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Biomedical subjects

J E Juni

Publications and source records attributed to J E Juni.

At least 37 records · Page 2Linked to original sources
PubMed1992

Ratio of hepatic arterial-to-portal venous blood flow--validation of radionuclide techniques in an animal model.

The ratio of hepatic arterial-to-portal venous blood flow can be determined from the analysis of a first-pass bolus through the liver by a number of techniques. This study examines the validity of four radiotracer techniques in an animal model. Thirty-four flow studies (3 mCi 99mTc-DTPA/study) were performed in seven anesthetized pigs. Images were acquired for 200 sec and time-activity curves were generated from lung, liver and kidney ROIs. These curves were analyzed using a slope-based (HPI), a height-based (mHAR) and two deconvolution-based methods employing exponential or gamma variate fits. There was an excellent correlation (r greater than 0.9) between results obtained with flow probes and the radiotracer techniques, with the exception of the HPI technique (r = 0.75). The mHAR and deconvolution techniques were inaccurate at very low and high arterial flows, due respectively to noise limitations and hemodynamic instability in the animal. Nevertheless, these techniques appear to be the most promising for routine clinical use.

Animals↗
PubMed1991

Gated cardiac blood pool studies in atrial fibrillation: role of cycle length windowing.

Cycle length windowing is gaining increasing acceptance in gated blood pool imaging of patients with atrial fibrillation (AF). The goals of this study were: to assess differences of ejection fraction (EF) in AF with and without windowing and to determine how EF varied with cycle length in patients with AF. Twenty patients with AF were prospectively studied by gated blood pool imaging, with simultaneous collection in each patient of 5-7 studies with cycle length windows spanning the cycle length histogram. Each window accepted beats of only a narrow range of cycle lengths. EF was determined for each of the narrow cycle length windows as well as for the entire gated blood pool study without cycle length windowing. For every patient an average of the windowed EFs was compared with the non-windowed EF. EF values were similar (mean windowed: 46.6; non-windowed: 45.5; P = 0.16), and there was a good correlation between the two techniques (r = 0.97). The data were then examined for a relationship of EF with cycle length. The difference from average windowed EF (delta EF) was calculated for each window and plotted vs. the cycle length of the center of each window. No predictable linear or nonlinear relationship of delta EF with window position was observed. Lack of predictable variation of EF with cycle length is likely due to lack of a predictable amount of ventricular filling for a given cycle length, as the amount of diastolic filling in AF depends on the random cycle length of the preceding beat.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Fibrillation↗
PubMed1991

Submaximal exercise thallium-201 SPECT for assessment of interventional therapy in patients with acute myocardial infarction.

Submaximal thallium-201 stress testing has been shown to provide important diagnostic and prognostic information in patients with acute myocardial infarction. The purpose of this investigation was to evaluate the diagnostic value of early submaximal stress testing and thallium-201 single photon emission computed tomography (SPECT) after interventional therapy. Scintigraphic results from 56 patients with infarctions, who underwent acute thrombolytic therapy, angioplasty, or both, were compared with late (6 weeks) functional outcome as assessed by radionuclide ventriculography and with results of discharge coronary angiography. A linear correlation was found between the extent of thallium-201 SPECT perfusion defect and late ventricular function (r = 0.74, p less than 0.01). Forty-two percent of patients with large SPECT perfusion defects had normal left ventricular ejection fractions, suggesting an overestimation of infarct size by early imaging. Sensitivity and specificity of thallium-201 SPECT for detection of coronary artery stenosis in noninfarct territories was 57% and 46%, respectively, indicating limited diagnostic definition of extent of underlying coronary artery disease. Results of follow-up coronary angiography showed a significant relationship between the size of the initial perfusion defect and early restenosis or reocclusion of the infarct artery. Thus the extent of early thallium-201 perfusion defects correlates with late functional outcome but appears to overestimate the degree of injury. Submaximal thallium-201 stress testing allows only limited characterization of underlying coronary artery disease. Early assessment of infarct size may identify a patient population at high risk for reocclusion of the infarct artery.

Adult↗
PubMed1991

Lung scanning in the diagnosis of pulmonary embolism: the emperor redressed.

