Presentation on theme: "European Diagnostic Reference Levels in Paediatric Imaging"— Presentation transcript:
1 European Diagnostic Reference Levels in Paediatric Imaging Stephen Evans, Head of Medical Physics, Northampton General Hospital, UKEFOMP Officer, Chair Projects
2 “Children are at a much higher risk compared to adults from developing cancer”
3 It’s not child’s play UNSCEAR (2010) estimates 250 million paediatric radiological examinations (including dental) per annum worldwideChildren may receive substantial radiation dosesin early lifelife-threatening diseaseChildren may developchildhood leukaemiabreast cancer orthyroid cancer
4 It’s not child’s play Children need special attention: diseases specific to childhoodadditional risksChildren need special care:provided by parents and carersfrom specially trained personnelJustification and optimization principles are even more important for children
6 Why so high ? Higher sensitivity to radiation Longer life expectancy Paediatric doses will exceed adult doses if the same exposure settings are used
7 Paediatric effective dose and risk ExaminationEffective dose (mSv)Lifetime risk of fatal cancerLimbs<0.0051/few millionChest (PA)0.011/millionSpine (AP, PA, Lat)0.071/150,000Pelvis0.081/120,000AXR0.101/100,000CT Head21/5,000CT Body101/1,000?Twice the adult riski.e. 10% per Sv.Cook JV, Imaging, 13 (2001), Number 4
8 Paediatric riskCHILDADULTIs this sensitive enough?
9 Risk from single CT exam Not1 in 10001 in 1000Not1 in 5000Estimated Risks of Radiation-Induced Fatal Cancer from Pediatric CT David J. Brenner1, Carl D. Elliston1, Eric J. Hall1 and Walter E. Berdon2,AJR February 2001, Volume 176, Number 2 Read More:
10 What’s the main issue? Estimated about 85% paediatric dose from CT, interventional fluoroscopy and cardiac nuclear medicine15% paediatric dose from radiography and general fluoroscopy
13 COUNCIL DIRECTIVE 2013/59/EURATOM of 5 December laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom(28) …important technological and scientific developments have led to a notable increase in the exposure of patients. …Directive should emphasise the need for justification of medical exposure, … the use of diagnostic reference levels and the availability of dose-indicating devices.
14 COUNCIL DIRECTIVE 2013/59/EURATOM Art 4 (20) "diagnostic reference levels" means dose levels in medical radiodiagnostic or interventional radiology practices, or, in the case of radio-pharmaceuticals, levels of activity, for typical examinations for groups of standard-sized patients or standard phantoms for broadly defined types of equipment;Art 22 (iii) where practicable, specific diagnostic reference levels are put in place;Art Member States shall ensure the establishment, regular review and use of diagnostic reference levels for radiodiagnostic examinations, having regard to the recommended European diagnostic reference levels where available, and where appropriate, for interventional radiology procedures, and the availability of guidance for this purpose.Art 58 (f) appropriate local reviews are undertaken whenever diagnostic reference levels are consistently exceeded and that appropriate corrective action is taken without undue delay.Art 53 MPE (a) optimisation of the radiation protection of patients and other individuals subject to medical exposure, including the application and use of diagnostic reference levels;
15 And, we have many many scientific studies and Reports…
19 EUR 16261, 1996used the 3rd quartile entrance-surface-dose for a standard five-year old child as the reference dose for all paediatric patients
20 EUR 16261, 1996 Good general principles Patient identification! Quality control of x-ray systemUse of low attenuation materialsImmobilisationField size limitationGood knowledge of paediatric anatomyProtective shieldingGonads, breastRadiographic exposure factorsNumber of exposuresNEVER EVENTDRLsGood Radiographic PracticeJUSTIFICATION
21 Conclusions of EUR 16261Every effort should be made to reduce doses for children less than 5 years of age to below the values presentedStrict adherence to all the radiographic technique factors recommended can lead to significant dose reductionX-ray generators employed in paediatric examinations should be capable of selecting the low mAs values required to ensure that the recommended kV values can be employed
23 "Guidance on diagnostic reference levels DRLs for medical exposure", European Commission Radiation Protection 109 (RP 109), 1999)exposures requiring the most attention and are of the most importance for the establishment of DRLs are the high-dose medical examinations, especially computed tomography (CT) and interventional procedures (IR)
