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Biomedical subjects

A T Elliott

Publications and source records attributed to A T Elliott.

At least 37 records · Page 2Linked to original sources
PubMed1990

Simultaneous measurement of left ventricular function and perfusion.

A new radiopharmaceutical, methylisobutyl isonitrile (MIBI), has been developed as a technetium-99m-labelled alternative to thallium 201 for myocardial imaging. By virtue of the high specific activity of 99mTc, some 600 MBq may be administered as a 0.3 ml bolus, permitting the acquisition of a first-pass nuclear angiogram at rest and at peak exercise. The agent was assessed in ten sequential patients referred for routine cardiac catheterisation, who also underwent an exercise electrocardiographic (ECG) test. Good quality nuclear angiograms, planar perfusion and tomographic perfusion images were obtained; the results correlated well with the catheterisation data. Of 30 myocardial segments for which wall motion was judged normal/abnormal from the nuclear angiogram, results concordant with contrast studies were obtained in 27 (90%). In the case of the 50 segments analysed from the perfusion images, concordant results were obtained in 43 (86%) from the planar studies and in 42 (84%) from the tomographic studies. All normal segments were classified correctly.

Adult↗
PubMed1990

Fifteen years of radiological protection experience in a regional radiopharmacy.

Radiological protection experience in a regional radiopharmacy, currently handling 28.5 TBq (770 Ci) 99mTc y-1, is reviewed for the period 1974-1988. The results of personnel monitoring have shown a downward trend (by more than a factor of two) in radiation exposure of individual staff members, despite the workload per person [6000 GBq (162 Ci) 99mTc y-1] remaining virtually constant. Adequate staff selection and training contribute to the reduction in dose. A significant reduction in dose to the eyes was achieved by installing lead glass screens in the radiopharmacy work stations, and tungsten syringe shields reduced radiation dose to the hands. The use of commercially available kits for producing 99mTc radiopharmaceuticals, rather than relying on in-house preparations that require more operator handling, has also contributed to reduction in radiation exposure. Internal contamination of staff members with 125I was markedly reduced when the practice of sub-dispensing high-specific activity solutions of the radionuclide was discontinued. Annual doses from external radiation currently average less than 6 mSv (600 mrem) to the trunk, less than 7 mSv (700 mrem) to the eyes, and 50 mSv (5 rem) to the hands. Internal contamination of personnel with 125I, 131I, and 99mTc, as detected by thyroid and whole-body monitoring, contributed less than 65 mSv y-1 (6.5 rem) to the thyroid gland and less than 0.1 mSv y-1 (10 mrem) to the whole body.

Humans↗
PubMed1990

Investigation of factors affecting adhesion of 99Tcm labelled colloids to glass vials.

Factors which may possibly influence the adhesion of 99Tcm labelled colloid to glass vials were investigated. Of five colloids studied, two protein-free tin colloids were affected most by the problem, some 12-18% being lost by adhesion to the glass vial when the colloid was left resting on the bench, or 60-87% when it was rotated for a period of 4 h. The proportion of activity which adhered to the vial was dependent on the time the product had been contained within it, whether on the bench or rotated. Two of the colloids, both of which contained protein, were affected only slightly by the problem, one being a tin colloid and the other a sulphur colloid. An antimony sulphide colloid, which contained no added protein, was virtually unaffected by the problem. The degree of adhesion was not related to the pH of the product, nor to the temperature at which the product was stored, nor to the tendency of the colloid particles to grow in size upon vigorous agitation.

Colloids↗
PubMed1989

A comparative study of the relative sensitivity and specificity of radiolabelled monoclonal antibody and computerised tomography in the detection of sites of disease in human malignant melanoma.

