Dosimetric issues in radiation protection of radiotherapy patients

As life expectancy increases, thanks to improving general medical practices, cancer treatments for the ageing population become evermore necessary. Radiation therapy is increasingly a treatment of choice, promoted by continuing improvements in dose delivery technologies. Some techniques, collectively referred to as intensity-modulated radiation therapy, are encountering widespread acceptance and implementation, promoted by reports of superior tumour control and reduced toxicity. However, these new techniques pose new challenges in terms of radiation protection of patients, as they cause a more extensive low-dose exposure of normal tissues compared with conventional radiation therapy. The related dosimetric challenges and the methods available to tackle them are reviewed in this paper, which also emphasises the need for standard radiation protection dosimetry procedures so that information may be consistently gathered for a comparative evaluation of the different treatment modalities.     

Small-animal CT - Its Difference from, and Impact on, Clinical CT

For whole-body CT images of small rodents, a voxel resolution of at least 10(-3) mm(3) is needed for scale-equivalence to that currently achieved in clinical CT scanners (～1 mm(3)) in adult humans. These "mini-CT" images generally require minutes rather than seconds to complete a scan. The radiation exposure resulting from these mini-CT scans, while higher than clinical CT scans, is below the level resulting in acute tissue damage. Hence, these scans are useful for performing clinical-type diagnostic and monitoring scans for animal models of disease and their response to treatment. "Micro-CT", with voxel size <10(-5) mm(3), has been useful for imaging isolated, intact organs at an almost cellular level of resolution. Micro-CT has the great advantage over traditional microscopic methods in that it generates detailed 3D images in relatively large, opaque, volumes such as an intact rodent heart or kidney. The radiation exposure needed in these scans results in acute tissue damage if used in living animals.Experience with micro-CT is contributing to exploration of new applications for clinical CT imaging by providing insights into different modes of x-ray image formation as follows:Spatial resolution should be sufficient to detect an individual Basic Functional Unit (BFU, the smallest collection of diverse cells, such as hepatic lobule, that behaves like the organ), which requires voxels ～10(-3) mm(3) in volume, so that the BFUs can be counted.Contrast resolution sufficient to allow quantitation of:New microvascular growth, which manifests as increased tissue contrast due to x-ray contrast agent in those vessels' lumens during passage of injected contrast agent in blood.Impaired endothelial integrity which manifests as increased opacification and delayed washout of contrast from tissues.Discrimination of pathological accumulations of metals such as Fe and Ca, which occur in the arterial wall following hemorrhage or tissue damage.Micro-CT can also be used as a test bed for exploring the utility of several modes of x-ray image formation, such as the use of dual energy x-ray subtraction, x-ray scatter, phase delay and refraction-based imaging for increasing the contrast amongst soft tissue components. With the recent commercial availability of high speed, multi-slice CT scanners which can be operated in dual energy mode, some of these micro-CT scanner capabilities and insights are becoming implementable in those CT scanners. As a result, the potential diagnostic spectrum that can be addressed with those scanners is broadened considerably.     

The IAEA's activities in radiological protection in digital imaging

The success achieved to minimise the radiation exposure to staff to levels much below the prescribed dose limits encourages a similar approach in patient protection where dose limits do not exist but where reference levels are provided. A number of radiation injuries among patients have been reported, per capita dose is increasing and medical exposure has become the largest contributor to population dose. The International Atomic Energy Agency (IAEA) has supported a number of research projects, produced a wide range of guidance publications, conducted over 60 training courses in the past 5 y, produced for free dissemination training CDs on radiation protection and established a dedicated Web site on the radiological protection of patients (http://rpop.iaea.org). The number of countries that is currently receiving assistance in this field exceeds 80, as compared to about half a dozen 5 y ago. Significant results on patient dose management, demonstrating dose reduction of more than 30% while maintaining image quality, have been made available through IAEA projects.     

