Dose To Patients From Dental Radiographic X-ray Imaging .

PHE-CRCE-59: Dose to patients fromdental radiographic X-ray imagingprocedures in the UK2017 review

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewAbout Public Health EnglandPublic Health England exists to protect and improve the nation’s health and wellbeing,and reduce health inequalities. We do this through world-leading science, knowledgeand intelligence, advocacy, partnerships and the delivery of specialist public healthservices. We are an executive agency of the Department of Health and Social Care,and a distinct delivery organisation with operational autonomy. We providegovernment, local government, the NHS, Parliament, industry and the public withevidence-based professional, scientific and delivery expertise and support.Public Health EnglandWellington House133-155 Waterloo RoadLondon SE1 8UGTel: 020 7654 8000www.gov.uk/pheTwitter: @PHE ukFacebook: www.facebook.com/PublicHealthEnglandPrepared by: JR Holroyd, JRH Smith and S EdyveanFor queries relating to this document, please contact: medicalradiationdoses@phe.gov.uk Crown copyright 2020You may re-use this information (excluding logos) free of charge in any format ormedium, under the terms of the Open Government Licence v3.0. To view this licence,visit OGL. Where we have identified any third party copyright information you will needto obtain permission from the copyright holders concerned.Published September 2020PHE publicationsgateway number: GW-1261PHE supports the UNSustainable Development Goals2

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 lPanoramicLateral cephalometricCone beam computed tomographySummary of typical doses669111416DiscussionRepresentationDigital imagingCephalometric imagingDental CBCTNational DRLsDose ledgements233

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewIntroductionPublic Health England (PHE) and its predecessor organisations have carried outnational reviews of patient dose indices at regular intervals for over 2 decades.The last review of radiographic and fluoroscopic imaging procedures in 2010 formed thebasis of the current UK National Diagnostic Reference Levels (NDRLs) for theseapplications (Hart et al, 2012). As it has been a significant time since the 2010 review itis necessary to carry out the next review of current practice in the UK to either confirmthat the existing NDRLs are still suitable or to set new values. The current review willconsider patient doses from all types of radiographic and fluoroscopic procedures.However, unlike the 2010 review it is the intention to collect and report on data inseveral stages. This first stage is a review of patient doses from dental radiography.National Diagnostic Reference Levels (NDRLs) for dental radiography are currently setfor a set of standard examinations, with separate NDRLs for adults and children. DentalX-ray equipment is typically far less complex than general diagnostic medical X-rayequipment, with fixed exposure parameters and collimation, meaning that there is littlevariation in patient exposure for the same examination. It is therefore not necessary tocollect individual patient data; the doses for these standard examinations assessedduring routine quality assurance testing are adequate.NDRLs currently exist for intra-oral and panoramic radiography which are by far themost common dental X-ray modalities (PHE, 2018). For intra-oral radiography thestandard examination chosen is a mandibular molar radiograph and for panoramicradiography it is the standard full panoramic radiograph. For this survey, data wasalso requested for cephalometric radiography and Cone Beam ComputedTomography (CBCT).Although cephalometric radiography has been an available technique for many years,by comparison to intra-oral or panoramic radiography it is a much less commontechnique and, as such, was not considered in previous reviews. It was decided toinclude it in this review as there is evidence of a wide range of doses from theequipment currently in use (Holroyd, 2011). The examination chosen as representativefor this technique is a standard lateral radiograph.The use of CBCT equipment is a relatively recent development in dental radiography,having been in clinical use for less than 15 years. The doses delivered to patientsduring CBCT are typically much higher than those from other modes of dentalradiography, therefore it is considered particularly important to include doses fromCBCT in this review. Previous work by PHE established an achievable dose for CBCT(Holroyd and Walker, 2010) as a dose guide for users of CBCT. A lack of available data4

