Iodine-131 monitoring in sewage plant outflow.

Three different hospital sites (Oxford, Sutton and Guildford) have performed sampling of their local sewage plant outflow to determine levels of radioactivity resulting from iodine-131 patients undergoing radionuclide therapies. It was found that a maximum of 20% of activity discharged from the hospitals was present in the sewage plant final effluent channel. This is significantly below the level predicted by mathematical models in current use. The results further show that abatement systems to reduce public exposure are unlikely to be warranted at hospital sites.

Patient and operator dose during fluoroscopic examination of swallow mechanism.

Dose-area product (DAP) measurements were made for 21 patients undergoing a modified barium swallow. The procedures were performed by a radiologist and speech and language therapist, to characterize swallowing disorders in patients with head or spinal injury, stroke, other neurological conditions or simple globus symptoms, in order to inform feeding strategies. The DAP values were used to estimate effective dose to the patient, in order to provide a measure of the radiation risk associated with the procedure. Whole body doses to operators, together with equivalent doses to extremities and eyes were also measured to inform the employer's risk assessment. Median DAP for the series was 3.5 (3.1-5.2) Gycm(2) with a corresponding effective dose to the patient of 0.85 (0.76-1.3) mSv, and a low associated risk, mainly of cancer induction, of about 1 in 16 000. The organ receiving the greatest dose was the thyroid, with a calculated median equivalent dose of 13.9 (12.3-20.7) mSv. Median screening time was 3.7 (2.5-4.3) min. Mean operator doses were 0.5 mSv equivalent dose (eyes), 0.9 mSv (extremities), and less than 0.3 mSv whole body dose. Extrapolating for an annual workload of 50 patients per year, this work will lead to annual operator doses of less than 0.6 mSv whole body dose, and approximately 1 mSv equivalent dose (eyes) and 1.8 mSv (extremities), against corresponding legal dose limits of 20 mSv, 150 mSv and 500 mSv, respectively.

A low-dose radioisotope procedure for assessment of subcutaneous drug delivery systems used for slow intrathecal infusion of antispasmodic agents.

STUDY DESIGN: Retrospective single centre study. OBJECTIVES: To evaluate a low-dose radioisotope imaging procedure for assessment of implanted intrathecal drug delivery and to compare the radiation dose and diagnostic value of these studies with other reported studies using higher administered radiation dose. SETTING: National Spinal Injuries Centre, Stoke Mandeville Hospital, UK. METHOD: A total of 11 spinally injured patients with subcutaneous drug delivery systems and uncontrolled spasm were investigated for catheter failure using a low-dose radioisotope procedure with an administered dose of radioactivity of 40 MBq Technetium-99m. RESULTS: Loss of catheter patency was demonstrated in six patients, enabling identification of the site of blockage. Catheter patency and subsequent perfusion of CSF (ie normal result) was demonstrated in five patients. Radiation effective dose was estimated at 1.3 mSv per patient study, with a low associated risk of deleterious effect of one in 13,000. CONCLUSION: Radioisotope investigation using a reduced administered dose of 40 MBq Technetium-99m DTPA, formulated according to a strict radiopharmaceutical protocol, provides a safe test for assessment of intrathecal drug delivery systems.

Reducing dose at barium enema: radiographers do it digitally.

It has been previously shown that, whilst radiographers in our hospital can undertake barium enema examinations with the same degree of diagnostic accuracy as consultant radiologists, there was a dose penalty to the patient arising from the use of a restrictive protocol requiring radiographers to take a series of plain radiographs for reporting purposes. For the past 3 years radiographers at this hospital have worked to a new protocol that replaces all routine radiographs with digital spot films. In the present study, dose-area product (DAP) measurements for 801 barium enema examinations performed by consultant radiologists and radiographers, using the revised protocol, were analysed and compared to ascertain whether there were still significant differences in radiation dose to the patient depending on the category of staff performing the examination. All examinations were reported by a consultant radiologist. The radiologists' reports were analysed against the known outcomes to compare the diagnostic accuracy of the examination when carried out by the two categories of staff. This study shows that using a modified protocol, in which digital spot films replace the series of overcouch radiographs for reporting, our radiographers are able to perform barium enemas without dose penalty to the patient, and without compromizing diagnostic accuracy. Means with 95% confidence intervals for DAP in the two groups were 9.8 Gycm(2) (9.4-10.3 Gycm(2)) and 10.7 Gycm(2) (10.2-11.1 Gycm(2)) for radiographers and radiologists, respectively.

