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Biomedical subjects

R J Callahan

Publications and source records attributed to R J Callahan.

At least 55 records · Page 3Linked to original sources
PubMed1987

Tumor-derived interleukin-2-dependent lymphocytes in adoptive immunotherapy of lung cancer.

A trial of adoptive immunotherapy was performed in which long-term cultured, interleukin-2 (IL2)-dependent T-lymphocytes were administered to patients with metastatic adenocarcinoma of the lung. Lymphocytes were isolated from explants of cancer tissues that were cultured in medium with recombinant IL-2. These T-cells expressed surface markers of activation, and killed a broad panel of tumor targets. Intravenously injected 111indium-labeled T-cell blasts distributed primarily to lungs, liver, and spleen. Despite a paucity of infused lymphocytes detected by external imaging at sites of tumor, five of seven patients showed reduction of their cancers. However, in no case was greater than 50% reduction of total tumor burden achieved. Evidence of increased delayed cutaneous hypersensitivity to protein antigens was observed in three patients following therapy. We conclude that long-term cultured tumor-derived T-cells can be transferred safely into humans and that these cells may be capable of enhancing immune responses and mediating tumor reduction in vivo.

Adenocarcinoma↗
PubMed1987

Biodistribution of tantalum-178: a short-lived radiopharmaceutical for blood pool imaging.

178Ta is a short lived radionuclide (half life = 9.3 min), which results in favorable radiation exposure compared to 99mTc (half life 6 h). The energy spectrum of 178Ta consists of imageable photons in the 55-65 keV (61.2%) and 93 keV (33.7%) range but also 6% of disintegrations result in photons with energies greater than 500 keV. These high energy photons cause septal penetration in low energy collimators so that resolution is degraded. However, a medium energy collimator prevents the septal penetration of these higher energy photons. Serial blood samples obtained from dog and rabbit models indicate that 178Ta is retained in the blood pool for at least 20-30 min after intravenous injection. The 178Ta appears to be associated with the protein fraction of the plasma and not primarily with the red blood cell fraction as determined by centrifugation and column chromatography. Gated equilibrium blood pool images using 178Ta were comparable in quality to images using the 99mTc labelled red blood cell technique. Therefore, 178Ta may allow comparable equilibrium gated blood pool imaging with much more favorable radiation dosimetry. Thus, serial studies over prolonged periods of observation may be obtained.

Animals↗
PubMed1986

Usefulness of oral dipyridamole suspension for stress thallium imaging without exercise in the detection of coronary artery disease.

Stress thallium imaging with intravenous dipyridamole permits assessment of coronary artery disease (CAD) without the need for exercise. However, intravenous dipyridamole is available in the United States only on an experimental basis. To study the use of oral dipyridamole as a clinically available alternative to intravenous dipyridamole for this purpose, 100 patients underwent thallium imaging with oral dipyridamole. Each patient received 300 mg of pulverized tablets in a 30-ml suspension. Maximal increase in mean heart rate and decrease in mean blood pressure occurred 30 minutes after ingestion. At 45 minutes, 2 mCi of thallium was given intravenously and serial imaging was begun within 7 minutes. The serum dipyridamole level (mean +/- standard deviation) 45 minutes after 300 mg was administered orally (3.7 +/- 2.2 micrograms/ml) was similar to that 5 minutes after 0.56 mg/kg was given intravenously (4.6 +/- 1.3 micrograms/ml). Fifty-five patients had some adverse effects between 15 and 75 minutes after oral ingestion, including nausea, headache, dizziness, chest pain (25 patients) and electrocardiographic changes (14 patients). Intravenous aminophylline was used to resolve these adverse effects in 21 patients. There were no severe arrhythmias, myocardial infarctions or deaths. Of the 43 patients with angiographically documented CAD, 39 had an initial perfusion defect that redistributed on the delayed images. When the results in patients who had undergone catheterization were analyzed by individual segment, the presence of thallium redistribution was associated with normal or hypokinetic contrast left ventriculographic wall motion of that segment, whereas the presence of a persistent defect was associated with akinesia or dyskinesia (Fisher's standardized Z = 9.14).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1985

Power in client and nurse-therapist relationships.

