Standardization and regulatory control on radiation processing dosimetry in China

In 1983, in order to suit the rapid development of radiation processing, a programme of high dose standardization was initiated in China. As a result, a high dose measurement system for gamma - rays including primary standards, transfer standards and working dosimeters, has been established. In this paper, the scheme of dosimetry traceability to national standards for gamma - rays is illustrated. The aspects of standardization and the progress of dosimetry of radiation processing are also outlined.

In order to implement “the Law on Metrology of the Peoples Republic of China” and to guarantee the product quality of radiation processing. SBTS and SCTS have jointly issued “the Provisional Regulation of Metrological Supervision and Management for Radiation Processing”. A series of national standards, verification regulations and technical norms have been enacted and issued on the radiation processing dosimetry and on the approval of irradiation facilities. These documents are expected to play significant roles in the dose measurement standardization and the regularity control.     

Radioactivity from natural,industrial, and other sources

Natural radioactivity and the use of x-rays and radioactive substances in the practice of medicine are the main sources of radiation exposure to the general public. The protection standards used in all countries are based on the recommendations of the International Commission on Radiological Protection. These standards are being observed by the nuclear industry and have succeeded in protecting both nuclear workers and members of the general public. The dose received from nuclear power generation is a tiny fraction compared to the doses received from nature and medical practice.However, a great gap exists between the risks of low-level radiation exposure as perceived by the public and the risk that actually exists. This is true not only concerning nuclear power generation, but also with respect to the need to dispose of both high-level and low-level wastes. In addition, the dangers of plutonium have become distorted in the public mind. Fifty years of research into the biological effects of plutonium have been reassuring and an excellent safety record has been achieved in the industrial production of this material.     

Powder state alanine ESR dosimeter for measuring the absorbed dose of electron beam

This paper describes the application of powder state alanine/ESR dosimeter for measurement of the absorbed dose of electron beam, for transfer the dose standards and for quality controls of the products processed by electron beam irradiation.The dosimeter is a sealed plastic container containing pre-treated alanine powder. Spectra of the internal standard and the alanine sample are measured simultaneously by using dual - cavity of a ESR spectrometer. The internal standard is a CuCl₂. 2H₂O monocrystal which gives stable ESR signals. A diamond sample is regard as working standard. With these two standards, the measurement accuracy can be improved apparently. The standard dose value is determined with a electron beam calorimeter made in our laboratory for dose calibration purpose.The advantages and the dosimetry characteristics of the application of powder state alanine/ESR dosimeters are discussed. This method is proved accurate and easy to use. In the region of 10-10⁴Gy, the dose response show a linear relationship and the precision is better than ± 2%.     

High resolution two-dimensional dose mapping of electron beam processed polymers

The recent advances in electron beam processing of polymer samples require increasingly dose mapping techniques with depth and volume resolution capability. In this paper, the use of micro-indentation and thermo-mechanical analysis is proposed to fulfill the necessary requirements in terms of resolution and accuracy. Experimental procedures are used to acquire mechanical data that are successively converted into dose levels based on dedicated calibrated samples. Physical principles, experimental artifacts, and limitations are discussed with special focus on calibration and validation of a simulator for dosimetry in electron beam cross-linking of electrical cables.     

Dicholorbenzyl alkyl ether homologs as retention index markers and internal standards for the analysis of environmental samples using capillary gas chromatography

A homologous series of 2,4-dichlorobenzyl alkyl ethers (DCBEs) have been synthesized and purified for use as retention index calibrants and internal standards. They are stable, sensitive to ECD and FID and ideal for GC-MS, with base peaks at m/z 159/161. The retention index calibration against the n-alkanes for a linear temperature program (LTP) series is given and recommendations made for the most suitable members of the DCBE series for use as internal standards in organochlorine (OC) residue analysis.     

