Guardians of precision: advancing radiation protection, safety, and quality systems in nuclear medicine

BACKGROUND

In the rapidly evolving field of nuclear medicine, the paramount importance of radiation protection, safety, and quality systems cannot be overstated. This document provides a comprehensive analysis of the intricate regulatory frameworks and guidelines, meticulously crafted and updated by national and international regulatory bodies to ensure the utmost safety and efficiency in the practice of nuclear medicine.

METHODS

We explore the dynamic nature of these regulations, emphasizing their adaptability in accommodating technological advancements and the integration of nuclear medicine with other medical and scientific disciplines.

RESULTS

Audits, both internal and external, are spotlighted for their pivotal role in assessing and ensuring compliance with established standards, promoting a culture of continuous improvement and excellence. We delve into the significant contributions of entities like the International Atomic Energy Agency (IAEA) and relevant professional societies in offering universally applicable guidelines that amalgamate the latest in scientific research, ethical considerations, and practical applicability.

CONCLUSIONS

The document underscores the essence of international collaborations in pooling expertise, resources, and insights, fostering a global community of practice where knowledge and innovations are shared. Readers will gain an in-depth understanding of the practical applications, challenges, and opportunities presented by these regulatory frameworks and audit processes. The ultimate goal is to inspire and inform ongoing efforts to enhance safety, quality, and effectiveness in nuclear medicine globally.

Recurrent medical imaging exposures for the care of patients: one way forward

Medical imaging is both valuable and essential in the care of patients. Much of this imaging depends on ionizing radiation with attendant responsibilities for judicious use when performing an examination. This responsibility applies in settings of both individual as well as multiple (recurrent) imaging with associated repeated radiation exposures. In addressing the roles and responsibilities of the medical communities in the paradigm of recurrent imaging, both the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) have issued position statements, each affirmed by other organizations. The apparent difference in focus and approach has resulted in a lack of clarity and continued debate. Aiming towards a coherent approach in dealing with radiation exposure in recurrent imaging, the IAEA convened a panel of experts, the purpose of which was to identify common ground and reconcile divergent perspectives. The effort has led to clarifying recommendations for radiation exposure aspects of recurrent imaging, including the relevance of patient agency and the provider-patient covenant in clinical decision-making. CLINICAL RELEVANCE STATEMENT: An increasing awareness, generating some lack of clarity and divergence in perspectives, with patients receiving relatively high radiation doses (e.g., ≥ 100 mSv) from recurrent imaging warrants a multi-stakeholder accord for the benefit of patients, providers, and the imaging community. KEY POINTS: • Recurrent medical imaging can result in an accumulation of exposures which exceeds 100 milli Sieverts. • Professional organizations have different perspectives on roles and responsibilities for recurrent imaging. • An expert panel reconciles differing perspectives for addressing radiation exposure from recurrent medical imaging.

Safety in radiation oncology (SAFRON): Learning about incident causes and safety barriers in external beam radiotherapy

PURPOSE

Safety in Radiation Oncology (SAFRON) is a reporting and learning system on radiotherapy and radionuclide therapy incidents and near misses. The primary aim of this paper is to examine whether any discernible patterns exist in the causes of reported incidents and safety barriers within the SAFRON system concerning external beam radiotherapy.

METHODS AND MATERIALS

This study focuses on external beam radiotherapy incidents, reviewing 1685 reports since the inception of SAFRON until December 2021. Reports that did not identify causes of incidents and safety barriers were excluded from the final study population.

RESULTS

Simple two-dimensional radiotherapy or electron beam therapy were represented by 97 reports, three-dimensional conformal radiotherapy by 39 reports, modulated arc therapy by 12 reports, intensity modulated radiation therapy by 11 reports, stereotactic radiosurgery by 4 reports, and radiotherapy with protons or other particles by 1 report, while for 92 of them, no information on treatment method had been provided. Most of the reported incidents were minor incidents and were discovered by the radiation therapist. Inadequate direction/information in staff communication was the most frequently reported cause of incident, and regular independent chart check was the most common safety barrier.

CONCLUSIONS

The results indicate that the majority of incidents were reported by radiation therapists, and the majority of these incidents were classified as minor. Communication problems and failure to follow standards/procedures/practices were the most frequent causes of incidents. Furthermore, regular independent chart checking was the most frequently identified safety barrier.

Communication of radiation risk from imaging studies: an IAEA-coordinated international survey

The purpose of this IAEA-coordinated international study was to understand aspects related to the communication of radiation risk from imaging studies, such as how often imaging department personnel and referring physicians are asked about radiation risks in diagnostic imaging, who asks about these risks, how often professionals are able to provide satisfactory answers using qualitative metrics and how often quantitative risk estimates are needed. A web-based questionnaire with ten questions was completed by 386 healthcare professionals from 63 countries from all four continents, including clinicians/referring physicians (42.5%), radiologists or nuclear medicine physicians (26.7%), medical physicists (23.1%), radiographers/radiological technologists (6.2%) and others (1.6%). The results indicate that radiation risk-related questions are largely asked by patients (73.1%) and parents of child patients (38.6%), and 78% of the professionals believe they are able to answer those questions using qualitative metrics such as very small/minimal, small, medium rather than number of cancers likely occurring. The vast majority, with over three times higher frequency, indicated the purpose of knowing previous radiological exams as 'both clinical information and radiation exposure history' rather than 'only clinical information'. Nearly two-thirds of the clinicians/referring physicians indicated that knowing the radiation exposure history of the patient will affect their decision-making for the next exam, as against only about one-fifth who said 'no, it will not affect their decision-making'. The same question, when addressed to radiologists, resulted in a slightly larger fraction of about three-quarters who said 'yes', as opposed to a smaller fraction of about 12% who said 'no, it will not affect their decision-making'. Mapping the present situation of communication of benefits and risks for patients is important and may be the basis of further analysis, regular monitoring and possibly a target for clinical audits. Further studies focused on specific professional groups might help in obtaining á deeper understanding of the need for practical communication tools.

