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Biomedical subjects

T R Simon

Publications and source records attributed to T R Simon.

At least 55 records · Page 3Linked to original sources
PubMed1990

A clinical comparison of bone imaging agents.

This study compares the six commercially available kits for preparing methylene diphosphonate. The kits were randomly assigned to 134 bone examinations such that neither the physicians nor the technologists knew which brand of tracer was used. Thigh activity quantitatively varied significantly among the kits (P = 0.019). Detectable gastric activity also varied by brand. Other qualitative and quantitative measures of bone and soft tissue uptake showed no significant differences among the kits but consistently favored the Squibb product.

Adult↗
PubMed1990

McCune-Albright syndrome: the patterns of scintigraphic abnormalities.

This study of 22 patients with the McCune-Albright syndrome examined the scintigraphic distribution of fibrous dysplasia. The most frequently affected areas were the base of the skull (82% of patients), mandible (50%), facial bones (45%), femora (59%), and legs (64%). The least frequently affected areas included the hands (none), wrists (none), ankles (none), feet (5%), sacrum (5%), and vertebrae (9%). The distribution varied somewhat from idiopathic fibrous dysplasia but generally agreed with the distributions reported in radiographic studies of patients with the McCune-Albright Syndrome. The serum alkaline phosphatase was not an accurate predictor of the extent of fibrous dysplasia.

Bone and Bones↗
PubMed1989

Comparison of dipyridamole-Doppler echocardiography to thallium-201 imaging and quantitative coronary arteriography in the assessment of coronary artery disease.

This study was undertaken to determine whether Doppler measurements of systolic aortic and diastolic mitral blood flow velocities could reliably detect the presence of reversible myocardial perfusion defects during intravenous dipyridamole-thallium-201 imaging. In addition, the ability of dipyridamole-Doppler echocardiography to predict the presence of significant coronary artery disease (CAD) was evaluated. Baseline and post-dipyridamole Doppler studies were performed in 10 normal control subjects and 23 patients with CAD. Aortic peak velocity and acceleration increased from baseline to post-dipyridamole in normal subjects by 0.07 +/- 0.07 m/s (p = 0.016) and 2.1 +/- 2.0 m/s2 (p = 0.009), respectively. The ratio of early to late peak transmitral velocities decreased slightly in normal subjects, by 0.18 +/- 0.72 (difference not significant), whereas the ratio of early to late transmitral velocity-time integrals increased by 0.07 +/- 0.93 (difference not significant). The response of aortic velocity and acceleration to intravenous dipyridamole was not significantly different between normal subjects, patients without reversible thallium-201 perfusion defects and patients with reversible thallium-201 perfusion defects. Furthermore, only 3 of 14 subjects with reversible thallium-201 perfusion defects had abnormal (greater than 2 standard deviations from the mean) responses of aortic velocity or acceleration to intravenous dipyridamole. No patient had an abnormal response of the early to late mitral peak velocity ratio. In addition, the response of Doppler aortic and mitral indexes to intravenous dipyridamole was not able to identify the presence of significant CAD as assessed by quantitative coronary arteriography.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1989

Regional cerebral function and blood flow: complementary single photon emission computed tomography of the brain using xenon-133 and [123I]iodoamphetamine.

Regional cerebral function and blood flow can be imaged using isopropyl[123I]iodoamphetamine (IMP), or 133Xe (DSPECT), respectively. Both of these essentially non-invasive, quantitative, methods are suitable for many nuclear medicine laboratories. This study assessed the in vivo information about intracerebral disease provided by IMP and DSPECT techniques to determine the optimal diagnostic use of these modalities. Single photon emission computed tomograms of 53 subjects were acquired using similar displays for IMP and DSPECT data. Lobar tracer distributions were graded by three experienced observers and analyzed using a kappa statistic to eliminate chance agreements. Overall, both IMP and DSPECT had similar patterns. However, while similar, one or the other technique often displayed abnormalities not present on both. Although technical factors may account for some differences between the modalities, a case of arteriovenous malformation proves that discordant findings can result directly from tracer localization properties. Thus at least some discordances provide truly complementary diagnostic information lacking in either single study taken alone.

Adult↗
PubMed1989

A realistic dynamic cardiac phantom for evaluating radionuclide ventriculography: description and initial studies with the left ventricular chamber.

