Biomedical subjects
Publications and source records attributed to A J Gilson.
We report a patient who had two episodes of bleomycin lung toxicity with a good clinical response following corticosteroid therapy. The first episode followed treatment with 120 units of bleomycin and was characterized by cough and dyspnea. The second resulted in ARDS following a surgical procedure that used an FIO2 level of 0.33.
A mathematical method has been developed by which the cerebral vascular extraction fraction of flow- and diffusion-limited tracers injected intravenously can be measured quantitatively. Successive injections of three tracers are required: a test tracer such as 15O-labeled water; a completely diffusible tracer as a reference tracer and also as a flow tracer; and a tracer for cerebral blood volume (CBV). The arterial tracer concentration curves and total integrated head counts of the test and reference tracers, as well as CBF and CBV values, are required to calculate the extraction fraction. No calibration is required between the head counts and arterial curves. No decay correction of the head and arterial activity is required, because isotopic decay is explicitly included in the equation. The effect of nonextracted test tracer can be corrected. Simulation studies have shown that the calculated extraction fraction values are not sensitive to measurement error in CBF, CBV, partition coefficient, change in measurement time, or time shift effect between the arterial and head data. If there is mixing of two different tissues in the brain, the calculated extraction fraction values are close to the weighted mean values of extraction fraction by relative weight of the tissues. It is concluded that it is possible to apply this method to human studies with a positron emission tomograph scanner and to animal studies with external coincidence detectors.
Innovations in design of a dedicated breast scanner resulted in automation of the scanning process, the production of high resolution images of the whole breast and an efficient mode of image review. The results of clinical evaluation of the prototype of this breast scanner investigating normal breasts as well as benign and malignant breast lesions are presented.
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A method for the detection and quantification of left-to-right intracardiac shunts is described which utilizes a single breath inhalation of oxygen-15 labeled carbon dioxide (C15O2). The inhaled gas rapidly crosses the alveolar membrane and the oxygen-15 label is exchanged through the carbonate cycle to form oxygen-15 labeled water within the pulmonary capillary blood. Pulmonary indicator clearance curves are measured by external scintillation probes. A simplified method of shunt flow quantification was developed from indicator dilution principles and used for the analysis of the clearance curves. Inhalation studies were performed with 62 children on the day prior to cardiac catheterization. The presence or absence of left-to-right shunt was confirmed by contrast angiography in all cases. Twenty-six children were found to have no shunts by C15O2 inhalation, oximetry or angiography. Of the 36 with shunts, 34 were detected by C15O2. Two of these were designated as equivocal because they were considered to be less than the threshold of definitive detection by C15O2 (having Qp/Qs less than 1.2); 32 were positive and there were two false negatives with small ventricular septal defects. There were no false positives by C15O2. The correlation coefficient between C15O2 and oximetry values of shunt flow for those patients with proven shunts was 0.82.
A new technique for the study of cardiac hemodynamics is described which utilizes single-breath inhalation of C15O2 (T 1/2 = 124 sec.) and the recording of activity vs. time curves with scintillation counters placed externally over the left ventricle and right lung. The results from 10 normal volunteers and 28 patients with acquired or congenital heart disease have been compared to the findings at cardiac catheterization. The technique is safe, rapid, and nontraumatic, and yielded no false positives or negatives in this series.
Accelerator-produced C15O2 (t 1/2 = 124 sec) is a uniquely useful radiopharmaceutical because it can be introduced rapidly and selectively into the left side of the heart by the simple noninvasive process of inhalation and breath-holding. A standard scintillation camera system was used to obtain images of the left heart by this technique. The procedure involves minimal radiation dose to the patient and may be repeated within a few minutes if necessary.
A practical method for preparing )23-I-rose bengal that allows for its rapid and efficient incorporation into the molecule is reported. Administration of 123-I-rose bengal to normal healthy patients showing the normal uptake and excretory pattern visualized with this radio pharmaceutical is also presented. The overall reduction in imaging time and radiation exposure together with the improved images possible should greatly improve our diagnostic capabilities in evaluating the jaundiced patient.
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