Ahmed Meghzifene

Detector to detector corrections: a comprehensive experimental study of detector specific correction factors for beam output measurements for small radiotherapy beams

PURPOSE The aim of the present study is to provide a comprehensive set of detector specific correction factors for beam output measurements for small beams, for a wide range of real time and passive detectors. The detector specific correction factors determined in this study may be potentially useful as a reference data set for small beam dosimetry measurements. METHODS Dose response of passive and real time detectors was investigated for small field sizes shaped with a micromultileaf collimator ranging from 0.6 × 0.6 cm(2) to 4.2 × 4.2 cm(2) and the measurements were extended to larger fields of up to 10 × 10 cm(2). Measurements were performed at 5 cm depth, in a 6 MV photon beam. Detectors used included alanine, thermoluminescent dosimeters (TLDs), stereotactic diode, electron diode, photon diode, radiophotoluminescent dosimeters (RPLDs), radioluminescence detector based on carbon-doped aluminium oxide (Al2O3:C), organic plastic scintillators, diamond detectors, liquid filled ion chamber, and a range of small volume air filled ionization chambers (volumes ranging from 0.002 cm(3) to 0.3 cm(3)). All detector measurements were corrected for volume averaging effect and compared with dose ratios determined from alanine to derive a detector correction factors that account for beam perturbation related to nonwater equivalence of the detector materials. RESULTS For the detectors used in this study, volume averaging corrections ranged from unity for the smallest detectors such as the diodes, 1.148 for the 0.14 cm(3) air filled ionization chamber and were as high as 1.924 for the 0.3 cm(3) ionization chamber. After applying volume averaging corrections, the detector readings were consistent among themselves and with alanine measurements for several small detectors but they differed for larger detectors, in particular for some small ionization chambers with volumes larger than 0.1 cm(3). CONCLUSIONS The results demonstrate how important it is for the appropriate corrections to be applied to give consistent and accurate measurements for a range of detectors in small beam geometry. The results further demonstrate that depending on the choice of detectors, there is a potential for large errors when effects such as volume averaging, perturbation and differences in material properties of detectors are not taken into account. As the commissioning of small fields for clinical treatment has to rely on accurate dose measurements, the authors recommend the use of detectors that require relatively little correction, such as unshielded diodes, diamond detectors or microchambers, and solid state detectors such as alanine, TLD, Al2O3:C, or scintillators.

Radiation therapy in Africa: distribution and equipment

BACKGROUND AND PURPOSE Africa is the least developed continent as regards radiation oncology resources. The documented ASR of cancer is of the order of 1 to 2 per 1000. With improving health care this is becoming more significant. This review was undertaken to help develop priorities for the region. MATERIALS AND METHODS Radiation Oncology departments in Africa were identified and a survey of their equipment performed. These were compared to the reported situation in 1991. Population tables for the year 2000 were compared to available megavoltage machines. RESULTS Of 56 countries in Africa, only 22 are confidently known to have megavoltage therapy concentrated in the southern and northern extremes of the continent. The 155 megavoltage machines operating represents over 100% increase over the past 8 years. The population served by each megavoltage machine ranges from 0.6 million to 70 million per machine. Overall, only 50% of the population have some access to Radiation Oncology services. CONCLUSION Progress has been made in initiating radiation oncology in Ghana, Ethiopia and Namibia. There has been some increase in machines in Algeria, Egypt, Libya, Morocco and Tunisia. However, a large backlog exists for basic radiation services.

Safety in radiation oncology: the role of international initiatives by the International Atomic Energy Agency.

The International Atomic Energy Agency (IAEA) has a wide range of initiatives that address the issue of safety. Quality assurance initiatives and comprehensive audits of radiotherapy services, such as the Quality Assurance Team for Radiation Oncology, are available through the IAEA. Furthermore, the experience of the IAEA in thermoluminescence dosimetric audits has been transferred to the national level in various countries and has contributed to improvements in the quality and safety of radiotherapy. The IAEA is also involved in the development of a safety reporting and analysis system (Safety in Radiation Oncology). In addition, IAEA publications describe and analyze factors contributing to safety-related incidents around the world. The lack of sufficient trained, qualified staff members is addressed through IAEA programs. Initiatives include national, regional, and interregional technical cooperation projects, educational workshops, and fellowship training for radiation oncology professionals, as well as technical assistance in developing and initiating local radiation therapy, safety education, and training programs. The agency is also active in developing staffing guidelines and encourages advanced planning at a national level, aided by information collection systems such as the Directory of Radiotherapy Centers and technical cooperation project personnel planning, to prevent shortages of staff. The IAEA also promotes the safe procurement of equipment for radiation therapy centers within a comprehensive technical cooperation program that includes clinical, medical physics, and radiation safety aspects and review of local infrastructure (room layout, shielding, utilities, and radiation safety), the availability of qualified staff members (radiation oncologists, medical physicists, and radiation technologists and therapists), as well as relevant imaging, treatment planning, dosimetry, and quality control items. The IAEA has taken the lead in developing a comprehensive program that addresses all of these areas of concern and is actively contributing to the national and international efforts to make radiation therapy safer in all settings, including resource-limited settings.