24 RP 109“DRLs should be set by Member States …………….. harmonised levels might be feasible and are certainly preferable.”
25 RP-109 - Factors affecting dose Equipment factorsinappropriate exposure protocolsdeterioration of the image chainHuman factorsinattention, indifference or too much work pressureindividual reluctance to accept generally-accepted standard procedures
26 DRLs in practice DRLs can be assessed using: entrance surface doses, measured with TLD, orDAP [Gy.cm2]DAP is more practical because(i) the whole examination is recorded;(ii) the position of the patient in the beam is less important(iii) there is no need to disturb the patientFor CTDose Length Product (DLP)
27 DAP DRL issues Disadvantages using DAP absorbed organ dose needs to be measurednot always a fixed relationship between the DAP and the absorbed dosewhere small areas are exposed,the DAP can be low while the absorbed dose is highwhen a large area is exposed,the DAP can be high but the absorbed dose lowthe field size is often changed during fluoroscopy procedure
28 CT DRL issues Disadvantages of using DLP DLP = scan length (cm) x CTDIvol (mGy)Depends on height of patientEquipment characteristicsiterative reconstruction -50%AEC variable mAs – ?%might be set too highdose could be more
32 IAEA No. 24, 2013“… standardized methodologies to determine paediatric dose for all major modalities, such as general radiography, fluoroscopy and computed tomography.” “children can receive doses in excess of those delivered to Adults”
33 IAEA No. 24, 2013 5y old 5y old Weight? Height? 25 kg 115 cm to to CENTRE FOR DISEASE CONTROL AND PREVENTION, 2000 CDC Growth Charts for the United States: Methods and Development, Vital and Health Statistics, Department of Health and Human Services, Rep. (PHS) , Hyattsville, MD (2002).
34 IAEA No. 24 – Patient size Options Age (v. Poor) Patient thickness good for projection radiographynot so good for CThow to measure?Equivalent Cylindrical Diameter (ECD)W is weight in gms and H is heightin cm
40 SSDEEffective diameter for typical 5 year old = 18.5 cm Conversion Factor for 5 year old (32 cm phantom) ~ 1.9 This means for a given CTDIvol the dose will be twice as much for a typical 5 year old compared to an adult. Q: Can these factors be used to define the required exposure conditions or do we need equivalent cylindrical diameter ?
41 Interventional Fluoroscopy Equipment should be appropriately designed. Consider:Beam filterBeam areaMinimum tube currentsReduced exposure pulse (need fast for heart)Removal of the anti-scatter gridDecreased magnificationAppropriate exposure levels - programmingRIS – PACS, Repeat proceduresAny repeat exposure within the last 60 days should be considered additive
42 Fluoroscopy What DRLs do we need? Incident air kerma Ki (mGy) Ki = Y(d)Pit(d/dFSD) Y(d) – output at distance dPit -- tube loading (mAs)dFSD – focus to skin distanceEntrance Surface Air Kerma (ESAK) Ke (mGy)Ke = Ki.B (Backscatter factor)Kerma-area-product (PKA) (mGy.cm2)KAP or DAP meterIAEA No. 24
43 Possibilities DAP ? Field size varies Is it possible to have DRLs for fluoroscopy?Probably yesSkin dose ?Would not expect for small patients to be highObese older patients!!DAP ?Field size variesSometime bigger (field) is better (visualisation)Monitor fluoroscopy exposure time + acquisitions runs (images) per procedure ?May be our best indicator for Optimised systems!TIME – Timely Intervention of Monitored Event
44 DRLs DRLs show what should be possible encourage changes in working proceduresNeed to be tailored or take account ofEquipment performancePatient demographics
45 So what more do we need to do? Identify Equipment factorsSort out Human factorsExtend the range of DRLsBase DRLs on individualsdo we use Equivalent Cylindrical Diameter ? oreffective diameter ? orsomething else ?Base DRLs on individualsPlanar CT Floro ?DAP DLP TIMEEEo
48 PiDRL - consortium European Society of Radiology, ESR European Society of Paediatric Radiology, ESPR European Federation of Radiographer Societies, EFRSEuropean Federation of Organisations for Medical Physics, EFOMPFinnish Radiation and Nuclear Safety Authority, STUK with two sub-contractors:Helsinki University Hospital, HUS, andPublic Research Centre Henri Tudor
49 PiDRL - objectivesAgree on a methodology for establishing and using DRLs for paediatric imaging, andUpdate and extend the European DRLs to cover more procedures and a wider patient age / weight range.
50 PiDRL – Work packagesWP0 - management and general coordination of the projectWP1 - methodology for DRLs, and producing European guidelinesWP2 updating and extending the existing European DRLsWP 3 organize the European workshop
51 THE END It’s TIME for a change Diagnostic procedures saves children’s livesthe effects of radiation lasts their lifetimebut rememberWe all have a duty as professionalsto make it safer for the childrenIt’s TIME for a change
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