Environmental risk analysis of ultraviolet phototherapy centres in Ireland.

BACKGROUND: Ultraviolet (UV) radiation is commonly used in the treatment of dermatological conditions such as psoriasis. It is known that high levels of exposure to UV radiation (UVR) will increase the risk of adverse biological effects. Exposure limit values for UVR have been developed by the International Commission on Non-Ionising Radiation Protection (ICNIRP) and occupational exposure to phototherapy staff should be kept within these limits. The use of environmental controls such as warning signs, good ventilation and UV-opaque curtains will significantly reduce the risks to staff, patients and members of the public. AIMS: The aim of the study is to identify hazards in phototherapy centres and present recommendations for reducing risks. METHODS: An environmental risk assessment has been carried out at eleven phototherapy centres in the Republic of Ireland. The study assessed a number of areas such as patient safety, staff safety, room design and UV leakage measurements. RESULTS: The majority of clinics are well designed and there is consistent use of protective equipment. CONCLUSIONS: The results show that on the whole there is a satisfactory level of risk management in phototherapy centres. Recommendations on maintaining good safety standards are presented.

Thyroid dosimetry in Europe following the Chernobyl accident.

Thyroid dose estimates for European populations following the Chernobyl accident in 1986 have been presented in the literature. These dose estimates used standard values for parameters such as thyroid mass, iodine uptake and biological half-life. Previous work has shown that these values are not representative of European populations and that local values should be utilized. Using published data on revised thyroid dose estimates, thyroid dosimetry data arising as a result of the Chernobyl accident are presented for 22 European countries. When these are compared with previously published estimates it is found that in all cases the previous results underestimate the thyroid dose by up to a factor of 4. Risk estimates on the incidence of fatal and non-fatal thyroid cancers are also determined from this new data and, again, the results are underestimated. The results show an increase in the number of fatal cancers, rising from 149 as predicted by the NEA to 310 under the new estimates, and from 180 as predicted by UNSCEAR to the new estimate of 380.

Digitized mammograms: a preliminary clinical evaluation and the potential for telemammography.

We performed a preliminary clinical evaluation of digitized mammograms to assess whether digital images suitable for telemammography could be obtained. Thirty mammograms were digitized at a resolution of 4000 x 4000 pixels and 12 bit/pixel. The series contained 17 carcinomas in 16 patients. Five consultant radiologists reported both the original mammograms and the digitized images. There was agreement between the reports of the mammograms and the digitized images in relation to whether a suspicious lesion was present or not in 95% of cases. No study considered benign on viewing the film images was interpreted as malignant on reporting the digitized images. This suggests that film digitizers may allow a digital image of a mammogram of acceptable quality for telemammography to be obtained in the absence of a purpose-built digital mammography system.

Gadopentetate dimeglumine as a contrast agent in peripheral angioplasty. A case report.

Gadopentetate dimeglumine (Gd-DTPA) is widely used as a contrast agent in MR imaging. We report on a case in which Gd-DTPA was used as the contrast agent during angioplasty in a patient who had recently had an adverse reaction to a non-ionic iodinated contrast medium. Gd-DTPA allowed a diagnostic angiogram to be performed with no side effects, and may thus be a useful contrast agent at angioplasty in patients with contra-indications to iodinated contrast media.

Calibration and assessment of a fluid-filled catheter-transducer system for the measurement of ventricular diastolic pressures.

A concise set of experiments is described which detail the calibration of a fluid-filled catheter-transducer system and the assessment of a widely used industrial algorithm for determining end-diastolic pressures using that system. First, the static response of the catheter-transducer system was evaluated in vitro by inserting the catheter into a graduated cylinder of saline. Twelve observations revealed a systematic undervaluation of pressure by the system of 1.78 mmHg with 95% limits of agreement ranging from -6.22 to 2.66 mmHg. Next, the dynamic response was evaluated in vivo by performing a transient step-response test. The system had an adequate dynamic response (fn = 11.12 Hz) for intraventricular pressure waveform replication but was considerably underdamped (beta = 0.16). Finally, the ability of the analysis software to detect the point of end-diastole and evaluate end-diastolic pressure was assessed by comparing system output with manual measurements of end-diastolic pressure in 12 patients. The mean difference between manually determined end-diastolic pressure and system output was 0.83 +/- 1.68 mm Hg. This difference is clinically insignificant and shows that the more noteworthy source of error is in the manometer-transducer emphasizing the importance of calibration and quality assurance of fluid-filled catheter-transducer systems for use in clinical cardiology or research.

Thyroid dosimetry of adult European populations.

Radioactive iodine, in the form of iodine-131, behaves similarly to stable iodine in small quantities, thus resulting in a radiation dose to the thyroid. Under the Medical Internal Radiation Dosimetry Committee formulation for radiation dose calculation to an organ, the resulting dose to the thyroid gland is dependent on the organ mass, its isotope uptake and the effective half-life of the element in the gland. Traditionally, values have been used for these parameters which, in some cases, were determined some decades previous. Iodine supply is a primary contributor to correct thyroid function and ultimately these values of mass, uptake and half-life. Recently, new data have become available on iodine kinetics throughout Europe. Here, the influence of the highly variable iodine supply in Europe on projected thyroid doses is determined. Thyroid mass values ranged from 9 g (Sweden) to 28 g (Poland) while uptake measurements were found to range from 18% (Finland) to approximately 60% (Germany and Poland). Resulting dose estimates ranged from 0.5 Gy MBq-1 (Finland) injested to 1.3 Gy MBq-1 (Czechoslovakia) injested. It was also found that among European populations the highest dose burden was to those populations with mild iodine deficiency. The results show that the use of generic metabolic data for the thyroid can lead to a misrepresentation of the absorbed dose to the thyroid. Thus, the data presented provide a better reflection of the actual thyroid dose following ingestion of iodine-131 for European countries.

