Showing papers on "Perfusion scanning published in 1982"

Assessment of myocardial perfusion abnormalities with contrast-enhanced two-dimensional echocardiography.

Abstract: A new echocardiographic contrast agent, gelatin-encapsulated microbubbles, that an intramyocardial contrast effect, was evaluated as a marker for the detection of regions of abnormal myocardial perfusion in nine open-chest dogs. The gelatin-encapsulated microbubbles were injected into the aortic root under control conditions and during circumflex coronary artery occlusion. Myocardial perfusion was simultaneously assessed with radioactive microspheres. Echocardiographic contrast enhancement (ECE) was measured in footlamberts (Ft-L) from the videoscreen of an off-line playback system, using a commercially available light meter. A single short-axis section of the left ventricle was divided into octants to analyze myocardial perfusion. The equivalent regions of the echocardiographic image were analyzed for contrast enhancement and wall motion. An ECE > 0.3 Ft-L was seen in all 120 octants analyzed before circumflex coronary artery occlusion and in 48 of 51 (94%) octants with > 50% of normal zone flow during circumflex artery occlusion. An ECE ≤ 0.3 Ft-L identified 19 of 21 octants (with ≤ 50% normal zone flow and all 13 octants with ≤ 25% normal zone flow during coronary artery occlusion. In contrast, wall motion abnormalities (akinesis or dyskinesis) were seen in 13 of 51 octants (25%) with > 50% normal zone flow, and normal wall motion was seen in two of 21 octants (10%) with blood flow ≤ 50% of normal zone flow during circumflex coronary artery occlusion. We could not demonstrate a linear correlation between ECE and the absolute level of myocardial blood flow. We feel this was due to the limitations imposed by imaging an open-chest animal preparation, variation in the number of gelatin-encapsulated microbubbles used for each injection and variations in the echocardiographic gain settings among experiments. We conclude that contrast-enhanced two-dimensional echocardiography with gelatin-encapsulated microbubbles can accurately identify ischemic regions of the left ventricular myocardium. This technique is more accurate than wall motion analysis for detecting myocardial ischemia.

Initial experience with SPECT (single-photon computerized tomography) of the brain using N-isopropyl I-123 p-iodoamphetamine: concise communication

Abstract: Forty-six patients were studied with N-isopropyl I-123 p-iodoamphetamine (IMP) and the Harvard Scanning Multidetector Brain System. In nine control patients, good differentiation between the gray and white matter of the cerebral cortex and the basal ganglia was evident. Regional uptake was affected by physiologic maneuvers (visual stimulation). In 24 patients studied for stroke, IMP images demonstrated areas that were involved in acute infarction in eight patients whose initial transmission computerized tomography (TCT) was normal; IMP also showed perfusion abnormalities larger than the TCT abnormality in ten patients. Perfusion abnormalities were present in 23/24 of these patients. Seven patients studied with a history of TIA had normal TCT and IMP images. In three patients studied during seizure activity, regions of hyperperfusion corresponded to the EEG seizure focus. Markedly decreased activity was present in three patients with brain tumor and corresponded to the focal abnormality on the TCT study. Our study demonstrates the feasibility of assessing regional brain perfusion using a radiopharmaceutical that is lipid soluble and has a high extraction fraction in the brain, together with single-photon ECT.

Perfusion scintigraphy (Tc-99m MAA) during surgery for placement of chemotherapy catheter in hepatic artery: concise communication.

Abstract: In 17 patients receiving regional hepatic chemotherapy, /sup 99m/Tc macroaggregated albumin imaging was used to aid arterial catheter placement and to assess perfusion patterns. Intraoperative imaging with a portable gamma camera allowed immediate monitoring of hepatic and extrahepatic perfusion patterns and assisted catheter manipulation when necessary to achieve optimal flow distribution. In all 12 patients with standard hepatic arterial anatomy, complete perfusion of both lobes of the liver was achieved, although three of them required intraoperative catheter manipulation and repeat imaging after initial placement. The remaining five patients had aberrant hepatic arterial anatomy, and complete perfusion was more difficult to achieve; they exemplified the need for dual catheters, ligation of accessory hepatic branches, and repeated imaging.

Clinical ventilation imaging with In-113m aerosol: a comparison with Kr-81m.

Abstract: Following routine ventilation (Kr-81m)/perfusion (Tc-99m) scanning, we obtained aerosol ventilation scans using a solution of In-113m albumin and a settling-bag system. The large-volume settling bag reduces deposition of particles in the large airway by removing large droplets. The patient inhales the aerosol with 5-10 min of tidal breathing, then lung scans are obtained on a gamma camera. The energy of In-113m allows the ventilation scanning to be performed after Tc-99m perfusion scanning. Semiquantitative scoring of regional ventilation showed a close correlation (r = 0.97) between Kr-81m and In-113m aerosol ventilation scans. The aerosol technique gave a slight underestimation of ventilation compared with Kr-81m. This is explained by a slightly reduced penetration of particles to the periphery of the lung in patients with severe obstructive airways disease. In all cases, however, the aerosol did visualize all ventilated regions. The results indicate that this readily available aerosol technique can be useful for clinical ventilation imaging in multiple views.