Domestic product failures – Case studies

Every year in the UK more than 4000 people die in accidents in and around the home and nearly three million turn up at accident and emergency departments seeking treatment. Intrinsic in this number are many incidents of injury or death directly attributable to poor product design or manufacture of domestic products. In and around the home, commodities that dominate so much of every-day life are becoming more numerous and complex and could be mooted as an argument for such dire statistics. Moreover, society in general is becoming more litigious. These converging trends are responsible for an increasing significance of product liability. When property is damaged, personal injury sustained or loss of life occurs there is an understandable need to determine where any fault may lie. The forensic (or failure) engineer will glean relevant information through meticulous investigation and a reverse engineering process. Reconstructing the failure will uncover any inherent defect in product design, manufacturing, incorrect installation or maintenance. However, product failure can also be attributable to careless use or abuse by the individual, rather than to any specific defect or design shortcoming being inherent within a product. Ultimately the outcome of any investigation will be a sound finding and a conclusion that clearly describes what happened and why. To illustrate typical failure modes that are currently emerging in the home-based UK market, a range of domestic product failures are presented from the author’s forensic casebook.     

Feasibility study of a system for combined light dosimetry and interstitial photodynamic treatment of massive tumors

A system for the photodynamic laser treatment of massive tumors that employs multiple optical fibers to be inserted into the tumor mass is described. The light flux through the tumor can be assessed by use of the individual fibers both as transmitters and as receivers. With a computer model that describes the diffusive light propagation, optical dosimetry is under development. The system has been tested in an experimental animal tumor model in preparation for clinical work. Currently, delta-aminolevulinic acid is used as a sensitizer, activated by 635-nm radiation from a 2.0-W compact diode laser system. With the availability of future, highly selective drugs absorbing approximately 750 nm, larger tumor volumes should be treatable, and surrounding, sensitive normal tissue should be spared.     

环糊精基复合吸附剂的制备及对水中有机污染物去除的研究进展

目前水环境中有机物污染问题日趋严重,在诸多水处理技术中,吸附法具有成本低、效率高、简单易操作等优点,研发高效吸附剂是决定高效能吸附处理过程的关键因素。环糊精因其价格低廉、无毒、环境友好等优势在水污染处理领域具有广阔的应用前景。环糊精具有外部亲水、内部疏水的圆台状独特结构,利用内腔可与极性分子形成主-客体包含物,因此,被用于水溶液中有机污染物的去除,其外部结构中存在大量羟基,表现出良好的亲水性和优异的化学反应特性,能够实现对溶液中有机污染物的高效去除,通过多种化学修饰或各种材料的有效复合,达到环糊精基复合吸附剂的高效功能化拓展。本文总结了多种环糊精基复合材料的制备方法,重点综述其对水体中有机污染物高效吸附去除的应用研究,探讨环糊精基复合材料的研究趋势和研究热点,对其未来研究方向进行展望。     

Radiation protection at Hadron therapy facilities

The Italian National Centre for Oncological Hadrontherapy is currently under construction in Pavia. It is designed for the treatment of deep-seated tumours (up to a depth of 27 cm of water equivalent) with proton and C-ion beams as well as for both clinical and radiobiological research. The particles will be accelerated by a 7-MeV u(-1) LINAC injector and a 400-MeV u(-1) synchrotron. In the first phase of the project, three treatment rooms will be in operation, equipped with four fixed beams, three horizontal and one vertical. The accelerators are currently undergoing commissioning. The main radiation protection problems encountered (shielding, activation, etc.) are hereby illustrated and discussed in relation to the constraints set by the Italian national authorities.     

Determination of thorium by ICP-MS and ICP-OES

Natural thorium (232-Th) has traditionally been measured by radiometric techniques such as alpha and gamma spectrometry. However. with both ICP-OES and ICP-MS instruments becoming relatively common in many analytical laboratories. these techniques have become more acceptable in thorium analysis. This paper will briefly describe an overview of the instrumentation currently available and the techniques themselves applied to thorium analysis. Both techniques have low detection limits and require little sample treatment after the sample digestion. Routine sample analysis time is short and spectra easy to interpret. usually giving results with low uncertainties, Whereas ICP-OES measures total thorium only, ICP-MS also offers the potential to measure other long-lived thorium isotopes (t 1/2 > 10(4) years), such as 232Th. However, other important isotopes, such as 228Th. are still out of reach for routine analysis. The main disadvantage of the techniques is the requirement for a sample digestion stage.     

