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Biomedical subjects

A Alavi

Publications and source records attributed to A Alavi.

At least 361 records · Page 20Linked to original sources
PubMed1983

Fourier analysis of a gated blood-pool study during atrial flutter.

First-harmonic Fourier analysis of a gated blood-pool study is based on the assumption that the cardiac chambers contract once per cardiac cycle. In atrial arrhythmias this condition may not exist for the atria. We recently studied a patient with atrial flutter and 2:1 atrioventricular conduction. There were predictable alterations in the first-harmonic Fourier phase and amplitude images. The observed changes from first-harmonic Fourier analysis were: (a) very low atrial amplitude values, and (b) absence of identifiable atrial regions on the phase image.

Aged↗
PubMed1982

Detection of gastrointestinal bleeding with 99mTc-sulfur colloid.

We have developed a single scintigraphic technique to detect and localize the site of bleeding in the gastrointestinal tract. This examination requires only intravenous administration of 99m-Technetium sulfur colloid and imaging of the abdomen. Very shortly after the introduction of the radiopharmaceutical, a fraction of the injected activity extravasates at the bleeding site and is eliminated from the circulation. This phenomenon is repeated each time the blood recirculates adding another, but smaller fraction to the extravasated activity at the site of hemorrhage. Because of continued clearance of the radiopharmaceutical from the vascular pool by the reticuloendothelial system, a contrast is eventually reached between the site of bleeding and surrounding background. Based on animal experiments bleeding rates as low as .05-0.1 cc/min can be detected with this technique. The sensitivity of the approach in the detection of the site of hemorrhage is significantly higher than arteriography or other techniques which utilize radioactive blood pool indicators. We have mainly used this technique in the evaluation of patients with GI bleeding. In more than 25 patients with negative scintigrams for hemorrhage, arteriography showed no evidence of bleeding. In 38 patients with scintigraphic evidence of bleeding. In 38 patients with scintigraphic evidence of hemorrhage, arteriograms were positive for bleeding in les than 50% of the cases. No false positive results have been noted in the latter group. This technique appears to offer a simple, practical and reliable approach to the evaluation of patients with gastrointestinal bleeding.

Angiography↗
PubMed1982

Use of 2-deoxy-D[1-11C]glucose for the determination of local cerebral glucose metabolism in humans: variation within and between subjects.

The deoxyglucose technique for the measurement of local cerebral glucose metabolism (LCMRgl) has been widely applied in animals utilizing 14C-deoxyglucose and in humans employing 18F-fluorodeoxyglucose. Repeat studies in humans over a relatively brief period of time have not been possible because of the 110-min half-life of fluorine-18. With the synthesis of 11C-deoxyglucose it has now become possible to utilize this short-lived (20 min) tracer for the measurement of LCMRgl and to determine its variability within subjects over a 2-h period. The kinetic rate constants for 11C-deoxyglucose were determined for gray and white matter and found to be very similar to those for 18F-fluorodeoxyglucose, suggesting that these two analogues of glucose have similar affinities for the facilitated transport system and are similar substrates for hexokinase in the brain. The coefficient of variation of repeated measurements of LCMRgl in a series of six normal subjects was 5.5% to 8.7% for various gray matter structures and 9.7% and 14.0% for white matter structures. The pattern of cerebral metabolic rates is relatively constant in a given individual when the conditions of the study are unchanged. The ability to make repeat measurements in the same subject reduces the variance due to between-subject differences, allowing smaller changes in LCMRgl to be detected with confidence.

Brain↗
PubMed1982

An outbreak of Achromobacter xylosoxidans related to diagnostic tracer procedures.

In December, 1978, an investigation was undertaken to determine the source of infection in five patients in one hospital with hospital-associated bacteremia due to Achromobacter xylosoxidans. Review of their records showed that each had a diagnostic tracer procedure preceding the bacteremia and that no other procedures were common to all. Further investigation revealed that patients from three other hospitals were studied using diagnostic tracer materials from the index hospital. Five patients with confirmed A. xylosoxidans bacteremia and four suspected cases were identified in these hospitals, and all had a scan before the bacteremia was detected. No other A. xylosoxidans isolates were identified in any of the hospitals in the preceding two years. Although not confirmed, the source appeared to be stored non-bacteriostatic saline. Effective control measures included a sterility testing program and use of pre-packaged single dose vials of saline. Diagnostic tracer studies should be added to the list of procedures known to cause hospital-acquired bacteremias.

Aged↗
PubMed1982

Incidence of rapid resolution of defects on stress thallium scans.

A prospective study was performed to determine the frequency with which defects on stress thallium images undergo rapid resolution. Analysis of paired views showed that 15% of the defects present in anterior views resolve in less than 30 minutes. This study documents the loss of sensitivity that can occur if imaging does not begin promptly after injection.