Strengthening radiation protection education and training of health professionals: conclusions from an IAEA meeting

In March 2021 the International Atomic Energy Agency (IAEA) organised an online Technical Meeting on Developing Effective Methods for Radiation Protection Education and Training of Health Professionals with attendance of 230 participants representing 66 Member States and 24 international organizations, professional bodies and safety alliances. By means of a pre-meeting survey, presentations by experts, topical panel discussions and post-meeting feedback to the meeting summary, the meeting identified strengths, common weaknesses and possible solutions and actions for improving radiation protection education and training of health professionals. Available guidelines and resources for radiation protection training were also reviewed. The meeting discussion resulted in a strong consensus for the need of: (a) international guidance on education and training in radiation protection and safety for health professionals, (b) an international description of minimum standards of initial and ongoing competence and qualification in radiation protection for relevant professional groups, considering the available recommendations at international and regional levels. The proposed actions include provisions for train-the-trainer credentialing and facility training accreditation, balance betwee the online and face-to-face training, improved on-the job training, as well as improved inclusion in training programmes of aspects related to application of new technologies, ethical aspects, development of communication skills, and use of software tools for improving justification and optimisation. The need for making the ongoing training practical, applicable, and useful to the trainee was highlighted. The international consultation initiated by the IAEA was appreciated as a good approach to understand and promote coordination and collaboration at all levels, for best results in education and training in radiation protection of health professionals. Implementing such a holistic approach to education and training in radiation protection would contribute towards qualification and competence of health professionals needed to ensure application of high standards for quality and safety in medical uses of ionizing radiation.

How often does it happen? A review of unintended, unnecessary and unavoidable high-dose radiation exposures

High-dose radiation exposures of humans occur every year around the world, and may lead to harmful tissue reactions. This review aims to look at the available information sources that can help answering the question of how often these events occur yearly on a global scale. In the absence of comprehensive databases of global occurrence, publications on radiation accidents in all uses of radiation and on rates of high-dose events in different medical uses of radiation have been reviewed. Most high-dose radiation exposures seem to occur in the medical uses of radiation, reflecting the high number of medical exposures performed. In therapeutic medical uses, radiation doses are purposely often given at levels known to cause deterministic effects, and there is a very narrow range in which the medical practitioner can operate without causing severe unacceptable outcomes. In interventional medical uses, there are scenarios in which the radiation dose given to a patient may reach or exceed a threshold for skin effects, where this radiation dose may be unavoidable, considering all benefits and risks as well as benefits and risks of any alternative procedures. Regardless of if the delivered dose is unintended, unnecessary or unavoidable, there are estimates published of the rates of high-dose events and of radiation-induced tissue injuries occurring in medical uses. If this information is extrapolated to a global scenario, noting the inherent limitations in doing so, it does not seem unreasonable to expect that the global number of radiation-induced injuries every year may be in the order of hundreds, likely mainly arising from medical uses of radiation, and in particular from interventional fluoroscopy procedures and external beam radiotherapy procedures. These procedures are so frequently employed throughout the world that even a very small rate of radiation-induced injuries becomes a substantial number when scaled up to a global level.

Radiation protection perspective to recurrent medical imaging: what is known and what more is needed?

This review summarises the current knowledge about recurrent radiological imaging and associated cumulative doses to patients. The recent conservative estimates are for around 0.9 million patients globally who cumulate radiation doses above 100 mSv, where evidence exists for cancer risk elevation. Around one in five is estimated to be under the age of 50. Recurrent imaging is used for managing various health conditions and chronic diseases such as malignancies, trauma, end-stage kidney disease, cardiovascular diseases, Crohn's disease, urolithiasis, cystic pulmonary disease. More studies are needed from different parts of the world to understand the magnitude and appropriateness. The analysis identified areas of future work to improve radiation protection of individuals who are submitted to frequent imaging. These include access to dose saving imaging technologies; improved imaging strategies and appropriateness process; specific optimisation tailored to the clinical condition and patient habitus; wider utilisation of the automatic exposure monitoring systems with an integrated option for individual exposure tracking in standardised patient-specific risk metrics; improved training and communication. The integration of the clinical and exposure history data will support improved knowledge about radiation risks from low doses and individual radiosensitivity. The radiation protection framework will need to respond to the challenge of recurrent imaging and high individual doses. The radiation protection perspective complements the clinical perspective, and the risk to benefit analysis must account holistically for all incidental and long-term benefits and risks for patients, their clinical history and specific needs. This is a step toward the patient-centric health care.

Medical imaging and nuclear medicine: a Lancet Oncology Commission

The diagnosis and treatment of patients with cancer requires access to imaging to ensure accurate management decisions and optimal outcomes. Our global assessment of imaging and nuclear medicine resources identified substantial shortages in equipment and workforce, particularly in low-income and middle-income countries (LMICs). A microsimulation model of 11 cancers showed that the scale-up of imaging would avert 3·2% (2·46 million) of all 76·0 million deaths caused by the modelled cancers worldwide between 2020 and 2030, saving 54·92 million life-years. A comprehensive scale-up of imaging, treatment, and care quality would avert 9·55 million (12·5%) of all cancer deaths caused by the modelled cancers worldwide, saving 232·30 million life-years. Scale-up of imaging would cost US$6·84 billion in 2020-30 but yield lifetime productivity gains of $1·23 trillion worldwide, a net return of $179·19 per $1 invested. Combining the scale-up of imaging, treatment, and quality of care would provide a net benefit of $2·66 trillion and a net return of $12·43 per $1 invested. With the use of a conservative approach regarding human capital, the scale-up of imaging alone would provide a net benefit of $209·46 billion and net return of $31·61 per $1 invested. With comprehensive scale-up, the worldwide net benefit using the human capital approach is $340·42 billion and the return per dollar invested is $2·46. These improved health and economic outcomes hold true across all geographical regions. We propose actions and investments that would enhance access to imaging equipment, workforce capacity, digital technology, radiopharmaceuticals, and research and training programmes in LMICs, to produce massive health and economic benefits and reduce the burden of cancer globally.