A monoclonal antibody raised against the high molecular weight melanoma antigen was labelled with indium-111 and injected intravenously into 25 patients with malignant melanoma. The results obtained from images at 24 and 96 h post i.v. administration of the antibody were compared with results obtained from computerised tomography studies with regard to detection of previously unrecognised sites of metastatic disease and apparent false positive localisation. Detailed study of the patients' clinical condition and detection rates using the two methods suggest that both methods detect approximately 80% of clinically and pathologically confirmed metastases. Of 62 known metastases, the antibody detected 50 (81%), with 17 false positive results. False negatives were most common in the lung. In eight patients the two methods were considered of equal value, in 10 the monoclonal gave a greater amount of clinically relevant information, and in seven the CT was superior. In three patients clinically significant metastatic lesions were detected by the radiolabelled monoclonal and had not been previously recognised either by CT scanning or on clinical grounds. No patients had any adverse reaction to the antibody and in the course of our study the dose of antibody was reduced from 20 mg to 200 micrograms with no apparent loss of sensitivity. In at least two patients uptake of the labelled monoclonal into tumour sites would have been adequate for effective targeted radiotherapy.

Antibodies, Monoclonal↗
PubMed1988

Angina pectoris during exercise--relationship to coronary anatomy and myocardial function.

We studied 34 patients with proven coronary heart disease to determine whether the presence or absence of angina pectoris during exercise testing was associated with greater disease, ST segment depression or fall in left ventricular ejection fraction. Angina pectoris was the limiting symptom in 19 and fatigue/breathlessness in 15 patients. Exercise time [421(31) vs. 455(64) s], ST depression [1.4(0.3) vs. 1.1(0.3)mm], fall in left ventricular ejection fraction [13(2) vs. 12(2)] and coronary score and fall in left ventricular ejection fraction [15(2) vs. 8(3), P less than 0.02]. The degree of ST segment depression correlated with the coronary score (r = 0.6) and fall in left ventricular ejection fraction (r = 0.5). ST segment depression but not angina pectoris during exercise predicted the extent of disease and its functional consequences.

Angina Pectoris↗
PubMed1988

A comparison of isometric exercise, cold pressor stimulation and dynamic exercise in patients with coronary heart disease.

Isometric exercise and cold pressor stimulation have been proposed as alternatives to dynamic exercise in the evaluation of patients with coronary heart disease. We evaluated all three, by gated radionuclide ventriculography, in 13 male controls and 44 male patients with coronary heart disease. In controls, mean left ventricular ejection fraction did not change during isometric exercise or cold pressor stimulation (64 +/- 2 to 63 +/- 2 and 63 +/- 3) but fell significantly in patients (56 +/- 1 to 53 +/- 1 and 53 +/- 1, both P less than 0.001). During dynamic exercise, mean left ventricular ejection fraction rose in controls (64 +/- 2 to 84 +/- 2, P less than 0.001) but did not change in patients (56 +/- 1 to 56 +/- 2). There was considerable overlap between the groups in the left ventricular ejection fraction response to isometric exercise and cold pressor stimulation; only dynamic exercise discriminated between them. Isometric exercise and cold pressor stimulation are of little value in the diagnosis of coronary heart disease by radionuclide ventriculography.

Adult↗
PubMed1988

Automated radiopharmaceutical dispensing.

An automated workstation, developed for clinical biochemistry, has been evaluated for potential use in preparing radiopharmaceuticals. It was found that substantial modifications, both hardware and software, would be required but the approach seemed feasible.

Equipment Design↗
PubMed1988

Immunoscintigraphy of human ovarian cancer xenografts using a radiolabelled monoclonal antibody to human pregnancy serum-derived immune complexes.

The in vivo imaging of xenografted human ovarian cancer in nude mice with a specific and control radiolabelled monoclonal antibody (MoAb) is described. The specific MoAb was previously raised by immunizing mice with immune complexes derived from late human pregnancy serum. In the first group of mice the specific MoAb 131I-5E3 F(ab')2 was injected, while a second group received equivalent amounts of a control MoAb 131I-UJ13A F(ab')2. The mice were imaged at various times up to a maximum of 2 weeks using a gamma camera, and the tumour to non-tumour (T/NT) ratio was recorded for each group. The T/NT ratio rose to 2.02 in the specific group, while the corresponding ratio in the control group was 0.70. In addition, the count rate in the tumour and non-tumour regions was determined on each imaging occasion. Biological half-lives of the divalent fragments of 5E3 and UJ13A in the tumour were 7.53 days and 0.62 days, respectively. Following sacrifice, the tumours were excised and counted relative to the rest of the animal, and the T/NT ratio was calculated. In vitro results were in direct agreement with those recorded in vivo using the gamma camera. From the results it would appear that the divalent fragment of 5E3, which has been raised to immune complexes derived from late human pregnancy serum, is specific for human ovarian tumour xenografts in the nude mouse model.