A phantom was devised to validate scintigraphically determined left ventricular ejection fractions (LVEFs) and cardiac chamber volumes in the following simulated cardiac situations: normal contraction, moderately impaired left ventricular contraction, severely impaired left ventricular contraction, mitral regurgitation, and cardiomyopathy. The phantom, assembled from anatomically realistic cardiac chambers, simulated contraction and expansion using individual chamber pumps coordinated by a microcomputer. Scintigraphic studies were performed by sequential imaging of [99mTc]pertechnetate introduced into each chamber. The images were analyzed like conventional clinical studies, using both automatic and manual techniques. Scintigraphic techniques correlated with chamber volumes that were determined by weight to yield the following regression formulae: LVEF (by automatic method 1) = 1.08 x LVEF (by weight) -5.11; LVEF (by automatic method 2) = 1.00 x LVEF (by weight) -3.15; and LVEF (by manual method) = 1.04 x LVEF (by weight) -5.08 ml (Correlation coefficients greater than 0.98). The absolute left ventricular volumes (LVVs), determined by scintigraphy, correlated well with LVVs determined by weight. These correlations were performed with separations between the center of the left ventricle and the collimator varying from 5 cm to 9 cm. The regression formulae for 5, 7, and 9 cm distances were: LVV (by counts) = 0.99 x LVV (by weight) + 0.13, LVV (by counts) = 1.04 x LVV (by weight) + 9.08, LVV (by counts) = 0.88 x LVV (by weight) + 15.25, respectively. At 9 cm, slight volumetric underestimation occurred, as predicted from the work of Fearnow et al., possibly because of oversubtraction of background. Thus, this phantom provides a useful tool for validating scintigraphic cardiac blood-pool studies simulating a wide range of clinically relevant situations.

Heart↗
PubMed1988

Nuclear medicine studies of aging--V. Uptake of 67Ga and 111In in the femoral vessels.

Fifty-nine males who had gallium-67-citrate or indium-111-oxine WBC scintigraphy (Ga/In) had the images reviewed to determine if increased activity was present in the femoral vessels and, if so, whether this was age related. The 59 subjects showed an age-associated increasing bilateral uptake (13% of 15 patients younger than 40 years, to 71% of the 7 who were older than 69 years). The combined unilateral and bilateral femoral uptake rose from 27% in those under age 40, to 86% in those over age 69. The group of 59 males included 30 (51%) who had bone scintigraphy with 99mTc-MDP within 3 months of the Ga/In examination. These men showed the expected increase in femoral vessel 99mTc-MDP uptake with age. Femoral vessel activity was more commonly observed with 99mTc-MDP than with Ga/In. Thus both Ga/In and 99mTc-MDP accumulate more frequently in the femoral vessels with advancing age. Ga/In displays this age-related phenomenon to a lesser extent than 99mTc-MDP.

Adult↗
PubMed1987

Direct determination of the attenuation coefficient for radionuclide volume measurements.

Correcting for the attenuation of photons between the cardiac chambers and chest surface is crucial for accurate nongeometric ventricular volume determinations from equilibrium radionuclide angiograms. Previous techniques have assumed that the attenuation coefficient of water for 99mTc (0.15/cm) should be used for this correction. In this study, this assumption was tested directly by measuring attenuation of the activity of a radioactive source within the right and left cardiac chambers. The balloon of a flow-directed catheter, filled with 99mTc, was used as a source and its depth within the body was measured with biplane fluoroscopy. In ten patients, a total of 36 measurements of attenuation were made. With linear regression analysis, the overall calculated attenuation coefficient, mu, was 0.12/cm (standard error of slope = 0.01, R = 0.93). Although the mean value of mu varied from 0.08 to 0.13 for four different intracardiac locations these differences were not significant. These direct measurements indicate that the attenuation of photons in the heart is not equivalent to that of water and suggest that an attenuation coefficient of 0.12/cm should be used in analyzing ventricular activity.

Adult↗
PubMed1987

Toxicity of indium-111 on the radiolabeled lymphocyte.

