3.232.
Paragraph 3.170 of GSR Part 3 [3] requires that radiology facilities have in place a comprehensive programme of quality assurance for medical exposures. General guidance on the management system is given in paras 2.138–2.149, and it is reiterated here that the programme of quality assurance for medical exposures should fit in with, and be part of, the wider management system at the facility.
3.233.
The purpose of the programme of quality assurance for medical exposures is to help to ensure successful optimization of protection and safety in the radiology facility and to minimize the occurrence of unintended and accidental medical exposures.
3.234.
The complexity of the programme of quality assurance for medical exposures will depend on the type of facility. A dental practice with only intraoral radiography will have a simpler programme compared with a facility that offers all modalities of diagnostic radiology as well as image guided interventional procedures. Nonetheless, most of the elements of the programme are common, and it is more in the degree of application that there are differences. Paragraph 3.171 of GSR Part 3 [3] establishes the common elements of the programme.
3.235.
Measurements on medical radiological equipment are one of the components of the comprehensive programme of quality assurance. Acceptance tests are required for new or significantly refurbished or repaired equipment, or after the installation of new software or modification of existing software that could affect protection and safety. The acceptance test should be followed immediately by commissioning, and then ongoing periodic quality control tests, including constancy tests. The purpose is to ensure that, at all times, all medical radiological equipment performs correctly, accurately, reproducibly and predictably. Acceptance and commissioning tests should be performed in the same way for equipment and software that has been donated.
3.236.
Depending on the equipment purchase agreement, acceptance tests can be performed by the manufacturer in the presence of the local medical physicist and the radiological medical practitioner representing the user, or, if acceptable to the manufacturer and the purchaser, by a medical physicist jointly with the manufacturer. The process should involve verification of all specifications and features of the equipment.
3.237.
After acceptance and before clinical use on patients, commissioning should be carried out by, or under the supervision of, the medical physicist. Commissioning should include measurements of all parameters and conditions of use that are expected in clinical use, including setting up and validating image acquisition protocols. For most modalities (CT, image guided interventional procedures, tomosynthesis, mammography, radiography and fluoroscopy), the medical physicist should be directly involved in the measurements, calculations and interpretation of data to characterize the equipment’s performance. For the least complex modalities (dental radiography and DXA), the medical physicist should provide documented advice on how the commissioning should be performed. During commissioning, the baseline for subsequent constancy tests is established.
3.238.
In addition to the acceptance testing and commissioning, para. 3.171 of GSR Part 3 [3] requires, periodically and after any major maintenance procedure or upgrade, the measurement of physical parameters of medical radiological equipment. There are many published reports from international and national organizations and national and regional professional bodies giving detailed guidance on the performance tests and quality control tests that should be performed on the various modalities, including recommended frequencies (see Refs [104, 105, 109–114, 156, 161, 166, 167, 170–173, 181–201]). In addition, many of these organizations and professional bodies publish on their web sites new or updated publications on the topic. The regulatory body may have its own specific requirements for the tests that should be performed, their frequencies and the competence of the specialists involved. Such specific requirements should be established with consultation between the regulatory body and the relevant professional bodies.
3.239.
While traditional approaches to constancy testing are based on measurements of technical parameters for the system or using test objects and phantoms, it is likely that in the future clinically derived data could be used in the monitoring of equipment and in ensuring consistency in clinical practice. For example, a particular region of an anatomical image could be analysed to produce an index of noise performance.
3.240.
Quality control tests should also be performed on other equipment or devices that have an impact on the successful outcome of the radiological procedure. Such equipment and devices include, but are not limited to: film processors, darkrooms and cassettes for facilities using film based imaging; flat detectors for DR systems; CR imaging plates and CR readers for facilities with CR systems; and view boxes, workstations, and display and interpretation rooms. Many of the references given in para. 3.238 are applicable here.
3.241.
The results of the quality control tests should be compared with established tolerance limits. These limits may have been established to ensure compliance with a regulatory requirement for the performance of particular physical parameters or they may be set on the basis of recommended values given in published reports, such as those referenced in para. 3.238. Paragraph 3.171(b) of GSR Part 3 [3] requires the implementation of corrective actions if the measured values fall outside established tolerance limits. Such corrective actions are likely to include maintenance or servicing of the equipment, and hence a preventive maintenance programme should be put in place at the radiology facility. In some cases, the equipment might be outside the tolerance limits by a significant amount and the equipment should be immediately taken out of clinical use and not returned until servicing has taken place and it has been ascertained that the equipment now meets the performance requirements.
3.242.
The programme of quality assurance for medical exposures in the radiology facility should include the use of checks to ensure that the facility’s protocols and procedures for imaging and interventional procedures, including radiation protection and safety, are being followed. The periodic review of the protocols and procedures themselves is part of the radiological review at the facility (see paras 3.269–3.271). In addition, a review of imaging procedures may have been triggered by a comparison with DRLs (see paras 3.224–3.231).
3.243.
As part of the programme of quality assurance for medical exposure, ‘repeat and reject analysis’ should be performed on a periodic basis. Further guidance is given in Refs [48, 111, 153].
3.244.
Paragraph 3.171(e) of GSR Part 3 [3] specifically requires that periodic checks of the calibration and conditions of operation of dosimetry equipment and monitoring equipment be part of the programme of quality assurance. This is to ensure that such instrumentation has a current calibration, typically conducted within the last two years (see para. 3.206), and that it is functioning correctly. The programme of quality assurance for medical exposures should establish a frequency for calibration for each instrument and a set of quality control checks on the operation of each instrument to be performed at set intervals. This applies to stand alone dosimetry equipment and to dosimeters integrated into the medical radiological equipment, such as air kerma–area product meters in fluoroscopic systems, and to software of the medical radiological equipment itself that calculates, displays and reports dose metrics such as CT air kerma index and air kerma–length product in CT and reference air kerma at the patient entrance reference point in image guided interventional procedures. Phantoms used in quality assurance and dosimetry should fulfil the requirements specified in the corresponding international standards.
3.245.
Maintaining records is a crucial aspect of the programme of quality assurance for medical exposures. This includes the procedures used in the programme and the results of the quality control tests, the dosimetry surveys, the DRL comparisons, the corrective actions, and the investigations of unintended and accidental medical exposures. When planning and developing an effective programme of quality assurance, the licensee should recognize that it demands strong managerial commitment and support in the form of training and allocation of time, personnel and equipment resources. The regulatory body, in its inspections of a radiology facility, should review the records of the programme of quality assurance for medical exposures.
3.246.
In line with standard practices for quality management, para. 3.172 of GSR Part 3 [3] requires that “regular and independent audits are made of the programme of quality assurance for medical exposures, and that their frequency is in accordance with the complexity of the radiological procedures being performed and the associated risks.” Such audits may be external audits or internal audits. Internal audits are usually logistically simpler to conduct, while an external audit generally has the advantage of bringing in an outside perspective. The audit of the programme of quality assurance for medical exposures can be incorporated into more comprehensive audits of the management system performed by the licensee. Furthermore, the results of the audit of the programme of quality assurance for medical exposures will be a major input into the radiological review performed at the facility (see paras 3.269–3.271).