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Biomedical subjects

A J Coakley

Publications and source records attributed to A J Coakley.

At least 19 recordsLinked to original sources
PubMed1996

Radiation dose rates from patients receiving iodine-131 therapy for carcinoma of the thyroid.

Patients treated with radioiodine present a radiation hazard and precautions are necessary to limit the radiation dose to family members, nursing staff and members of the public. The precautions advised are usually based on instantaneous dose rates or iodine retention and do not take into account the time spent in close proximity with a patient. We have combined whole-body dose rate measurements taken from 86 thyroid cancer patients after radioiodine administration with published data on nursing and social contact times to calculate the cumulative dose that may be received by an individual in contact with a patient. These dose estimates have been used to calculate restrictions to patients behaviour to limit received doses to less than 1 mSv. We have also measured urinary iodide excretion in 19 patients to estimate the potential risk from the discharge of radioiodide into the domestic drainage system. The dose rate decay was biexponential for patients receiving radioiodine to ablate the thyroid after surgery (the ablation group, A) and monoexponential for these receiving subsequent treatments for residual or recurrent disease (the follow-up group, FU). The faster clearance in the follow-up patients generally resulted in less stringent restrictions than those advised for ablation patients. For typical activities of 1850 MBq for the ablation patients and 3700 MBq or 7400 MBq for the follow-up patients, the following restrictions were advised. Patients could travel in a private car for up to 8h on the day of treatment (for an administered activity of 1850 MBq in group A) or 4 and 2h (for activities of 3700 or 7400 MBq in group FU) respectively. Patients should remain off work for 3 days (1850 MBq/group A) or 2 days (up to 7400 MBq/group FU). Partners should avoid close contact and sleep apart for 16 days (1850 MBq/group A) or 4-5 days (3700 or 7400 MBq/group FU). Contact with children should be restricted according to their age, ranging from 16 days (1850 MBq/group A) or 4-5 days (3700 or 7400 MBq in group FU) for younger children, down to 10 days (1850 MBq/group A) or 4 days (up to 7400 MBq/group FU) for older children. The cumulative dose to nursing staff for the week after treatment was dependent on patient mobility and was estimated at 0.08 mSv for a self-caring patient to 6.3 mSv for a totally helpless patient (1840 MBq/group A). Corresponding doses to nurses looking after patients in group FU were 0.18-12.3 mSv (3700 MBq) or 0.36-24.6 mSv (7400 MBq). Sensible guidelines can be derived to limit the dose received by members of the public and staff who may come into contact with cancer patient treated with radioiodine to less than 1 mSv. The rapid clearance of radioiodine in patients treated on one or more than one occasion means that therapy could be administered at home to selected patients with suitable domestic circumstances. In most cases the restriction times, despite the high administered activities, are less than those for patients treated for thyrotoxicosis. The concentration of radioiodide in domestic drainage systems should not pose a significant risk.

Adult↗
PubMed1996

Assessment of changes in dual-energy X-ray absorptiometry performance following a system upgrade.

System upgrades are a constant feature of many highly technical specialties and are normally assumed to have a negligible effect on patient data. We report on the assessment of an upgrade made to a Norland XR-26 dual-energy X-ray absorptiometry (DXA) system. The upgraded version (2.3) consisted of new hip positioning aids, hip image analysis software and updates to the normal ranges. Measurements of femoral neck and trochanteric bone mineral density correlated well between versions (r = 0.969 and r = 0.971), those for femoral neck and trochanteric bone mineral content less well (r = 0.956 and r = 0.911), and Ward's triangle values and femoral neck area measurements were poorly correlated (r = 0.719-0.881). The upgrade was claimed to improve precision while reducing analysis and imaging time. Improved precision was not demonstrated, with good precision found both before and after the upgrade. Correlation between femoral neck Z-scores were good for the European normal range (r = 0.970), but unacceptable for the UK range (r = 0.769). These correlations were not close enough to allow patients scanned with the old version to be followed up with scans using the upgrade. The upgrade was, however, preferred for new attenders because of the improved speed and automation of hip analysis, without loss of precision. The most important implication in terms of patient management was the change made to the UK normal range, which had a very large effect on the number of patients deemed to be at risk from osteoporosis. It is essential that any upgrade introduced to an existing DXA system is carefully evaluated, since it may affect system performance and patient results.

Absorptiometry, Photon↗
PubMed1995

Ventilation and perfusion lung imaging--which nebulizer?

