Implementation of the European protocol for quality control of the technical aspects of mammography screening in Bulgaria

The results from the national pilot project on implementation of the European protocol for the quality control (QC) of the technical aspects of mammography screening as well as the European protocol for dosimetry in mammography in Bulgaria are presented. A QC programme for mammography equipment and a standardised measurement protocol were created. The full QC programme was tested on four mammography units of different types and ages. A national survey was performed for entrance surface air kerma (ESAK) on 20 units using a 45 mm PMMA standard phantom. Average glandular dose (AGD) was calculated using the conversion coefficients from the European dosimetry protocol. The survey demonstrated considerable differences in the technical condition of the mammography units that resulted in varying image quality. The measured values of ESAK showed significant variations. Doses for approximately 45% of the units were found to be below the European reference level. The values for AGD ranged from 0.35 to 3.47 mGy. The main problems found were film processing, optical density (OD) control settings and AEC adjustment. The results showed the importance of film OD measurements parallel to dose measurements. The X-ray mammography in the country needs optimisation. Comprehensive quality assurance programme should be adopted in all departments covering permanent QC of the equipment, image quality and breast dose.     

State of the art of in vivo dosimetry

The complexity of modern radiotherapy requires a comprehensive quality assurance programme, including in vivo dosimetry. In this paper, the use of the detector systems most often used for in vivo dosimetry [diodes, thermoluminescence detectors, metal oxide field effect transistors and electronic portal imaging devices (EPIDs)] will be summarised. Although point detectors are useful for the verification of conventional 3-D conformal radiotherapy, the use of 2-D detector systems, such as EPIDs, is required for the verification of more complicated techniques, including intensity-modulated radiotherapy.     

Spanish intercomparisons for individual monitoring

The Spanish Nuclear Safety Council (CSN) carries out an intercomparison programme for individual monitoring every 5 years. The objective is to acquire valuable information on the performance of the dosimetry systems of the participating Spanish approved dosimetry services and to assess precision and accuracy as quality indicators of overall dosimetry performance. CSN has carried out two intercomparison programmes, the last one in 1995, in which 18 approved dosimetry services participated. The dosemeters were exposed to photon fields (137Cs gamma rays and two X ray beams of different qualities), at two standard laboratories in Spain. The irradiations were done for evaluating personal dose equivalent, Hp(10), using the ICRU 47 phantom. Presently, CSN is carrying out a new intercomparison, which will be finished in 2001. Twenty-three dosimetry services will participate; 22 from Spain and one from Cuba. The irradiations will be done in reference photon radiation fields.     

EURADOS self-sustained programme of intercomparisons for individual monitoring services

Within EURADOS working group 2, a system for self-sustained intercomparisons for individual monitoring services for external radiation was developed. With the intercomparison results, the participants can show compliance within their quality management system, compare their results with those from other participants and develop plans for improvement of their system. The costs of the exercises are covered by the participants fees. In this programme, the first intercomparison exercise for whole-body dosemeters has been executed in 2008 with 62 participating dosimetry systems from participants across Europe. In general, film systems show the largest deviations, although the results of some participants indicate that it is possible to achieve results with a film system with similar quality as for thermoluminescence dosimetry (TLD) systems. A second intercomparison has been organised for extremity dosemeters in 2009. For 2010 it is planned to organise a second intercomparison for whole-body dosemeters.     

Occupational dose assessment and National Dose Registry System in Iran

This report presents status of external and internal dose assessment of workers and introducing the structure of National Dose Registry System of Iran (NDRSI). As well as types of individual dosemeters in use, techniques for internal dose assessment are presented. Results obtained from the International Atomic Energy Agency intercomparison programme on measurement of personal dose equivalent H(p) (10) and consistency of the measured doses with the delivered doses are shown. Also, implementation of dosimetry standards, establishment of quality management system, authorisation and approval procedure of dosimetry service providers are discussed.     

Implementation of quality assurance in diagnostic radiology in Bosnia and Herzegovina (Republic of Srpska)

Application of a quality control (QC) programme is very important when optimisation of image quality and reduction of patient exposure is desired. QC surveys of diagnostics imaging equipment in Republic of Srpska (entity of Bosnia and Herzegovina) has been systematically performed since 2001. The presented results are mostly related to the QC test results of X-ray tubes and generators for diagnostic radiology units in 92 radiology departments. In addition, results include workplace monitoring and usage of personal protective devices for staff and patients. Presented results showed the improvements in the implementation of the QC programme within the period 2001--2005. Also, more attention is given to appropriate maintenance of imaging equipment, which was one of the main problems in the past. Implementation of a QC programme is a continuous and complex process. To achieve good performance of imaging equipment, additional tests are to be introduced, along with image quality assessment and patient dosimetry. Training is very important in order to achieve these goals.     

Quality assurance programme implemented in the Whole Body Monitoring Laboratory of IFIN-HH Romania

The Whole Body Monitoring Laboratory (WBML) of IFIN-HH, Bucharest, Romania, is since the year 2000, notified and was, for the first time, notified and nominated as a National Individual Dosimetry Body by the competent Romanian authority in the field, the National Commission for Nuclear Activities Control (CNCAN), in accordance with the WBML-specific quality assurance programme. It respects the national and international legislation in force, in the nuclear, radioprotection and quality assurance fields, implementing them for the internal dosimetry activity in the WBML.     

