Medisinsk bruk av stråling omfang og størrelsesorden av dose berettigelse, optimalisering og dosegrenser operasjonalisering av strålevernsarbeid

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1 Kurs Nr , 26. August 2009 Radiologiske Modaliteter Pst, Urvin, hva vil jeg at de skal sitte igjen med? Medisinsk bruk av stråling omfang og størrelsesorden av dose berettigelse, optimalisering og dosegrenser operasjonalisering av strålevernsarbeid Hiii, begeistring for teknologien og sans for teamwork... Hilde M. Olerud. Dr.ing. Seksjonssjef, Statens strålevern 1. Amanuensis, UiO/fysisk institutt

2 Røntgenstråling og annen stråling Tommelfingerregel: Elektromagnetisk stråling vekselvirker med objekter av omtrent samme størrelsesorden som bølgelengden!

3 Radiology in Norway 4,81 mill inhabitants 26 public Hospital Trusts/ 72 hospitals 8 private hospitals; 5 private trusts/ 24 institutes 600 radiologists, 2700 radiographers 30 diagnostic physicists X-ray units ~ 850 (all digital) Mammography units ~ 100 (60% digital) CT units ~ 130; MR units ~ 105 Interventional radiology/angiography: ~ NM centers ~ 60 gamma camera 10 RT centers ~ 40 Linear accelerators Norwegian Radiation Protection Authority Since 1939 (1993) Staff: ~ 100 Totally 40 enterprises and 104 clinics licensed to do X-ray Dentists, chiropractics, bone densitometry, veterinarian, X-ray in primary health care only object to notification

4 Key players in Norwegian health care Public entities Associations Ministry of Health Directorate of Health - Norwegian Board of Health Supervision Norwegian Radiation Protection Authority National cancer groups: Breast Lung GI Norwegian Association of Radiographers Norwegian Association of Medical Physics Public Hospitals Cancer Registry of Norway - Institute of Population-based Cancer Research Private X-ray institutes Norwegian Centre for Informatics in Health and Social Care (KITH) Gyn Norwegian Medical Association - Oncologists - Radiologists - Nuclear medicine - Intervention, etc Norwegian Cancer Society The research council of Norway

5 United Nations Scientific Committee on the Effects of Atomic Radiation, UNSCEAR since 1955 Radiation protection authorities report national data on radiological equipment and the use of it in certain intervals UNSCEAR Evaluate all published literature on the sources and effects of ionizing radiation Summarized in comprehensive reports about every 5th year

6 Regulations No of 21 November 2003 on Radiation Protection and Use of Radiation 34 Duty to provide information When requested by the Norwegian Radiation Protection Authority, the undertaking shall provide information on the annual number of therapies and diagnostic examinations carried out in various medical areas, as well as records of radiation doses to patients.

7 The Norwegian dose monitoring programme Examination frequencies and distributions ? Measurements of patient doses in conventional radiology 5000 measurements in 50 hospitals in the period Collection of representative DAP values from X-ray rooms from 2006 Measurements of patients doses in mammography National survey around 1990 of all clinical units MGD values From about 1995 part of QA of the national screening programme Measurements of patient doses in Computed tomography 50 laboratories, seven examination regions, 12 clinical indications (1995) Collection of representative CTDI vol and DLP values from CT rooms from 2006 The collected data are used for calculations of Collective effective dose Based on frequency data and national dose figures and for establishment of Diagnostic Reference Levels (DRL s)

8 European Commission RADIATION PROTECTION N o 154 European Guidance on Estimating Population Doses from Medical X-ray procedures EC Report in the RADIATION PROTECTION series. Annex 1 DD Report 1 Review of recent national surveys of population exposure from medical X-rays in Europe Annex 2 DD Report 1 (a) Review of national surveys of population exposure from nuclear medicine examinations in eight European countries available as a pdf files on the EC DGTREN Radiation Protection website cation_en-htm

9 Germany Luxembourg Estonia Croatia Radiology in Norway ( ) Lithuania Czeck Republic Portugal Slovakia Switzerland Norway Finland Poland Ukraine Netherland Bulgaria Sweden Denmark UK Hungary Romania Slovenia Norway 910 examination per 1000 inhab 742 X-ray based 72% in public sector, 28% in private sector During the last decade 16% increase in total number MRI frequency 11 US increased by 40% CT frequency 2 X-rays decreased by 10% 1.1 msv per caput CT contribute to 59% of the collective effective dose No. X-ray exams per 1000 inhabitants

