PubMed Health⌕ Search

Biomedical subjects

S Cochavi

Publications and source records attributed to S Cochavi.

17 recordsLinked to original sources
PubMed1982

Positron emission tomographic imaging of the myocardium with 81Rb.

An approach to the assessment of regional myocardial perfusion has been developed utilizing positron emission tomographic imaging of the heart after intravenous administration of 81Rb (T1/2=4.6 hr) and a multicrystal positron camera. In five intact anesthetized dogs, 1.0 to 2.0 mCi of 81 RbCl was administered and imaging begun 5 min later. A total of 7 to 9 transverse section images of the heart (1 cm thick) were obtained by the computer reconstruction of 208 images taken at uniformly spaced angles as the camera was rotated 180 degrees around the animal. Collection time was 18 min. Emission images of 81Rb activity were corrected for attenuation by first obtaining transmission data using a planar positron-emitting source. Transverse section images through the apex of the heart showed uniform uptake of 81Rb+ activity below the left ventricular (LV) cavity. Tomographic images through the midventricular level showed myocardial 81Rb+ distribution in an annular pattern around the LV cavity, and tomographic cuts through the base of the heart showed a horseshoe appearance of activity anteriorly and diminished tracer uptake posteriorly in the region of the left atrial wall. These studies demonstrate the feasibility of three-dimensional myocardial imaging by using the 33% positron emission of 81Rb+ and a positron camera.

Animals↗
PubMed1982

Planar imaging of positron-emitting radionuclides with a multicrystal camera.

A multicrystal gamma camera has been evaluated for the imaging of 511-keV photons resulting from positron emission. With minor instrument modifications, images of a phantom demonstrating good resolution are obtained. Satisfactory planar images are obtained in animals using fluorine-18 or rubidium-82. These findings establish the feasibility of planar imaging of positron emitters in a clinical setting, and may make possible the more rapid development assessment, and dissemination of positron-emitting radionuclides, thus promoting utilization of tomographic positron imaging techniques.

Animals↗
PubMed1980

Detection of pulmonary emboli by positron imaging of inhaled 15O-labeled carbon dioxide.

A new radionuclide approach to the scintigraphic detection of pulmonary emboli is described. This method utilizes cyclotron-produced C15O2, administered by inhalation, for rapid labeling of pulmonary blood. Following clearance of oxygen-15 from the lungs by pulmonary blood flow, focal retention of activity results from stasis of blood distal to emboli. On serial positron imaging, focally retained activity delineates embolized pulmonary segments and identifies the location and extent of pulmonary emboli. In animal studies this positron scintigraphic method detected emboli as small as 2 mm in diameter. In patients with suspected pulmonary emboli, this approach appears to be both sensitive and specific. Clinically, C15O2 inhalation imaging is most useful for the detection of pulmonary emboli in patients with chronic lung disease or congestive heart failure. It is rapid and safe and can be easily repeated, with minimal radiation exposure, for determining resolution rates of emboli and for assessing residual blood flow distal to emboli.

Animals↗
PubMed1980

Quantification of myocardial infarction by computer-assisted positron emission tomography.

The accuracy of three-dimensional transverse section positron emission imaging for quantification of myocardial infarction size was validated and compared with the accuracy of two dimensional planar positron imaging. After induction of acute anterior myocardial infarction in anaesthetised dogs, gallium-68 albumin microspheres were injected into the left atrium. Planar and transverse section images of the thorax were obtained with a multicrystal positron camera. After staining with tetrazolium tetrachloride injected intravenously, the hearts were excised, sectioned manually, and planar imaging repeated. Each myocardial infarction was clearly delineated by transverse section imaging with high contrast ratios (mean 0.68 +/- 0.02 SEM); planar imaging identified seven of nine infarcts but with lower contrast ratios (0.24 +/- 0.04; P < 0.001). The volume of infarcted myocardium determined from transverse section images correlated well with true infarct volume (r = 0.94); whereas planar images poorly predicted infarct size (r = 0.63). Thus, computer-assisted transverse section positron imaging provides in vivo localisation of microsphere distribution for improved radioisotopic quantification of myocardial infarction.

Animals↗
PubMed1980

Preliminary imaging results with 18F-2-fluoro-2-deoxy-D-glucose.

Transverse section imaging with 18F-2-fluoro-2-deoxy-D-glucose (2FDG) is of considerable interest because quantitative values of regional glucose metabolism may be obtained. We present preliminary results using 2FDG produced by the Brookhaven National Laboratory and imaged with the PCII at the Massachusetts General Hospital. Three studies are reported showing the distribution in dog, monkey, and in brain of an essentially normal patient.

Animals↗
PubMed1979

Assessment of regional myocardial perfusion by positron emission tomography after intracoronary administration of Gallium-68 labeled albumin microspheres.

Positron emission computed tomography (ECT) of the normal and ischemic canine heart was undertaken in eight anesthetized dogs after the intracoronary administration of 68gallium labeled human serum albumin microspheres (SAM). Bolus doses of 200 muCi of 68Ga-SAM were injected into the left anterior descending (LAD) and left circumflex coronary arteries of four normal dogs and four dogs undergoing LAD ligation. Positron imaging of 68Ga-SAM distribution was performed with a multicrystal positron camera and computer reconstruction. In normal dogs, five to six axial transverse section images of the heart demonstrated the transmural distribution of 68Ga-SAM in an annular pattern around the left ventricular cavity. In dogs with LAD ligation, perfusion defects in the anterolateral wall and septum were observed in tomographic cuts through ischemic areas. In conclusion, these studies demonstrate the feasibility of positron ECT imaging of the heart after intracoronary administration of 68Ga-SAM.

