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Научни трудове на Съюза на учените в България-Пловдив, Серия Г. Медицина, фармация и дентална медицина т. XIX. ISSN 1311-9427 юни 2016. Scientific works of the Union of Scientists in Bulgaria-Plovdiv, series G. Medicine, Pharmacy and Dental medicine, Vol. XIX, ISSN 1311-9427 Medicine and Dental medicine June 2016.
ДИЗАЙН, МЕТОДИКА И ЦЕЛИ НА ТРЕТОТО НАЦИОНАЛНО ПРОУЧВАНЕ НА ЛЪЧЕВОТО НАТОВАРВАНЕ НА ПАЦИЕНТИТЕ В РЕНТГЕНОВАТА ДИАГНОСТИКА
Асен Димов, Десислава Иванова, Филипа Василева Национален център по радиобиология и радиационн защита
DESIGN, METHODOLOGY AND PURPOSES OF THE THIRD NATIONAL PATIENT DOSE SURVEY IN DIAGNOSTIC RADIOLOGY
Asen Dimov, Dessislava Ivanova, Filipa Vassileva National Centre of Radiobiology and Radiation Protection, Sofia, Bulgaria
Abstract
In correspondence with requirements of National legislation and requirements of EC Directive 2013/59/Euratom, National Centre of Radiobiology and Radiation Protection (NCRRP) started the Third National Patient Dose Survey (TNPDS) with an aim to update the existing Diagnostic Reference Levels (DRL) in Radiology. The data of the survey will be delivered on special forms for X-ray equipment and patient doses elaborated by NCRRP. Methods for supplying the data to NCRRP are following: via internet based platform for automatic sending; via electronic tables sent by e-mail; via information for local typical doses; via paper hard copy. Collecting of main amount of data, processing and elaboration of firs results with recommendations for new NDRLs is planned to be explored until end of 2016.
Key words: Patient Dose, Typical Dose, Diagnostic Reference Levels, DRLs, NDRLs.
Резюме
В изпълнение на изискванията на националното законодaтелство, както и на изискванията на Директива 2013/59/ЕВРАТОМ, Националният център по радиобиология и радиационна защита започна провеждането на Третото национално проучване на облъчването на пациентите с цел актуализиране на съществуващите национални диагностични референтни нива (DRLs) в рaдиологията. Данните от проучването ще се предоставят чрез попълване на специално разработени от НЦРРЗ форми за рентгеновата апаратура и пациентните дози. Методите за предоставяне на тези данни са следните: чрез интернет базирана платформа за автоматично изпращане; чрез електронни таблици изпратени по е-мейл; чрез информация за съществуващи типични дози; чрез предоставянето им на хартиен носител. Планира се събирането на основния обем от данни, обработката и получаването на първите резултати с препоръки за нови NDRLs да стане до края на 2016 г.
Ключови думи: пациентна доза, типична доза, диагностични референтни нива, DRLs, NDRLs.
Short historical overview of DRLs
First step of defining boundary between necessary and unnecessary radiation exposure
was made by the Department of Public Health of the State of Illinois, USA. In 1969 the department started to collect specific information on patient exposure at regulatory inspections of different X-ray systems in the State [1]. Data were collected for radiation exposure to patient on photofluorographic X-ray systems used for screening of tuberculosis. This field was most interesting as patient exposure varied as much as tenfold and large number of population was screened. Analysis of data showed 75% of all facilities were able to obtain quality X-ray images of chest at patient exposure bellow 200 mR (1,74 mSv) and about 50% of them could obtain quality radiographs at less then 100 mR (0,87 mSv). This became a basis for adopting of the following rule by the State Health Department:
"The incident exposure to an average patient shell not exceed 200 mR per radiograph and should not exceed 100 mR per radiograph" [2]
Via change in the practice such as using more sensitive films, higher speed screens, higher anode potential (kVp) and better mirror optics, all facilities with higher patient exposure could bring it down to be within the mentioned limits. This way no X-ray system was lost because of this rule and collective dose of thousands man-Sv was saved. The surveys in this field has been continued and in 1974 Neuweg and Brunner have published data on which the regulation in this field was developed [2]. The authors stipulate the upper exposure limits shell be applied for standard exposure conditions only. Neuweg and Brunner conclude following:
- 75% of X-ray systems can produce clinically acceptable image giving exposure to patient bellow a specific limit;
- The applied techniques of all X-ray systems should be changed in a way that no unnecessary high exposure should be given to patient.