Social theory provided the perspective for this exploration of power as it relates to the nurse/client relationship. As the authors agree with Smith and Vetter (1982) that interactions are a legitimate basis for understanding behavior, we, have, therefore, presented actual nurse/client relationships as empirical cases to examine and to apply theory. These six vignettes provide examples of various responses of patients and therapists to power in therapeutic relationships. Although each situation differs in some respects, there are similarities regarding power as a phenomenon. Dependence and sanctions, the objective features of power, are present. On analyzing the audiotapes and process notes from the individual therapy of clients and nurses who were beginning therapists enrolled in a graduate psychiatric nursing program, it becomes clear that the therapists got involved in power struggles with their clients or used exploitive power when they, themselves, felt vulnerable or angry because they perceived their expert power to be threatened. It also becomes clear that the nurse-therapists were not always accustomed to, or comfortable with, an autonomous role. They, therefore, sometimes failed to use their legitimate powers. However, once they reviewed their interactions within a conceptual framework of power, and discussed these issues with clinical and academic supervisors, they could examine causes, characteristics, and potential changes in their reactions to their clients.

Adult↗
PubMed1985

Radiopharmaceuticals for cardiac imaging.

A number of new radiopharmaceuticals have been developed to increase the diagnostic utility of nuclear medicine in cardiac diseases. The radiochemistry and dosimetry of and clinical experience with these new agents are summarized, and are compared with more widely used methods for assessing myocardial perfusion (thallium-201 scintigraphy) and ventricular function (technetium-99m radioangiography). Emerging techniques for the evaluation of myocardial necrosis and metabolism are also presented, with emphasis on the use of radiolabeled antimyosin antibody and fatty acid analogue imaging in ischemic heart disease.

Glucose↗
PubMed1982

Detection of gastrointestinal bleeding with 99mTc-labeled red blood cells.

Using a modified in vivo Tc-99M red cell labeling technique, gastrointestinal bleeding scintigraphy was performed in 100 patients with GI bleeding. Sixty-two patients with melena or bright red blood per rectum had positive scintiscans. In comparison to results of angiography, endoscopy, surgery and contrast radiography, radionuclide scintigraphy correctly located the site of bleeding in 83% of patients. The procedures could be performed over a 24 hr period which increased the sensitivity of the test since 85% of the scintiscans were positive at one hr or greater after the onset of imaging. The procedure was more sensitive than angiography in detecting sources of GI bleeding. We conclude that GI bleeding scintigraphy 99mTc-red cells in an accurate and effective method to detect upper and lower GI bleeding in patients with acute intermittent gastrointestinal bleeding.

Adolescent↗
PubMed1982

Imaging of acute arterial injury with 111In-labeled platelets: a comparison with scanning electron micrographs.

The relationship between degree of acute arterial injury, extent of platelet deposition, and ability to visualize arterial injury with Indium 111-labeled platelets was studied in 18 rabbits. An aortic lesion was made with a balloon catheter in each animal immediately after injection of autologously labeled platelets. Three nonlesioned rabbits with 111In-labeled platelets served as controls. An additional control study was performed in 12 lesioned rabbits in which nine were injected with 111In-labeled plasma protein and three with 111In-labeled red blood cells. A postmortem scanning electron microscope study of the aortae was made to determine the degree of injury to the intima and the amount of platelet deposition on the damaged arterial wall. The radionuclide scans and scanning electron micrographs were then compared. Lesions were seen in ten of 18 animals with labeled platelets that had extensive regions of denuded endothelium covered by a contiguous layer of platelets. Lesions consisting of patchy deendothelialization and platelet deposition could not be visualized on the scans. Red blood cells and fibrin were not conspicuous on micrographs of the lesions. No lesions were visualized in animals receiving 111In-labeled plasma protein or red blood cells before arterial injury, despite platelet deposition in the lesions.

Animals↗
PubMed1982

A modified method for the in vivo labeling of red blood cells with Tc-99m: concise communication.

The rate of incorporation of Tc-99m into red blood cells pretinned in vivo was measured by collecting blood samples in stannous DTPA solution, which served as a competing ligand for Tc-99m. This collection technique permitted a measurement of high-affinity red-cell labeling efficiency at the instant of sampling. At 0.5 min after injection only 62% of technetium is tightly bound to the red cell; this rises to 94.5% at 10 min. Based on the graded labeling of the red cells, the in vivo labeling procedure was modified by isolating pertechnetate and red blood cells tinned in vivo in a syringe during the first 10 min of labeling. The pertechnetate is thus prevented from distributing to extravascular compartments, and 90% of the injected Tc-99m is firmly bound to red blood cells at the time of injection. In a series of 23 patients, seven were tested with the in vivo method and seven with the modified in vivo method, and nine patients were tested with each method on separate occasions. A decrease in gastric activity and improved image quality were found with the modified method compared with the standard method of in vivo red-cell labeling.

Binding, Competitive↗
PubMed1981

99mTc red blood cells for detection of gastrointestinal bleeding: experience with 80 patients.