Diagnosis and management of the patient with pulmonary embolism remains a vexing clinical problem. Emboli are often unsuspected clinically. Ventilation-perfusion (VQ) scintigraphy is known to miss some emboli found on pulmonary angiography. Some physicians recommend diagnostic approaches in which the lung scan plays a relatively minor role, and angiography is required for many patients. Major prospective studies recently have made available objective data for formulation and evaluation of diagnostic and therapeutic strategies. These data suggest that the lung scan is a better predictor of patient outcome than has been previously appreciated. The goal of V/Q scanning is not detection of pulmonary emboli per se, but rather the identification of patients at a high or low risk for future embolic events if they are not anticoagulated. Several studies have shown that some emboli found on angiography are clinically benign and, in the absence of persistent thrombosis of the lower extremities, do not require anticoagulation. Treatment trials and clinical follow-up studies have shown that although the V/Q scan is not always predictive of angiogram results, it is a reliable predictor of patient outcome. In the absence of deep vein thrombosis, the low-probability scan identifies a patient population not requiring anticoagulation. When combined with objective studies of the venous system, the ventilation-perfusion lung scan provides a guide to management in the great majority of patients. Pulmonary angiography is required only occasionally.

Angiography↗
PubMed1990

NucNet: a single-vendor clinical picture archiving and communication system--description and reflections.

In 1984 to 1985, work commenced at the University of Michigan to develop, in cooperation with commercial vendors, a picture archiving and communication system capable of handling all clinical imaging in the division of nuclear medicine. The guiding features of NucNet are the optimization of the system for perceived, rather than actual speed, and the use of technology appropriate to the majority of clinical activity rather than to the entirety. This has resulted in a cost-effective system that has been easy to use and well accepted for routine clinical work. A new image management system currently being developed at William Beaumont Hospital is based on these principles but uses the latest generation of powerful microcomputers to perform most of the actions currently performed by larger computers on NucNet. It is anticipated that, using current technology, the key functionality of NucNet can be obtained for a fraction of its original cost.

Costs and Cost Analysis↗
PubMed1990

Measurement of hepatocellular function with deconvolutional analysis: application in the differential diagnosis of acute jaundice.

A direct, noninvasive technique was developed to quantitate hepatocyte function with computer assessment of scintiscans obtained after administration of technetium-99m disofenin in 53 patients with acute jaundice: 32 patients with normal livers, 10 patients with acute biliary obstruction, and 11 patients with acute hepatocellular dysfunction. In all patients a final clinical diagnosis was obtained with follow-up for a minimum of 4 months and, in most patients with obstruction or dysfunction, with surgery, intraoperative cholangiography, ultrasound, and/or computed tomography. Heart (blood pool) and liver time-activity curves were generated for 32 minutes after intravenous injection of 5-15 mCi (185-555 MBq) of Tc-99m disofenin and were subjected to deconvolutional analysis to determine the first-pass hepatocyte extraction fraction (HEF) of the tracer. The difference in HEF between patients with obstruction and those with dysfunction was highly significant (P = 3.3 X 10(-19)). Deconvolutional analysis eliminates the effects of tracer recirculation, thus permitting direct measurement of hepatic disofenin extraction, and appears to provide functional information useful in evaluation of the patient with acute jaundice.

Acute Disease↗
PubMed1990

Blood flow in the gluteus maximus of seated individuals during electrical muscle stimulation.

Blood flow was measured under the ischial tuberosites of seated individuals during electrical stimulation of the gluteus maximus muscles. Eight able-bodied and six spinal cord injured subjects were studied. Muscle blood flow was measured via radioactive tracer (133xenon) clearance. Retention of xenon in adipose tissue prevented accurate measurement of blood flow in cutaneous and subcutaneous tissue. Average muscle blood flow for both subject groups was increased during stimulation as compared to rest. All subjects showed an increase in muscle blood flow during stimulation. The statistical significance from a paired student t-test was greater for able-bodied subjects (p less than .05) than for spinal cord injured subjects (p = .12). The increase in muscle blood flow produced by electrical muscle stimulation in seated individuals supports the hypothesis that electrical muscle stimulation can help prevent pressure sores.

Buttocks↗
PubMed1989

Modulation of liver tumor blood flow with hepatic arterial epinephrine: a SPECT study.