A Brazilian government external individual monitoring service: experience since 1972

Instituto de Radioprote??o e Dosimetria, a Brazilian government research institute, provides individual monitoring services since 1972. Its dosemeters are: film-based thorax for whole body photons, thermoluminescence dosimetry (TLD) albedo for whole body neutrons and TLD ring for extremity photons. About 6000 radiation workers are currently being monitored with film dosemeters in 256 different facilities in Brazil, most of them working in health-related activities. Around 400 Brazilian radiation workers are monitored with TLD albedo neutron monitor and about 500 workers use TLD rings. This paper describes the monitoring systems used, presents the results obtained in internal quality programs and in intercomparison exercises and analyses the measured dose values from 1985 to 2009.     

Monte Carlo estimation of dose difference in lung from 192Ir brachytherapy due to tissue inhomogeneity

Lung brachytherapy using high-dose rate (192)Ir technique is a well-established technique of radiation therapy. However, many commercial treatment planning systems do not have the ability to consider the inhomogeneity of lung in relation to normal tissue. Under such circumstances dose calculations for tissues and organs at risk close to the target are inaccurate. The purpose of the current study was to estimate the dose difference due to tissue inhomogeneity using the Monte Carlo simulation code MCNP-5. Results showed that there was a relative sub dosage by treatment planning systems calculations in neighbouring tissues around the radioactive source due to inhomogeneity ignorance. The presence of lung instead of normal tissue resulted in an increase in relative dose, which approached 8 % at 4-cm distance from the source. Additionally, the relative increase was small for the lung (2.1 %) and larger for organs at risk such as the heart (6.8 %) and bone marrow (7.6 %).     

Macro-engineering and global environmental issues

As more countries economically develop, their low costs allow them to become highly competitive, particularly in the area of manufacturing. Consequently, it is only by developing more advanced technologies that currently developed countries can maintain a sound balance of trade while trading freely with developing countries. As a neighbor of the rapidly developing countries of Southeast Asia, a region in which the environmental problems associated with economic and population growth are becoming acute, it is natural for Japan to be particularly eager to achieve rapid technological progress — perhaps more so than the US or Europe. In this context, the author discusses macro-engineering, a topic that includes such things as large scale infrastructure projects which are greatly needed in less-developed countries. The author also reviews civilization theory and considers modern culture and its effects on large-scale migrations, racial self-determination in the absence of a capable administration, and the prospects for sustainable growth on the limited Earth. The development of a macro-engineering diplomacy is proposed as a fundamental framework for solving global environmental problems, which might result in avoiding wasted efforts at national and regional levels.     

Microdosimetric analysis for high LET radiation

For short range high linear energy transfer (LET) radiation therapy the biological effects are strongly affected by the heterogeneity of the specific energy (z) distribution delivered to tumour cells. Three-dimensional (3-D) dosimetry information at the cellular level is required for this study. An ideal approach would be the reconstruction of the cell and the radiation source microdistribution from sequential autoradiographic sections, which is, however, not a practical solution. In this paper, a novel microdosimetry analysis method, which obtains the specific energy (z) distribution directly from the morphological information in individual autoradiographic sections, is applied to human glioblastoma multifore (GBM) and normal brain tissue specimens in boron neutron capture therapy. The results are consistent with Monte Carlo simulation and demonstrate a uniform radiation source distribution in both GBM and normal brain tissues. We also hypothesise a biophysical model based on specific energy for survival analysis. The specific energy distributions to cell nuclei were calculated with a uniform radiation source distribution. By combining this microdosimetric analysis with measured cell survival data at the low dose region, a cell survival curve at high doses is predicted, which is consistent with the commonly used simple exponential curve model for high LET radiation.     