Animals↗
PubMed1979

Transverse-sectional imaging with Na18F in myocardial infarction.

The potential utility of Na18F for acute infarct imaging was assessed in a canine model with a positron camera. Transverse-section imaging of radiofluoride in five dogs with acute myocardial infarction, using a multicrystal positron camera, clearly demonstrated the zones of damage as areas of increased activity. The F-18 uptake in the infarct zones was found to peak at 48 to 72 hr after coronary ligation, as does Tc-99m pyrophosphate. Preliminary in vitro studies indicate that the relative F-18 uptake, 48 after ligation, is an inverse linear function of regional blood flow.

Ammonia↗
PubMed1979

Resolution rates of pulmonary embolism assessed by serial positron imaging with inhaled O-15-labeled carbon dioxide.

Embolic obstruction of pulmonary blood flow results in delayed regional clearance of inhaled C15O2. Focally retained C15O2 appears as zones of increased O-15 activity on serial positron scintigrams, which show the locations of occluded pulmonary segments. Inhalation of C15O2, with serial imaging by a multicrystal positron camera, was used to locate and assess the magnitude of occluded pulmonary segments in eight patients with arteriographically documented pulmonary emboli. The imaging with C15O2 inhalation was repeated after 1 wk of i.v. heparin therapy to evaluate the ability of this technique to determine resolution rates of pulmonary emboli during anticoagulant therapy. In all patients, zones of increased C15O2 activity corresponded with sites of emboli identified arteriographically. After 1 wk of continuous heparin therapy, zones of focally retained C15O2 were totally resolved in three patients, diminished in four, and unchanged in one. The regional pulmonary clearance rate of C15O2 was delayed over embolized pulmonary segments in all patients (men clearance half-time = 42.2 sec +/- 11.2 s.e.m.) and improved after heparin therapy (13.9 +/- 3.9 sec; p less than 0.05). Serial C15O2 inhalation imaging is a rapid noninvasive radionuclide technique for detection of pulmonary emboli. It can be repeated at frequent intervals to assess the resolution of emboli during anticoagulant therapy.

Adult↗
PubMed1978

Scintigraphic detection of pulmonary emboli by serial positron imaging of inhaled 15O-labeled carbon dioxide.

Inhaled radioactive carbon dioxide is retained in pulmonary blood distal to embolic obstruction and appears as an area of increased radioactivity that delineates the site and magnitude of the affected zone. The scintigraphic detection of pulmonary emboli by serial imaging of inhaled carbon dioxide labeled with cyclotron-produced 15O2 was evaluated in 27 patients undergoing conventional pulmonary ventilation/perfusion imaging and pulmonary arteriography. Fifteen patients proved to have pulmonary emboli on arteriography. Sensitivity (87%) and specificity (92%) rates for inhalation imaging were superior to those of conventional ventilation/perfusion imaging (P less than 0.05). Clearance of 15O2 activity was markedly delayed over embolized pulmonary segments (mean half time of 47.0 +/- 11.1 seconds [S.E.M.]) in comparison to normal segments (mean of 3.6 +/- 0.08 seconds; P less than 0.001). Pulmonary imaging by this method provides an approach to the detection of pulmonary emboli that is relatively sensitive and specific and permits analysis of persisting perfusion in embolized pulmonary segments. A major practical limitation, however, is the necessity of a nearby cyclotron.

Adult↗
PubMed1978

Transverse section imaging with carbon-11 labeled carbon monoxide.

The inhalation of small quantities of carbon-11 labeled carbon monoxide results in a useful red cell label to identify vascular structures in the body and quantitate red cell concentration in tissues. Transverse section images are obtained using PC-II, the Massachusetts General Hospital (MGH) Positron Camera. Attenuation correction is performed either by means of transmission data or by analytical methods. Sets of transverse section images give information on red cell distribution in head and torso. Such images may be useful in identifying vascular abnormalities or in quantitating red cell physiology.

Aorta, Thoracic↗
PubMed1978

Detection of experimental pulmonary emboli in dogs by sequential positron imaging after inhalation of 15O-carbon dioxide.

After inhalation, C15O2 (T1/2 = 2 minutes) rapidly diffuses into pulmonary blood and is cleared from the lungs within 10 seconds. The purpose of this study was to determine whether impaired clearance of inhaled C15O2 from oligemic zones, distal to areas of obstructed pulmonary blood flow, could be detected by serial pulmonary imaging with a positron camera. Experimental obstruction of branches of the pulmonary artery was induced in 19 anesthetized dogs by inflation of balloon-tipped catheters (8-12 mm in diameter), injection of radiopaque silicone spheres (0.5-4.0 mm), and embolization with barium-impregnated autologous blood clots (1-5 mm) via the right external jugular vein. After a single bolus injection of 2 mCi of C15O2 into the endotracheal tube, serial lung images of 15O activity were obtained over 60-180 seconds. Obstruction of pulmonary arterial branches resulted in visualization of discrete zones of impaired 15O clearance which varied in area with catheter diameter. Location and size of these zones were confirmed by repeat imaging after direct injection of 15O-labeled blood through the distal catheter lumen. In dogs receiving autologous clots (n = 8), similar zones of impaired 15O clearance were consistently imaged, and single emboli as small as 2 mm in diameter produced regions of retained 15O activity. Zones of retained 15O activity corresponded to the location of radiopaque emboli on chest radiographs. This study introduces a new technique of radionuclide imaging for detection of pulmonary emboli that is noninvasive, safe, sensitive, and repeatable at short intervals.

Animals↗