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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 IAEA 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 IAEA 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/ IAEA 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 IAEA UK – Submitting the data • Data were accepted in any format – paper and computer files • Most were emailed • Using a spreadsheet for the data IAEA 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 IAEA 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 IAEA 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 IAEA 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 IAEA Australia • Very large country – long distances between hospitals • Web based approach to establishing and using DRLs • Started with CT only IAEA 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 IAEA 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 IAEA 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) IAEA 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 IAEA 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?? IAEA 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 IAEA 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 IAEA 2012 ChestAbdoPelvis Lumbar Spine 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 IAEA 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