Dosimetry in diagnostic radiology.

Dosimetry is an area of increasing importance in diagnostic radiology. There is a realisation amongst health professionals that the radiation dose received by patients from modern X-ray examinations and procedures can be at a level of significance for the induction of cancer across a population, and in some unfortunate instances, in the acute damage to particular body organs such as skin and eyes. The formulation and measurement procedures for diagnostic radiology dosimetry have recently been standardised through an international code of practice which describes the methodologies necessary to address the diverging imaging modalities used in diagnostic radiology. Common to all dosimetry methodologies is the measurement of the air kerma from the X-ray device under defined conditions. To ensure the accuracy of the dosimetric determination, such measurements need to be made with appropriate instrumentation that has a calibration that is traceable to a standards laboratory. Dosimetric methods are used in radiology departments for a variety of purposes including the determination of patient dose levels to allow examinations to be optimized and to assist in decisions on the justification of examination choices. Patient dosimetry is important for special cases such as for X-ray examinations of children and pregnant patients. It is also a key component of the quality control of X-ray equipment and procedures.

International Conference on Advances in Radiation Oncology (ICARO): Outcomes of an IAEA Meeting

The IAEA held the International Conference on Advances in Radiation Oncology (ICARO) in Vienna on 27-29 April 2009. The Conference dealt with the issues and requirements posed by the transition from conventional radiotherapy to advanced modern technologies, including staffing, training, treatment planning and delivery, quality assurance (QA) and the optimal use of available resources. The current role of advanced technologies (defined as 3-dimensional and/or image guided treatment with photons or particles) in current clinical practice and future scenarios were discussed.ICARO was organized by the IAEA at the request of the Member States and co-sponsored and supported by other international organizations to assess advances in technologies in radiation oncology in the face of economic challenges that most countries confront. Participants submitted research contributions, which were reviewed by a scientific committee and presented via 46 lectures and 103 posters. There were 327 participants from 70 Member States as well as participants from industry and government. The ICARO meeting provided an independent forum for the interaction of participants from developed and developing countries on current and developing issues related to radiation oncology.

The radiation overexposure of radiotherapy patients in Panama 15 June 2001.

The IAEA received a request for assistance from the Panamanian Government to investigate a radiation overexposure at a radiotherapy facility in the National Oncology Institute in Panama City affecting 28 patients undergoing radiotherapy to the pelvic area. Advisory information was released by the IAEA at different stages, following the notification of the event, to the Contact Points (Identified under the Convention on Early Notification of a Nuclear Accident and the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency (‘Assistance Convention’)). The purpose of this rapid communication is to inform the medical community of the event and call for the establishment of and adherence to a quality assurance programme, as an absolute necessity, to avoid such events occurring in the future. An international team composed of experts in radiopathology, radiotherapy, radiology, medical physics and radiation protection was sent by the IAEA to assist the Panamanian government under the auspices of the Assistance Convention. The experts performed a detailed review of the radiotherapy practices at the National Oncology Institute. They found that the radiotherapy equipment had been working properly and had been adequately calibrated; they verified the radiotherapy beam output with independent measurements using a calibrated ionization chamber and following the IAEA Code of Practice TRS-277 [1]. The experts reviewed the treatment planning process and confirmed that the cause of the overexposure lay with the entering of data into the 2-D computerized treatment planning system (TPS), specifically with the procedure for outlining shielding blocks. Until August 2000 the practice had been to enter block co-ordinates in separate data batches for each individual block, used for a complex field shaped with blocks. Unfortunately, the TPS in question has a limitation on the number of shielding blocks that can be used for a blocked field. It was reported that the practice at the facility had changed starting from August 2000 in order to overcome this limitation for those fields that require more shielding blocks than the system allows. For the 28 patients affected, block outlining was done by looping all the blocks as if they were a single block of complex shape. The TPS accepted the unorthodox way of block outlining without any warning or error message. This resulted in the incorrect calculation of radiation doses and, consequently, incorrect treatment times. The team found that, of the different possible methods for outlining complex blocked fields, all were handled correctly by the TPS except for the method used for the 28 patients in question; this method alone caused incorrect dose calculations. Unfortunately, the TPS produced a printout that showed the treatment field and the shielding blocks as if the data had been entered correctly. Although for a single blocked field the isodose curves showed differences compared to the expected dose distributions derived from BJR-25 [2], for multiple treatment fields with beam modifiers the differences were not obvious. These factors, together with an apparent omission of (i) manual checking of computer calculations, and (ii) verifying the new planning procedure by ion chamber measurements in a phantom, resulted in the patients being exposed at radiation levels that were set too high. The IAEA team was informed that, of the 28 patients affected, eight have since died; and the team confirmed that five of these deaths are probably attributable to the patients’ overexposure to radiation. Of the other three deaths, one is considered to have been related to the patient’s cancer, while there is insufficient information available to draw conclusions in respect of the remaining two deaths. Of the surviving 20 patients, most injuries are related to the bowel, with a number of patients suffering persistent bloody diarrhoea, necrosis (tissue death), ulceration and anaemia. About three-quarters of the surviving 20