Transventricular pressure-velocity wave propagation in diastole: adherence to the Moens-Korteweg equation.

In the latter half of the diastolic phase of the cardiac cycle, the left atrium contracts and generates a pressure-velocity wave which enters the left ventricle. The wave moves through the inflow tract of the ventricle, reflects off the apex and heads towards the aortic valve. The time taken for the pressure-velocity wave to propagate through the ventricle, referred to as the A-Ar interval, may be measured using pulsed Doppler echocardiography and occurs in the range 20-80 ms. It has been shown previously that there is a significant negative linear correlation between the A-Ar interval and the passive elastic modulus of the ventricular wall (r = -0.782, p < 0.001). This relationship may be explained by modelling the left ventricle as a folded-over elastic tube through which the pressure-velocity wave is propagated according to the principles of the Moens-Korteweg equation.

Estimation of foetal brain dose from I-131 in the foetal thyroid.

The ingestion of I-131 by pregnant women can have consequences for the developing foetus, in particular brain function. As the foetal thyroid accumulates iodine from the twelfth week of gestation onwards, the determination of foetal brain dose resulting from such I-131 accumulation is essential. Normal dosimetric methods fail to treat the case of foetus. Using an approximation method based on the MIRD approach, a foetal dose estimation scheme is developed to allow the determination of foetal brain dose from foetal thyroid irradiation. Dose values are obtained for the foetus based on the maternal intake of I-131. It was found that the choice of biokinetic model for the mother/foetus has a large impact on the determined dose estimate.

Correlation of end-diastolic pressure and myocardial elasticity with the transit time of the left atrial pressure wave (A-Ar interval).

Contraction of the left atrium in diastole generates a pressure wave that moves along the postero-lateral wall of the left ventricle (LV), rebounds off the LV apex, and is then directed toward the outflow tract. The movement of this atrial pressure wave may be detected with pulsed Doppler echocardiography by placing a sample volume in the LV outflow tract. The resulting spectral profile shows the initial. A velocity wave and also the Ar velocity wave, which is caused by the atrial pressure wave rebounding off the LV apex. The transit time from the inflow tract to the outflow tract of the atrial pressure wave (A-Ar interval) may be determined from the time axis of the spectral profile by measuring the peak-to-peak separation of the A and Ar, velocity waves. It occurs in the range 25 to 80 milliseconds. The primary determinant of the A-Ar interval is the elasticity of the LV myocardium. We correlated ventricular elasticity with the A-Ar interval in 47 patients and found a significant negative linear correlation (r = -0.782, p < 0.001). Because the pressure in a viscoelastic conduit such as the LV is determined by the elasticity of the ventricular wall, we correlated end-diastolic pressure with the A-Ar interval and again showed a significant negative linear correlation (r = -0.701, p < 0.001). The A-Ar interval is an easily measured noninvasive index of the diastolic function of the LV that reflects its intrinsic elasticity and end-diastolic pressure. It is therefore a quantitative measurement of LV wall stiffness and end-diastolic pressure.

Specification and initial evaluation of a multiple application teleradiology system.

The digitization and transmission of medical images is becoming increasingly more important and available. The selection of appropriate clinical applications for teleradiology systems is an important factor in determining the success of such ventures. In this paper, the selection of such applications and the evaluation of the teleradiology system is described. The system (LIAISON, CAPTEC Ltd, Malahide, Ireland) is PC based and is capable of digitization and transmission of three categories of medical images: (1) plain film radiographs; (2) CT film data and (3) video sequences such as ultrasound scans. A comprehensive technical evaluation was carried out on the acquisition and display station in which various parameters such as spatial resolution, signal-to-noise ratio (SNR), and distortion were investigated. Results showed that the system performed well within specifications. An exploratory clinical evaluation was performed using a case mix of subtle fractures, chests and dislocations, and CT scans. Here the system performed well with a diagnostic accuracy of 95% for the digital image compared with the analogue image.

Gd-DTPA: an alternative contrast medium for CT.

OBJECTIVE: The purpose of this study was to demonstrate that gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) could be used as a contrast medium in CT as an alternative to iodine-based compounds. MATERIALS AND METHODS: Solutions of different concentrations of Gd-DTPA and iopromide were scanned in a tissue equivalent phantom and it was shown that Gd-DTPA caused 2.5 times the attenuation of an equimolar solution of iopromide. From these in vitro studies an in vivo dose of 0.5 mmol/kg Gd-DTPA was calculated to be equivalent to 50 ml iopromide 300. RESULTS: Pre- and postenhancement CT was performed in a volunteer using Gd-DTPA intravenously, and adequate enhancement occurred in intracranial vessels. CONCLUSION: Gd-DTPA can be used to provide enhancement during CT and might be of value in iodine-sensitive patients.

Imaging of bronchial carcinoid tumours with indium-111 pentetreotide.

Neuroendocrine tumours are characterised by the expression of high affinity binding sites for somatostatin. The detection of bronchial carcinoid tumours through scintigraphic imaging is described in two patients using the novel radiolabelled somatostatin analogue indium-111 pentetreotide.

Contrast agent CT imaging in variable sized organs using single energy synchrotron radiation.

A theoretical and experimental study has been performed to determine which element, when used as a contrast agent in CT, requires the lowest concentration when delivered to various sized organs. Iodine is at present the primary contrast agent used in contrast enhanced CT imaging. The results presented here show that iodine is not the optimum element to use in terms of concentration needed for visibility. When administered to very small organs, the use of gadolinium reduces the concentration required for visibility by at least a factor of 3 over that required when using iodine.