Moving beyond quality control in diagnostic radiology and the role of the clinically qualified medical physicist.

Quality control (QC), according to ISO definitions, represents the most basic level of quality. It is considered to be the snapshot of the performance or the characteristics of a product or service, in order to verify that it complies with the requirements. Although it is usually believed that "the role of medical physicists in Diagnostic Radiology is QC", this, not only limits the contribution of medical physicists, but is also no longer adequate to meet the needs of Diagnostic Radiology in terms of Quality. In order to assure quality practices more organized activities and efforts are required in the modern era of diagnostic radiology. The complete system of QC is just one element of a comprehensive quality assurance (QA) program that aims at ensuring that the requirements of quality of a product or service will consistently be fulfilled. A comprehensive Quality system, starts even before the procurement of any equipment, as the need analysis and the development of specifications are important components under the QA framework. Further expanding this framework of QA, a comprehensive Quality Management System can provide additional benefits to a Diagnostic Radiology service. Harmonized policies and procedures and elements such as mission statement or job descriptions can provide clarity and consistency in the services provided, enhancing the outcome and representing a solid platform for quality improvement. The International Atomic Energy Agency (IAEA) promotes this comprehensive quality approach in diagnostic imaging and especially supports the field of comprehensive clinical audits as a tool for quality improvement.

Cobalt-60 Machines and Medical Linear Accelerators: Competing Technologies for External Beam Radiotherapy.

Medical linear accelerators (linacs) and cobalt-60 machines are both mature technologies for external beam radiotherapy. A comparison is made between these two technologies in terms of infrastructure and maintenance, dosimetry, shielding requirements, staffing, costs, security, patient throughput and clinical use. Infrastructure and maintenance are more demanding for linacs due to the complex electric componentry. In dosimetry, a higher beam energy, modulated dose rate and smaller focal spot size mean that it is easier to create an optimised treatment with a linac for conformal dose coverage of the tumour while sparing healthy organs at risk. In shielding, the requirements for a concrete bunker are similar for cobalt-60 machines and linacs but extra shielding and protection from neutrons are required for linacs. Staffing levels can be higher for linacs and more staff training is required for linacs. Life cycle costs are higher for linacs, especially multi-energy linacs. Security is more complex for cobalt-60 machines because of the high activity radioactive source. Patient throughput can be affected by source decay for cobalt-60 machines but poor maintenance and breakdowns can severely affect patient throughput for linacs. In clinical use, more complex treatment techniques are easier to achieve with linacs, and the availability of electron beams on high-energy linacs can be useful for certain treatments. In summary, there is no simple answer to the question of the choice of either cobalt-60 machines or linacs for radiotherapy in low- and middle-income countries. In fact a radiotherapy department with a combination of technologies, including orthovoltage X-ray units, may be an option. Local needs, conditions and resources will have to be factored into any decision on technology taking into account the characteristics of both forms of teletherapy, with the primary goal being the sustainability of the radiotherapy service over the useful lifetime of the equipment.

Medical Physics Challenges for the Implementation of Quality Assurance Programmes in Radiation Oncology.

The importance of quality assurance in radiation therapy, as well as its positive consequences on patient treatment outcome, is well known to radiation therapy professionals. In low- and middle-income countries, the implementation of quality assurance in radiation therapy is especially challenging, due to a lack of staff training, a lack of national guidelines, a lack of quality assurance equipment and high patient daily throughput. According to the International Atomic Energy Agency (IAEA) Directory of Radiotherapy Centres, the proportion of linear accelerators compared with Co-60 machines has increased significantly in recent years in low- and middle-income countries. However, this increase in the proportion of relatively more demanding technology is not always accompanied with the necessary investment in staff training and quality assurance. The IAEA provides supports to low- and middle-income countries to develop and strengthen quality assurance programmes at institutional and national level. It also provides guidance, through its publications, on quality assurance and supports implementation of comprehensive clinical audits to identify gaps and makes recommendations for quality improvement in radiation therapy. The new AAPM TG100 report suggests a new approach to quality management in radiation therapy. If implemented, it will lead to improved cost-effectiveness of radiation therapy in all income settings. Low- and middle-income countries could greatly benefit from this new approach as it will help direct their scarce resources to areas where they can produce the optimum impact on patient care, without compromising patient safety.

Poster - Thur Eve - 46: The upcoming international code of practice for small static photon field dosimetry.

The increased use of small photon fields in stereotactic and intensity-modulated radiotherapy has raised the need for standardizing the dosimetry of such fields using procedures consistent with those for conventional radiotherapy. An international working group, established by the IAEA in collaboration with AAPM and IPEM, is finalising a Code of Practice for the dosimetry of small static photon fields. Procedures for reference dosimetry in nonstandard machine specific reference (msr) fields are provided following the formalism of Alfonso et al. (Med. Phys. 35: 5179; 2008). Reference dosimetry using ionization chambers in machines that cannot establish a conventional 10 cm × 10 cm reference field is based on either a direct calibration in the msr field traceable to primary standards, a calibration in a reference field and a generic correction factor or the product of a correction factor for a virtual reference field and a correction factor for the difference between the msr and virtual fields. For the latter method, procedures are provided for determining the beam quality in non-reference conditions. For the measurement of field output factors in small fields, procedures for connecting large field measurements using ionization chambers to small field measurements using high-resolution detectors such as diodes, diamond, liquid ion chambers, organic scintillators and radiochromic film are given. The Code of Practice also presents consensus data on correction factors for use in conjunction with measured, detector-specific output factors. Further research to determine missing data according to the proposed framework will be strongly encouraged by publication of this document.

