on adults
3 types of X-ray exams on children

14. Australia Very large country – long distances between hospitals
Web based approach to establishing and using DRLs
Started with CT only

15. Australia – Gathering the data – Who?
ARPANSA (Federal Regulatory Body)
But in consultation with:
Royal Australian & New Zealand College of Radiology
Australian Institute of Radiography
Australasian College of Physical Scientists & Engineers in Medicine
Australian & New Zealand Society of Nuclear Medicine
Department of Health and Aging
State and Territory radiation protection regulators

16. Australia – Gathering the data – How?
Online survey
Accessed via ARPANSA web page
Participants (CT practices) have to register online first
Contact details
CT scanner details
Once registered, access to data entry sections

17. Australia – Gathering the data – What?
6 common CT examinations
CT Head
CT Neck
CT Chest
CT AbdoPelvis
CT ChestAbdoPelvis
CT Lumbar Spine
3 age groups
Adults (15+ years)
Children (5-14 years)
Baby/infant (0-4 years)

18. But what about scan differences?
ARPANSA defined the scan margins for each examination
Facility scan had to fall within those margins to be included in the survey

19. E.g. AbdoPelvis Scan region is within the red lines Gives examples
Above diaphragm to below symphysis pubis
Gives examples
Oncology, trauma, renal colic, abdominal pain, other pathology
Volume based vs clinical purpose??

20. E.g. Chest Scan region is within the red lines Gives examples
Lung apices to adrenal glands
Gives examples
Mediastinal, pleural, pulmonary pathology, oncology
Volume based vs clinical purpose??
No HRCT

21. Australia – Examination data
For each examination:
Technical parameter data on protocol settings used on the CT scanner, including:
kVp, starting mAs, pitch
If contrast media was used
If dose modulation was used
Rotation time
Number of phases
Helical or axial acquisition
Detector configuration
Reconstruction slice width, Reconstruction algorithm/kernel
Scan field of view, Beam shaping filter
Noise index
For all parameters, online help was given, and the entered value had to be within defined limits

22. Australia – Patient dose data
Basic dose data from 20 patients on the same CT scanner
Average CTDIvol for the examination
Total Dose Length Product (DLP) for the exam
Patient weight (kg)
Dose metrics from the scanner console display – not measured
Help given for exams with multiple runs – separate scans, multiple phases
A survey is based on a calendar year
Dose data are able to be input in several stages

23. Australia – Reporting back
For each set of data submitted to the National DRL Database
A Practice Reference Level was calculated (median), specific to:
Examination
Age group
CT scanner used
A comparison made with national DRL
Recommendation back to the CT facility

24. Australia – DRLs – what has been achieved?
~ 800 CT scanners
~ CT examinations per year
At the end of 2011, there were:
80 registered practices in NDRLD
51 practices contributed 255 exam surveys of ≥ 10 patients
4700 patients
At the end of 2012, there were:
173 registered practices in NDRLD
94 practices contributed 553 exam surveys of ≥ 10 patients
patients

25. Australia – growth in participation

26. Australia – DRLs CT national DRLs established in 2012 3 age groupings
Volume based rather than exam purpose
All patient weights used
No selection on basis of weight

27. Summary Two approaches UK Australia
Well established with good participation rate
4 review cycles completed
Australia
Early days, low participation
CT only
Pragmatic approach on some issues
Dosimetry
Age groups
Patient weight