Follow-up of surgically treated patients with massive pulmonary embolism--with reference to 12 operated patients.

Abstract: Since 1978, 17 patients have undergone surgery for massive pulmonary embolism in our department. Twelve patients survived and have been followed up for between 2 and 31 months postoperatively (mean 16 months). Reassessment of these patients included exercise tolerance test, pulmonary function test, perfusion scan, right heart catheterization and coagulation screening. Two survivors present major sequelae, namely vascular pruning and definite signs of pulmonary hypertension. The other 10 patients have minimal or no residual vascular occlusion, but show a high incidence of minor abnormalities: slight rise in pulmonary arterial pressure during exercise (3 cases), small angiographic and scintigraphic defects (5 cases), arterial hypoxemia (5 cases) and disturbances of pulmonary function (10 cases). Systemic venous problems were found to be frequent and to be a handicap in 5 cases, and an abnormal pattern of response to exercise was observed in 4 patients. These disturbances may be related to ligation of the vena cava. Various derangements of coagulation were found in all but one of the patients.

Ischemia-induced transient left bundle branch block during exercise documented by 201Tl perfusion imaging

Abstract: We report the ischemic etiology of exercise-induced left bundle branch block by noninvasive 201Tl exercise/rest perfusion imaging. The establishment of an ischemic etiology for this phenomenon may have prognostic value in such patients and may modify subsequent therapeutic approaches.

201Tl perfusion study of "ischemic" ulcers of the leg: prognostic ability compared with Doppler ultrasound.

Abstract: Thallium 201 perfusion analysis was compared with Doppler ultrasound as a means of determining the healing potential of an ischemic ulcer of the leg in 27 patients. The degree of hyperemia was determined by comparative point counting of the 201Tl distribution in and about the ulcer. Using established Doppler criteria and a hyperemia ratio greater than 1.5:1, ultrasound alone correctly predicted healing in 15 out of 23 cases and 201Tl in 20 out of 23. Ultrasound correctly predicted non-healing in 3 out of 6 cases, compared with 5 out of 6 for 201Tl. The positive predictive value of the 201Tl study was 63%, versus 27% for ultrasound, and the negative predictive value was 95% for 201Tl and 83% for ultrasound. The accuracy of 201Tl and ultrasound was 86% and 62%, respectively. This limited study suggests that 201Tl perfusion scanning is a useful noninvasive test of ulcer healing potential and may be more sensitive than Doppler ultrasound.

Physiological influences on perfusion imaging in transient myocardial ischaemia: importance of early distribution of thallium-201

Abstract: We tested the hypothesis that visualisation of defects on thallium-201 (201T1) myocardial perfusion images (MPI) depends on the duration of the ischaemic state between 201T1 injection and the time of reperfusion of an occluded coronary artery. Praecordial imaging with a gamma camera was performed in 24 anaesthetised, open-chest dogs with transient coronary occlusion. Results indicated that if the duration of the ischaemic state after 201T1 injection was less than 3 min before reperfusion, then the MPI 5 to 15 min after 201T1 injection was falsely negative (201T1 activity in ischaemic zone (IZ)/normal zone (NZ)>0.85). Dogs which were ischaemic more than 5 min always had MPI defects 5 to 15 min after 201T1 injection (IZ/NZ 201T1 ratio<0.85). MPI results (201T1 IZ/NZ)15 min after 201T1 injection were determined by the duration of the ischaemic state after 201T1 injection (r= −0.86) because prolonged ischaemia allowed 201T1 to distribute from blood to myocardium before reperfusion: 201T1 (IZ/NZ)=0.356± 1.00 (fraction of total 201T1 remaining in blood at the end of the ischaemic state), r=0.94.

The imaging of myocardial perfusion with 81mKr during coronary arteriography.

Abstract: The use of 81mKr was investigated for imaging myocardial perfusion during coronary arteriography using conventional catheters. When the significance of stenosis judged by arteriography is unclear, the effect on tissue perfusion can be established and the contribution to collateral flow by each artery separately evaluated. The distribution of 81mKr, due to its 13-s half-life, represents regional blood flow. In order to evaluate interventions, studies can be repeated at a low radiation risk to patients. A sterile pyrogenfree 81Rb−81Kr generator was developed. With slow infusion, inadequate mixing and streaming takes place due to laminar flow in coronary arteries. Fast intermittent 3-ml 81Kr-dextrose bolus injections convincingly eliminated streaming artefacts. Imaging was performed in 13 patients with a mobile scintillation camera and digital imaging system. Blood flow was calculated using the inert gas washout technique. There was good correlation (r=0.91) between coronary blood flow determinations using 81mKr and 133Xe respectively. The perfusion images correlated well with the coronary angiograms. Total coronary arterial occlusions as demonstrated by arteriography were all shown as perfusion defects during rest. During atrial pacing myocardial flow was increased two-fold in normal coronary arteries and to a lesser extent in arteries with significant disease. The most critical lesion in a branch of a left coronary artery leads to a redistribution of perfusion during pacing.