The radiolabeling of lymphocytes with 111In has resulted in detectable toxic changes in the cells. The mechanisms of toxicity for lymphocytes have been related to the label's radioactivity and to the chelator used to mediate the intracellular localization. These mechanisms were examined by assessing cellular function with mitogen-mediated blastogenesis after labeling lymphocytes with either the chelator (tropolone) alone, 111In complexed with tropolone, or cadmium (the decay product of 111In) complexed with tropolone. Successful lymphocyte labeling with 111In was shown to be dependent upon the concentration of the chelator (tropolone). Increasing concentrations of tropolone inhibited lymphocyte function to a variable degree. Further reduction in cellular function was detected after incorporation of a constant amount of 111In or 111In's decay product, cadmium. Lymphocyte function was decreased by these two labels in a parallel linear manner. This same toxic effect was seen after labeling with small constant amounts of tropolone and increasing quantities of 111In or cadmium. Thus, although both the required chelator and the radiobiologic exposure have a deleterious effect on the lymphocyte, significant lymphocyte toxicity appears to result from the metal-to-cell interaction as a result of the metal decay product (cadmium).

Cadmium↗
PubMed1986

Effect of the radiolabel mediator tropolone on lymphocyte structure and function.

The in vitro use of the radioisotope indium 111 (111In) was examined as a radiolabel for lymphocytes obtained from both normal individuals and patients with a variety of lymphoid malignancies. Successful cell labeling requires a chelator. The traditional agent oxine, has proved to be toxic to the lymphoid lineage. Cellular uptake of 111In mediated by the chelator oxine was compared with that of a new chelator, tropolone. Oxine provided better labeling efficiency (48%) than tropolone (35%) for the labeling of normal lymphocytes. By contrast, lymphocytes from patients with chronic lymphocytic leukemia had a nearly twofold greater labeling efficiency when tropolone was substituted for oxine. Further studies demonstrated that tropolone induced functional injury to lymphocytes when mitogenic response to concanavalin A, pokeweed mitogen, and phytohemagglutinin was assessed. Similar toxicity was found when tropolone was compared with oxine. In addition, tropolone produced damaging structural changes seen by both scanning and transmission electron microscopic examination. These changes were both variable and not predictable. Shortening of the incubation time of the chelator with the cell provided the least amount of cellular injury. These findings suggest that tropolone be used as an alternative mediator of lymphocyte labeling with 111In only under critically defined conditions.

Cells, Cultured↗
PubMed1986

Dynamic process captured on a single image: an approach to screening for abnormal superior vena caval flow.

A strategy for displaying and archiving dynamic quantitative data from scintigraphic imaging is described and applied to diagnosing obstructed thoracic veins. A prospective series of 25 patients with concurrent radiographic contrast and tracer venograms along with 49 controls showed a 33% sensitivity, comparable to previously published data. The use of first harmonic Fourier analysis enhanced the screening value of the test by identifying all abnormals. Moreover, this format captured the dynamic physiologic data on a single photograph. This technique is readily available to nearly any nuclear imaging laboratory equipped with a gamma camera and a computer.

Computers↗
PubMed1985

Correlation of scintigraphy and angiography for ventricular volume determinations using realistic cardiac phantoms: the unimportance of self-attenuation.

The volumes of the left ventricle (LV) and right ventricle (RV) were determined by scintigraphy, radiography, and weight, using hollow, morphologically accurate cardiac phantoms that ranged from 99-415 ml (RV) and 72-364 ml (LV). Self-attenuation within these simulated ventricles appeared negligible in view of the nearly linear correlation between scintigraphic and weight determined volumes. Scintigraphy compared favorably with radiography for estimating clinically encountered volumes of the RV and LV.

Angiography↗
PubMed1984

Gastric emptying of solid radiopaque markers: studies in healthy subjects and diabetic patients.

