Transcript 03 National DRL programmes Uganda 2013

National DRL Programmes
Regional Meeting on the Establishment and Utilization of Diagnostic Reference Levels
Kampala, Uganda, 14-18 February, 2013
John Le Heron
Radiation Protection of Patients Unit
Radiation Safety and Monitoring Section
Division for Radiation, Transport and Waste Safety
IAEA
International Atomic Energy Agency
Outline
• Experiences and approaches of 2 countries
• UK
• Australia
IAEA
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
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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
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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
• http://www.hpa.org.uk/Topics/Radiation/UnderstandingRadiation/Un
derstandingRadiationTopics/MedicalRadiation/DiagnosticRadiology/
diag_Npdd/
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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
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UK – Submitting the data
• Data were accepted in any format – paper
and computer files
• Most were emailed
• Using a spreadsheet for the data
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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
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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, 10 15 years
IAEA
• Based on thickness of body part being x-rayed
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
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UK – last cycle, Jan 2006 to Dec 2010
• 320 Hospitals
• ~ ¼ of hospitals and clinic with X-ray facilities
• Dose data
• For single radiographs
• 165 000 ESAK values
• 185 000 KAP values
No. of radiograph data
increased significantly
over previous cycle
• For complete examinations
• 221 000 KAP values
• 146 000 fluoroscopy times
IAEA
About 96% of ESAK
values were calculated,
4% using TLD
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
110 500
Lumbar Spine AP
101
206
5 500
Pelvis AP
144
305
19 000
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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
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Australia
• Very large country – long distances between
hospitals
• Web based approach to establishing and
using DRLs
• Started with CT only
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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
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Australia – Gathering the data – How?
• Online survey
• Accessed via ARPANSA web page
• http://www.arpansa.gov.au
• Participants (CT practices) have to register
online first
• Contact details
• CT scanner details
• Once registered, access to data entry
sections
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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)
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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
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E.g. AbdoPelvis
• Scan region is
within the red lines
• Above diaphragm
to below
symphysis pubis
• Gives examples
• Oncology, trauma,
renal colic,
abdominal pain,
other pathology
• Volume based vs
clinical purpose??
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E.g. Chest
• Scan region is
within the red lines
• Lung apices to
adrenal glands
• Gives examples
• Mediastinal,
pleural, pulmonary
pathology,
oncology
• Volume based vs
clinical purpose??
• No HRCT
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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
For all parameters,
• If dose modulation was used
online help was given,
• Rotation time
and the entered value
• Number of phases
had to be within
• Helical or axial acquisition
defined limits
• Detector configuration
• Reconstruction slice width, Reconstruction algorithm/kernel
• Scan field of view, Beam shaping filter
• Noise index
IAEA
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
IAEA
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
IAEA
Australia – DRLs – what has been achieved?
• ~ 800 CT scanners
• ~ 3 000 000 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
• 10 100 patients
IAEA
Australia – growth in participation
Adult surveys submitted per examination, 2011-2012
120
113
100
No of compliant surveys submitted
100
78
80
75
69
60
57
56
51
44
40
40
34
30
20
0
Head
Neck
Chest
AbdoPelvis
Examination
2011
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2012
ChestAbdoPelvis
Lumbar Spine
Australia – DRLs
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•
•
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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
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Summary
• Two approaches
• UK
• 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
IAEA