Traceability of absorbed dose in photon radiation therapy: from primary standard to patient treatment

The relevant standard quantity for radiation therapy is the absorbed dose to water. This quantity refers to the amount of energy locally absorbed in a small volume of water divided by the mass of this volume. The aim of this paper is to present a short overview on the establishment of traceability to national standards of absorbed doses delivered to patients in radiation therapy. The approach used at LNE-LNHB, the French national metrology laboratory for ionizing radiation, to determine the reference value of absorbed dose to water is presented and the chain of traceability from the reference value to the treatment of the patient is described.     

News from CEN/BT/WG 122 uncertainty and EA expert group on uncertainty

Since the publication in 2000 of the standard ISO/IEC 17025 "General requirements for the competence of testing and calibration laboratories", the concept of uncertainty of measurement or test results seems to be a key issue for laboratories and their clients. Two working groups are trying to implement this concept in testing activities. The CEN/BT/WG122 has proposed to the technical bureau of CEN a series of recommendations on how to introduce this concept in European standards and the EA expert group on uncertainty has prepared a guidance document in order to help the testing community in uncertainty evaluation. The objective of this paper is to report the current situation of these two groups.     

CCRI supplementary comparison of standards for absorbed dose to water in 60Co gamma radiation at radiation processing dose levels

Six national standards for absorbed dose to water in ⁶⁰Co gamma radiation at the dose levels used in radiation processing have been compared over the range from 5 to 30 kGy using the alanine dosimeters of the NIST and the NPL as the transfer dosimeters. The standards are in agreement at the level of around 0.5%, which is significantly smaller than the stated standard uncertainties.     

Metrology in service of society: the role of proficiency testing

A sound system of competent measurements, underpinned by standards and accreditation, is an essential component of the infrastructure of any modern society. Proficiency Testing is an indispensible tool for developing and maintaining this infrastructure. It is used to verify compliance with standards, for ongoing monitoring of laboratory performance, for demonstration of competence, and for evaluating the performance of measurement procedures; it is used to indicate performance problems that might not be detected otherwise; and it is used as a tool for education and self-improvement. The new International Standard, ISO/IEC 17043, contains requirements and recommendations to make optimal use of this important tool.     

Bias, reporting, and sharing: computational evaluations of docking methods

Computational methods for docking ligands to protein binding sites have become ubiquitous in drug discovery. Despite the age of the field, no standards have been established with respect to methodological evaluation of docking accuracy, virtual screening utility, or scoring accuracy. There are critical issues relating to data sharing, data set design and preparation, and statistical reporting that have an impact on the degree to which a report will translate into real-world performance. These issues also have an impact on whether there is a transparent relationship between methodological changes and reported performance improvements. This paper presents detailed examples of pitfalls in each area and makes recommendations as to best practices.     

ISO radiation sterilization standards

This presentation provides an overview of the current status of the ISO radiation sterilization standards. The ISO standards are voluntary standards which detail both the validation and routine control of the sterilization process. ISO 11137 was approved in 1994 and published in 1995. When reviewing the standard you will note that less than 20% of the standard is devoted to requirements and the remainder is guidance on how to comply with the requirements.

Future standards developments in radiation sterilization are being focused on providing additional guidance. The guidance that is currently provided in informative annexes of ISO 11137 includes: device/packaging materials, dose setting methods, and dosimeters and dose measurement, currently, there are four Technical Reports being developed to provide additional guidance:

1. 1. AAMI Draft TIR, “Radiation Sterilization Material Qualification”

2. 2. ISO TR 13409-1996, “Sterilization of health care products — Radiation sterilization — Substantiation of 25 kGy as a sterilization dose for small or infrequent production batches”

3. 3. ISO Draft TR, “Sterilization of health care products — Radiation sterilization Selection of a sterilization dose for a single production batch” li]4. ISO Draft TR, “Sterilization of health care products — Radiation sterilization-Product Families, Plans for Sampling and Frequency of Dose Audits.”