Dose evaluation in criticality accidents using response of panasonic TL personal dosemeters (UD-809/UD-802)

This study gives the results of dosimetry measurements carried out in the Silène reactor at Valduc (France) with neutron and photon personal thermoluminescence dosemeters (TLDs) in mixed neutron and gamma radiation fields, in the frame of the international accident dosimetry intercomparison programme in 2002. The intercomparison consisted of a series of three irradiation scenarios. The scenarios took place at the Valduc site (France) by using the Silène experimental reactor. For neutron and photon dosimetry, Panasonic model UD-809 and UD-802 personal TLDs were used together.     

IAEA/WHO TLD postal dose audit service and high precision measurements for radiotherapy level dosimetry. International Atomic Energy Agency/World Health Organization

Since 1969 the International Atomic Energy Agency (IAEA), together with the World Health Organization (WHO), has performed postal TLD audits to verify calibration of radiotherapy beams in developing countries. The TLD programme also monitors activities of Secondary Standard Dosimetry Laboratories (SSDLs). The programme has checked approximately 4000 clinical beams in over 1100 hospitals. and in many instances significant errors have been detected in the beam calibration. Subsequent follow-up actions help to resolve the discrepancies, thus preventing further mistreatment of patients. The audits for SSDLs check the implementation of the dosimetry protocol in order to assure proper dissemination of dosimetry standards to the end-users. The TLD audit results for SSDLs show good consistency in the basic dosimetry worldwide. New TLD procedures and equipment have recently been introduced by the IAEA that include a modified TLD calibration methodology and computerised tools for automation of dose calculation from TLD readings.     

Introduction to constancy check protocols in fluoroscopic systems

Reference dose or guidance levels are a well established approach to the reduction of patient doses in diagnostic radiology. There are two main methods of determining reference doses, one involves patient dose measurements and the other phantom dosimetry. The latter approach lends itself to the development of constancy test protocols, which may be used as part of an acceptance testing programme or to compare the performance of different imaging systems. Various constancy test protocols and procedures have been proposed and these are reviewed. The constancy test protocols developed within the DIMOND concerted action will be described in detail. The advantages and disadvantages of the various methods and approaches are compared and contrasted. The complementary nature of constancy check protocols with patient dosimetry studies is discussed.     

Intercomparison on measurements of the quantity personal dose equivalent Hp(d) in mixed (neutron-gamma) fields--an IAEA project

Within its occupational radiation protection programme, the International Atomic Energy Agency (IAEA) initiated and funded an international intercomparison exercise of personal dosemeters to determine the quantity personal dose equivalent in mixed neutron-photon radiation. The objectives of the intercomparison are to assess the capabilities of the dosimetry services in measuring the quantity Hp(10) in mixed neutron-gamma fields; to assist IAEA member states in achieving sufficiently accurate dosimetry; and, if necessary, to provide guidelines for improvements (not simply a test of the performance of the existing dosimetry service). The intercomparison is directed to passive dosemeters to determine, in mixed neutron-gamma radiation fields, either these two components separately or the total personal dose equivalent. The intercomparison consists of two phases: Phase I--Type-test intercomparison: irradiation in selected calibration fields and results used to improve dosimetric procedures of participating laboratories, where needed. Phase II--Simulated workplace field intercomparison: irradiation in radiation fields similar to those in workplaces as a final check of performance. The exercise revealed clear deficiencies in the methodology used by several laboratories and necessitated a detailed analysis of the existing discrepancies. This papers summaries the finding and conclusions for radiation fields similar to those found in nuclear industry.     

Thermoluminescence dosimetry for quality assurance in radiation therapy

A methodology based on thermoluminescence dosimetry was developed to check the output of teletherapy units and the given doses. It was applied in a hospital as a part of an extemal quality audit programme. Over a 7 year period the mean ratios of the output doses measured by TLDs calibrated free-in-air to the doses measured at the hospital in a 6 MV X ray and in a 60Co unit were 1.000 +/- 0.024 (n = 86) and 0.997 +/- 0.027 (n=61), respectively. TLDs in capsules were attached to the patient's body or to a phantom to assess entrance, exit and midline doses and transmission. Factors were determined experimentally to relate the doses measured with TLDs in capsules and inside the body. The accuracy in given doses with pelvic and tangential breast fields and assessed via 752 in vivo measurements, was considered to be adequately good, taking into account the limitations of the equipment available in the hospital.     

Cyclic pressure test of a filament-wound vessel containing liquid nitrogen

This paper describes a test programme whereby a filament wound vessel was filled with liquid nitrogen and subjected to 2000 pressure cycles to 2068 N cm⁻² (3000 psi) without degradation of the structural capability of the vessel. This programme was initiated and organized by the Boulder Division of Beech Aircraft as a joint effort with the Brunswick Corporation which supplied the composite vessel and design expertise.     