10 Norwegian College of Radiology: National system for coding X-ray procedures, NORACO The examination/procedure part consists of five elements: Modality Location Procedure Side Additional Modality Location Procedure Side Additional C T A B I V Modality Location Procedure Side Additional R G G E S Modality: Location: Procedure: Side: Additional: X-rays, US, CT, MRI The examined organ, anatomical location, organ system or region Specifies the examination Left, right, bilateral Information for local use Modality, location and procedure are mandatory

11 EC RP No 154 The x-ray examination definition An x-ray examination or interventional procedure is defined as one or a series of x-ray exposures of one anatomical region/organ/organ system using a single imaging modality (i.e. radiography/ fluoroscopy or CT) needed to answer a specific diagnostic problem or clinical question during one visit to the radiology department, hospital or clinic One type of exam may consist of several subgroups of exams reflecting different clinical indications and various medical practices across the country

12 Examination frequencies interpretation of code system in Norway (2002) Example: The code combination CT abdomen with and without intra venous contrast Modality Location Procedure Side Additional C T A B I V Modality Location Procedure Side C T A B Additional represents two different scenarios: Either: One examination with iv contrast and another without, i.e. TWO different patients Or: One examination with and without iv contrast, i.e. ONE patient

13 The use of IV contrast, CT abdomen (1995) CT av Abdomen Abdomen 3.0 Abdomen 3.1 Abdomen 3.2 0,0 10,0 20,0 30,0 40,0 50,0 % Uten kontrast Med kontrast Med og uten kontrast Without IV With IV With and without IV Various clinical indications: 3.0 Typical examination, 3.1 Suspected metastasis, 3.2 Diffuse illness Data from a national CT survey in 1995 Information on the number of CT series included in the examination of the patient and the use of IV contrast For typical exams of the abdomen: 34% without IV 34 % with IV only 32% both (two series) Used to estimate the number of exams from the number of codes CT AB + CT AB IV From # codes to # exams (16% red) It is possible to extract info on the # exams from # codes if you know the procedures!

14 National variations in frequency Overall rates varied by a factor 2.4 Frequency per 1000 population: County of Oslo: 1487 exams County of Finnmark: 613 exams Explained by: differences in accessibility coexistence of public and private radiological institutions socioeconomic factors Sparsely populated areas and long travel distances in western and northern parts of Norway ECR 2007 Børretzen, Lysdahl, Olerud. 9

15 Oslo Vest-Agder Østfold Telemark Vestfold Troms Nordland Buskerud Sør-Trøndelag Akershus Sogn og Fjordane Rogaland Aust-Agder Nord-Trøndelag Møre og Romsdal Oppland Hordaland Hedmark Finnmark MR CT Use of CT versus MR in various counties Counties with high CT frequencies also have high MR frequencies MR is used in addition to CT not instead of Very different access to radiological services in Norway 0,0 0,5 1,0 1,5 2,0 2,5 3,0 Examination Undersøkelsesfrekvens frequency of MR and relativt CT til relative landsgjennomsnitt to the country mean

16 Ulik bruk av koder (2002) Antall CT koder TS* Totalt Sykehus Røntgeninstitutt Univ.sykehus Privat sykehus Bruk av tilleggsserier innen CT eksempel på ulik tolkning av kodeverket i ulike virksomheter innen rammene av NORAKO

17 Collective effective dose (S E ) from X-ray and CT during the last 25 years in Norway CT Røntgen Dose (msv) % increase in S E from msv/inhabitant (2002) CT answer for 59% of the dose and 14% of the frequency

18 Dosebegreper Absorbert energi, ε : Joule (J) Absorbert dose, D : Gray (Gy) D = ε/m (Gy) absorbert energi per masseenhet 1 Gy = 1 J/kg 1 mgy = 1/1000 Gy Ekvivalent dose, H : Sievert (Sv) H T = Σ w R D T,R biologisk ekvivalent dose (α, β, γ) Effektiv dose, E : Sievert (Sv) H T = Σ w T H T vektet etter stokastisk risiko

19 Organ or tissue ICRP Tissue Weighting Factors /1990 Gonads Bone marrow Lower large intestine Lung Stomach Bladder Breast Liver Oesophagus Thyroid Bone surface Skin Brain 0.01 Salivary glands 0.01 Remainder organs* E = Σ w T H T