In 1978 Environmental Protection Agency and the Department for, education and welfare of USA develop recommendations for limitation of exposure on federal medical systems. These recommendations have been approved by the president of United States and published in the federal register. They have been translated and published in Europe - in Germany in 1979 for example. In Table 1 recommendations for the entrance exposure values for some projections are shown.
In 1985 the Center for equipment and radiological health of USA repots as a result of measures undertaken and significant reduction of patient exposure has been registered, but linked improvement of image quality is absent. In analysis of results of application of concept for entrance exposure Xentrance published in 1980 by Lows and Rosenstain conclude that optimal reduction of exposure can be achieved when X-ray systems exposing with value of dose over third quartile, diminish their entrance surface dose (ESD) employing techniques similar to those employed by units with ESD laying within first three quartiles. This patient dose reduction shell be accompanied by a Quality Assurance (QA) Program, identifying reasons for higher exposure in a way that the technics shell be appropriately modified without lost of image quality.
Organ, Projection Entrance Exposure (mR)
Chest (PA) 30
Skull (LAT) 330
Abdomen (AP) 750
Cervical spine (AP) 250
Thoracic Spine (AP) 900
Full Spine (AP) 300
Lumbosacral Spine (AP) 1000
Retrogradic Pyelogram 900
Foot (DP) 270
Dental (Bitewing, Intraoral) 700
Table 1. Recommendation developed by the Department of Health, education and welfare of USA for several standard projections (1978).
Definitions of Diagnostic Reference Levels (DRLs).
According to International Commission of Radiological Protection (ICRP): "A diagnostic reference level is a level set for standard procedures for groups of standard-sized patients or a standard phantom. It is strongly recommended that the procedure and equipment are reviewed when this level is consistently exceeded in standard procedures (ICRP 73, § 100) [3]. Corrective action should be taken as appropriate. According to Medical Exposure Directive [4]"Diagnostic Reference Levels: dose levels in medical radiodiagnostic practices or, in the case of radiopharmaceuticals, levels of activity, for typical examinations for groups of standard-sized patients or standard phantoms for broadly defined types of equipment. These levels are expected not to be exceeded for standard procedures when good and normal practice regarding diagnostic and technical performance is applied. According the Internatonal BSS: Diagnostic reference level is "A level used in medical imaging to indicate whether, in routine conditions, the dose to the patient or the amount of radiopharmaceuticals administered in a specified radiological procedure is unusually high or unusually low for that procedure" [5]. DRLs are recommended by ICRP, EC, IAEA, National Regulations. In Bulgaria they are first recommended by Ordinance 30 of Ministry of Health (MoH)/2005 [6].
Quantities for expressing DRLs.
Following quantities are recommended for expressing typical patient doses and DRLs: ESK or KAP for simple procedures; KAP, total number of images and total fluoroscopy time for complex procedures; Maximum skin dose for some complex interventional procedure; CTDI, CTDIw, number of slices, DLP for Computed Tomography.
Measurement of DRLs
There are different protocols for measurement of Patient doses and elaboration of NDRLs [79]. In Bulgaria a National protocol for measurement methods of patient doses in X-ray Diagnostics was prepared under Phare Twinning project Bulgaria - Gemany [10] Recommendations and Guidance for use of Diagnostic Reference Levels in Radiology was prepared under same project [11]. Both above mentioned documents need to be revised, updated and published officially. According to the protocol 20 X-ray systems shell be used for each projection as a minimum. On each unit a sample of at least 20 standard sized patients shell be collected for each standard projection. The patient's weight shell lay in interval of 50 to 90 kg with an average of 70±3 kg. A typical dose for each projection has to be calculated as a mean of relevant dosimetric quantity for patients in the sample. Bulgarian guidance as well as foreign protocols recommends the DRL to be defined closer to the third quartile of distribution of typical doses estimated for each projection. This is applicable to adult patients. For children different approach may be employed in accordance with amount and quality of data collected during Third National Patient Dose Survey.
Organization of Third National Survey.
Four methods of data collection are foreseen:
A. Via internet based platform for automatic sending: www.drl-bg.com [12];
B. Via electronic tables sent by e-mail to the electronic address of the survey: rzmo@ncrrp.
org;
C. Via information for local typical doses defined in hospitals;
D. Via paper hard copy.
All information regarding Third National Survey is available on web page of NCRRP [13]. It is accessible form the main page of NCRRP: www.ncrrp .org (fig. 1a) by clicking on field: "DRL2016" or by clicking on the special banner mounted on the main page: (fig.1b).