A practical approach to the first iteration in the optimization of radiation dose and image quality in CT: estimates of the collective dose savings achieved.

CT is a diagnostic imaging modality giving higher patient dose in comparison with other radiological procedures. It contributed an estimated 20% to the collective effective dose to the UK population from medical X-rays in 1990, rising to an estimated 40% in 1999. Tremendous national effort has been expended in reducing patient doses from other radiological procedures with considerable success, but much of the collective dose reduction achieved has been offset by a corresponding increase in the collective dose from CT. Over a period of about 2 years, following the installation of a helical CT scanner, CT scan parameters in this hospital have been adjusted with the aim of working towards optimization of image quality and patient dose. A 33% reduction in annual collective effective dose has been achieved, from about 16.5 manSv to 11 manSv. However, despite this dose reduction, the annual collective effective dose to our sub-population is 2.8 times the value 9 years ago. The increase is almost entirely the result of an increased application of CT; 6149 examinations per annum in 1999 compared with 2210 in 1991. The crucial importance of reducing patient doses from this modality is discussed. Indicative effective doses and image noise values are presented for examination protocols approaching optimization.

Calibration frequency of dose--area product meters.

Calibration of patient dose monitoring devices in diagnostic radiology has become increasingly important in the light of new legislation that requires monitoring of patient dose against local and national diagnostic reference levels. An investigation was conducted into the long-term stability of 41 dose-area product (DAP) meters over a period of approximately 5 years, to assess the suitability of an annual calibration regimen. For DAP meters fitted to overcouch X-ray tubes, 77% of calibrations were within 10%, whilst for undercouch tubes only 50% of calibrations were within 10%. These findings suggest that annual calibration may be too infrequent. Suitable calibration frequencies for different clinical workloads are discussed.

Dose-area product measurements in a range of common orthopaedic procedures and their possible use in establishing local diagnostic reference levels.

There is a national drive towards establishing reference doses for radiological procedures with the aim of optimizing patient doses. Furthermore, the establishment of diagnostic reference level doses became a legal requirement for all hospitals on 13 May 2000. However, to date there are little published data on patient radiation doses from fluoroscopic procedures during orthopaedic surgery. Data relating to patient dose for 492 patients undergoing fluoroscopic examinations during a range of surgical orthopaedic procedures in 1997-1998 have been analysed. Median dose-area product (DAP) readings and interquartile ranges for a variety of common fluoroscopic orthopaedic procedures are presented. In general, the median DAP for procedures on limbs and extremities was quite low (0.04-1.62 Gy cm2), with screening times in the range 0.2-2.0 min, whilst for procedures involving the hips and spine the median DAP was considerably higher (0.4-10.2 Gy cm2), although overall screening times were similar, in the range 0.2-1.4 min. Approximate effective doses have been estimated. For procedures involving the limbs and extremities, the effective dose was generally less than 10 microSv, and for procedures involving the hips and spine it was found that the effective dose could rise to about 1 mSv. Collective doses for each procedure have been calculated to inform prioritization of procedures for local dose reduction strategies.

Application of regulations to cosmetic lasers in private practice.