Three commercially available 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) aerosol delivery nebulizers for lung ventilation imaging were investigated. Two were air-jet systems, 'Optimist' (Medicaid) and 'Microcirrus' (Amersham), and one was an ultrasonic device (Europlus). Altogether, 112 consecutive patients were scanned, 37 using the Optimist, 40 using the Microcirrus and 35 the Europlus. The age mix, FEV1, FVC and PEFR measurements of the patients in each group were similar. Each contained a proportion of patients with poor respiratory function, with PEFR rates ranging from 30 to 582 l min-1 for patients studied with all systems. Ease of use, image quality and cost were evaluated as well as radioactive and microbiological contamination. The Optimist system gave the best combination of image quality and cost, and was associated with the lowest level of radioactive contamination. It also proved the most popular. Airborne contamination for all nebulizers was lower than previously reported and was largely dependent on patient compliance. With poorly compliant patients, the contamination levels are sufficient to warrant an extraction device. There was no evidence of bacterial contamination of the nebulizers or tubing on repeated use over 5 days.

Forced Expiratory Volume↗
PubMed1995

Parathyroid imaging.

Developments in technology mean that it is now possible to localize abnormal parathyroid glands by a variety of imaging methods. There remain a number of unresolved issues. With all commonly used methods (radionuclide imaging, ultrasound, computed tomography and magnetic resonance imaging), there are wide variations in sensitivity of detection of glands, and in many cases this variation is not explained satisfactorily. The necessity for imaging is questioned by many parathyroid surgeons, particularly before a first operation. However, parathyroid surgery is itself changing, with a trend towards more limited neck exploration, which requires localization of the glands pre-operatively. This review describes the methods available for localizing parathyroid glands, with their advantages and limitations, and discusses the role of the techniques prior to surgery.

Angiography↗
PubMed1995

A survey of dual-energy X-ray absorptiometry (DEXA) normal reference ranges used within the UK and their effect on patient classification.

Differences between dual-energy X-ray absorptiometry (DEXA) normal ranges can lead to patients being characterized as osteoporotic using one range and normal using another. To investigate the diversity of normal ranges used within the UK, a survey of all DEXA sites was carried out with a 60.6% response rate. The effect of the different ranges was evaluated by translating each range to an equivalent range for a Norland XR-26 system and applying the ranges to stratify a representative sample of over 1000 patients into grades of bone density based on percentages of age-matched mean BMD, Z-scores and T-scores. The effect of femoral neck and P/A spine L2-L4 regions was considered both separately and jointly. Large differences between the normal ranges were apparent, which resulted in the classification of the number of patients with a Z-score of less than -2.0 varying by a factor of more than 20 for the femoral neck and more than 3 for the spine. The number of patients defined as osteoporotic by a T-score less than -2.5 varied from none to over one-third of patients for the hip and by a factor of almost 3 for the spine. The exclusion criteria used for construction of the normal ranges varied markedly with none constructed using population-based sampling. Smoothing of normal ranges was carried out by DEXA manufacturers, while local normal ranges made use of raw unprocessed data. There is reason to question the validity of such processing. We recommend the construction of a unified UK normal range applicable to all UK DEXA systems in order to harmonize patient management and care.

Absorptiometry, Photon↗
PubMed1995

Home reporting for the nuclear clinician?

The computer-based 'home office' is becoming a widely accepted mode of operation for modern businesses. It is implausible to believe that a nuclear medicine department can be covered permanently at a distance by a single physician, but it should be possible to provide cover for colleagues during sickness or at night or weekends. We have used a 486 PC with a high-resolution screen and software provided by LINK Medical Ltd to obtain images from hospital sites using a modem link to ADAC, Bartec and Nuclear Diagnostic SUN workstations. The data were transferred via standard telephone lines to the homes of two of the authors. During a trial period lasting several months, 60 lung scans, 20 bone scans, 1 gastrointestinal bleeding study, 4 leukocyte scans, 5 bone tomograms, 9 renograms, 6 myocardial perfusion tomograms and 2 gated cardiac studies were transferred. The system allowed transfer of a 128 x 128 eight-view lung scan to be completed in approximately 2 min. The program on the PC allowed alteration of individual image contrast, image rotation, cine display and a variety of colour scales to enhance image interpretation. A system to transfer chest X-rays has been developed and typical transfer times are approximately 3.5 min. Within the viewing protocol on the PC, a reporting window was available with the ability to fax the report directly to the hospital. The system allowed consultants who live at a distance from their nuclear medicine departments to provide cover and is now used as an integral part of our out-of-hours service. The system also allows cover of satellite units or to provide cover for junior staff at night or weekends.

Computer Communication Networks↗
PubMed1995

Dual energy X-ray absorptiometry normal reference range use within the UK and the effect of different normal ranges on the assessment of bone density.