Application of radiation technology to sewage sludge processing: a review

Sewage sludge is unwanted residual solid wastes generated in wastewater treatment and its management is one of the most critical environmental issues of today. The treatment and disposal of sludge contribute a considerable proportion of the cost for running a wastewater treatment plant. The increasing amount of sewage sludge and more and more legislative regulation of its disposal have stimulated the need for developing new technologies to process sewage sludge efficiently and economically. One ideal consideration is to recycle it after proper treatment. Radiation technology is regarded to be a promising alternative for its high efficiency in pathogen inactivation, organic pollutants oxidation, odor nuisance elimination and some other characteristics enhancement, which will facilitate the down-stream process of sludge treatment and disposal. Here we present a brief review of application of radiation technology on sewage sludge processing. Some basic information of two currently available irradiation systems and fundamental radiation chemistry are introduced firstly; then the world-wide application of this promising technology is reviewed; various effects of radiation on sludge is discussed in detail; and some concluding remarks are given and some future directions are also proposed.     

Triage, monitoring and dose assessment for people exposed to ionising radiation following a malevolent act

The part played by individual monitoring within the context of the overall response to incidents involving the malevolent use of radiation or radioactive material is discussed. The main objectives of an individual monitoring programme are outlined, and types of malevolent use scenario briefly described. Some major challenges facing those with responsibilities for planning the monitoring response to such an incident are identified and discussed. These include the need for rapid selection and prioritisation of people for individual monitoring by means of an effective triage system; the need for rapid initiation of individual monitoring; problems associated with monitoring large numbers of people; the particular difficulties associated with incidents involving pure-beta and alpha-emitting radionuclides; the need for techniques that can provide retrospective estimates of external radiation exposures rapidly and the need for rapid interpretation of contamination monitoring data. The paper concludes with a brief review of assistance networks and relevant international projects planned or currently underway.     

Evaluating research: from informed peer review to bibliometrics

National research assessment exercises are becoming regular events in ever more countries. The present work contrasts the peer-review and bibliometrics approaches in the conduct of these exercises. The comparison is conducted in terms of the essential parameters of any measurement system: accuracy, robustness, validity, functionality, time and costs. Empirical evidence shows that for the natural and formal sciences, the bibliometric methodology is by far preferable to peer-review. Setting up national databases of publications by individual authors, derived from Web of Science or Scopus databases, would allow much better, cheaper and more frequent national research assessments.     

Identifying emerging failure phenomena in complex systems through engineering data mapping

In the past, standard reliability and risk approaches have sufficed to identify the dominant causes of failure in forensic analyses, and the dominant risk contributors for proactive risk investigations. These techniques are particularly applicable when individual or even simple common failure events of a similar type dominate the analysis. However, nowadays due to increased understanding of the ‘simple’ mechanisms and the increasing complexity of the systems we build, failures in highly dependable systems arise from unexpected interactions between subsystems and the external and internal environment.

Engineering data analysis is the process of data collection and investigation from a variety of perspectives, alternatively dissecting it into its underlying (yet often unknown) patterns; this process is becoming ever more necessary as systems become more complex. Some of the techniques employed are slicing the data sets according to known underlying variables, or overlaying data gathered from different perspectives, or imbedding data into previously established logical or phenomenological structures.

This paper addresses the issues involved in visualizing patterns in data sets by providing examples of interesting maps from the past, indicating some of the maps currently in use, and speculating on how these visual maps might be developed further and used in the future to discover problems in complex systems before they lead to failure. Guidance is proposed as to how to explore and map data from different technical perspectives in order to evoke potentially significant patterns from reliability data. The techniques presented have been developed by combining approaches to common cause failure (CCF) classification with multidimensional scaling (MDS) to produce a new method for exploratory engineering data mapping.     

