Diathermy resection and radioactive gold grains for palliation of obstruction due to recurrence of bronchial carcinoma after external irradiation.
(17/31)
During 1985-7 15 patients previously treated by external radiotherapy for inoperable carcinoma of the lower trachea and major bronchi underwent endobronchial insertion of radioactive gold grains as a palliative procedure for relief of symptoms. Four patients had undergone three or more endobronchial laser treatments before being referred. Under general anaesthesia diathermy was used to resect obstructing tumour before the insertion of the gold grains into the tumour and the compressed endobronchial wall. Four patients died within one month. The remaining 11 patients were symptomatically and objectively improved when assessed at one month. Both collapsed lungs and three out of six collapsed lobes had re-expanded. Fourteen of the 15 patients died within 13 months (median survival 2.5 months); one patient with recurrent symptoms after 10 months underwent a further implantation and is alive after two years. (+info)
A model of the peritoneal cavity for use in internal dosimetry.
(18/31)
Several therapeutic and diagnostic techniques involve injection of radioactive material into the peritoneal cavity. Estimation of the radiation dose to the surface of the peritoneum or to surrounding organs is hampered by the lack of a suitable source region in the phantom commonly used for such calculations. We have modified the Fisher-Snyder phantom to include a region representing the peritoneal cavity which may be employed to estimate such radiation doses. A geometric model is described which is coordinated with the existing organ regions in the phantom. Specific absorbed fractions (derived by Monte Carlo techniques) for photon emissions originating within the cavity are listed. Photon S-values for several radionuclides which have been administered intraperitoneally are shown. Dose conversion factors for electrons irradiating the peritoneal cavity wall, from either a thin plane or volume source of activity within the cavity, are also given for several nuclides. (+info)
Quantification of intracardiac shunts by gold-195m, a new radionuclide with a short half life.
(19/31)
Gold-195m, a radionuclide with a short half life (30.5 s) was used to quantify left to right intracardiac shunts. The results of this method were compared with those obtained with technetium-99m, a method that was validated against oximetry. In five patients the pulmonary to systemic flow ratio (greater than 3:1) obtained by both radionuclides indicated that the level of shunting was too high to be measured accurately. In one patient fragmentation of the bolus meant that no satisfactory gamma fit could be obtained. In the remaining 16 patients there was no significant difference between two successive 195mAu studies. The agreement between 99mTc results and 195mAu results was excellent. Oxygen administration, straight leg raising exercise, and the use of oblique projections did not affect the values of the pulmonary to systemic flow ratio. The technique of quantification of intracardiac shunts by 195mAu gives reproducible and accurate results and the low radiation dose means that it is suitable for use in children with suspected left to right shunts. (+info)
Evidence for immunoglobulin Fc receptor-mediated prostaglandin2 and platelet-activating factor formation by cultured rat mesangial cells.
(20/31)
The possibility of Fc-dependent uptake of IgG immune complexes was examined in subcultured rat mesangial cells free of monocytes. 195Au-labeled colloidal gold particles were coated either with BSA only or with BSA followed by rabbit anti-BSA-IgG or the F(ab')2 fragment of the IgG. Mesangial cells preferentially took up 195Au particles covered with BSA-anti-BSA-IgG over those covered with BSA or the F(ab')2 fragment. This uptake was a time-dependent and saturable process inhibitable by sodium azide or cytochalasin B. Using phase-contrast microscopy in the light reflectance mode, it was established that essentially all mesangial cells took up IgG-coated gold particles. By electron microscopy the process was shown to consist of vesicular uptake with delivery to endosomes. Mesangial binding-uptake of the IgG-covered particles was associated with stimulation of PGE2 synthesis and production of platelet-activating factor, a lipid mediator of inflammation. To characterize the potential Fc receptor for IgG we used the rosetting technique with sheep red blood cells coated with IgG subclass-specific mouse monoclonal antibodies. 50% of mesangial cells exhibited rosetting with red cells coated with mouse IgG2a, whereas negligible rosetting was observed with IgG2b or IgG1. Competition experiments confirmed the specificity of IgG2a binding. We conclude that cultured rat mesangial cells exhibit specific receptors for IgG and that occupancy of Fc receptors results in endocytosis and is associated with generation of PGE2 and platelet-activating factor. These observations may be of significance for immune-mediated glomerular diseases. (+info)
Gated right ventricular studies using krypton-81m: comparison with first-pass studies using gold-195m.