The purpose of these studies was to develop a radiologic method for assessing gastric emptying of an indigestible solid in humans and to apply this technique to the evaluation of patients with diabetes mellitus. Thirty healthy subjects ingested 10 solid radiopaque markers (small pieces of nasogastric tubing) together with a standard meal (donuts and 7-Up). Radiographs of the upper abdomen were obtained hourly for up to 6 h until all markers had emptied from the stomach. Although most of the liquid component of the meal, labeled with 111In, emptied during the first hour (as assessed simultaneously by radionuclide scintigraphy), few radiopaque markers emptied from the stomach during the first 2 h after the meal. Most markers emptied during the fourth postprandial hour, and all 10 markers had emptied by 6 h in 45 of 46 experiments. In contrast, not all of the solid radiopaque markers emptied from the stomach by 6 h in 16 of 26 experiments in patients with diabetes mellitus (p less than 0.001 vs. healthy controls). In some experiments, 99mTc-labeled scrambled eggs were added to the meal so that emptying of this digestible solid, assessed by scintigraphy, could be compared with emptying of liquids and solid radiopaque markers. In healthy subjects, the digestible solid emptied more slowly than the liquid (t 1/2 = 154 +/- 11 min vs. 30 +/- 3 min, p less than 0.001), but emptying of digestible solid was significantly faster than the emptying of the indigestible solid radiopaque markers. In diabetics, emptying rates for the digestible solid and liquid were close to normal (t 1/2 = 178 +/- 5 min and 40 +/- 3 min, respectively), whereas indigestible solid markers were retained in the stomach 6 h after the meal in 50% of the patients. Radiopaque markers proved to be a simple method for measuring gastric emptying of indigestible solids in humans. Using this technique, patients with insulin-dependent diabetes mellitus had a high incidence of abnormally slow gastric emptying of indigestible solids; the method may be a more sensitive indicator of gastric motor dysfunction than radionuclide scintigraphy.

Adult↗
PubMed1983

Role of cardiovascular nuclear medicine in evaluating trauma and the postoperative patient.

In the patient with cardiac trauma, radionuclide imaging may provide important information about cardiac mechanical function, vascular anatomy and integrity, myocardial perfusion, and myocardial metabolism. Studies require only minimal patient cooperation, can be performed relatively rapidly and often at the bedside, and may be repeated at frequent intervals for serial evaluations. These studies provide valuable adjunctive knowledge when selected and interpreted with knowledge of the mechanism of injury, timing of the examination relative to the time of injury, and most likely differential diagnoses.

Aged↗
PubMed1981

Scintigraphic diagnosis of cirrhosis: a receiver operator characteristic analysis of the common interpretative criteria.

Receiver operator characteristic (ROC) techniques were used to determine relative importance of heterogeneity, bone marrow uptake, hepatomegaly, splenomegaly, and focal lesions in the scintigraphic diagnosis of cirrhosis, as well as to determine whether each of the criteria should be used as an identifier (high sensitivity) or as a discriminator (high specificity). Heterogeneity, splenomegaly, and bone marrow uptake were found to be good identifiers of hepatic disease. However, heterogeneity was found to be a poor discriminator for cirrhosis, splenomegaly showed some value as a discriminator, and bone marrow uptake was found to be a reliable discriminator for alcoholic liver disease. The presence of focal lesions was a good discriminator for metastatic disease, and was not specific for cirrhosis. Hepatomegaly also was not specific for cirrhosis. This method of analysis provides a relatively simple method for assembling a hierarchical guide to diagnostic criteria for the interpreting physician.

False Negative Reactions↗
PubMed1981

Multigated equilibrium radionuclide angiocardiography: improved detection of left ventricular wall motion abnormalities and aneurysms by the addition of the left lateral view.

The usefulness of adding the left lateral (LLAT) view to the standard anterior and left anterior oblique views in multigated equilibrium radionuclide angiocardiography was assessed in 50 patients. Contrast ventriculography was used as the standard. Receiver operating characteristic (ROC) curve analysis was used to assess results. Recognition of inferior wall motion abnormality and left ventricular aneurysms was improved significantly by the addition of the LLAT view. Sensitivity was improved for inferior wall motion abnormality and for aneurysms; there was no loss of specificity. There was no improvement in recognition of anterior wall and apical regional abnormalities in the absence of aneurysms.

Adult↗
PubMed1980

The nonspecificity of diffuse pulmonary uptake of 67Ga on 24-hour images.

Eighteen patients who underwent whole-body scintigraphy 24 and 48 hours after intravenous injection of 67Ga-citrate were evaluated retrospectively. At 24 hours, 7 of the 16 normal patients (44%) and both abnormal patients demonstrated significant pulmonary uptake. However, by 48 hours, only 2 normal patients (12%) remained positive, while both abnormal patients continued to show significant pulmonary activity. The authors conclude that 48-hour 67Ga images offer improved specificity and uncompromised sensitivty in patients with diffuse pulmonary disease.

Adult↗