Variations in CT Utilization, Protocols, and Radiation Doses in COVID-19 Pneumonia: Results from 28 Countries in the IAEA Study

Background

There is lack of guidance on specific CT protocols for imaging patients with coronavirus disease 2019 (COVID-19) pneumonia.

Purpose

To assess international variations in CT utilization, protocols, and radiation doses in patients with COVID-19 pneumonia.

Materials and Methods

In this retrospective data collection study, the International Atomic Energy Agency (IAEA) coordinated a survey between May and July 2020 regarding CT utilization, protocols, and radiation doses from 62 healthcare sites in 34 countries across five continents for CT exams performed in COVID-19 pneumonia. The questionnaire obtained information on local prevalence, method of diagnosis, most frequent imaging, indications for CT, and specific policies on use of CT in COVID-19 pneumonia. Collected data included general information (patient age, weight, clinical indication), CT equipment (CT make and model, year of installation, number of detector rows), scan protocols (body region, scan phases, tube current and potential), and radiation dose descriptors (CT dose index (CTDI_vol) and dose length product (DLP)). Descriptive statistics and generalized estimating equations were performed.

Results

Data from 782 patients (median age (interquartile range) of 59(15) years) from 54 healthcare sites in 28 countries were evaluated. Less than one-half of the healthcare sites used CT for initial diagnosis of COVID-19 pneumonia and three-fourth used CT for assessing disease severity. CTDI_vol varied based on CT vendors (7-11mGy, p<0.001), number of detector-rows (8-9mGy, p<0.001), year of CT installation (7-10mGy, p=0.006), and reconstruction techniques (7-10mGy, p=0.03). Multiphase chest CT exams performed in 20% of sites (11 of 54) were associated with higher DLP compared with single-phase chest CT exams performed in 80% (43 of 54 sites) (p=0.008).

Conclusion

CT use, scan protocols, and radiation doses in patients with COVID-19 pneumonia showed wide variation across healthcare sites within the same and different countries. Many patients were scanned multiple times and/or with multiphase CT scan protocols.

See also the editorial by Lee.

Chest CT practice and protocols for COVID-19 from radiation dose management perspective

The global pandemic of coronavirus disease 2019 (COVID-19) has upended the world with over 6.6 million infections and over 391,000 deaths worldwide. Reverse-transcription polymerase chain reaction (RT-PCR) assay is the preferred method of diagnosis of COVID-19 infection. Yet, chest CT is often used in patients with known or suspected COVID-19 due to regional preferences, lack of availability of PCR assays, and false-negative PCR assays, as well as for monitoring of disease progression, complications, and treatment response. The International Atomic Energy Agency (IAEA) organized a webinar to discuss CT practice and protocol optimization from a radiation protection perspective on April 9, 2020, and surveyed participants from five continents. We review important aspects of CT in COVID-19 infection from the justification of its use to specific scan protocols for optimizing radiation dose and diagnostic information.

Key Points

• Chest CT provides useful information in patients with moderate to severe COVID-19 pneumonia.

• When indicated, chest CT in most patients with COVID-19 pneumonia must be performed with non-contrast, low-dose protocol.

• Although chest CT has high sensitivity for diagnosis of COVID-19 pneumonia, CT findings are non-specific and overlap with other viral infections including influenza and H1N1.

The International Atomic Energy Agency action plan on radiation protection of patients and staff in interventional procedures: Achieving change in practice

INTRODUCTION

The International Atomic Energy Agency (IAEA) organized the 3rd international conference on radiation protection (RP) of patients in December 2017. This paper presents the conclusions on the interventional procedures (IP) session.

MATERIAL AND METHODS

The IAEA conference was conducted as a series of plenary sessions followed by various thematic sessions. "Radiation protection of patients and staff in interventional procedures" session keynote speakers presented information on: 1) Risk management of skin injuries, 2) Occupational radiation risks and 3) RP for paediatric patients. Then, a summary of the session-related papers was presented by a rapporteur, followed by an open question-and-answer discussion.

RESULTS

Sixty-seven percent (67%) of papers came from Europe. Forty-four percent (44%) were patient studies, 44% were occupational and 12% were combined studies. Occupational studies were mostly on eye lens dosimetry. The rest were on scattered radiation measurements and dose tracking. The majority of patient studies related to patient exposure with only one study on paediatric patients. Automatic patient dose reporting is considered as a first step for dose optimization. Despite efforts, paediatric IP radiation dose data are still scarce. The keynote speakers outlined recent achievements but also challenges in the field. Forecasting technology, task-specific targeted education from educators familiar with the clinical situation, more accurate estimation of lens doses and improved identification of high-risk professional groups are some of the areas they focused on.

CONCLUSIONS

Manufacturers play an important role in making patients safer. Low dose technologies are still expensive and manufacturers should make these affordable in less resourced countries. Automatic patient dose reporting and real-time skin dose map are important for dose optimization. Clinical audit and better QA processes together with more studies on the impact of lens opacities in clinical practice and on paediatric patients are needed.