Emission computed tomography vs perfusion scanning in lung disease.

Abstract: Emission computed tomography has achieved considerable credibility in thallium-201 cardiac imaging and in brain imaging studies. To date the procedure has had only limited application in the study of other organs. In the present study traditional perfusion lung scans were compared with horizontal, sagittal and frontal tomograms in 30 patients. Preliminary results showed agreement between the two methods in most cases. Tomography, however, gave more precise information about the site and extent of areas of deficient lung perfusion. In a small number of cases tomography also revealed defects not seen on conventional scans. In patients with cardiomegaly in whom conventional scanning data were difficult to assess, tomography proved enlightening.

Modified Perfusion and Loading Technique of the Isolated Canine Heart

Abstract: The technique of donor perfusion of the isolated canine heart is described. It is carried out with the aid of a specially developed system providing both retrograde resuscitational coronary perfusion

Clinical evaluation of emission tomography using seven-pinhole collimator: improved detection of perfusion defect by the addition of the right anterior oblique projection.

Abstract: The clinical efficacy of thallium emission myocardial tomography using a seven-pinhole collimator in the right anterior oblique (RAO) projection was evaluated. Myocardial tomography in left anterior oblique (LAO) and RAO projections was performed following planar thallium perfusion imaging at rest in 11 patients with myocardial infarction. The RAO tomogram was useful, especially in detecting apical perfusion defects, while the LAO tomogram was useful in detecting inferior and anteroseptal wall defects. For the four patients without an apparent myocardial perfusion defect seen on the planar image, the LAO tomogram showed a perfusion defect in three, and the RAO tomogram also showed the defect in three. One or the other of the two views demonstrated the defect for all 11 patients. The myocardial tomogram in the RAO projection, providing a sufficiently high-quality and high-contrast image, gives useful information complementary to the findings of the commonly used LAO projection in the evaluation of myocardial infarctions.

Radionuclide Perfusion Techniques

Abstract: Radionuclide perfusion imaging to quantitate ischemic and infarcted myocardium employs four general groups of tracers (Tables 1 and 2).

Performance of the rotating slant-hole collimater for the detection of myocardial perfusion abnormalities

Abstract: To determine the usefulness of the rotating slant-hole (RSH) collimator, a new imaging device for tomographic myocardial imaging, we evaluated its performance in phantom studies. Perfusion defects of variable size, location, and tracer concentration were simulated and imaging was performed with a conventional parallel-hole collimator and the RSH collimator. Planar and depth resolutions assessed with a line source compared favorably with those reported previously for the seven-pinhole collimator. The results also showed RSH tomography to be more sensitive than planar imaging in detecting simulated myocardial defects but indicated some limitations, especially the occurrence of artifactual defects that may reduce the specificity of the imaging device for the detection of perfusion abnormalities.

Contribution of Nuclear Cardiology to the Diagnosis of the Various Stages of Coronary Artery Disease

Abstract: Nuclear cardiology claims to be able to contribute information on various aspects of myocardial diseases. The complete description of the myocardial state includes the perfusion, metabolism, and function of the myocardium. The immediate cause of myocardial disease is insufficient oxygen delivery, whereaus substrate delivery is not that important. The sensitivity of the system to very small perfusion defects results from the high extraction rate of oxygen, which in the myocardium reaches 75%; in normal muscle the extraction rate is only 25%. This is a critical point, because oxygen delivery cannot be effectively improved by an increase in extraction rate. Improvement is possible only by increasing the myocardial blood flow. Thus far, perfusion imaging is of paramount importance for detection of oxygen deficiency in the myocardium. Subsequent metabolic disorders, e.g., anaerobic glycolysis, call for their respective metabolic radionuclide indicators [1]. Finally, the metabolic failure results in functional abnormalities of the myocardium, which implies motion abnormalities (hypokinesis, dyskinesis), which can be visualized by radionuclide ventriculography.

Pharmacologic effects of a nitrate coronary vasodilator on cardiac perfusion and function, measured semiquantitatively.

Abstract: Peritrate (pentaerythritol tetranitrate), a nitrate coronary vasodilator, was capable of significantly increasing perfusion and function in ischemic heart muscle. The A2 image-processing computer with software developed by Burow was used to evaluate regional perfusion and segmental wall motion in six patients with ischemic areas in the myocardium. These image-processing techniques were satisfactory for evaluation of ischemic heart muscle.