Changes in the relative arterial flow to hepatic tumors and adjacent normal liver, in response to varied doses of hepatic arterial epinephrine, were studied with single photon emission computed tomography. In 18 patients with known hepatic tumors, hepatic artery perfusion scans were obtained with the concurrent infusion of technetium-99m-labeled macroaggregated albumin and escalating doses of epinephrine (0-10 micrograms/min). Regions of interest were drawn around tumor and adjacent normal liver in three planes, and the average tumor-to-liver ratio (T:L) was calculated. In all 18 patients, there was a measurable baseline T:L perfusion advantage (range, 1.7-18.7; mean, 4.8). In 12 of 18 patients, this ratio increased with epinephrine (range, 1.1-53.6 times the baseline value; mean, 7.1). In six patients, no improvement in T:L could be demonstrated. In 14 patients the lung shunt index, a measurement of arteriovenous shunting, increased with escalating doses of epinephrine. This pilot study suggests that the infusion of epinephrine may improve the therapeutic index of certain regional therapies such as bolus drug infusions, hepatic arterial embolization, and radioactive microsphere therapy.

Epinephrine↗
PubMed1989

SPECT of the peritoneal cavity: method for delineating intraperitoneal fluid distribution.

Seventeen single-photon emission CT (SPECT) studies were performed after intraperitoneal administration of 99mTc-sulfur colloid in patients with a history of colon cancer to assess the extent of intraperitoneal fluid distribution prior to intraperitoneal chemotherapy. Planar gamma images were also obtained in all patients for correlation with the SPECT findings. Four patients had transmission CT scans of the abdomen after intraperitoneal administration of iodinated contrast material. In seven patients, repeat planar and SPECT studies were performed with the original or a different infusion volume to determine if different volumes altered the fluid distribution qualitatively or quantitatively (using a linear profile method). We found that 360 degrees peritoneal SPECT is easily performed after intraperitoneal administration of 99mTc-sulfur colloid. SPECT provides more detailed anatomic information than planar scans do. Spaces of the upper abdomen, such as the lesser sac, were resolved better with SPECT than with planar imaging. SPECT assessment of intraperitoneal fluid distribution also correlated well with transmission CT scans. Quantitative linear-profile radionuclide plots were reproducible at the same volume and showed no major differences in relative intraperitoneal fluid distribution between the 1.5- and 3.0-l infusion volumes, suggesting that the two delivery volumes were equivalent in relative distribution. SPECT appears to be a useful procedure to define the extent and location of intraperitoneally administered fluids. Thus, it may be of value in determining the intraperitoneal distribution of drugs and radiopharmaceuticals used in the treatment of intraabdominal tumors.

Adult↗
PubMed1988

Comparison of left ventricular function and contractile reserve after successful recanalization by thrombolysis versus rescue percutaneous transluminal coronary angioplasty for acute myocardial infarction.

To determine how coronary reperfusion affects rest and exercise ventricular function after acute myocardial infarction (AMI), 63 patients with a patent infarct artery after intravenous thrombolytic therapy (lysis) were compared with 27 patients who failed thrombolysis but had successful acute recanalization by percutaneous transluminal coronary angioplasty (PTCA) as a "rescue" procedure. Contrast ventriculography was performed acutely and on day 7. Resting radionuclide ventriculography was performed at 24 hours and repeated with exercise on day 30. There were no differences in global ejection fraction (EF) between the 2 groups during acute contrast ventriculography. However, by 24 hours, the EF had deteriorated in the rescue group (40 +/- 17 vs 49 +/- 11% in the lysis group, p less than or equal to 0.05). No improvement occurred in either group on day 7. By day 30, an improvement in resting radionuclide EF 5.9 +/- 1.9% occurred in rescue patients and the difference between rescue and lysis groups was no longer significant (46 +/- 14 vs 50 +/- 11%, p = 0.12). A normal (greater than or equal to 5%) increase in EF with exercise occurred in 64%, with either normal or exercise-enhanced regional wall motion present in 67% of patients. A significant increase in EF occurred within the rescue group, from 46 +/- 14% at rest to 50 +/- 15% at peak exercise (p less than or equal to 0.0005). The EF increased with exercise from 50 +/- 11 to 58 +/- 15% in the lysis group (p less than or equal to 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1988

Localization and imaging with radioiodine-labeled monoclonal antibodies in a xenogeneic tumor model for human B-cell lymphoma.