Establishing measurement traceability for national laboratories: Results of an IAEA comparison of (131)I.

A radioactivity measurement comparison for solutions of (131)I was conducted by the International Atomic Energy Agency for participants in one of its Cooperative Research Projects aimed at enhancing quality assurance practices in nuclear medicine. The comparison solutions were prepared from a single master stock solution and distributed to the participating laboratories, who measured the activity concentration of the solution using either the laboratory's radionuclide activity calibrator or primary standardization methods. From the 7 results received, a Comparison Reference Value was calculated to be 37.35(78)MBqg(-1) at the reference time. Degrees of equivalence, as defined by the Mutual Recognition Agreement (MRA) of the Comité International des Poids et Mesures (CIPM), were calculated for each laboratory, demonstrating that equivalence to within +/-4% could be achieved. The comparison has been registered as a supplementary comparison with the CIPM, Consultative Committee for Ionizing Radiation, Section II-measurement of radionuclides (CCRI(II)) for the purposes of allowing the participants to establish traceability to international standards for this radionuclide.

Results of the regional intercomparison exercise for the determination of operational quantity HP(10) in Latin America.

Several intercomparison exercises were organised by the International Atomic Energy Agency (IAEA) on the determination of operational quantities at the regional or interregional basis. In the Latin American region an intercomparison for the determination of the operational quantity Hp(10) was completed mid-2004, as a follow-up to previous exercises carried out during the 1990s. Eighteen individual external monitoring services from nineteen Member States participated in the first phase. The second phase grouped 15 services that had participated in the first phase. Dosemeter irradiations in photon beams were done by four Secondary Standard Dosimetry Laboratories (SSDLs) of the region. The preparation of this exercises involved an audit by the IAEA SSDL, where reference irradiations were provided to all participants for verification of their systems. During the first phase (2002-2003) only 9 out of 18 services met the performance requirements for such monitoring services. Necessary corrective actions and procedure verification were implemented. During the second phase (2004) 11 out of 15 services fulfilled the performance criteria. This intercomparison shows that there has been improvement in the second phase and most participants demonstrated a satisfactory performance of the quantity tested.

The Third International Intercomparison on EPR Tooth Dosimetry: part 2, final analysis.

The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.

The 3rd international intercomparison on EPR tooth dosimetry: Part 1, general analysis.

The objective of the 3rd International Intercomparison on Electron Paramagnetic Resonance (EPR) Tooth Dosimetry was the evaluation of laboratories performing tooth enamel dosimetry below 300 mGy. Participants had to reconstruct the absorbed dose in tooth enamel from 11 molars, which were cut into two halves. One half of each tooth was irradiated in a 60Co beam to doses in the ranges of 30-100 mGy (5 samples), 100-300 mGy (5 samples), and 300-900 mGy (1 sample). Fourteen international laboratories participated in this intercomparison programme. A first analysis of the results and an overview of the essential features of methods applied in different laboratories are presented. The relative standard deviation of results of all methods was better than 27% for applied doses in the range of 79-704 mGy. In the analysis of the unirradiated tooth halves 8% of the samples were identified as outliers with additional absorbed dose above background dose.

IAEA TLD based audits for radiation protection calibrations at Secondary Standard Dosimetry Laboratories. International Atomic Energy Agency.

The IAEA has developed a TLD system with the aim of checking 137Cs radiation protection calibrations provided by the Secondary Standard Dosimetry Laboratories (SSDLs). The SSDLs are supplied with TLDs and they are asked to irradiate them at 5 mGy air kerma. The dosemeters are evaluated by the IAEA. The routine service was established in 1999. The service is organised in two runs per year. Each run involves 15 laboratories. The results of two pilot studies (1997-1998) and audits (1999-2000) are presented. They show that about 30% of the results are outside the acceptance limit of +/-3.5%. This limit has been set up as an acceptable deviation and is based on the value of the relative standard uncertainty of the TL measurements, evaluated at 1.8%. Participants with results outside the acceptance limit were approached with the aim to resolve discrepancies.

Calibration of plane parallel ionization chambers: a new service for secondary standard dosimetry laboratories?

This paper presents the results of calibration of PTW Markus and NACP ionization chambers following the procedures outlined in the TRS 381 International Atomic Energy Agency code of practice. According to this dosimetry protocol, calibration of plane parallel chambers follows 2 methods. The first method uses a high-energy electron beam and consists of comparing the plane parallel chamber with a cylindrical chamber whose N(D,air) calibration factor, traceable to cobalt-60 (60Co), is known, while the second method applies to a 60Co gamma beam whose air kerma rate is known at the calibration point. As the second method is generally applied in Secondary Standard Dosimetry Laboratories, the consistency of calibrations free in-air and in a water phantom has been studied. A close agreement is shown between the 2 methods (the calibration factors differ by at most 0.98%). These results lead to the conclusion that either of the 2 calibration methods can be used, provided that the correction factors given by the TRS 381 code of practice are applied.

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.