     

A new approach for standard preparation in microbeam analysis: Development and validation

Microbeam analysis is used in biomedical and environmental sciences to determine the presence and concentration of trace elements. However, quantitative analyses of biological samples are challenging because the chemical and physical compositions of existing standards differ from those typically encountered in biological samples. We developed a thin standard using polyvinyl alcohol and assessed its quality by microbeam scanning particle induced X-ray emission (micro-PIXE) analysis. The relationship between metal concentration and X-ray intensity was linear for certain standards up to 500 μg·g⁻¹. Using this new thin standard, micro-PIXE analysis of Zn content in samples of human hair agreed well with analysis performed by inductively-coupled plasma mass spectrometry, validating the use of these new thin standards for quantitative mapping with microbeam analysis.     

Design and initial characterization of a glow discharge atomic emission instrument for macro-scale elemental composition mapping of solid surfaces

An instrument intended for rapid, accurate, precise, macro-scale (i.e. up to many tens of square centimeters) elemental composition mapping of solid surfaces has been designed and constructed. The spatial resolution provided by the instrument, on the order of 1 mm at best, is coarse by today's standards but is appropriate for selected analytical problems. The instrument is based on a novel glow discharge atomic emission device capable of sustaining multiple discharges simultaneously. Each discharge exhibits atomic emission characteristic of the sample surface beneath it. Using Hadamard transform spatial imaging, the emissions are selectively multiplexed, and the individual emission intensities are recovered from the multiplexed data through matrix multiplication. In this publication, the instrument is described, and its performance for elemental composition mapping is demonstrated. The data indicate that internal standardization should be employed to reduce the likelihood of mapping errors.     

Status of radiation processing dosimetry

Several milestones have marked the field of radiation processing dosimetry since IMRP 7. Among them are the IAEA symposium on High Dose Dosimetry for Radiation Processing and the international Workshops on Dosimetry for Radiation Processing organized by the ASTM.

Several standards have been or are being published by the ASTM in this field, both on dosimetry procedures and on the proper use of specific dosimeter systems. Several individuals are involved in this international cooperation which contribute significantly to the broader understanding of the role of dosimetry in radiation processing.

The importance of dosimetry is emphasized in the standards on radiation sterilization which are currently drafted by the European standards organization CEN and by the international standards organization ISO. In both standards, dosimetry plays key roles in characterization of the facility, in qualification of the process and in routine process control.

As a function of the work on the standards, several issues are now receiving major attention. These include traceability and uncertainty limits of the dose measurements, calibration procedures, environmental influence and combination of influence factors such as dose rate and temperature.

The increased attention to these factors have increased the demands on existing dosimeter systems, and rather than new dosimeters, the latest years have seen improvements on established dosimeters.     

Basic steps towards a self-sustainable quality system and laboratory accreditation

 Laboratory managers are facing the task of altering the attitudes of themselves and their employees in order to implement a quality lifestyle, which is the prerequisite for successful implementation of a quality system complying with appropriate international standards. The alterations require a painstaking and constructive approach. Not all laboratories have the resources to secure the assistance of quality consultants. For those laboratory managers who have to find their way towards quality management on their own, some recommendations are given for a path towards a self-sustaining quality system. Several practical aspects of the basic steps in this path, which starts with assessing the current status of the laboratory and is followed by awareness building, are discussed. The recommendations are derived from the experience of the authors in their own laboratories. Received: 5 June 1997 · Accepted: 7 December 1997     

Determination of the catecholamines and serotonin, their precursors tyrosine and tryptophan, and their main metabolites in rat brain using reversed-phase high-performance liquid chromatography with fluorimetric and oxidative amperometric detection in series.

A high-performance liquid chromatographic method for the determination of catecholamines and serotonin, their precursors and their main metabolites was developed applied to rat cerebellum, hypothalamus, striatum and cortex. A fluorimetric and an oxidative amperometric detector were used in series. For both detectors, detection limits (25-520 pg) were useful for this application, linearity of standards was excellent (average r greater than 0.9997), between-run precision for sample analytes was generally acceptable (coefficient of variation less than 10% with appreciable concentrations present) and average recoveries of standard additions to sample analytes were better than 90%. Particular attention was paid to peak identification, including both a thorough treatment of retention time agreement of peaks in standards and sample analytes, and a comparison of results for the seven compounds amenable to quantitation by both detectors. Considerable attention was also given to determining the stability of standards and sample analytes under a wide variety of conditions, and practical recommendations were made.     