20 Dose survey methods: the practical dose parameters Radiography and fluoroscopy Mammography CT ESD DAP CTDI w CTDI vol DLP D air MGD For radiography and fluoroscopy the practical dose parameter is the dose area product, DAP for mammography it is the calculated mean glandular dose while for CT it is the weighted and pitch corrected CTDI vol and the dose length product, DLP

21 Use of Monte Carlo simulations in radiology Theoretical simulations of interactions between ionizing radiation and matter by means of a computer Radiation sensitive organs and tissue are given certain coordinates in designed mathematical phantoms The spectra and fluence of photons towards the phantom must be known (kv, filtration, distance and geometry) The examination is simulated (X-ray, mammography, CT) while keeping track of all energy depositions in different part of the phantom The conversion coefficients can be established between simple practical dose parameters such as the entrance surface dose (ESD), dose area product (DAP) or the CT dose index (CTDI), and the corresponding organ doses. The effective dose can be calculated MATEMATICAL PHANTOMS Simple models based on geometrical figures VOXEL phantoms based on CT or MR uptake of real patients Glandular tissue/fat 50% / 50%

22 National variation in X-ray doses ( ) No of hospitals/laboratories (a) Chest NGL=0,6 Gycm 2 0,1 0,3 0,5 0,7 0,9 1,1 1,3 1,5 More KAP (Gycm 2 ) Example of the distribution of dosearea products from chest X-rays in Norway Diagnostic radiology in Norway from Examination frequency and collective effective dose to patients. Radiat.Prot. Dosim. (1997) 74; Nordic guidance levels for patient doses in diagnostic radiology. Radiat Prot Dosim (1998) 80; A Nordic survey of patient doses in diagnostic radiology. Eur Radiol (2000) 10; Nordic guidance levels for selected interventional procedures. Radiat Prot Dosim (2001) 94;133-35

23 National variation in CT doses (1995) Olerud, HM. Radiat Prot Dosim 1997;71(2): CT chest With and without contrast With contrast Without contrast No laboratories ,5 5 7, , , , , , ,5 40 Effective dose (msv) The national average dose for CT chest was 11,5 msv Corresponding to DLP= 605 mgycm

24 National variation in CT doses (1995) Olerud, HM. Radiat Prot Dosim 1997;71(2): CT abdomen With and without contrast With contrast Without contrast No laboratories ,5 5 7, , , , , , ,5 40 Effective dose (msv) The national average dose for CT adomen was 12,8 msv Corresponding to DLP= 753 mgycm

25 Effective dose for 7 typical CT procedures RESULTS BASED ON 49 LABORATORIES (1995) CT examination E (msv) mean E (msv) median E (msv) 3. quartile Max/Min value Head/brain 2,0 1,8 2,7 8,0 Chest 11,5 10,0 15,5 19,5 Abdomen 12,8 9,9 17,2 13,3 Lumbar spine 4,5 4,4 5,2 10,5 Lever 11,9 11,1 16,4 8,7 Kidney 9,9 10,1 14,4 19,7 Pelvis 9,8 8,3 11,8 17,2 NRPB - SR250 phantom and conversion coefficients Scanner model, kv, mas, slice thickness, increment, CTDI, scan length CTDOSE software for calculation of organ doses and effective dose New scanners: The Impact dose calculator Olerud, HM. Radiat Prot Dosim 1997;71(2):

26 Explanations for the differences in patient dose No laboratories CT head/brain, mean effective dose = 2 msv (1995) W ith and without contrast W ith contrast W ithout contrast 1 0 0,5 0,75 1 1,25 1,5 1,75 2 2,25 2,5 2,75 3 3,25 3,5 3,75 4 4,25 Effective dose (msv) The total scan length and scanner model were the two most important variables, i.e. technical factors as well as protocol used (optimisation) Different clinical indications could sometimes explain the various protocols (use of contrast, number of series, total scan length)

27 Explanations for the differences in patient dose DRL=800mGycm Reidun Silkoset, master thesis (2008) Analyses of more recent collected local DRL s in CT rooms in Norway clearly demonstrate that dedicated multi disciplinary optimization work gives results In departments where radiologists, radiographers and medical physicists collaborate in working out the examination procedures and scan protocols, the local DRL s are significantly lower Departments having radiographers with postgraduate studies in CT also show significantly lower DRL s.