A call for recognition of the medical physics profession.

Medical physics is the science that deals with the application of physical principles to medicine, especially in the prevention, diagnosis, and treatment of disease. As discussed in an accompanying Series in The Lancet, medical physics has an important role in clinical medicine, and in biological and medical research. In the context of radiation technology, medical physics includes subspecialties, such as radiotherapy, diagnostic radiology, nuclear medicine, and radiation protection. The scope of a medical physicist’s duties covers a wide range of activities in hospitals in which radiation technology is used. As part of a team of health professionals, medical physicists have a central role in assuring the safe and eff ective use of radiation. In each subdiscipline, medical physicists are heavily involved in the design of facilities, and in the purchase and implementation of new technologies. Quality control and radiation safety for patients, staff , and the general public are major responsibilities. All these activities rely on an in-depth understanding of radiation physics principles and radiation technology. Thanks to the results of medical physics research, radiation technology has advanced substantially in the past decade. However, because of the highly specialised nature of medical physics, and the relatively small numbers of medical physicists, the scope of their work is not always well defi ned, nor well understood, by health-care professionals and health authorities worldwide. Much needs to be done to ensure full recognition of medical physics as a profession, especially in some regions of the world. I draw this conclusion after 14 years of work in dosimetry and medical radiation physics, at the International Atomic Energy Agency’s Division of Human Health. During this time, I visited many hospitals, and met hospital directors and offi cials from health ministries. I also organised and attended meetings with medical physics professional societies, and with medical physicists working in clinical environments and academia. In the USA and Canada and some countries in western Europe, medical physics is fully recognised as a profession; however, this is not the case in most other countries. A major contributing factor to the absence of professional recognition is the omission of an appropriate listing for medical physicists in the international list of occupations known as the International Standard Classifi cation of Occupations. In many countries where the profession is not offi cially recognised, the recruitment and employment of medical physicists are often listed under various other designations, such as technician, bio-medical engineer, or research assistant. The inadequate recognition of medical physicists has a direct eff ect on their socioeconomic and professional role in health-care teams. dropped in the 1980s, although physics remains part of the medical degree syllabus elsewhere in Europe. In the UK today, we have reversed the long-term decline in the number of students taking A level Physics or the equivalent, with a steady year-on-year increase since 2007. Record numbers of qualifi ed physicists are entering teacher training, with the prospect—albeit some years in the future—that all parts of the UK will have enough specialist physics teachers to ensure that every child has access to a high quality physics education. Against this background, I would ask UK medical schools to consider restoring the requirement for applicants to hold Physics A level or equivalent qualifi cations. The Lancet’s Physics and Medicine Series clearly shows the potential to diagnose and treat increasing numbers of patients, with increasing eff ectiveness, using physicsbased techniques. Understanding the physics that underpins these techniques would be a real advantage to medical practitioners, and to their patients.