A coincidence transmission electron microscope with digital waveform measuring system for analytical microscopy

We have been developing a new analytical transmission electron microscope (TEM), called a coincidence TEM, which in principle enables elemental mapping images to be observed at a high signal‐to‐noise (S/N) ratio under very low dose radiation conditions. In this paper, we report the development of a coincidence TEM with a digital waveform measuring system for obtaining a coincidence elemental mapping image. In this system, analog signals detected by a Si(Li) detector and a multianode, position‐sensitive photomultiplier (PSPM) are continuously converted into 12‐bit digital waveform data at a rate of 100 MHz, and transferred to a PC. From the transferred digital waveform data, information on X‐ray photon energy, electron incident position, and detection times of both X rays and electrons are calculated by digital waveform measurement, which lead to the observation of a successful coincidence elemental mapping image. Copyright © 2005 John Wiley & Sons, Ltd.     

On-line protein digestion and peptide mapping by capillary electrophoresis with post-column labeling for laser-induced fluorescence detection

A nanoliter enzyme microreactor was developed for on-line capillary electrophoresis (CE) peptide mapping of proteins, allowing picomole quantities of proteins to be digested. The enzyme microreactor was formed by immobilizing trypsin onto a monolithic capillary column, which was prepared by in situ polymerization of glycidyl methacrylate and ethylene dimethacrylate in a capillary. Highly efficient digestion of three protein standards was demonstrated. The detection of peptide fragments in CE was enhanced by post-column derivatization and laser-induced fluorescence detection. The microreactor has a volume of about 30 nL and is coupled with a separation capillary via a fluid joint for on-line digestion. The overall analysis, including digestion and separation, lasted only about 16 min. Column efficiencies > 300 000 plates/m were obtained for most peaks in the electropherogram of an on-line peptide mapping experiment of denatured alpha-lactalbumin under optimal conditions.     

French experience in the field of internal dosimetry assessment at a nuclear workplace: Methods and results on industrial uranium dioxide

The implementation of the new ICRP recommendations and the diversity of industrial exposure materials make it necessary to modify our approach of assessing internal dosimetry.This paper describes a methodology developed to assess different parameters such as (1) activity concentration and particle size distribution at the workplace; (2) physico-chemical characteristics of industrial dust handled, and (2) in vitro and in vivo, solubility in order to determine the absorption rate into blood. The determination of such specific parameters will lead to dose calculation in terms of committed effective Dose Per Unit of Intake (DPUI). Results obtained for an industrial uranium dioxide, UO₂, at a French nuclear facility are presented.     

Advancements in internationally accepted standards for radiation processing

Three subcommittees of the American Society for Testing and Materials (ASTM) are developing standards on various aspects of radiation processing. Subcommittee E10.01 “Dosimetry for Radiation Processing” has published 9 standards on how to select and calibrate dosimeters, where to put them, how many to use, and how to use individual types of dosimeter systems. The group is also developing standards on how to use gamma, electron beam, and x-ray facilities for radiation processing, and a standard on how to treat dose uncertainties. Efforts are underway to promote inclusion of these standards into procedures now being developed by government agencies and by international groups such as the United Nations' International Consultative Group on Food Irradiation (ICGFI) in order to harmonize regulations and help avoid trade barriers.

Subcommittee F10.10 “Food Processing and Packaging” has completed standards on good irradiation practices for meat and poultry and for fresh fruits, and is developing similar standards for the irradiation of seafood and spices. These food-related standards are based on practices previously published by ICGFI.

Subcommittee E10.07 on “Radiation Dosimetry for Radiation Effects on Materials and Devices” principally develops standards for determining doses for radiation hardness testing of electronics. Some, including their standards on the Fricke and TLD dosimetry systems are equally useful in other radiation processing applications.