Two MoAbs directed towards human B-cell malignancies have been studied in a preclinical animal model to evaluate their potential for in vivo imaging and therapy of B-cell lymphomas. Anti-B1 reacts with virtually all immunoglobulin-bearing malignancies and non-T acute lymphoblastic leukemia. Anti-J5 reacts with the common acute lymphoblastic leukemia antigen found on non-T acute lymphoblastic leukemia and follicular lymphomas. Anti-T1 which recognizes the CD5 antigen on most T-cell leukemias and lymphomas was used as a control antibody. These monoclonal antibodies were radiolabeled with 125I or 131I by the ICl method. Namalwa (B-cell) and MOLT-4 (T-cell) tumors were grown s.c. in irradiated nude mice. The highest tissue concentration of 125I-labeled anti-J5 in Namalwa-bearing mice was in blood and tumor. The tumor/blood ratio ranged from 0.7-1.2, with the highest ratio 4 days after injection. Pharmacokinetic analysis indicated that the t1/2 beta of anti-J5 from blood and other tissues ranged from 40-50 h, while the t1/2 beta for tumor averaged 65 h. The area under the curve of tumor was 2- to 5-fold higher than the area under the curve of liver, kidney, skin, and muscle. The peak tissue levels of 125I-labeled anti-B1 in Namalwa-bearing mice were again in blood and tumor and 6 days following injection more than 5-fold greater activity was found in tumor compared to normal tissues other than blood. The tumor/blood ratio was 1.2 and 0.7 at 4 and 6 days after injection. 125I-labeled anti-B1 showed minimal uptake in antigen-negative MOLT-4 tumors and 125I-labeled anti-T1 showed little uptake in Namalwa tumors. Scintigraphic images were obtained following the injection of 131I-labeled anti-J5 and anti-B1 in nude mice bearing Namalwa tumors. These results indicate that radiolabeled anti-J5 and anti-B1 show promise as diagnostic and possibly therapeutic agents for human B-cell lymphoma, although there may be a limitation to clinical utility due to cross-reactivity with some normal cells.

Animals↗
PubMed1988

A randomized controlled trial of hospital discharge three days after myocardial infarction in the era of reperfusion.

To evaluate the feasibility and cost savings of hospital discharge three days after acute myocardial infarction, we screened 507 consecutive patients prospectively for clinical complications and exercise-test performance. Of 179 patients whose condition was classified as uncomplicated (no angina, heart failure, or arrhythmia 72 hours after admission), 126 underwent early exercise testing and 90 had no provocable myocardial ischemia. Eighty of these patients were randomly assigned to early (day 3) or conventional (days 7 to 10) hospital discharge. Seventy-six of them had received coronary reperfusion therapy (thrombolysis, angioplasty, or both). At six months of follow-up, there were no deaths or new ventricular aneurysms, and the early-discharge and conventional-discharge groups had similar numbers of hospital readmissions (6 and 10), reinfarctions (none and 5), and patients with angina (3 and 8). In the early-discharge group, 25 of 29 previously employed patients returned to work 40.7 +/- 21.9 days (mean +/- SD) after admission, as compared with 25 of 27 patients in the conventional-discharge group, who returned to work after a mean of 56.9 +/- 30.3 days (P = 0.054). The mean cumulative hospital and professional charges were $12,546 +/- 3,034 in the early-discharge group, as compared with $17,868 +/- 3,688 in the conventional-discharge group (P less than 0.0001). In carefully selected patients with uncomplicated myocardial infarction, hospital discharge after three days is feasible and leads to a substantial reduction in hospital charges. Before this strategy can be widely recommended, however, its safety must be confirmed in larger prospective clinical trials.

Clinical Trials as Topic↗
PubMed1988

The appended curve technique for deconvolutional analysis--method and validation.

Deconvolutional analysis (DCA) is useful in correction of organ time activity curves (response function) for variations in blood activity (input function). Despite enthusiastic reports of applications of DCA in renal and cardiac scintigraphy, routine use has awaited an easily implemented algorithm which is insensitive to statistical noise. The matrix method suffers from the propagation of errors in early data points through the entire curve. Curve fitting or constraint methods require prior knowledge of the expected form of the results. DCA by Fourier transforms (FT) is less influenced by single data points but often suffers from high frequency artifacts which result from the abrupt termination of data acquisition at a nonzero value. To reduce this artifact, we extend the input (i) and response curves to three to five times the initial period of data acquisition (P) by appending a smooth low frequency curve with a gradual taper to zero. Satisfactory results have been obtained using a half cosine curve of length 2-3P. The FTs of the input and response I and R, are computed and R/I determined. The inverse FT is performed and the curve segment corresponding to the initial period of acquisition (P) is retained. We have validated this technique in a dog model by comparing the mean renal transit times of 131I-iodohippuran by direct renal artery injection to that calculated by deconvolution of an intravenous injection. The correlation was excellent (r = 0.97, P less than 0.005). The extension of the data curves by appending a low frequency "tail" before DCA reduces the data termination artifact. This method is rapid, simple, and easily implemented on a microcomputer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Infarct vessel status after intravenous tissue plasminogen activator and acute coronary angioplasty: prediction of clinical outcome.