Clinical imaging guidelines part 2: Risks, benefits, barriers, and solutions

A recent international meeting was convened by two United Nations bodies to focus on international collaboration on clinical appropriateness/referral guidelines for use in medical imaging. This paper, the second of 4 from this technical meeting, addresses barriers to the successful development/deployment of clinical imaging guidelines and means of overcoming them. It reflects the discussions of the attendees, and the issues identified are treated under 7 headings: ■ Practical Strategy for Development and Deployment of Guidelines; ■ Governance Arrangements and Concerns with Deployment of Guidelines; ■ Finance, Sustainability, Reimbursement, and Related Issues; ■ Identifying Benefits and Radiation Risks from Radiological Examinations; ■ Information Given to Patients and the Public, and Consent Issues; ■ Special Concerns Related to Pregnancy; and ■ The Research Agenda. Examples of topics identified include the observation that guideline development is a global task and there is no case for continuing it as the project of the few professional organizations that have been brave enough to make the long-term commitment required. Advocacy for guidelines should include the expectations that they will facilitate: (1) better health care delivery; (2) lower cost of that delivery; with (3) reduced radiation dose and associated health risks. Radiation protection issues should not be isolated; rather, they should be integrated with the overall health care picture. The type of dose/radiation risk information to be provided with guidelines should include the uncertainty involved and advice on application of the precautionary principle with patients. This principle may be taken as an extension of the well-established medical principle of "first do no harm."

IAEA experience in communicating radiation risks through the RPOP website

The authors report here their successful experience of communicating information to health professionals, patients and the public on benefits and risks of ionising radiation in medical applications. The approaches used have been based on giving importance to clinical benefits against risks, as well as safety in use against risk of use. Communicating brief messages against catchy questions with positive and pragmatic approach resulted in making website on radiation protection of patients (RPOP) as the top website of the world in this area. Credibility of information has been maintained. The results show immense outreach in 213 countries/territories.

Addressing patient safety through the use of 'criteria of acceptability' for medical radiation equipment

Patient safety should be considered in the use of ionising radiation equipment in medicine. The International Atomic Energy Agency (IAEA) establishes standards of safety and provides for the application of these standards, also in the area of medical use of radiation. Equipment acceptability, as it relates to radiation in medicine, is the need to satisfy the requirements or standards prior to the use of the device in patient imaging or treatment. Through IAEA activities in establishing and developing Safety Standards, Safety Reports and recommendations to regulatory authorities and end-users, it encourages the adoption of acceptability criteria that are relevant to the medical equipment and its use.

Justification of diagnostic medical exposures: some practical issues. Report of an International Atomic Energy Agency Consultation

OBJECTIVES

The Radiation Protection of Patients Unit of the International Atomic Energy Agency (IAEA) is concerned about the effectiveness of justification of diagnostic medical exposures. Recent published work and the report of an initial IAEA consultation in the area gave grounds for such concerns. There is a significant level of inappropriate usage, and, in some cases, a poor level of awareness of dose and risk among some key groups involved. This article aims to address this.

METHODS

The IAEA convened a second group of experts in November 2008 to review practical and achievable actions that might lead to more effective justification.

RESULTS

This report summarises the matters that this group considered and the outcome of their deliberations. There is a need for improved communication, both within professions and between professionals on one hand, and between professionals and the patients/public on the other. Coupled with this, the issue of consent to imaging procedures was revisited. The need for good evidence-based referral guidelines or criteria of acceptability was emphasised, as was the need for their global adaptation and dissemination.

CONCLUSION

Clinical audit was regarded as a key tool in ensuring that justification becomes an effective, transparent and accountable part of normal radiological practice. In summary, justification would be facilitated by the "3 As": awareness, appropriateness and audit.

International action plan on the radiation protection of patients

Realising that the major part of radiation protection efforts had been directed for over half a century at radiation protection of workers, and that there are major issues in relation to medical exposure, which contributes to over 95 % of the dose to the global population from man-made sources, with increasing individual patient doses in diagnostic examinations, unnecessary or inappropriate examinations and continued accidents in radiotherapy, the International Atomic Energy Agency established an International Action Plan (IAP) in 2002 in cooperation with international organisations and professional bodies. The achievements of the IAP, which include harmonised training material, guidance documents, a number of publications, a website on radiation protection of patients (http://rpop.iaea.org) and a series of actions in Member States that have shown positive impacts on patient protection, are summarised in this paper.

Radiation Oncology Safety Information System (ROSIS)--profiles of participants and the first 1074 incident reports

BACKGROUND AND PURPOSE

The Radiation Oncology Safety Information System (ROSIS) was established in 2001. The aim of ROSIS is to collate and share information on incidents and near-incidents in radiotherapy, and to learn from these incidents in the context of departmental infrastructure and procedures.

MATERIALS AND METHODS

A voluntary web-based cross-organisational and international reporting and learning system was developed (cf. the www.rosis.info website). Data is collected via online Department Description and Incident Report Forms. A total of 101 departments, and 1074 incident reports are reviewed.

RESULTS

The ROSIS departments represent about 150,000 patients, 343 megavoltage (MV) units, and 114 brachytherapy units. On average, there are 437 patients per MV unit, 281 per radiation oncologist, 387 per physicist and 353 per radiation therapy technologist (RT/RTT). Only 14 departments have a completely networked system of electronic data transfer, while 10 departments have no electronic data transfer. On average seven quality assurance (QA) or quality control (QC) methods are used at each department. A total of 1074 ROSIS reports are analysed; 97.7% relate to external beam radiation treatment and 50% resulted in incorrect irradiation. Many incidents arise during pre-treatment but are not detected until later in the treatment process. Where an incident is not detected prior to treatment, an average of 22% of the prescribed treatment fractions were delivered incorrectly. The most commonly reported detection methods were "found at time of patient treatment" and during "chart-check".

CONCLUSION

While the majority of the incidents that reported to this international cross-organisational reporting system are of minor dosimetric consequence, they affect on average more than 20% of the patient's treatment fractions. Nonetheless, defence-in-depth is apparent in departments registered with ROSIS. This indicates a need for further evaluation of the effectiveness of quality controls.