Second European Workshop on Low Temperature Detectors: Annecy, France, 2–6 May 1988

The workshop was concluded with a comprehensive summary and discussion (Pretzel, MPI, Munich, FRG). Clearly there is a growing interest in the development of low temperature devices for neutrino and dark matter detectors. Other applications are spectroscopic ultra-high spatial resolution X-ray imaging, optical and infrared radiation detectors, cold neutron and other low energy particle detectors, and phonon detectors. However, it is also clear that the fundamental experiments that were the original motivation of this research are a long way from realization. Slow but steady progress is being made on all fronts. In the process this research is enhancing an understanding of the particle/radiation interactions and revealing important phenomena in cryogenic devices. Each of the technologies under development has individual strengths and weaknesses so no single device is expected to solve all the detection problems. The state of the current research is still exploratory. It appears that at least two to three years of research will be required to demostrate the viability of one or more of these ideas. At that point, full-scale development of one or more detector systems will hopefully begin to address the many fundamental problmes posed at this workshop.     

The national dose register in Finland

The Finnish Dose Register includes exposure data for all workers engaged in radiation work. These data already cover a period of almost 50 y. The earliest data in the register apply to workers in health care, research and industry. Data on nuclear power plant workers have been recorded since 1977 and data on aircrews since 2001. The Dose Register is an extensive national register with doses currently recorded for more than 15,000 workers annually. This paper presents the content and structure of the register, together with recently completed and forthcoming reforms. It also describes how the recorded data are used in the regulatory control of radiation practices.     

Dose quantities in radiation protection and their limitations

For more than 50 years the quantity absorbed dose has been the basic physical quantity in the medical applications of ionising radiation as well as radiological protection against harm from ionising radiation. In radiotherapy relatively high doses are applied (to a part of the human body) within a short period and the absorbed dose is mainly correlated with deterministic effects such as cell killing and tissue damage. In contrast, in radiological protection one is dealing with low doses and low dose rates and long-term stochastic effects in tissue such as cancer induction. The dose quantity (absorbed dose) is considered to be correlated with the probability of cancer incidence and thus risk induced by exposure. ICRP has developed specific dosimetric quantities for radiological protection that allow the extent of exposure to ionising radiation from whole and partial body external radiation as well as from intakes of radionuclides to be taken into account by one quantity. Moreover, radiological protection quantities are designed to provide a correlation with risk of radiation induced cancer. In addition, operational dose quantities have been defined for use in measurements of external radiation exposure and practical applications. The paper describes the concept and considerations underlying the actual system of dose quantities, and discusses the advantage as well as the limitations of applicability of such a system. For example, absorbed dose is a non-stochastic quantity defined at any point in matter. All dose quantities in use are based on an averaging procedure. Stochastic effects and microscopic biological and energy deposition structures are not considered in the definition. Absorbed dose is correlated to the initial very short phase of the radiation interaction with tissue while the radiation induced biological reactions of the tissue may last for minutes or hours or even longer. There are many parameters other than absorbed dose that influence the process of cancer induction, which may influence the consideration of cells and/or tissues at risk which are most important for radiological protection.     

Managing innovation networks in the knowledge-driven economy

Innovation has been widely recognized as the key driver of economic growth. However, in the knowledge-driven economy, the nature of innovation is changing. Both technologies and innovations are becoming more complex as the knowledge content has increased. Due to the amount of different knowledge domains, individual players cannot develop anymore all the competencies necessary to create innovation in the knowledge-driven economy. Successful innovators therefore join to form innovation networks that allow them to source flexibly competencies and to offer innovations that are complete solutions and not just products. The traditional linear model from research and development as a basis of innovations is thus shifting to a model with a wide network of sources and partners integrating complementary competencies. Managing innovation in such a network poses new challenges for companies as they need to adapt their way of working and develop?‘networking’?competencies. In this paper, success factors are derived that networks and companies need to adopt to create innovation. For the support of the management of such networks, the innovation roadmapping methodology is proposed. Previously only applied for innovation management in individual organizations, innovation roadmapping should be used as a means to identify and exploit ideas and to align the innovation efforts in the network.