28 Trends in CT doses Norway national mean doses CT examination DLP mgycm 1995 survey (49 rooms) DLP mgycm 2006 d.d. (# rooms) CT head ,5 (61) CT neck CT chest ,3 (45) CT spine (21) CT abdomen ,3 (49) CT pelvis 576 CT sinuses (3) Chest HR CT (7) CT coronary angiography (4) CT urografi (invest) (4) CT urography (stone) (15) CT colonscopy (3) Stable or somewhat decreasing doses from CT procedures?

29 Approaches to decrease frequency of X-ray based examinations Examinations to the spine Total no of exams CED (mansv) Year No Examinations Annual CED mansv A deliberate strategy to use non ionizing modalities whenever possible was implemented in this hospital from 1993 This lead to a significantly lower collective effective dose

30 Conclusions from Norway.. Small increase in the total frequency of radiological examinations Large increase in the use of CT and non ionizing modalities (MR, US), small decrease in some conventional X-ray procedures Large geographical variations in the use of radiology, activities in private enterprises adds to what is going on in public hospitals Use of referral criteria and deliberate strategies may give lower total frequency of examinations and collective effective doses Huge variation in patient doses for same examination done in different X- ray rooms, explained by both technology and the use of technology Multidisciplinary work on optimization, education and training give results! Need to develop harmonized radiological code systems consistent with the understanding of what is ONE radiological examination Need for developing dose parameters reflecting the patient risk, and systems to easily record such data from radiological information systems

31 Strålevernsprinsipper i røntgendiagnostikk Berettigelse, kostnad-nytte vurderinger For den enkelte pasient skal nytten ved å få stilt diagnose være større enn eventuell risiko Undersøkelsen skal ha betydning for diagnosen, og for videre behandling av pasienten Alternative metoder som ikke involverer bruk av ioniserende stråling bør vurderes Sett fra samfunnets side må en gitt virksomhet vurderes med tanke på kostnad og samfunnsmessig gevinst

32 Strålevernsprinsipper i røntgendiagnostikk Optimalisering Den enkelte røntgenundersøkelse skal utføres slik at det diagnostiske utbyttet sikres ved lavest mulig stråledose til pasient Krav til bildekvalitet i forhold til stråledose vil variere med undersøkelsestype og klinisk spørsmålsstilling Optimalisering handler om valg av apparatur, utstyr og undersøkelsesteknikk Optimalisering er nøye knyttet til kvalitetskontroll og kompetanse ALARA : As low as reasonable achievable

33 Strålevernsprinsipper i røntgendiagnostikk Stråledose til pasient Det finnes ingen dosegrenser for pasient, så lenge prinsippene om berettigelse og optimalisering er oppfylt ICRP60 tok imidlertid til orde for etablering av dose constraints (doseføringer) knyttet til røntgendiagnostiske undersøkelser Implementert ved diagnostic reference levels (DRL s) og representative doser (local DRL s) No of observations Undersøkelser av korsryggen MEDIAN Nordic guidance level 3.QUARTILE Total no. of observations 527 Mean KAP=9.15 Gycm 2 Mean patient weight 70 kg Mean no. of films Kerma-area product (Gycm 2 ) Kvalitetskriterier knyttet til tekniske fantom og/eller kliniske bilder nødvendig for optimalisering GRUNNLAG : Målinger av doser ved alle sykehus

34 Riktig bruk av røntgen - DIAGNOSTISK UTBYTTE, STRÅLEDOSE, KOSTNADER I VID FORSTAND Bruken av radiologi ved utredning av mistenkt sykdom og diffuse plager Rekvisisjon versus henvisning; henvisningskriterier til vurdering av berettigelse Valg av modalitet (røntgen, CT, MR, ultralyd, nukleærmedisin ) Hvor ofte skal pasienter med diagnostisert sykdom følges opp radiologisk, og med hvilken protokoll; optimalisering Oppfølging av kronisk syke, for eksempel MS Crohn, cancer testis pasienter, CT av barn med vannhode, skoliose,. Screening programmer (gruppe, intervall, protokoll) Mammografi, Colon cancer, lunge cancer.. Etiske aspekter ved Medico-legal exposures Sikkerhetskontroll ved grensen, immigranter Undersøkelser i forsikrings- eller juridisk øyemed Ikke indiserte undersøkelser av idrettsutøvere

