Search PubMed⌕ Search

Biomedical subjects

R F Uren

Publications and source records attributed to R F Uren.

At least 73 records · Page 4Linked to original sources
PubMed1983

Geometric determination of left ventricular volume from gated blood-pool studies using a slant-hole collimator.

A geometric method of measuring absolute left ventricular volumes from gated blood-pool studies obtained in a single-plane modified left anterior oblique view was evaluated prospectively in 30 patients who also underwent single-plane contrast ventriculography. The gated studies used a 30 degrees straight-bore slant-hole collimator with the holes slanted caudally. Left ventricular end-diastolic volume was calculated using the area-length method, with semiautomatic definition of the left ventricular region of interest and the maximum length of the left ventricle. Ejection fraction was determined from the left ventricular time/activity curve. The left ventricular end-systolic volume was derived using the end-diastolic volume and ejection fraction. Correlation coefficients between the two methods were 0.93 for end-diastolic volume, 0.95 for end-systolic volume, and 0.91 for ejection fraction. This method provided accurate and highly reproducible measurements of actual left ventricular volumes and was easily applicable in routine clinical studies.

Adult↗
PubMed1983

Cost effectiveness of the all-digital nuclear medicine department.

The costs of an all-digital nuclear medicine department are compared to a nuclear medicine department using and storing conventional photographic images. The digital format results in a savings of $1.27 per study or an annual savings of $7,620.00 for a department which does 6,000 examinations each year.

Computers↗
PubMed1982

Comparison of thallium-201 scanning in idiopathic dilated cardiomyopathy and severe coronary artery disease.

To determine whether cardiomyopathy could be distinguished from coronary artery disease, we used thallium scanning to study 25 patients with severe left ventricular dysfunction and chronic heart failure. Ten patients had normal coronary arteries and idiopathic cardiomyopathy (ejection fraction 20 +/- 5%), and 15 patients had multivessel coronary disease and left ventricular dysfunction (ejection fraction 25 +/- 6%). The exercise time and maximal heart rate were similar in the two groups. Two patients with cardiomyopathy and 11 with coronary artery disease had a positive exercise ECG (p less than 0.05). Thallium scans showed perfusion defects in all 25 patients. The perfusion defects were complete in nine coronary artery disease patients (60%) and in one patient (10%) with cardiomyopathy (p less than 0.05). Extensive defects involving more than 40% of the left ventricular circumference, the number of segments involved, redistribution on the 4-hour scan, lung uptake and ventricular size were similar in the two groups. Perfusion defects on thallium scanning can occur in patients with idiopathic dilated cardiomyopathy and chronic heart failure. Thallium scanning cannot be reliably used in patients with chronic heart failure to distinguish coronary artery disease from cardiomyopathy unless complete defects are present.

Adult↗
PubMed1981

Localization of coronary artery disease with exercise electrocardiography: correlation wit thallium-201 myocardial perfusion scanning.

In 61 patients with single vessel coronary artery disease (70 percent or greater obstruction of luminal diameter in only one vessel) and no previous myocardial infarction, the sites of ischemic changes on 12 lead exercise electrocardiography and on thallium-201 myocardial perfusion scanning were related to the obstructed coronary artery. The site of exercise-induced S-T segment depression did not identify which coronary artery was obstructed. In the 37 patients with left anterior descending coronary artery disease S-T depression was most often seen in the inferior leads and leads V4 to V6, and in the 18 patients with right coronary artery disease and in the 6 patients with left circumflex artery disease S-T depression was most often seen in leads V5 and V6. Although S-T segment elevation was uncommon in most leads, it occurred in lead V1 or a VL, or both, in 51 percent of the patients with left anterior descending coronary artery disease. A reversible anterior defect on exercise thallium scanning correlated with left anterior descending coronary artery disease (probability [p] less than 0.0001) and a reversible inferior thallium defect correlated with right coronary or left circumflex artery disease (p less than 0.0001). In patients with single vessel disease, the site of S-T segment depression does not identify the obstructed coronary artery; S-T segment elevation in lead V1 or aVL, or both, identifies left anterior descending coronary artery disease; and the site of reversible perfusion defect on thallium scanning identifies the site of myocardial ischemia and the obstructed coronary artery.

Coronary Disease↗
PubMed1980

Uremic cardiomyopathy--effect of hemodialysis on left ventricular function in end-stage renal failure.