ICRP publication 112. A report of preventing accidental exposures from new external beam radiation therapy technologies

Disseminating the knowledge and lessons learned from accidental exposures is crucial in preventing re-occurrence. This is particularly important in radiation therapy; the only application of radiation in which very high radiation doses are deliberately given to patients to achieve cure or palliation of disease. Lessons from accidental exposures are, therefore, an invaluable resource for revealing vulnerable aspects of the practice of radiotherapy, and for providing guidance for the prevention of future occurrences. These lessons have successfully been applied to avoid catastrophic events with conventional technologies and techniques. Recommendations, for example, include the independent verification of beam calibration and independent calculation of the treatment times and monitor units for external beam radiotherapy, and the monitoring of patients and their clothes immediately after brachytherapy. New technologies are meant to bring substantial improvement to radiation therapy. However, this is often achieved with a considerable increase in complexity, which in turn brings opportunities for new types of human error and problems with equipment. Dissemination of information on these errors or mistakes as soon as it becomes available is crucial in radiation therapy with new technologies. In addition, information on circumstances that almost resulted in serious consequences (near-misses) is also important, as the same type of events may occur elsewhere. Sharing information about near-misses is thus a complementary important aspect of prevention. Lessons from retrospective information are provided in Sections 2 and 4 of this report. Disseminating lessons learned for serious incidents is necessary but not sufficient when dealing with new technologies. It is of utmost importance to be proactive and continually strive to answer questions such as 'What else can go wrong', 'How likely is it?' and 'What kind of cost-effective choices do I have for prevention?'. These questions are addressed in Sections 3 and 5 of this report. Section 6 contains the conclusions and recommendations. This report is expected to be a valuable resource for radiation oncologists, hospital administrators, medical physicists, technologists, dosimetrists, maintenance engineers, radiation safety specialists, and regulators. While the report applies specifically to new external beam therapies, the general principles for prevention are applicable to the broad range of radiotherapy practices where mistakes could result in serious consequences for the patient and practitioner.

Current issues and actions in radiation protection of patients

Medical application of ionizing radiation is a massive and increasing activity globally. While the use of ionizing radiation in medicine brings tremendous benefits to the global population, the associated risks due to stochastic and deterministic effects make it necessary to protect patients from potential harm. Current issues in radiation protection of patients include not only the rapidly increasing collective dose to the global population from medical exposure, but also that a substantial percentage of diagnostic imaging examinations are unnecessary, and the cumulative dose to individuals from medical exposure is growing. In addition to this, continued reports on deterministic injuries from safety related events in the medical use of ionizing radiation are raising awareness on the necessity for accident prevention measures. The International Atomic Energy Agency is engaged in several activities to reverse the negative trends of these current issues, including improvement of the justification process, the tracking of radiation history of individual patients, shared learning of safety significant events, and the use of comprehensive quality audits in the clinical environment.

The importance and unique aspects of radiation protection in medicine

Radiation protection in medicine has unique aspects and is an essential element of medical practice. Medical uses of radiation occur throughout the world, from large cities to rural clinics. It has been estimated that the number of medical procedures using radiation grew from about 1.7 billion in 1980 to almost 4 billion in 2007. In spite of these large numbers, there are many parts of the world without adequate equipment, where the ability to perform additional medical procedures would likely result in a net benefit. Medicine accounts for more than 99.9% of the per caput effective dose from man-made sources. The goal in medical exposure is not to give the lowest dose, but to provide the correct dose to enable the practitioner to make the diagnosis or cure a tumour. Too little or too much dose is problematic and the risk of any given procedure ranges from negligible to potentially fatal. Radiation protection in medicine must deal with the issues of not having dose limits, purposely exposing sensitive subgroups, and purposely using doses that could cause deterministic effects. Radiation accidents involving medical uses have accounted for more acute radiation deaths than from any other source including Chernobyl. Many physicians have little or no training in radiation protection, and many have no qualified medical physics support. In many countries, medical radiation devices and uses are only minimally regulated and the rapidly evolving technology is a challenge. Medicine also accounts for the largest number of occupationally exposed workers and collective dose.

Escalated dose for non-small-cell lung cancer with accelerated hypofractionated three-dimensional conformal radiation therapy

BACKGROUND AND PURPOSE

To prospectively assess the feasibility and efficacy of a hypofractionated accelerated radiotherapy regimen (72 Gy in 24 daily fractions, 3 Gy per fraction) in patients (pts) with non-resectable non-small-cell lung cancer (NSCLC).

MATERIAL AND METHODS

We included 25 pts with a histologically or cytologically proven NSCLC, with KPS > or = 70 and < or =10% weight loss over prior three months, and with tumour stage I/II medically inoperable (9 pts) or non-resectable stage III a/b without pleural effusion (16 pts). Eleven pts received induction chemotherapy. No more than 30% of the combined lung volume could receive more than 25 Gy and the maximal biological effective dose to the spinal cord was maintained below 44 Gy.

RESULTS

No grade-4 acute toxicity event was reported. Two pts had a treatment break because of grade-3 acute oesophagitis. Twenty-two pts were evaluable for long-term toxicity (median follow-up=9.7 months, range 4 to 30.2 months). There were 4 Grade-1 pulmonary and 2 Grade-1 oesophageal long-term toxicity events. Twenty-two pts were evaluable for tumour response with 7 complete and 8 partial responses, 5 stable diseases and 2 progressive diseases. The actuarial 1-year overall and thoracic-progression-free survival rates were 68% and 72% respectively.

CONCLUSIONS

This study demonstrates the feasibility of the experimental radiotherapy schedule, however more data are needed to confirm its efficacy.