35 Kvinne 24 år med Mb Crohn over 10 års periode Undersøkelse Effektiv dose (msv) Antall Akkumulert (msv) Rtg.thorax Tynntarm serie Tarmpassasje Oversikt abdomen Fistulografi Intervensjon bekkenkar CT thorax CT abdomen CT bekken CT LS-columna TOTAL AKKUMULERT DOSE ~ 250 msv

36 Hva skjuler seg bak røntgenstatistikken? Norge, 2002 (Statens strålevern): 742 røntgenbaserte u.s per 1000 innbyggere Danmark, 2004 (SIS, Danmark): 23 % av befolkningen var til røntgen i ,4 % av alle menn - 26,9 % av alle kvinner Unntatt tann- og kiropraktorrøntgen Over halvparten av dem til gjentatte undersøkelser

37 Henvisnings kriterier innen radiologi UNSCEAR 2000, undersøkelsesfrekvensen klart økende i health level I countries Store forskjeller mellom land med samme helsenivå, forskjeller mellom by og land JUSTIFICATION (berettigelse) Introdusert av den internasjonale strålevernskommisjonen, ICRP Poengtert i EU s Pasientdirektiv (97/43 Euratom) Implementert i norsk strålevernforskrift gjeldene fra 2004 Tatt opp av RCR i UK Making the best use of the department of radiology (nå i 7 ende versjon) Utgitt av EU i RP serien Diskutert i konsensuskonferanse 19. September 2001 (Helseregion sør) Radiologforeningen har oversatt kriteriene for implementering i Norge Vel?

38 SSM rapport Publikationer/Rapport/Stralskydd/2009/200903/ The objective of the study was to investigate the degree of justification for CT-examinations in Sweden. Referrals for all examinations performed during one day were retrospectively evaluated by a group of physicians. The principle result was that approximately 20 % of all examinations were not justified. The degree of justification varied strongly with organ examined, moderately with prescriber affiliation and weakly with geographical region. If unjustified examinations could be avoided a large dose reduction for the population would be achieved.

39 Justification

40 Utfordringer m.h.t. optimalisering Medisinsk røntgendiagostikk gir det desidert høyeste bidrag til total befolkningsdose fra menneskeskapte kilder. Det er store variasjoner mellom ulike sykehus i både stråledose til pasient og bildekvalitet. Det synes derfor mulig å redusere befolkningsdosene ved å optimalisere undersøkelsene. Optimalisering av CT undersøkelser er viktig fordi de øker i antall, og utgjør stor andel av total befolkningsdose. Optimalisering av mammografi-undersøkelser viktig p.g.a. krav til bildekvalitet og oppstart av nasjonal screening. VIKTIG SATSING MED NY FORSKRIFT: Etablering av referansedoser knyttet til røntgendiagnostiske undersøkelser (DRL) og sykehusenes oppfølging med målinger av representative doseverdier til sammenligning med DRL NRPA studier har vært konsentrert om etablering av landsmiddelverdier sykehusenes utfordring ligger i lokal doseregistrering, og bruk av dette til protokollutvikling

41 Stråledoser ved vanlig røntgen 5000 MÅLINGER VED 50 SYKEHUS ( ) LANDSMIDDELVERDIER Røntgen undersøkelse : Skalle Lunger Thoracal columna Lumbar columna Abdomen Bekken Magesekk Tykktarm Urografi Antall bilder Rør D Effektiv spenning dose (kv) (mgy) (msv) E > D DERSOM EN STUDERER TIDSROMMENE ( ) OG ( ) SEPARAT, SER EN EN TREND MOT NOE LAVERE STRÅLEDOSER FOR FLERE UNDERSØKELSER

42 17 CT rooms in Norway CT abdomen Effektive dose CTDI vol DLP CC 0,15 Effektive Effektive Abdomen mgy mgycm msv/mgycm dose (male) dose (female) N Mean Minimum Maximum Reidun Silkoseth, master thesis (2008) Impact Dose calculator

43 Stråledose til øyelinsene ved COMPUTED TOMOGRAFI Av betydning ved u.s. av hode/hjerne Svært avhengig av vinkling på gantry ICRP terskelverdier : Målbar forandring av linsen Gy Linse doser (mgy) Katarakt > 2-10 Gy Mean Min Max Parallell med skalle basis aksiale snitt NB: gjentatt undersøkelser av samme pasient kan gi lavere terskel