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewand a wide variability in patient doses meant it was not possible to set a NDRL at thattime. However, CBCT equipment is now much more widely used, so in this review itwas possible to obtain enough data to propose a NDRL. Unlike other dental X-rayequipment where dose data was collected for a standard examination and a standardpatient, due to the wide range of uses of CBCT equipment 2 specific clinical indicationswere included in the request, to ensure comparable patient dose data was obtained.The clinical indications were:a) imaging prior to placement of a maxillary molar implant in a standard adult patient,andb) imaging of an impacted maxillary canine tooth of a 12-year-old child.MethodAn Excel (Microsoft, USA) workbook was designed to collect information on each dentalX-ray set, exposure parameters and patient dose delivered for the standardexaminations identified. The workbook was trialled with 1 NHS Hospital Trust thatfrequently carries out dose measurements on all types of dental X-ray equipment withthe feedback from this Trust being used to refine the workbook.The template workbook was posted to the MEDICAL-PHYSICS-ENGINEERING e-maildistribution list (JiscMail, 2018). This distribution list is viewed by the UK medicalphysics community and those who carry out dose assessments on dental X-rayequipment. A 2-month period was allowed for providing data, during November andDecember 2017, and regular reminder e-mails were sent during this period. Data wasrequested from measurements made since 2014 to account for the fact that therecommended frequency for making measurements of patient dose is every 3 years(NRPB, 2001), apart from CBCT equipment for which it should be measured annually(Holroyd and Walker, 2010). Data was only requested for sets which were currently inclinical use and for only the most recent measurement. All the data was compiled into asingle workbook for analysis. Any data which appeared to be anomalous was queriedwith the respondent for clarification, and either confirmed or removed from the analysis.A small number of workbooks were returned shortly after the deadline and these werealso included in the analysis.5

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewResultsData was received from 32 respondents. This covered patient dose measurementsmade on a total of 11,331 intra-oral X-ray sets, 1,500 panoramic X-ray sets, 152cephalometric X-ray sets and 215 CBCT X-ray sets.In the following tables, CR is used to denote computed radiography systems (for example,the use of phosphor plates) and DR for digital radiography systems (for example, the useof charge coupled devices or complementary metal oxide semiconductor sensors). Dosemeasurement results are presented as percentiles of the total dose distribution. The 50thpercentile, or median, can be considered a typical dose for that examination and the 75thpercentile (third quartile) is the value used to establish a NDRL for dental radiography.Intra-oralA breakdown of the imaging method used with each X-ray set can be seen in Table 1and the choice of collimation is shown in Table 2.Table 1 Choice of imaging method for intra-oral radiographyImaging typeD speed filmE/F speed filmE speed filmF speed filmSelf-developing filmFilm (unknown type)CRDRDigital (unknown type)TotalNumberof X-raysets11536186315727145699145945210542% of total1%3%8%15%0%0%54%14%4%Table 2 Choice of collimation for intra-oral rof X-raysets3595732110961% of total33%67%6% Film or digital28%72%

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewThe 5th to 95th percentile values for the patient dose distribution are shown in Table 3.The dose distribution was sub-divided by the choice of imaging method and the resultsare shown in Table 4.Table 3 Patient entrance doses (mGy) reported for a standard adult mandibular molarintra-oral radiographPatient groupAdultChildRatio - Child/AdultNumberof X-raysets113207888Dose (mGy) at a given th1.20.70.695th2.01.20.6Table 4 Intra-oral adult mandibular molar patient entrance doses (mGy) sorted byimaging methodImaging methodD speed filmE speed filmE/F speed filmF speed filmCRDRNumberof X-raysets115863361157256991459Dose (mGy) at a given h2.72.21.72.11.91.9In order to visualise the range of doses delivered for the standard mandibular molarradiograph, the dose results were sorted into 0.2 mGy bins and a histogram plotted toshow the range of doses for adult examinations (Figure 1) and child examinations(Figure 2).7

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewFigure 1 Dose distribution for adult intra-oral mandibular molar radiographs. The verticalbar approximately represents the third quartile value.Number of X-ray sets2500200015001000500 332.82.62.42.221.81.61.41.210.80.60.40.20Patient Entrance Dose (PED), mGyFigure 2 Dose distribution for child intra-oral mandibular molar radiographs. The verticalbar approximately represents the third quartile value.Number of X-ray sets2500200015001000500 332.82.62.42.221.81.61.41.210.80.60.40.20Patient Entrance Dose (PED), mGyThe operating potential for each X-ray set is shown in Figure 3. Data was requested forthe actual operating potential as measured during the most recent equipment testing;however, it was apparent from the data received that some data were a measuredoperating potential and other data were the rated operating potential for that X-ray set.Figure 3 includes all the data received, which provides useful information on likelyoperating potentials in use, but as it combines both measured and rated values, moremeaningful analysis is not possible.8

PHE-CRCE-59: Dose to patients from dental radiographic X-ray imaging procedures in the UK – 2017 reviewFigure 3 Distribution of operating potential for intra-oral X-ray sets4500Number of X-ray sets400035003000250020001500100050085moreOperating potential, kVp807570656055500PanoramicThe different types of image receptor in use are shown in Table 5.Table 5 Choice of imaging method for panoramic radiographyImaging methodFilmCRDRDigital (unknown type)TotalNumberof X-raysets2902385601791267% of total% Film or digital23%19%44%14%23%77%The 5th to 95th percentile values for the patient dose distribution are shown in Table 6.The dose distribution was sub-divided by choice of imaging method and the results areshown in Table 79