Left ventricular ejection fraction was measured by radionuclide left ventriculography before and immediately after hemodialysis in 20 uremic patients, 11 of whom presented with congestive heart failure. Ejection fraction and contraction were normal in 15 patients (Group A), six of whom had signs of congestive failure; they were abnormal in five patients (Group B), all of whom were in clinical heart failure. Mean arterial pressure and body weight decreased by a similar amount after dialysis in both groups, and heart rate did not change. In Group A ejection fraction was unchanged by dialysis (0.63 +/- before vs. 0.62 +/- 0.09 after) (mean +/- S.D.), but in Group B it was improved significantly (0.32 +/- 0.04 before vs. 0.44 0.08 after) (P less than 0.01). In three patients in Group B cardiomegaly and ejection fraction returned to normal with long-term hemodialysis. In end-state renal failure, radionuclide left ventriculography can separate patients with circulatory congestion due to fluid overload from patients with left ventricular dysfunction in whom hemodialysis can provide immediate and long-term improvement.

Adolescent↗
PubMed1980

Cardiac tamponade: accurate diagnosis by radionuclide angiography.

This study was performed to define the signs of cardiac tamponade on radionuclide angiography. The first pass studies were performed on a large field gamma camera, using a bolus of technetium pertechnetate. Three hundred and seventy-two studies were analysed. Cardiac tamponade requiring surgical intervention was present at the time in 28 studies. The diagnostic signs of cardiac tamponade on radionuclide angiography were: (1) Right ventricular compression--sensitivity 82%, specificity 97%, predicitive value of a positive result 72%, predictive value of a negative result 99%, and (2) Right atrial compression--sensitivity 21%, specificity 99%, predictive value of a positive result 75%, predictive value of a negative result 94%. Cardiac tamponade can be accurately diagnosed on radionuclide angiography and thus indicate those pericardial effusions which require urgent drainage.

Cardiac Tamponade↗
PubMed1980

Serial thallium-201 myocardial perfusion scanning in acute myocardial infarction.

Serial myocardial perfusion scanning was performed in 30 patients with acute myocardial infarction. Scanning was commenced less than six hours after onset of symptoms in 12 patients, 6-24 hr in eight and 24-120 hr in ten. All 30 patients showed thallium defects corresponding to the ECG site of infarction. When initial and four-hour scans were compared, constant defects were present in ten patients and changing defects in 20. Of the 169 segments with defects on the initial scan, 117 (69%) remained constant, 41 (24%) improved, and 11 (7%) deteriorated. More defects changed in the patients scanned earlier (less than 6 hr) than in the patients scanned later (more than 6 hr) (42% vs 23% P less than 0.025), and more defects changed in patients with subendocardial compared to transmural infarction (49% vs 26% P less than 0.025). During a mean follow-up period of 18 months, seven patients died, two developed left ventricular failure, seven had angina and 14 remained asymptomatic. The non-survivors had significantly larger thallium defects than the survivors (55 +/- 15% vs 37 +/- 14%, P less than 0.005). Serial change on thallium scanning was not related to the clinical course. Perfusion defects on serial thallium scanning are useful in detecting and localising early myocardial infarction and the size of defects is related to the subsequent clinical course. Changing perfusion defects on serial scanning suggesting peri-infarctional ischaemia are common, and make assessment of therapeutic interventions to limit infarct size difficult, but are not related to the clinical course.

Adult↗
PubMed1980

The value of exercise electrocardiography and exercise thallium-201 myocardial perfusion scanning in determining the presence of single vessel coronary artery obstruction.

In 39 patients with single vessel coronary artery disease and no previous myocardial infarction, exercise thallium-201 myocardial perfusion scanning and 12 lead exercise electrocardiography (ECG) were compared to see how reliably each method identified the site of coronary artery obstruction. Significant (greater than or equal to 70% diameter) stenosis was present in the left anterior descending (LAD) coronary artery in 21 patients, in the right coronary artery (RCA) in 14 patients and in the left circumflex (LCX) in four patients. Thallium defects on the scan in the septal (SEPT), anteroseptal (ANT SEPT) and anterior (ANT) segments correlated (P less than 0 . 0005) with LAD disease and defects in the inferior (INF), posteroinferior (POST INF), and posterior (POST) segments correlated (P less than 0 . 0005) with RCA or LCX disease. Exercise induced ST segment elevation in VI and/or AVL correlated with LAD disease. The site of ischaemic ST depression did not correlate with disease in any vessel. ST segment depression in leads L2, 3, AVF (67%) and in leads V4--6 (67%) was most sensitive for detecting patients with LAD disease and ST depression in leads V4--6 was most sensitive (56%) for detecting patients with RCA or LCX disease but neither differentiated LAD from RCA/LCX disease.