Imaging was done in 80 patients with gastrointestinal hemorrhage using red blood cells labeled with 99mTc by a modified in vivo technique. Bleeding was detected in 65% of 40 patients with bright red blood per rectum, 71% of 35 patients with melena, and in none of the five patients with occult bleeding and chronic anemia. No clinical evidence of further gastrointestinal hemorrhage occurred in 26 of the 29 patients who were negative on imaging. The imaging study could be carried out for over 24 hr which increased the sensitivity of the test, since only 16% of the studies were abnormal on the initial images. Neither the need for blood replacement nor the presence of bright red blood per rectum correlated strongly with early image positivity, supporting the contention that patients with gastrointestinal hemorrhage do not necessarily bleed continuously. Labeled red cell imaging was more sensitive in the detection of bleeding than angiography. It corresponded to the overall angiographic findings in 23 of 31 cases and in 17 of the 18 patients who had demonstrable extravasation. 99mTc red blood cells may be used effectively in patients with melena as well as with bright red blood per rectum, and thus would seem to be the preferred radiopharmaceutical for imaging.

Erythrocytes↗
PubMed1980

Urinary excretion of 99mTc administered as microspheres.

99mTc-albumin microspheres were administered intravenously and urinary radioactivity was determined for various periods up to 25 hours. The average accumulated urinary level was 0.68% of the injected dose at 1 hour and 18.6% at 24 hours. The averaged bladder wall dose was 101.98 mrad (1,019.79 muGy) based on an administered dose of 3 mCi (111 MBq). While the chemical state of the excreted 99mTc was primarily free pertechnetate, some reduced 99mTc species were also excreted. The appearance of 99mTc in the kidneys within the first 15 minutes following injection should not be considered unusual, nor necessarily indicative of right-to-left shunting.

Humans↗
PubMed1980

111In oxine labeled red cells for detection of simulated lower gastrointestinal bleeding in an animal model.

111In oxine in vitro labeled red cells were evaluated in rabbits for the ability to detect gastrointestinal (GI) bleeding. A mean labeling efficiency of 81% (+/- 15.5%) was achieved. Biodistribution and translocation data demonstrated 81% of the activity within the blood pool at four hours after intravenous injection, falling to 29% by 72 hours. Peak urine excretion occurred after 60-150 minutes. Normal GI excretion was less than 1% over 72 hours. Simulated lower GE bleeding was imaged at 4, 12, and 72 hours, and amounts as small as 2 ml (1% blood volume) were seen. In rabbits the total body dose of injected 111In is 0.15 mGy/MBq (0.56 rad/mCi), and the critical organ is the spleen which received 0.49 mGy/MBq (1.82 rad/mCi). 111In oxine labeled red cells provide a sustained blood pool label without significant accumulation in the GI tract, and may have a potential use in the detection of intermitent GI bleeding in humans.

Animals↗
PubMed1977

Pharmacokinetics of technetium-99m diphosphonate.

Increased diagnostic information may be derived with Tc-99m diphosphonate from a detailed kinetic analysis of blood disappearance, urinary excretion, and quantitative assessment of skeletal uptake. Blood and urine determinations were studied in three populations: normal volunteers, patients with negative bone scans, and patients with positive bone scans. Quantitative imaging studies were performed in normal volunteers and patients with a scintillation camera interfaced to a computer. All subjects were scanned in the lower lumbar region up to 1 hr after Tc-99m diphosphonate administration. Blood levels exhibited a triexponential clearance pattern. Significant (p less than 0.05) differences were observed for the 5-min blood and 0-1 hr urine values among the various groups. The computer-generated images showed an initial early uptake in bone, kidneys and soft tissue. Thereafter, a parallel fall-off in activity was observed in kidney and soft tissue, with a concomitant increase in bone. Skeletal uptake was different for normal and diseased bone.

Adult↗
PubMed1976

Technetium-99m-human serum albumin: evaluation of a commercially produced kit.

Results are reported on the use of a commercial kit for the labeling of human serum albumin with 99mTc. One-hour blood levels obtained in 20 subjects undergoing gated cardiac imaging were found to be 46.0 +/- 10.5% (s.d.) of the administered dose. The highest labeling efficiencies (94.2 +/- 9.3%) were obtained when human serum albumin 25% (salt-poor) was used. Satisfactory nuclear cardiac ventriculographic images were obtained in patients receiving the radiopharmaceutical when the labeling efficiency was at least 85%. Occasional batches were milky in appearance, contained black particulate matter, were acidic, or contained a high percentage of unbound 99mTc activity. Although this kit makes 99mTc-human serum albumin accessible to most nuclear medicine facilities for general clinical use, an active quality control program is required prior to use in patients.

Evaluation Studies as Topic↗