A Method of Predicting Workload and Staffing Level for Radiotherapy Treatment Planning as Plan Complexity Changes

When assessing the impact on workload from an expanding number of new patients and increasing treatment complexity, radiotherapy clinics find that oversimplified workload parameters, such as number of patients or number of fields, are not suitable for managing and predicting workload and organisational dimension. Although the basic treatment equivalent concept is available for predicting linear accelerator utilisation, no corresponding parameter has been available for radiotherapy treatment planning. In this study, we derive a simple workload indicator for treatment planning. The dose plan unit (DPU) takes the complexity of the treatment plan into account. Categorising plans according to complexity in their production, and measuring corresponding time for completing the plans in these categories, leads to the following baseline values for workload prediction: 1 DPU (non-computed tomography [CT]), 3 DPU (CT-contour) and 6 DPU (full-CT). The measured average productivity of 0.65 DPU per hour (1 standard deviation, SD = 0.08 DPU), or alternatively 1 DPU = 92 min, for a dosimetrist in this clinic indicates that 79.0 DPU can be produced by each dosimetrist per month within normal working hours. The predictive power of the DPU is shown in terms of using it to quantify the impact on workload in treatment planning of changing treatment protocols for a particular anatomic treatment site.

Analysis of dose distribution in the 'Rind'--a volume outside the PTV--in 3-dimensional conformal radiation therapy of non-small cell lung cancer

BACKGROUND AND PURPOSE

Appropriate planning target volume (PTV) definition is critical for local disease eradication in the treatment of non-small cell lung cancer (NSCLC). When margins are added to the gross tumour volume (GTV) in the standard way, the PTV formed may be too large to facilitate dose escalation due to normal tissue tolerance. To increase the feasibility of dose escalation with 3-dimensional conformal radiotherapy (3DCRT), this study examines an alternative method for the formation of the PTV in NSCLC. This strategy is based on the reduced probability of tumour cells from the GTV outwards and on the associated lower dose requirements to eradicate such subclinical disease.

MATERIALS AND METHODS

3DCRT plans were generated from the CT scans of 15 patients with NSCLC (stages Ib to IIIb). Each PTV was formed by adding a margin for geometric uncertainties directly onto the GTV. The success of this approach is dependent on the volume immediately outside this smaller PTV, the Rind volume, receiving 50 Gy, the minimum dose requirement that is considered sufficient for eradication of the reduced tumour cell density in this volume. While optimizing the treatment plans for each PTV to 70 Gy, the dose distribution in the Rind volume, and the factors affecting it, were assessed.

RESULTS

One hundred percent of each PTV received a minimum of 95% of the prescribed dose. The percentage of the Rind volume receiving 50 Gy or more (V50) had a median value of 94%. The minimum dose in this volume, however, ranged from 5.6 to 32.1 Gy. The V50 was highest for apical tumours (96.1%) and lowest for peripheral tumours (86%) and correlated positively with the size of the PTV (Kendall's rank correlation (Kt)=+0.3, P=0.05) and the number of beams used (Kt=+0.3, P=0.03) but not with the conformity index. The average volume outside the Rind which still received >/=50 Gy (the Wasted 50 Gy) increased significantly with the V50 of the Rind volume and was inversely proportional to the Rind <50 Gy, correlating significantly with the dose to the organs at risk.

CONCLUSIONS

Using this strategy with standard 3DCRT, all PTVs were irradiated to the required dose with this approach, but none of the corresponding Rind volumes had an acceptable dose distribution. The addition of dual volume planning or the use of intensity modulated radiation therapy may achieve an appropriate dose distribution in the Rind volume while not increasing the dose to the organs at risk and may thereby facilitate dose escalation.

Dose escalation of chart in non-small cell lung cancer: is three-dimensional conformal radiation therapy really necessary?

PURPOSE

To evaluate, preclinically, the potential for dose escalation of continuous, hyperfractionated, accelerated radiation therapy (CHART) for non small-cell lung cancer (NSCLC), we examined the strategy of omission of elective nodal irradiation with and without the application of three-dimensional conformal radiation technology (3DCRT).

METHODS AND MATERIALS

2D, conventional therapy plans were designed according to the specifications of CHART for 18 patients with NSCLC (Stages Ib, IIb, IIIa, and IIIb). Further plans were generated with the omission of elective nodal irradiation (ENI) from the treatment portals (2D minus ENI plans [2D-ENI plans]). Both sets were inserted in the patient's planning computed tomographies (CTs). These reconstructed plans were then compared to alternative, three-dimensional treatment plans which had been generated de novo, with the omission of ENI: 3D minus elective nodal irradiation (3D-ENI plans). Dose delivery to the planning target volumes (PTVs) and to the organs at risk were compared between the 3 sets of corresponding plans. The potential for dose escalation of each patient's 2D-ENI and 3D-ENI plan beyond 54 Gy, standard to CHART, was also determined.

RESULTS

PTV coverage was suboptimal in the 2D CHART and the 2D-ENI plans. Only in the 3D-ENI plans did 100% of the PTV get > or = 95% of the dose prescribed (i.e., 51.5 Gy [51.3-52.2]). Using 3D-ENI plans significantly reduced the dose received by the spinal cord, the mean and median doses to the esophagus and the heart. It did not significantly reduce the lung dose when compared to 2D-ENI plans. Escalation of the dose (minimum > or = 1 Gy) with optimal PTV coverage was possible in 55.5% of patients using 3D-ENI, but was possible only in 16.6% when using the 2D-ENI planning strategy.

CONCLUSIONS

3DCRT is fundamental to achieving optimal PTV coverage in NSCLC. A policy of omission of elective nodal irradiation alone (and using 2D technology) will not achieve optimal PTV coverage or dose escalation. 3DCRT with omission of ENI can achieve true escalation of CHART in 55.5% of tumors, depending on their site and N-stage.

What margins should be added to the clinical target volume in radiotherapy treatment planning for lung cancer?

BACKGROUND

The planning target volume in radiotherapy treatment planning takes into account both movements of the clinical target volume (CTV) and set-up deviations.

MATERIALS AND METHODS

A group of patients who received radiotherapy for lung cancer were studied. In order to measure the CTV movements due to respiration and other internal organ motions, fluoroscopy was performed for 20 patients. To study the accuracy and reproducibility of patient and beam set-up, 553 electronic portal images from 20 patients were evaluated. Discrepancies between planned and actual field positions were measured and the systematic and random errors were identified. The combined effect of these geometrical variations was evaluated.