44 CT av kvinner i fertil alder Dårlige kunnskaper om doser og risiko i primærhelsetjenesten Fosterdoser <100 mgy ingen indikasjon for abort Likevel en tilleggs risiko for senskader en ønsker å unngå Uklare rutiner etter bortfall av 10 dagers regelen Strålevernet har ca 10 saker i året der foster utilsiktet er blitt eksponert for stråling Nødvendige undersøkelser må gjennomføres! DOSE TIL GONADER Av betydning ved CT av bekken og nedre abdomen I primær scanvolum kan dosene komme opp mot 100 mgy Pelvis Abdomen Lumbar spine Liver/ kidneys Ovary Testes Gonade dose (mgy)

45 Formidling av risiko Stort fokus i USA på artikkel i AJR om epidemiologisk bevist sammenheng mellom CT og barnekreft 1500 i året vil dø som voksne etter CT undersøkelse som barn! 1.6 mill CT undersøkelser av barn < 15 år hver år i USA ville dødd av kreft av alle mulige andre årsaker Grunnen til CT undersøkelsen (skader, kreft, akutt sykdom) utgjør større og mer akutt fare enn den lille økningen i risiko

46 Typiske stråledoser fra røntgendiagnostikk Prosedyre Effektiv dose [msv] Ekviv. med antall thorax Ekviv. naturlig* bakgrunnstråling Thorax PA 0, dager Cranium 0,1 5 8,5 dager LS-col 1,2 60 3,5 måneder Urografi ,5 måneder Ventrikkel db 4, år Colon db 9, år CT cerebrum ,5 måneder CT thorax 11, ,5 år CT abdomen 12, år * Gjennomsnittlig dose fra naturlig bakgrunnstråling - ca. 4,5 msv/år (3 msv/dag)

47 Strålevern på røntgenavdelingen Berettigelse Kunne avvise pasienter med uklar medisinsk spørsmålsstilling Kjenne apparaturen godt Knottologi - Tekniske spesifikasjoner - Kvalitetskontroll Optimalisering Utvikle generelle protokoller ved å spille på parametere som påvirker bildekvalitet og stråledose til pasient, tilpasse individuelt m.h.t. medisinsk spørsmålsstilling, pasientvekt Kunnskap om doser - størrelsesorden - risiko Informere pasienter om doser ved vanlige røntgenundersøkelser Dosenivå bakgrunn - personaldoser - pasient diagnostikk - terapi Kjenne til hvordan dere beskytter dere selv Avstand, beskyttelsesutstyr, persondosimetri, gravide ut av lab

48 DOSEDATAMED TREN/04/NUCL/S Barry Wall (chair), David Hart Abbas Aroua, Philipp Trueb Bernard Aubert, Pascale Scanff, Phillippe Pirard, Hélène Beauvais Elke Nekolla, Jurgen Griebel Paul Stoop, Els Meeuwsen, Marco Brugmans Hilde Olerud, Ingelin Borretzen Wolfram Leitz Ferid Shannoun Hanne Waltenburg, Peter Grøn Alfred Lecluyse, Harrie Mol UK Switzerland France Germany Netherlands Norway Sweden Luxembourg Denmark Belgium

49 EC RP N o 154 Annex 1 DD Report 1 REVIEW OF RECENT NATIONAL SURVEYS OF POPULATION EXPOSURE FROM MEDICAL X-RAYS IN EUROPE 1. Introduction 2. History of population dose assessments from medical x-rays in Europe 3. National arrangements and responsibilities 4. National regulatory frameworks 5. National healthcare systems in 10 European countries 6. National strategies for assessing population dose from medical x-rays 7. Methods for assessing the frequency of x-ray examinations 8. Methods for assessing patient doses 9. Results 10. Discussion 11. Conclusions 12. References Look back explain differences! Appendix 1: Recent national surveys of population dose from medical x-rays Appendix 2: Accuracy of population dose estimates Appendix 3: Tables showing detailed frequency and patient dose results for the Top 20 Exams in each country

50 EC RADIATION PROTECTION N o 154: EUROPEAN GUIDANCE ON ESTIMATING POPULATION DOSES FROM MEDICAL X-RAY PROCEEDURES 1. Introduction 2. Purposes for making population dose estimates for medical x-rays and the dose quantities used 3. Guidance on assessing frequency of x-ray examinations 3.1 How to categorise examinations 3.2 X-ray examination frequency survey methods 3.3 Sources of uncertainty in frequency estimates and how to reduce them 4. Guidance on assessing patient doses 4.1 Patient dose survey methods 4.2 How to convert measured doses into organ and effective doses 4.3 Sources of uncertainty in patient doses and how to reduce them 5. Guidance on assessing age/sex distributions of x-ray patients 6. Guidance on presenting the results of population dose estimates 7. Use of electronic information stored in modern medical imaging equipment and RIS 8. Summary of recommendations 9. References Appendix 1: Detailed descriptions of Top 20 Exams Appendix 2: Typical European age/sex data for x-ray patients Appendix 3: NRPB CT Dose Survey questionnaire Tell us how to do it in the future!