To determine the risk of arterial reocclusion or recurrent ischemia after acute intervention in myocardial infarction, we analyzed the results of coronary arteriography performed acutely and at 1 week in 50 consecutive patients who received acute intervention. Successful recanalization of the infarct vessel was achieved in 46 (92%) patients after therapy with intravenous tissue plasminogen activator, percutaneous coronary angioplasty, or both. Follow-up angiography in 44 showed early reocclusion in 10 patients (23%). Intermittent patency during acute arteriography was always associated with reocclusion; suboptimal (Thrombolysis in Myocardial Infarction [TIMI] class 2) flow was associated with a 50% rate of reocclusion. Although residual stenosis of greater than 50% alone was not predictive of rethrombosis, 90% of all reocclusions were associated with either stenosis greater than 50%, TIMI 2 flow, or intermittent patency. Absence of these angiographic risk factors predicted a 95% patency rate at follow-up. In-hospital cardiac complications occurred in 17 of 23 (74%) patients with residual stenosis of greater than 50% (death in four, ischemia in 13), and late revascularization was required in 53% of survivors. Only 15% of the group with less than 50% stenosis had an in-hospital ischemic event (p less than 0.001). Thus, after acute intervention, an infarct vessel with intermittent patency or suboptimal flow is associated with a high rate of reocclusion. Residual stenosis greater than or equal to 50% appears to predict a high incidence of negative in-hospital clinical outcomes and the need for subsequent revascularization.

Adult↗
PubMed1988

Scintigraphic demonstration of accessory hepatic duct leak following liver transplantation.

Few noninvasive methods are available to diagnose complications following liver transplantation. Hepatobiliary scintigraphy can differentiate rejection from primary biliary complications such as obstruction or extravasation in patients with nonspecific clinical findings such as fever and rising liver function studies. In the following case report, an unexpected biliary leak from a recipient accessory hepatic duct was demonstrated by [99mTc] DISIDA scintigraphy following liver transplantation.

Adult↗
PubMed1988

Hepatocyte versus biliary disease: a distinction by deconvolutional analysis of technetium-99m IDA time-activity curves.

A combination of quantitative hepatobiliary imaging techniques was developed to study normal control subjects and patients with 3 categories of hepatobiliary disease: 1) alcoholic cirrhosis; 2) sclerosing cholangitis; and 3) isolated common bile duct obstruction. Scintigraphic images were supplemented by quantitative measurement of hepatic extraction fraction by deconvolutional analysis and liver excretion T 1/2 by a nonlinear least squares method. In diseases confined primarily to the biliary tract (isolated common bile duct obstruction and sclerosing cholangitis), the mean hepatic extraction fraction as measured by deconvolutional analysis was not different from that in normal controls. In severe alcoholic cirrhosis, considered primarily a hepatocyte disease, the hepatic extraction fraction was markedly reduced. The T 1/2 excretion, compared to normal subjects, was prolonged in all three liver disease categories. We conclude that these quantitative parameters were able to detect hepatobiliary disease and to separate severe hepatocyte disease from biliary tract disease.

Biliary Tract Diseases↗
PubMed1988

Effects of gating modes on the analysis of left ventricular function in the presence of heart rate variation.

Variations in cardiac cycle length during ECG-gated radionuclide ventriculography cause errors in measurement of left ventricular (LV) diastolic function. We used a computer model to investigate the relative accuracy of forward gating (FG), backward gating (BG), and three methods of combined forward-backward gating (FBG). LV time-activity curves (TAC) were simulated with total cycle lengths randomly varied (1 s.d. = +/- 10%). To match the known differential effects of cycle-length variation on various parts of the cardiac cycle, 90% this variation was placed in diastasis and 10% in the rapid filling phase. Three hundred cycles of TACs were summed to form one "study". A total of 25 studies were performed and systolic and diastolic parameters were determined for each. These were compared to those of the mean length TAC. With a 20% cycle-length acceptance window, error in peak filling rate by FG was 0.7% root-mean-squared (RMS) compared to 18.5% RMS by BG. With a 5% window, RMS error by FG was 0.2% and 2.4% RMS by BG. Combined FBG algorithms gave intermediate results. We conclude that the simplest and most accurate method of analysis is to acquire forward gated TACs with appropriate cycle-length windows.

Algorithms↗