(21/31)
Krypton-81m, given by continuous i.v. infusion, has been successfully used for the equilibrium ECG-gated assessment of right ventricular function. We compared gated studies with 81mKr (half-life 13 sec) with first-pass studies using 195mAu (half-life 30.5 sec). Krypton studies analyzed using variable regions of interest (ROIs) led to a significantly higher calculated right ventricular ejection fraction (RVEF) than with a fixed ROI, both with and without background correction. The differences between first-pass studies and gated studies without background correction were significant (p less than 0.01), whereas they were not with background correction. These data suggest that large systematic errors exist in the calculation of RVEF depending on the analysis method and that background correction is important when different techniques are compared. (+info)
Relation between coronary anatomy and serial changes in left ventricular function on exercise: a study using first pass radionuclide angiography with gold-195m.
(22/31)
Serial changes in left ventricular function on exercise were assessed by first pass radionuclide angiography with gold-195m (half life 30.5 s) in 25 men with known coronary anatomy. In the seven patients with three vessel disease, abnormalities of global left ventricular function and regional wall motion occurred earlier during exercise, were of greater extent at peak exercise, and persisted longer after exercise than in the 11 patients with one and two vessel disease or the seven with normal coronary arteries. Although there were significant differences between the groups in absolute change in ejection fraction and the rate of change in ejection fraction related to exercise duration and heart rate, a considerable overlap of values between groups precluded the accurate prediction of coronary anatomy in individuals. These data suggest that the amount of myocardium at risk from ischaemia in some patients with one and two vessel disease may resemble that in patients with three vessel disease. This study shows that an anatomical classification based solely on the number of diseased vessels will not predict the extent of the impairment of left ventricular function on exercise. (+info)
Gold-195m: a steady-state imaging agent for venography that gives blood velocity measurement.
(23/31)
Gold-195m has found applications in first-pass studies for investigating both right and left ventricular activity as well as lung transit. Owing to its reasonably short half-life of 30 sec we have found it particularly useful for imaging leg veins up to and including the inferior vena cava. Its short half-life prevents recirculation activity from appearing, so continuous perfusion into a superficial foot vein and application of ankle tourniquets yield a steady-state image of the deep veins, with particularly good resolution. Its decay pattern along a vessel is very sensitive to blood velocity, so measurement of activity at various points on a vein in a computer static image can give velocity values that reveal abnormalities due to partial or complete thrombosis. The radiation dosimetry of 195mAu used in this way is lower than contrast and technetium-99m macroaggregated albumin [( 99mTc]MAA) venography, making it particularly useful for investigating deep vein thrombosis (DVT) in pregnancy. (+info)
Gold-195m, an ultra-short-lived generator-produced radionuclide: clinical application in sequential first pass ventriculography.
(24/31)
Gold 195m (Au-195m) has a half-life of 30.5 sec and can be produced at the bedside from the parent mercury-195m (T 1/2 = 41.6 hr). The generator produced sterile pyrogen-free Au-195m with mercury breakthrough of 0.75 +/- 0.09 (s.e.m.) muCi per mCi of Au-195m. Approximately 20 to 25 mCi of Au-195m was produced per elution from a generator containing 155 mCi of Hg-195m. We compared first-pass resting Tc-99m angiograms with Au-195m angiograms in 28 patients. The correlation coefficient between the two studies was 0.92 over an ejection-fraction range from 0.22 to 0.83. In addition, we tested the reproducibility of Au-195m first-pass angiograms by performing two studies 3 min apart. In 25 patients with ejection fractions ranging from 0.20 to 0.78, the correlation coefficient between such pairs was 0.93. The nuclide is reliably and reproducibly produced, and its short half-life allows the performance of background-free sequential first-transit studies with unusually low radiation exposure to the patient. (+info)