The web page of the Survey has a Short and a Full Instruction for collection of data, as well as contacts of Section of Radiation Protection at Medical Exposure It has also a link to the system 132
for registering of typical doses at X-ray examinations and procedures. On the web page all forms on MS Excel and Adobe Acrobat format files are available for download. A Circular Letter signed by the Director of NCRRP is available for download on top of the page, as a Letter of MoH will be uploaded and available for download when it becomes available.
Terms of survey.
- Until 01.10.2016 - collection of initial data and preliminary results;
- Until 31.12.2016 - main conclusions and recommendations;
- During 2017: publishing of new and updated National DRLs and continuation of work for collection of data (for children).
- Continuous process of data collection:2017- - mainly using methods: A, B and D.
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Fig. 1. Screenshots of relevant parts of webpage of TNPDS at website of NCRRP.
Problems and limitations related to TNS;
First and Second NPDS were explored under large international EC Phare Twinning projects: Bulgaria-Germany (2002-2004) with total budget: 2 650 000 EUR (two million six hundred and fifty thousands euro) and Bulgaria-Finland (2008-2009) with total budget: 4 750 000 EUR (four million seven hundred and fifty thousand euro) , as the TNPDS has no dedicated budget. This leads to lack of motivation for hospital staff, Regional Health Inspectorates (RHI) and all staff involved into the project. The measurement equipment in Section of Section of Radiation Protection at Medical Exposure (SRPME) in NCRRP is more than 12 years old and this makes the process of assuring traceability of dosimetry calibration and Quality Assurance of Dosimetric data problematic.
Conclusion.
Success of practical implementation of TNPDS depends on joint efforts of staff of SRPME, support from Management of NCRRP, support from Ministry of Health (MoH), active involvement of Radiation control departments of Regional Health Inspectorates (RHI), medical physicist and other responsible staff in the hospitals throughout the country. Availability of dedicated budget for additional staff employment, equipment calibration and upgrade, business trips and other inherent expenses is critical for project implementation.
Literature:
1. Neuveg, Maury. Implementation of patient exposure limits by a state radiological health pogram. Application of Optical Instrumentation in Medicine VIII, Proceedings of the Society of Photo-optical instrumentation Engineers 233:235-7, 1980.
2. Neuweg, M.E. and P.N. Brunner. Radiation exposure ion the health arts. Applied Radiology, 11/12/1974: pp.35-8.
3. ICRP, 1996. Radiological Protection and Safety in Medicine. ICRP Publication 73. Ann. ICRP 26 (2).
4. Council Directive 97/43/EURATOM of 30 June 1997 on health protection of individuals against the dangers of ionising radiation in relation to medical exposure, Official Journal of the European Commission, No L 180.
5. IAEA Safety Standards Series No. GSR Part 3 Padiation protection and safety of radiation sources: International Basic Safety Standards. General Safety Requirements. IAEA, VIENNA, 2014.
6. Ordinance of the Ministry of Health No30 from 31 October 2005 for Protection of Individuals at Medical Exposure, promulgated in State Gazette № 91 of November 15, 2005 (in Bulgarian).
7. European Commission. Radiation Protection 109. Guidance on diagnostic reference levels (DRLs) for medical exposures. Directorate-General for Environment, Nuclear Safety and Civil Protection, 1999.
8. National Protocol for Patient Dose Measurements in Diagnostic Radiology. IPSM, NRPB, CoR. NRPB,1992.
9. Patient dose reduction in diagnostic radiology. Documents of the NRPB. London: HMSO, 1(3), 1990.
10. Karadjov, A. Dimov, A. Vassileva, J. Anatschkowa, E. Protocol on the methods for patient dose measurements in x-ray diagnostics. Phare Project BG/2000/IB/EN 01-05. National Centre of Radiobiology and Radiation Protection, Bulgaria, 2003.
11. Karadjov, A. Dimov, A. Vassileva, J. Anatschkowa, E. Recommendations and guidance for the use of the diagnostic reference levels (DRLs) in radiology. Phare Project BG/2000/IB/EN 01-05. National Centre of Radiobiology and Radiation Protection, Bulgaria, 2003.
12. National Centre for Radiobiology and Radiation Protection. Web site of: System for registration of typical doses of patients at X-ray examinations and procedures (in Bulgarian). URL: www.drl-bg.com (visited on 14/07/2016).
13. National Centre for Radiobiology and Radiation Protection. Web page of National Survey DRL2016. URL: http://www.ncrrp.org/new/bg/DRL2016-c437 (visited on 14/07/2016).