Animals↗
PubMed1988

Nonistropic point spread function as a result of collimator design and manufacturing defects.

A point spread function (PSF) which was of an unusual form was observed when using a low energy collimator and a 99mTc point source. A lack of radial symmetry and the detection of events over 20 cm away from the center of the source were noted. The major quantitative effect of this was a variation in the resolution of the system with direction. The consequences of this are likely to be of importance especially for single photon emission computed tomographic (SPECT) imaging. The effect was produced by a combination of faults in the design and manufacture of the low energy collimators. It demonstrates the importance of making quantitative measurements of collimator performance in the quality control assessment of gamma camera systems. For SPECT imaging the replacement of lead foil collimators with cast collimators should be considered.

Equipment Design↗
PubMed1988

Digital filtering of the bladder in SPECT bone studies of the pelvis.

A data processing technique for the removal of bladder activity from single photon emission computed tomographic bone studies of the pelvis has been developed. The method involves the replacement of count values in the bladder on all projection views by data which are representative of the activity in surrounding structures. Reconstruction is then performed using the amended set of projection views. The method was tested by examining a group of 13 patients referred for investigation of avascular necrosis of the femoral head. Significant improvements in image quality were observed, particularly with respect to the level of artifact production, which increased the number of cases in which a confident and correct diagnosis was made.

Femur Head Necrosis↗
PubMed1987

Cardiovascular effects of training for a marathon run in unfit middle aged men.

The effects of a 30 week exercise programme on serum lipid values, blood pressure, and cardiac function were assessed in a group of sedentary men aged 35-50 training for their first marathon. Mean serum cholesterol concentration (n = 33) fell by 12% from 6.54 (SE 0.18) to 5.76 (0.15) mmol/l (mean fall 0.78 mmol/l; 95% confidence interval 0.52 to 1.04 mmol/l), serum triglyceride concentration (n = 33) by 22% from 1.56 (0.17) to 1.21 (0.09) mmol/l (mean fall 0.34 mmol/l; 95% confidence interval 0.12 to 0.56 mmol/l), and mean blood pressure (n = 27) by 10% from 102 (2) to 92 (2) mm Hg (mean fall 10 mm Hg; 95% confidence interval 7 to 13 mm Hg). These changes were not explained by changes in body composition. Peak exercise left ventricular end diastolic volume (n = 16) increased with training; as a result of this and an increased exercise left ventricular ejection fraction peak exercise cardiac output increased from 19.9 (1.2) to 23.1 (3.0) l/min (mean rise 3.2 l/min; 95% confidence interval 1.5 to 5.0 l/min). Maximum oxygen consumption increased from 33.9 (1.6) to 39.0 (1.3) ml/kg/min (mean rise 5.0 ml/kg/min; 95% confidence interval 1.8 to 8.2 ml/kg/min). This study showed favourable effects on coronary risk factors and cardiac function and supports the place of regular exercise in coronary prevention programmes.

Blood Pressure↗
PubMed1987

Gold 195m in the assessment of the cold pressor test by first pass radionuclide ventriculography.

