IAEAInternational Atomic Energy Agency

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

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Outline

• Experiences and approaches of 2 countries• UK

• Australia

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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/

UnderstandingRadiationTopics/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

• Based on thickness of body part being x-rayed

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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

• For complete examinations• 221 000 KAP values

• 146 000 fluoroscopy times

No. of radiograph data increased significantly over previous cycle

About 96% of ESAK values were calculated, 4% using TLD

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UK – numbers of data used in updating the DRLs

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

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

ESD data per radiograph:

KAP data per radiograph:

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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

• 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

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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 yearDose data are able to be input in several stages

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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

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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

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Australia – growth in participation

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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

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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