RESULTS

The average CTV movement with quiet respiration was about 2.4 mm in the medio-lateral and dorso-ventral directions. Movement in the cranio-caudal direction was on average 3.9 mm with a range of 0-12 mm. The systematic set-up errors were on average 2.0 mm in the transversal plane and 3.0 mm in the cranio-caudal direction. The random errors can be described by their standard deviations of 3.2 and 2.6 mm. In this study, the combined effect of the two parameters (CTV movement and set-up deviations) varied between 7.5 and 10.3 mm in different anatomical directions.

CONCLUSIONS

In our daily clinical routine, we use a margin of 11 mm in the transversal plane and 15 mm cranially and caudally, also taking into account other unquantified variations and uncertainties.

Improvements in absorbed dose measurements for external radiation therapy using ferrous dosimeter gel and MR imaging (FeMRI)

A ferrous gel, based on ferrous (Fe) sulphate and agarose, was used with a clinical magnetic resonance imaging (MRI) scanner to obtain relative dose distribution data from therapeutic photon and electron beams. The FeMRI gel was scanned using a new MRI acquisition protocol optimized for T1 measurements. Thorough comparisons with silicon semiconductor detector and ionization chamber measurements, as well as with Monte Carlo calculations, were performed in order to quantify the improvements obtained using FeMRI for dose estimations. Most of the relative doses measured with FeMRI were within 2% of the doses measured with other methods. The larger discrepancies (2-4%) found at shallow depths are discussed. The uncertainty in relative dose measurements using FeMRI was significantly improved compared with previously reported results (5-10%, one standard deviation, 1 SD), and is today between 1.6% and 3.3% (depending on dose level, 2 SD). This corresponds to an improvement in the minimum detectable dose (3 SD above background) from approximately 2 Gy to better than 0.6 Gy. The results obtained in this study emphasize the importance of obtaining basic FeMRI dose data before the method is extended to complicated treatment regimes.

Effect of set-up uncertainties on the dose distribution in the match region of supraclavicular and tangential breast fields

BACKGROUND

The objective of this paper is to illustrate the effect of a gap of 5 mm, an overlap of 5 mm and a perfect match on the dose distribution across the junction of tangential breast fields and adjacent supraclavicular and axillary fields.

MATERIALS AND METHODS

For this purpose film dosimetry was applied to measure relative dose distributions in two sagittal planes in an anthropomorphic breast phantom having cork lungs, simulating a radiation therapy treatment of the breast and adjacent supraclavicular lymph nodes. Two different treatment techniques, an SSD match technique and a geometrically exact isocentric match technique, as routinely applied in the two institutes were examined. The three-dimensional treatment planning system of each institute was used to calculate the dose distribution in the match region of the supraclavicular fields and the two opposing tangential fields. The measured and calculated dose distributions were evaluated and compared along lines in two sagittal planes from the supraclavicular fields down to the tangential fields crossing the match planes. These dose distributions in the match region were extremely dependent on the set-up of the fields.

RESULTS

Although the reproducibility of the film measurements was within 2%, it became clear that the set-up of the fields to achieve a gap of 5 mm, a perfect match or an overlap of 5 mm required a lot of attention, even when using a phantom.

CONCLUSIONS

It can be concluded that in clinical practice, these set-up difficulties do influence the dose distribution in the match region much more than the systematic uncertainties in the dose calculation algorithms of the treatment planning systems and the type of treatment technique.

Respiratory burst activity of phagocytic cells isolated from the mammary glands and blood of camels (Camelus bactrianus)

The oxidative burst activity of phagocytic cells isolated from camel blood and mammary glands was studied using a chemiluminescence (Cl) assay. The polymorphonuclear leucocytes (PMNL) isolated from camel blood mounted a luminol-dependent Cl response upon stimulation with opsonized zymosan or opsonized Staphylococcus aureus. These responses showed an overall similarity to those described in other mammalian species. The leucocytes isolated from the mammary glands mounted Cl responses similar to those observed with blood PMNL but to a lower magnitude. Like the Cl responses of blood cells, the Cl responses induced by mammary gland leucocytes were associated with degranulation and the release of lysosomal enzymes such as myeloperoxidase (MPO).

In vivo determination of the accuracy of field matching in breast cancer irradiation using an electronic portal imaging device

The purpose of this study was to investigate the accuracy of field matching in patients treated by irradiation of the breast and adjacent lymph nodes. Field matching is performed by the radiographers during each session on a match line drawn on the patient's skin. Field edge positions were assessed in the cranial match plane of tangential breast fields and supraclavicular-axillary fields using an electronic portal imaging device and match line markers placed on the skin of the patients. The mean gap/overlap of the four fields for individual patients during each treatment session, derived from 374 marker projections, was +0.5 mm indicating that no systematic gap or overlap was observed. The uncertainty in the position of the four fields with respect to the match plane ranges from 3.1 to 5.1 mm (1 SD) for the individual patients. Gaps and overlaps between fields were also related to an absolute match line position, found by comparison of simulator and portal images, showing a small systematic uncertainty of 2.4 mm and a standard deviation of 3.3 mm. It can be concluded that the use of an electronic portal imaging device in combination with match line markers is a good method to quantify the accuracy of field matching in vivo. The results showed good stability and reproducibility in the field matching region for this treatment technique of breast cancer irradiation.