First pass radionuclide ventriculography was performed with gold 195m in a sequential evaluation of left ventricular ejection fraction during cold pressor stimulation. We studied 10 normal controls, 10 patients with angina pectoris who had proven coronary artery disease and normal left ventricular function during contrast angiography and 10 patients with dilated cardiomyopathy with normal coronary arteries and impaired left ventricular function at contrast angiography. Mean resting ejection fraction was similar in controls and patients with coronary heart disease (57 +/- 2 vs 58 +/- 3) but was significantly lower in the cardiomyopathic subjects (27 +/- 4, P less than 0.001). After 30 seconds cold pressor stimulation, mean left ventricular ejection fraction fell in the normal controls (57 +/- 2 to 52 +/- 2, P less than 0.05) but was unchanged in those with coronary heart disease and dilated cardiomyopathy (58 +/- 3 to 55 +/- 3 and 27 +/- 4 to 24 +/- 4, both NS). No further significant change occurred after 2.5 minutes stimulation (53 +/- 1, 58 +/- 3 and 23 +/- 3, respectively). There was no difference in the pattern of left ventricular ejection fraction response between the groups. Six controls, 4 patients with coronary heart disease and 4 patients with dilated cardiomyopathy had a significant fall in left ventricular ejection fraction and 4, 5 and 6, respectively, developed a new or further deterioration in regional wall motion. Thus neither changes in regional wall motion nor left ventricular ejection fraction response distinguished either patient group from the normal controls. We do not recommend cold pressor stimulation as a diagnostic test for coronary heart disease.

Adult↗
PubMed1987

A double blind placebo controlled comparison of verapamil, atenolol, and their combination in patients with chronic stable angina pectoris.

The efficacy and effect on cardiac function of verapamil 120 mg three times a day and atenolol 100 mg once a day, singly and in combination, were evaluated in 15 patients with angina pectoris. While they were on the combination treatment four patients withdrew from the study. Episodes of angina pectoris and glyceryl trinitrate consumption were significantly reduced only on the combination. On the combination only four patients developed evidence of ischaemia during exercise compared with seven on verapamil and ten on atenolol. ST segment depression at peak exercise, assessed by 16 point precordial mapping, was reduced by all active treatments from 7.1 on placebo to 2.7, 0.9, and 0.6 mm on atenolol, verapamil, and the combination respectively. Mean left ventricular ejection fraction fell significantly from 60% on placebo to 53% on the combination but was unchanged on verapamil and atenolol. Verapamil was an effective alternative to atenolol; the combination was the most effective treatment but was associated with a significant morbidity.

Aged↗
PubMed1987

Stolen heart valves?

A patient having had both aortic and mitral valves replaced complained of triggering shop security alarms, attributing the problem to the prosthetic valves. It was demonstrated that the valves were not the cause of the problem and the source identified.

Female↗
PubMed1986

Formation of labelled colloid in 99Tcm-DMSA due to the presence of bactericidal fluid.

The possibility that traces of bactericidal fluid in 99Tcm-DMSA could lead to the formation of labelled colloid, was explored. In vitro investigations were undertaken using ultracentrifugation techniques and photon correlation spectroscopy. The latter showed that both contaminated and uncontaminated DMSA contained colloidal (or particulate) material. However the presence of 10 microliters bactericidal fluid as contaminant was shown by ultracentrifugation to result in labelling of this colloidal material when 99Tcm was added to DMSA. Studies in a normal volunteer confirmed the results of the in vitro studies, in that significant liver and spleen uptake was observed after the administration of contaminated 99Tcm-DMSA.

Anti-Infective Agents, Local↗
PubMed1986

Formation of large particles in a 99Tcm-tin colloid preparation.

The effect of prolonged continuous movement on particle size within a 99Tcm-tin colloid preparation was investigated, making use of photon correlation spectroscopy for size estimation. No increase in particle size was found when the preparation was left undisturbed for up to 7 h, the mean (+/- S.D.) size being found to be 239 +/- 24 nm. When the preparation was placed in a laboratory rotator for the same period of time, there was a gradual increase in mean particle size to 404 +/- 127 nm. The increase in size was much greater, however, after 7 h of continuous agitation in a laboratory shaker, a mean value of 2260 +/- 746 nm being observed. An antimony sulphide colloid was subjected to continuous agitation for the same period of time but there was no evidence of aggregation. It is supposed that continuous movement of reconstituted 99Tcm-tin colloid, leading to a marked increase in particle size, may explain occasional instances of significant lung intake.

Humans↗