Aged↗
PubMed1982

Positron emission tomography in two cases of childhood epileptic encephalopathy (Lennox-Gastaut syndrome).

Two patients with childhood epileptic encephalopathy were studied by positron emission tomography before and after corpus callosotomy. Preoperatively, both patients showed in the temporal lobe unilateral hypometabolism that is characteristic of interictal epileptic foci. Postoperatively, the first patient had no seizures by the time of scanning, and his temporal lobe metabolism was bilaterally symmetric. Seizure control in the second patient did not improve by the time of scanning, and unilateral temporal hypometabolism persisted. This finding suggests a temporal lobe focus in two patients with Lennox-Gastaut syndrome.

Adult↗
PubMed1982

Metoclopramide to treat gastroparesis due to diabetes mellitus: a double-blind, controlled trial.

Ten patients with diabetic gastroparesis were selected for a randomized, double-blind, controlled trial of metoclopramide. Each patient had longstanding insulin-requiring diabetes mellitus and symptoms of gastric stasis. The patients were evaluated for the symptoms of gastric stasis and radionucleotide gastric emptying was measured before the patients entered the study and after they were given either metoclopramide or placebo treatment. Metoclopramide, 10 mg orally, stimulated an increase in the rate of gastric emptying (56.8% +/- 7.4%) in contrast to the response to placebo (37.6% +/- 7.7%) (p less than 0.01). The overall symptoms and symptoms of vomiting were markedly reduced during metoclopramide treatment in contrast to those during placebo treatment. Before the study five patients were constipated (less than three bowel movements per week); during metoclopramide treatment the patients' bowel habits were improved. There was a poor correlation between improved gastric emptying and decreased symptoms. Metoclopramide may improve symptoms of diabetic gastric stasis through two mechanisms: its peripheral effect on gastric smooth muscle, which increases gastric emptying; and its central effects on the chemoreceptor vomiting zone, which decrease nausea.

Adult↗
PubMed1982

The radiation dosimetry of 2 [F-18]fluoro-2-deoxy-D-glucose in man.

Bladder and brain time-activity measurements in humans were performed after the intravenous administration of 2-[F-18]fluoro-2-deoxy-D-glucose. Radiation doses were calculated using the MIRD schema. The bladder wall received an average of 440 mrad/mCi (s.e. 76) in ten subjects who voided at 2 hr after administration of tracer. If these subjects had voided at 1 hr, the bladder-wall dose would have been reduced to 220 mrad/mCi. The brain received an average of 81 mrad/mCi in eight subjects. The doses to other organs, calculated from published dog biodistribution data, are between 50 and 85 mrad/mCi except for spleen and heart, which both received 160 mrad/mCi. These time-activity measurements for the critical organ in the human avoid the assumptions made in using animal biodistribution data for human dosimetry calculations.

Adult↗
PubMed1981

Metabolic mapping of functional activity in human subjects with the [18F]fluorodeoxyglucose technique.

The 2-[18F]fluoro-2-deoxy-D-glucose technique was used to measure regional cerebral glucose utilization by human subjects during functional activation. Normal male volunteers subjected to one or more sensory stimuli (tactile, visual, or auditory) exhibited focal increases in glucose metabolism in response to the stimulus. Unilateral visual hemifield stimulation caused the contralateral striate cortex to become more metabolically active than the striate cortex ipsilateral to the stimulated hemifield. Similarly, stroking the fingers and hand of one arm with brush produced an increase in metabolism in the contralateral postcentral gyrus, compared with the homologous ipsilateral region. The auditory stimulus, which consisted of a monaurally presented factual story caused an increase in glucose metabolism in the auditory cortex in the hemisphere contralateral to the stimulated ear. These results demonstrate that the technique is capable of providing functional maps in vivo related to both body region and submodality of sensory information in the human brain.

Adult↗
PubMed1981

Splenic-gonadal fusion: identification by radionuclide scanning.

Splenic-gonadal fusion is an unusual congenital anomaly resulting from the fusion of the splenic and gonadal anlagen at approximately the sixth week of gestation. A 14-mo-old male presenting with signs and symptoms of testicular torsion underwent scrotal exploration, and ectopic splenic tissue was found adjacent to the left testis. The operative diagnosis of splenic-gonadal fusion prompted abdominal scanning with 99mTc-sulfur colloid. The radionuclide image demonstrated an unusual pattern of activity that was consistent with surgical description of the intraabdominal appearance of this disorder. It is suggested that 99mTc-sulfur colloid scanning may prove to be a useful adjunct in the evaluation of patients with this anomaly.

Abnormalities, Multiple↗