Towards better and safer use of radiation in medicine

Radiation is indispensable in modern health care and saves lives. Many applications have evolved that use radiation for diagnosis and treatment, which are less invasive and have lower morbidity and mortality than other techniques. New technology and innovative ideas have also increased radiation safety. However, users of radiation in medicine must consider carefully the potential side-eff ects, such as cancer risks, especially in children. Every year, about 3600 million diagnostic radiology procedures are done worldwide. In the USA, more than 500 million imaging tests are done, with CT being the major source of radiation exposure. The increase in use of CT is due to appropriate and inappropriate reasons. Expanded indications, patients’ demand, defensive medicine, self-referral, industry marketing, and wellness screening all play a part. As many as 20 million adults and more than a million children could have been exposed to CT examinations unnecessarily in the USA per year. One study of 148 988 patients showed that 77% of lumbar spine, 36% of head, and 37% of abdominal CT examinations in individuals younger than 35 years were not justifi ed. Most of these examinations could have been replaced by MRI, if accessible, whereas some patients did not need any radiological examination. Health professionals need guidance on appropriate use of radiation and information about radiation protection and ethical issues. Would MRI or ultrasound be better, safer, or more appropriate than CT? Do the benefi ts of CT outweigh the potential radiation risks? For management The Paris Declaration has been signed but the problem now lies in getting donors to practise what they preach. Bilateral donors are clinging to funding disease-specifi c programmes, and skewing health fi nancing towards their interests not only in donor-dependent countries in sub-Saharan Africa but also in more independent countries such as Brazil and India. Countries that have improved their management systems for public expenditure are still not receiving more budget support. In Ghana, for example, an increase in the quality of such management systems has been accompanied by an 11% decrease in the use of these systems. In the debate about how to channel health aid, the behaviour of donors has to be taken into account. So too does the diffi cult question of who should decide about, and take responsibility for, how public funding is allocated within a country. We commend Lu and colleagues for presenting an important paper on fungibility and development assistance. Their evidence provokes profound questions about who, in practice, is the most accountable and eff ective recipient of health funding. We underscore their calls for more research into this vital question.

Accuracy requirements and uncertainties in radiotherapy: a report of the International Atomic Energy Agency

Abstract Background: Radiotherapy technology continues to advance and the expectation of improved outcomes requires greater accuracy in various radiotherapy steps. Different factors affect the overall accuracy of dose delivery. Institutional comprehensive quality assurance (QA) programs should ensure that uncertainties are maintained at acceptable levels. The International Atomic Energy Agency has recently developed a report summarizing the accuracy achievable and the suggested action levels, for each step in the radiotherapy process. Overview of the report: The report seeks to promote awareness and encourage quantification of uncertainties in order to promote safer and more effective patient treatments. The radiotherapy process and the radiobiological and clinical frameworks that define the need for accuracy are depicted. Factors that influence uncertainty are described for a range of techniques, technologies and systems. Methodologies for determining and combining uncertainties are presented, and strategies for reducing uncertainties through QA programs are suggested. The role of quality audits in providing international benchmarking of achievable accuracy and realistic action levels is also discussed. Recommendations: The report concludes with nine general recommendations: (1) Radiotherapy should be applied as accurately as reasonably achievable, technical and biological factors being taken into account. (2) For consistency in prescribing, reporting and recording, recommendations of the International Commission on Radiation Units and Measurements should be implemented. (3) Each institution should determine uncertainties for their treatment procedures. Sample data are tabulated for typical clinical scenarios with estimates of the levels of accuracy that are practically achievable and suggested action levels. (4) Independent dosimetry audits should be performed regularly. (5) Comprehensive quality assurance programs should be in place. (6) Professional staff should be appropriately educated and adequate staffing levels should be maintained. (7) For reporting purposes, uncertainties should be presented. (8) Manufacturers should provide training on all equipment. (9) Research should aid in improving the accuracy of radiotherapy. Some example research projects are suggested.

Improving Quality and Access to Radiation Therapy—An IAEA Perspective

The International Atomic Energy Agency (IAEA) has been involved in radiation therapy since soon after its creation in 1957. In response to the demands of Member States, the IAEA׳s activities relating to radiation therapy have focused on supporting low- and middle-income countries to set up radiation therapy facilities, expand the scope of treatments, or gradually transition to new technologies. In addition, the IAEA has been very active in providing internationally harmonized guidelines on clinical, dosimetry, medical physics, and safety aspects of radiation therapy. IAEA clinical research has provided evidence for treatment improvement as well as highly effective resource-sparing interventions. In the process, training of researchers occurs through this program. To provide this support, the IAEA works with its Member States and multiple partners worldwide through several mechanisms. In this article, we review the main activities conducted by the IAEA in support to radiation therapy. IAEA support has been crucial for achieving tangible results in many low- and middle-income countries. However, long-term sustainability of projects can present a challenge, especially when considering health budget constraints and the brain drain of skilled professionals. The need for support remains, with more than 90% of patients in low-income countries lacking access to radiotherapy. Thus, the IAEA is expected to continue its support and strengthen quality radiation therapy treatment of patients with cancer.