Recent years have seen a growth in the number of non-NHS premises, for example beauty salons, offering cosmetic laser treatments such as laser hair removal. By law, such practices are subject to registration and monitoring by Health Authorities. However, a national consensus on appropriate standards is urgently required, particularly on interpretation of the legal requirements for medical direction and operator training, in order to ensure consistency of standards in private practice with lasers across the country. This paper outlines the difficulties experienced in the inspection and registration process, and makes recommendations on appropriate interim standards, pending formal guidance from professional bodies and the promulgation of revised regulations. Until such guidance is in place, it may be wise for Health Authorities to include within their inspection protocols a requirement that applicants for laser registrations produce a statement as to the exact form which medical direction of laser treatment will take, to enable the Health Authority to consider and take advice on its suitability. Similarly a requirement that laser operators are state-registered health professionals will ensure that these potentially hazardous devices are only used by properly qualified operators, whilst professional bodies work towards a consensus on minimum training standards.

Radiation dose and diagnosticity of barium enema examinations by radiographers and radiologists: a comparative study.

With the current emphasis on the extension of the role of the radiographer, radiographers in some hospitals now undertake some of the procedures traditionally performed by radiologists. In the present study, dose-area product (DAP) measurements for over 1000 barium enema examinations performed by radiologists and radiographers were analysed and compared to ascertain whether there were significant differences in the radiation dose to the patient, depending on the category of staff performing the examination. All examinations were reported by a radiologist. The radiologist's reports were analysed against the known outcomes to compare the diagnosticity of the examination when carried out by the two categories of staff. The study shows that although radiographers are able to produce consistent diagnostic results, there is an increase in patient dose due to extra films taken for reporting, which may be difficult to justify. Measures for reducing the dose from this component of the examination were explored.

External radiation protection audit in National Health Service hospitals. Radiation protecgtion advisors (RPA) of the Nottingham City Hospital NHS Trust and the Oxford Radcliffe Hospital NHS Trust.

Radiation protection advisers are accustomed to carrying out internal audit in organizations for which they provide services but, traditionally, external audit has not been a part of the radiation protection adviser function. To provide an external audit function, two teams of radiation protection advisers undertook external radiation protection audits of their respective organizations, including the radiation protection adviser function itself. These audits were more representative of audits or inspections carried out by government agencies, for example the Health and Safety Executive and the former Inspectorate of Pollution, now the Environment Agency. Subsequently, reports, including recommendations for remedial action, were prepared for each management by the external auditors. The process of setting up and carrying out the external audits is described. Guidelines are suggested for those seeking to carry out an external audit.

A comparison of computed tomography practice in 1989 and 1991.

In December 1991, the National Radiological Protection Board (NRPB) published the results of national surveys of the frequency, quality assurance and dosimetric aspects of computed tomography (CT) examinations carried out in hospitals in the UK in 1989. A study of the patient records at two of the original participating hospitals was undertaken to establish whether there had been any change in CT practice between the years 1989 and 1991. Aspects of examination frequency, age distribution and dose were analysed. The results showed significant variations in the patient age distributions between the sub-population studied and the larger sample used by the NRPB, and between the patient age distribution for CT examinations in the years 1989 and 1991 at the two hospitals in this study. The results also showed that in one hospital, where magnetic resonance imaging (MRI) was available and where dose reduction measures had been implemented, there was a net decrease in the collective effective dose from 1989 to 1991, whilst at the other hospital, where MRI was not available and where the introduction of dose saving strategies had been delayed, there was a substantial increase in the collective effective dose from 1989 to 1991. The possibility of continuing increases in the annual collective effective dose attributable to CT underlines the importance of local CT audit to ensure that CT doses are as low as reasonably achievable.

Radiotherapy treatment planning for patients fitted with prostheses.

The effects of prostheses on radiotherapy treatment planning are discussed. The compositions of commonly used materials are tabulated. Sample plots show the size of perturbations produced by typical absorbers at 8 MV. A technique for estimating the density of a prosthesis in a patient is demonstrated and the effects of prostheses on representative radiotherapy plans are illustrated.