Isolation and purification of bovine myeloperoxidase from neutrophil granules

Bovine myeloperoxidase (MPO) was isolated and purified from neutrophil granules using protein extraction at pH 4 and gel filtration combined with fast protein liquid chromatography. The extracted protein was identified as MPO based on its absorption spectrum, amino acid composition, peroxidase activity and polypeptide structure. Bovine neutrophils contained three different forms of MPO (I, II and III). When subjected to sodium dodecyl sulphate polyacrylamide gel electrophoresis each of the three purified forms showed two distinct bands corresponding to heavy and light polypeptide chains of approximately 57,000 and 15,000 molecular radius. Amino acid analysis of the three forms showed that there was an overall similarity between them. Slight differences were found between MPO Form III and the other two forms. The three forms of bovine MPO were shown to differ in their specific enzyme activities in a luminol-dependent chemiluminescence assay. MPO Form III showed the highest enzyme activity. The amount recovered during purification of the respective MPO forms varied, with the recovery being highest for MPO I. Our findings suggest that there are intrinsic differences between the three forms of bovine MPO. In terms of their amino acid composition and molecular weight, the bovine MPO closely resembled human and canine MPO.

Species identification and some characteristics of coagulase-negative staphylococci isolated from bovine udders

The species of 203 strains of coagulase-negative staphylococci (CNS), isolated from bovine udder quarters was determined; all were tested for hydrophobicity and encapsulation, attributes that may relate to virulence. Twelve species were identified, of which Staphylococcus simulans, (34.5%), S. chromogenes (16.7%), S. epidermidis (13.8%) and S. xylosus (8.9%) were the most frequent. The majority of strains possessed a hydrophilic cell surface. However, strains from two species (S. chromogenes and S. epidermidis) were more hydrophobic than the others. Only five strains were encapsulated (S. xylosus, 3; S. saprophyticus, 1; and S. sciuri, 1). Judging from the low frequencies of hydrophobic and encapsulated strains, and comparing with strains isolated from clinical cases, it is suggested that these properties are not major virulence determinants of CNS.

Bacteriological investigations of clinical mastitis in heifers in Sweden

Bacterial analyses were carried out of 2069 udder secretions, isolated from 1481 heifers with mastitis in eight veterinary districts in Sweden. Streptococci, e.g. Streptococcus dysgalactiae and Str. uberis, dominated the bacterial flora, being isolated from 34.4 and 19.5% respectively of heifers with clinical mastitis occurring from puberty up to 14 d post partum. Bacterial species generally regarded as important pathogens in the summer mastitis complex, e.g. Actinomyces pyogenes, Stuart-Schwan coccus and strictly anaerobic bacteria such as Peptostreptococcus indolicus, Fusobacterium necrophorum and Bacteroides melaninogenicus were isolated at low frequencies (13.2, 6.3, 9.4, 3.8 and 1.3% respectively). When the cases of mastitis studied were restricted to those appearing in heifers pre partum, May 15 to October 14 (summer mastitis), these bacterial species were isolated at higher percentages (27.1, 14.4, 21.4, 13.5 and 5.2% respectively). These figures were, nevertheless, still lower than those published in reports from other countries. Whether considered up to 14 d post partum or only pre partum, there were no significant differences in the frequencies of A. pyogenes isolated at different seasons. There were geographical differences in bacterial incidence, e.g. Staphylococcus aureus was isolated significantly more often in northern regions whereas Str. dysgalactiae was more common in the south. This and other Swedish investigations support the theory that A. pyogenes and strictly anaerobic bacteria are 'secondary invaders' that depend on Str. dysgalactiae to cause a primary infection. It is stressed that the udders of all heifers should be examined daily so that cases of mastitis can be treated immediately.

Adhesive proteins of haemagglutinating Staphylococcus aureus isolated from bovine mastitis

Two proteins derived from the cell wall of Staphylococcus aureus, exhibiting apparent molecular masses of 116 kDa and 145 kDa, were found to bind to human buccal and bovine lactiferous sinus epithelial cells. By using antibodies specific for fibronectin-binding protein of S. aureus of human origin, the 116 kDa protein, but not the 145 kDa protein, was identified as a fibronectin-binding protein. The 145 kDa protein bound to bovine fat globule membranes, human buccal epithelial cells, bovine lactiferous sinus epithelial cells and sheep erythrocytes. The properties of the 145 kDa protein suggest that it is an adhesin with a possible role in the early stages of the development of bovine mastitis.

Ability of bovine mammary macrophages to enhance proliferation of autologous blood and mammary secretion lymphocytes

Cells were obtained by centrifuging the mammary secretion of healthy udders of 19 cows during the dry-period and during mid-lactation. The suspended cells were incubated in plastic wells. Those adhered cells classified as mammary macrophages were incubated with pokeweed mitogen (PWM). Autologous peripheral blood lymphocytes were added to wells containing untreated macrophage cultures or cultures pretreated with PWM. In seven cows autologous dry-period mammary lymphocytes were added instead of blood lymphocytes. The macrophages + lymphocyte cultures were subjected to the lymphocyte stimulation test (LST). For comparison, peripheral blood lymphocytes and dry-period secretion lymphocytes were also subjected to the LST in the presence of PWM. In all cases, mitogenic responses were higher in pretreated macrophage cultures than in background control cultures. The stimulation indices (SI) showed that PWM-pretreated dry-period mammary macrophages enhanced the proliferation of autologous peripheral blood lymphocytes to a greater extent than did blood lymphocytes plus PWM (49 +/- 10 v. 30 +/- 6; P less than or equal to 0.05). Mammary macrophages taken from the same cows but during midlactation also clearly induced proliferation of autologous peripheral blood lymphocytes but to a lesser extent than dry-period macrophages (16 +/- 2 v. 49 +/- 10; 16 +/- 2 v. 30 +/- 6; P less than or equal to 0.01 and P less than or equal to 0.05). The PWM pretreatment of mammary macrophages increased the proliferation of autologous dry-period mammary lymphocytes by at least a factor of three (28 +/- 8 v. 8 +/- 2 P less than or equal to 0.05). The present results indicate that bovine mammary macrophages pretreated with PWM enhance proliferation as well as modulation of mammary and peripheral blood lymphocytes. The modulation of lymphocyte stimulation as demonstrated here in vitro, has great significance regarding aspects of local immunostimulation related to modern treatment of mastitis.