Evaluation of individual dosimetry in mixed neutron and photon radiation fields (EVIDOS). Part I: Scope and methods of the project

Supported by the European Commission, the EVIDOS project started in November 2001 with the broad goal of evaluating state of the art dosimetry techniques in representative workplaces of the nuclear industry. Seven European institutes joined efforts with end users at nuclear power plants, at fuel processing and reprocessing plants, and at transport and storage facilities. A comprehensive programme was devised to evaluate capabilities and limitations of standard and innovative personal dosemeters in relation to the mixed neutron-photon fields of concern to the nuclear industry. This paper describes the criteria behind the selection of dosimetry techniques and workplaces that were analysed, as well as the organisation of the measurement campaigns. Particular emphasis was placed on the evaluation of a variety of electronic personal dosemeters, either commercially available or previously developed by the partners. The estimates provided by these personal dosemeters were compared to reference values of dose equivalent quantities derived from spectrometry and fluence-to-dose equivalent conversion coefficients. Spectrometry was performed both with conventional multisphere and with some original instrumentation providing energy and direction resolution, based on silicon detectors and superheated drop detectors mounted on or in spherical moderators. The results were collected in a large, searchable database and are intended to be used in the harmonisation of dosimetric procedures for mixed radiation fields and for the approval of dosimetry services in Europe.     

上海SSDL参加国际剂量比对总结（1983—1994）

文章总结了上海ＳＳＤＬ自１９８３年至１９９４年期间参加国际原子能机构组织的各种剂量比对活动的目的、方法和结果．十多年来的比对数据表明，上海ＳＳＤＬ在放射治疗水平、辐射加工水平和个人剂量防护水平及对Ｘ、γ射线吸收剂量测量和控制等方面以满意的量值准确度与国际标准量值相统一。文章对测量误差进行了讨论．     

Patient dosimetry measurements in 50 radiology departments in Belgium

Since July 2001, the Belgian law requires a yearly quality control measurement on all medical radiological equipment. The medical physicists of the AV Controlatom are certified experts in Belgium and perform these quality control measurements, including a patient dosimetry study. In this study, patient dosimetry results since January 2002 are presented for the following examinations: chest PA and LAT, abdomen and pelvis. Since conventional film-based imaging is currently being replaced by phosphorplate technology, a comparison between both technologies is made. In some radiology departments, digital imaging is already in use. These dosimetry results are also analysed. Dose reductions of >70% can be achieved. For the chest examinations, several departments still use fluoroscopy for positioning the patient. Results show that about half of the patient dose is due to the fluoroscopy. A comparison between the dose results and the European Diagnostic Reference Levels (EDRL) is made.     

Concepts of ISO for the monitoring of workers for internal exposure and the present approach for the dose assessment

Besides ongoing developments in the dosimetry of incorporated radionuclides, there are various efforts to improve the monitoring of workers for potential or real intakes of radionuclides. The disillusioning experience with numerous inter-comparison projects identified substantial differences between national regulations, concepts, applied programmes and methods and dose assessment procedures. Measured activities were not comparable because of severe differences between measuring frequencies and methods, but also results of case studies for dose assessments revealed differences of orders of magnitudes. Besides the general common interest in reliable monitoring results, at least the cross-border activities of workers (e.g. nuclear power plant services) require consistent approaches and comparable results. The International Standardisation Organisation (ISO) therefore initiated projects to standardise the monitoring of workers, the requirements for measuring laboratories and the processes for the quantitative evaluation of monitoring. This presentation is intended to give an introduction into some important aspects addressed in these standards: the need for a monitoring programme, the design of a monitoring programme: methods and intervals, reference levels and approaches for dose assessments.     

Progress report of the CR-39 neutron personal monitoring service at PSI

At the Paul Scherrer Institute a personal neutron dosimetry system based on chemically etched CR-39 detectors and automatic track counting is in routine use since the beginning of 1998. The quality of the CR-39 detectors has always been a crucial aspect to maintain a trustable personal neutron dosimetry system. This paper summarises the 7 y experience in routine use. The effect of detector material defects which could lead to false positive neutron doses is described. The potentiality of improving the background statistics by extending the pre-etch time is investigated and involves as a drawback a quite lower sensitivity to thermal neutrons. Furthermore, the impact of small changes in the production process of the detectors on the response to fast and thermal neutrons is shown. For the personal dosimetry at CERN, a new dosimetry concept was launched by combining a CR-39 neutron dosemeter with a Direct-Ion Storage (DIS) dosemeter for photon and beta radiation. The usage period of the CR-39 dosemeters is prolonged now from 3 months up to 12 months. In this context, the long-term behaviour over 1 y of the background track density and the response to Am-Be are described.     

Track counting and the blots

Track detectors are very useful devices for alpha particle dosimetry. Alpha particle tracks are registered on the detector's surface. The registered track density is proportional to the dose. When the dose is low the greatest effect on the total error of dose assessment has a Poisson distribution (random error). When the dose is high, the greatest contribution to the total error is the effect of track overlapping (systemic error). This paper describes how to solve the problem of overlapping tracks when a computer aided image analyser is used. The formulae presented in this paper were proven in the international calibration programme run by NRPB and EU.