The number of different normal ranges used on dual energy X-ray absorptiometry (DEXA) machines in the United Kingdom was determined by means of a postal questionnaire. Both femoral neck and posteroanterior spine L2-L4 regions were considered. It was clear from this survey that a variety of normal ranges were in use for all manufacturers of DEXA systems. The effects of four normal ranges supplied by Norland for use within the UK on the stratification of over 1000 consecutive patients into different grades of bone mineral density (BMD) and Z-score were examined. The main outcomes measure the number of patients with BMD less than 80% of mean age-matched BMD and Z-score less than -1.5 over the femoral neck and spine for each normal range. The percentage of patients for each normal range with BMD less than 80% of mean for the femoral neck were 24.6%, 7.4%, 17.5% and 11.1% and for the spine 12.1%, 7.4%, 16.5% and 14.4%, respectively. For the femoral neck, 21.2%, 5.0%, 12.9% and 12.1% of patients had Z-scores of less than -1.5, for the spine this was 7.9%, 8.1%, 14.2% and 13.6% of patients. These differences between ranges are large enough to influence patient management--patients may be diagnosed as osteoporotic using one range and normal using another. The relationship between hip and spine measurements was also studied as some therapeutic agents do not affect BMD equally at all anatomical sites. The number of patients with a lower hip than spine BMD grade varied from 12.3% to 34.4%, and with a lower hip than spine Z-score from 14.0% to 43.4%. Choice of normal range thus has a critical effect on the categorization of osteoporotic patients using DEXA. The wide variety of normal ranges indicates that there are likely to be differences in patient management throughout the country. This will be an increasing problem due to the ability of NHS purchasers to switch contracts from one provider to another.

Absorptiometry, Photon↗
PubMed1994

Intraoperative localization of recurrent medullary carcinoma of the thyroid using indium-111 pentetreotide and a nuclear surgical probe.

A patient with recurrent medullary thyroid cancer in the neck in whom previous surgery for recurrence had been undertaken with only partial success had the diseased tissue localized preoperatively by indium-111 pentetreotide. Scanning with technetium-99m V dimercaptosuccinic acid and iodine-123 metaiodobenzylguanidine failed to localize the tumor. Utilization of a nuclear surgical probe after preoperative 111In pentetreotide allowed accurate surgical localization of the tumour tissue.

Adult↗
PubMed1994

Effect on patient management of a weekend 'on-call' nuclear medicine service.

The Nuclear Medicine Department at Kent and Canterbury Hospital operates a limited weekend on-call service staffed on a rota basis by a technician, a nurse and a doctor. Following a review of the service over a 2-year period, a prospective study was carried out to analyse the workload of the on-call service from August 1991 to July 1992. The aim was to assess the impact of the service on patient management and examine the cost implications. Sixty-two scans were performed during the year (38 Saturday, 22 Sunday, 2 Bank Holiday) of which 52 were ventilation/perfusion (V/Q) lung scans. The study examined the reports on the scans and the subsequent course of treatment and changes in patient management. For V/Q lung scans, anticoagulation therapy was changed in 13 cases as a result of the scan report. Of the lung scans showing low probability of pulmonary emboli, four patients were discharged on the day of the scan and a further eight within 48 h. The total cost of the on-call service (staff and consumables) was 6020 pounds, i.e. less than 100 pounds per patient and less than 2% of the departmental budget. The low cost and high number of changes in patient management indicate a reasonable cost-benefit ratio.

Cost-Benefit Analysis↗
PubMed1993

Radiation dose rates from adult patients receiving 131I therapy for thyrotoxicosis.

Recommendations for restricting the exposure to radiation of members of the public coming into contact with thyrotoxic patients treated with 131I are currently based on the activity retained by the patient, and not on the doses likely to be received by such individuals. In order to examine whether these current implications of a reduction in this limit to 1 mSv, measurements were made of the dose rates at distances of 0.1, 0.5 and 1.0 m from 60 patients just before they left the nuclear medicine department. These measurements were repeated 1, 3, 6, 8 and 10 days after administration for 30 patients, and the radioactivity in samples of saliva taken on each of these days and secreted in sweat over the first 24 h were also measured. Doses were estimated for administered activities of approximately 200-600 MBq, assuming appropriate values for the times and distances spent near other individuals while travelling, at work, at home and near to young children considered in three age groups (< 2, 2-5 and 5-11 years). Periods of restriction were derived which would reduce these doses to 5 or 1 mSv. For a dose limit of 5 mSv, there is no need to restrict private travel, public transport journeys can last up to 7 h, a patient can return to work immediately, but sleeping with a partner will have to be restricted even for the minimum activity of 200 MBq.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

123I-methylene blue: an unsatisfactory parathyroid imaging agent.

This study was designed to examine the possible use of 123I-labelled methylene blue as a parathyroid imaging agent. Five patients were studied, all of whom had parathyroid adenomas which were successfully localized preoperatively with 201Tl and 99Tcm-sestamibi, and which were subsequently proven at surgery. The 123I-labelled methylene blue localized only one of these adenomas, was negative in two and had equivocal uptake in the remaining two patients. It is therefore concluded that compared to other radionuclide methods for localizing parathyroid adenomas this agent is unsatisfactory.

Adenoma↗