51 EC RP N o 154 Frequency survey methods How to categorize examinations Plain film radiography, Radiography/fluoroscopy, CT, Interventional 225 specific exams 70 broader categories top 20 How to estimate the number of examinations from a sample of hospitals, clinics or practices from central statistics held by government departments or insurance companies sample scaled up to cover the whole country Identifying uncertainties in frequency estimates Relating codes into actual numbers Insufficiently differentiated codes Bias in the sample and invalid assumptions Lack of frequency data from some important providers of radiology Mistakes in the data recorded or collected

52 Exam type or category % of total frequency* % of total S* Plain film radiography 1. Chest/thorax Cervical spine Thoracic spine Lumbar spine (inc. LSJ) Mammography Abdomen Pelvis & hip Radiography/Fluoroscopy 8. Ba meal Ba enema Ba follow IVU Cardiac angiography All angiography CT 13. CT head CT neck CT chest CT spine CT abdomen CT pelvis CT trunk All CT Interventional 20. PTCA All interventional The Top 20 Exams TOTAL

53 An examination description Appendix 1 in RP 154 Exam Type Specific exams included in Exam type Common Technique Examples for indications 17. CT abdomen Abdominal organs With or without contrast Cancer diagnosis and staging, infectious lesions, inflammatory diseases, major trauma, acute abdominal pain, suspected haemorrhage, chronic hepatic illness, liver metastases or suspected obstruction of hepatic vessels.

54 Exam type Mean E per examination (msv) Highst Middle Lowest DE CH ALL 10 NL UK 1. Chest/thorax Cervical spine Thoracic spine Lumbar spine Mammography Abdomen Pelvis & hip Ba meal Ba enema Ba follow IVU Cardiac angio All Angiography CT head CT neck CT chest CT spine CT abdomen CT pelvis CT trunk All CT The Top 20 Exams 20. PTCA All Interventional

55 National average dose figures (NDF) should be established for each of the Top 20 Exams, by collecting information about representative doses from a sample of hospitals and practices in the practical patient dose quantities introduced in Chapter 4.1 in the report The basic data would normally be the same as providing national dose distributions used for establishments of diagnostic reference levels the dose figures are converted to effective dose by means of the conversion coefficients provided in Chapter 4.3. guidance in identifying uncertainties in patient dose estimates is provided in Chapter 4.6 in the report. table 16 concludes it is recommended to collect representative dose figures from >100 rooms.

56 Sample size and matching of conversion coefficients >100 rooms Good CC match rooms Good CC match 5-19 rooms Good CC match >100 rooms Poor CC match rooms Poor CC match 5-19 rooms Poor CC match Foreign data only Uncertainties at 95% confidence level Sample size CC Overall Table 17: Overall uncertainties in mean effective dose estimates as a function of sample size and matching of exposure conditions for conversion coefficients ±10% ±10% ±14% ±25% ±10% ±27% ±50% ±10% ±51% ±10% ±25% ±27% ±25% ±25% ±35% ±50% ±25% ±56% 100 % -50 %

57 Status from Norway in collecting dose figures No The "TOP 20 list" RP154 NDF Dose Unit #X-ray rooms 1 Chest/Thorax 0.46 Gycm Cervical spine 3 Thoracic spine 4 Lumbar spine (inc.lsj) 6.11 Gycm Mammography 6 Abdomen 4.76 Gycm Pelvis & hip 1.74 Gycm Ba meal 9 Ba enema 8.32 Gycm Ba follow-through 11 IVU 12.3 Gycm Cardiac angiography CT head mgycm CT neck 15 CT chest mgycm CT spine 347 mgycm 21

58 RiS a chest with treasures Patient Information Coded procedures Image Information Exposure parameters Dose parameters Examination frequencies based on code systems Age and sex distributions Dose distribution Examination technique Reference dose values Collective effective dose