Adult↗
PubMed1980

Exercise thallium imaging: location of perfusion abnormalities in single-vessel coronary disease.

Exercise-induced thallium defects were segmentally analyzed in four standard views (anterior, 40 degrees left anterior oblique, 60 degrees left anterior oblique, and left lateral) and correlated with the arteriographic findings in 49 patients with single-vessel disease (> 70% diameter narrowing). Defects in the septal (SEPT), anteroiseptal (ANT SEPT), and anterior (ANT) segments correlated (p < 0. 0005) with stenosis of the left anterior descending coronary artery (LAD). For LAD disease the ANT SEPT segment had the highest sensitivity (84%) and specificity (100%). Defects in the inferior (INF), posteroinferior (POST INF), and posterior (POST) segments correlated (p < 0.0005) with either right (RCA) or circumflex (LCX) stenosis. For RCA or LCX disease, the POST segment had the highest sensitivity (82%) and specificity (100%). The site of single-vessel coronary artery disease can be accurately predicted noninvasively by segmental analysis of thallium images in four anatomical projections.

Adult↗
PubMed1979

Preoperative and postoperative technetium-99m pyrophosphate myocardial scintigraphy in the assessment of operative infarction in coronary artery surgery.

The incidence of operative myocardial infarction was assessed by electrocardiogram (ECG) and technetium-99m pyrophosphate (99mTc-PyP) myocardial scintigrams in 89 consecutive patients undergoing coronary artery bypass grafting (CABG). Myocardial scintigrams were performed on the day before operation and repeated 2 to 3 days postoperatively. All patients survived operation, with three in-hospital deaths not related to myocardial infarction (mortality rate 3 percent). Operative infarction was assessed to have occurred in four of 89 patients (4 percent). Two had new Q waves and positive scintigrams; one, major ST-T wave changes and a positive scintigram; and the fourth, new Q waves without a positive scintigram. Three further patients (3 percent) had Q waves and positive scintigrams postoperatively, but myocardial infarction was evolving before anesthesia and operation. Twenty-seven of 89 patients (30 percent) were found to have abnormal scintigrams preoperatively. In two patients, both operated upon with evolving myocardial infarction, the scintigram was worse postoperatively. In 13 patients the scintigram was improved after operation. In 12 patients (13 percent) the abnormal preoperative scintigram was unchanged after operation. Preoperative and postoperative myocardial scintigrams and ECG's must be compared to assess the incidence of operative myocardial infarction in patients undergoing CABG.

Adult↗
PubMed1978

A model for the radionuclide measurement of ascitic fluid volumes.

Technetium-99m phytate colloids formed in vitro and in vivo were examined as radioindicators for estimation of the volume of third-space fluid in an ovarian ascites model using C3HeB/FeJ mice. In double-label experiments, the accuracy of the colloids for dilution analysis was found to be equal or superior to that of I-125 HSA. Sampling times 3--5 min after intraperitoneal administration were found to produce the best volume estimates. Four needle-stopcock assemblies inserted sequentially into the quadrants of the peritoneal cavity were used for administration and sampling of the radioindicators. The stopcocks could be closed to prevent leakage of ascitic fluid during the procedure. In contrast to radiolabeled albumin, Tc-99m phytate colloids have clinical use for simultaneous imaging of radiotracer migration to assess potential occlusion of diaphragmatic lymphatics by neoplastic cells, and for dilution analysis to estimate volume of ascitic fluid.

Animals↗
PubMed1977

Radionuclide left ventriculography with the slant hole collimator.

A 30 degrees slant-hole collimator was used during radionuclide ventriculography of the cardiac blood pool to improve imaging of the heart in both the modified left anterior oblique (MLAO) and right anterior oblique (RAO) views. In the MLAO view, with the holes slanted caudally, good separation between the left atrium and left ventricle was achieved, and the septum was displayed without foreshortening. In the RAO view with the collimator flat against the chest there was better resolution of the cardiac apex. The results of ejection fraction and wall motion analysis in these patients correlated well with contrast ventriculography (r=0.94). Combination of the slant-hole collimator, in vivo red blood cell labeling with stannous pyrophosphate, simultaneous collection of all phases of the cardiac cycle, and cine mode display, provide a practical system for the noninvasive measurement of left ventricular performance parameters.

Coronary Disease↗