Showing papers on "Perfusion scanning published in 1983"

Augmentation of cerebral perfusion by simultaneous chest compression and lung inflation with abdominal binding after cardiac arrest in dogs.

Abstract: Recent studies have demonstrated that for the same chest compression force during mechanical cardiopulmonary resuscitation (CPR), the carotid artery-to-jugular vein pressure gradient and carotid blood flow are increased when the phasic rise of intrathoracic pressure is enhanced by abdominal binding and simultaneous ventilation at high airway pressure with each chest compression (SCV). The objective of the present study was to assess whether cerebral blood flow is also enhanced, since it is known that fluctuations in intrathoracic pressure are transmitted to the intracranial space and affect intracranial pressure (ICP). In two series of pentobarbital-anesthetized dogs, one of two CPR techniques was initiated immediately after inducing ventricular fibrillation. Brain blood flow was measured by the radiolabeled microsphere technique immediately before cardiac arrest and at 1 and 3 minutes after commencing CPR. Evidence of adequate mixing of spheres and lack of sedimentation under these low-flow conditions was verified by correlation with brain venous outflow, comparison of the arterial concentration-time profile of spheres and a nonsedimentary marker (thallium-201 in solution), and use of multiple arterial sampling sites. During SCV CPR with abdominal binding, mean carotid artery pressure (60 +/- 3 mm Hg) was higher than that during conventional CPR (25 +/- 2 mm HG). Pulsations of ICP occurred that were in phase with chest compression and greater than jugular venous pressure. Mean ICP was higher during SCV (46 +/- 2 mm Hg) than conventional CPR (20 +/- 2 mm Hg). However, the net brain perfusion pressure gradient (carotid artery pressure - ICP) was greater with SCV (14 +/- 3 mm Hg) than with conventional CPR (5 +/- 0.4 mm Hg). Cerebral blood flow was significantly greater during SCV CPR (32 +/- 7% of prearrest cerebral flow) than during conventional CPR (3 +/- 2%). We conclude that SCV CPR combined with abdominal binding substantially improved brain perfusion by enhancing cerebral perfusion pressure in this experimental model.

A New Brain Perfusion Imaging Agent: [I-123]HIPDM;N,N,N′-Trimethyl-N′-[2-Hydroxy-3-Methyl-5-Iodobenzyl]-1,3-Propanediamine

Abstract: Based on the pH-shift mechanism, a new brain imaging agent I-124 HIPDM (N,N,N'-trimethyl-N'-[2-hydroxy-3-methyl-5-[123I]iodobenzyl]-1,3-propanediamine ) has been developed. This agent can be prepared by a simple exchange reaction suitable for routine clinical use. The physicochemical parameters, partition coefficient vs. pH profile, and protein binding, as well as biodistribution in rats, were very similar to those of I-123 IMP (N-isopropyl-p-iodoamphetamine). High brain uptake was found in animals after i.v. injection. The brain radioactivity persists for at least 1 hr in rats and monkeys. Regional distribution in sections of rat brain appeared to reflect regional perfusion. In conjunction with single-photon emission tomography (SPECT), this agent may provide useful information on local cerebral perfusion in humans.

Role of lung scanning in assessing the resectability of bronchial carcinoma.

Abstract: Ventilation and perfusion lung scans were performed in 58 patients before operation for bronchial carcinoma to determine in which patients the lung scan was most useful for assessing mediastinal spread and resectability of the tumour. Perfusion of the affected lung was less with larger and more centrally situated tumours. Perfusion was also less for left-sided than for right-sided tumours but this is explained by the normal differential perfusion of the right and left lungs. The lung scan was unhelpful in predicting resectability of peripheral tumours, but with central tumours if perfusion of the affected lung was less than 25% of the total perfusion the lesion was likely to be non-resectable because of spread to the mediastinum. Airways obstruction was present in 67% of the patients but did not interfere with the interpretation of the scans. In most cases ventilation scans provided no additional information, and the use of krypton-81 m as a sensitive indicator of regional ventilation did not improve on the predictive value of the perfusion scan.

Serial lung scintigraphy: utility in diagnosis of pulmonary embolism.

Abstract: Pairs of sequential perfusion lung scans and pulmonary angiograms obtained in 45 patients were reviewed to investigate the utility of short-term, sequential scintigraphy in the diagnosis of pulmonary embolism (PE). Forty-six sequential scan pairs were reviewed; 13 were ventilation-perfusion (V-P) pairs. Angiograms were obtained within 48 hours of either the first (65%) or second (35%) perfusion scan in each pair. Sequential scintigraphic patterns were classified as showing change (i.e., improvement in defects, new defects), no change, or as being indeterminate. A changing perfusion pattern was associated with a high (20/23) likelihood of PE, but seven of 16 patients with stable perfusion patterns also had PE. The sensitivity of a changing perfusion pattern for PE was 0.74 (20/27) and its specificity was 0.75 (9/12). In two of six patients who had serial V-P studies that showed changing perfusion defects, there were matched changes in regional ventilation and angiograms were negative. The findings suggest ...

Quantification of Regional Myocardial Perfusion by Exponential Infusion of 11C-Butanol

Abstract: This study was designed to determine whether regional myocardial perfusion can be assessed quantitatively in vivo in dogs by administration of a freely diffusible tracer intravenously at an exponentially increasing-rate. Previously, we reported the mathematical basis of the approach and its use for assessment of global perfusion in isolated hearts. In this study, computer simulations demonstrated that inter-regional diffusion of tracer perturbs results by no more than 7 percent under worst case conditions. Regional myocardial blood flow assessed in open chest dogs with myocardial activity deternined by well counting by the exponential infusion method correlated closely to values obtained with radiolabeled microspheres (r = 0.986, n = 35 determinations). Thus, regional myocardial perfusion can be quantified with an infusion technique potentially applicable to the tomographic characterization of impaired perfusion in experimental animals and ultimately in patients with positron emission tomography.

Mean transit time image--a new method of analyzing brain perfusion studies.

Abstract: Point-by-point calculation of the mean transit time based on gamma fit was used to analyze brain perfusion studies in a vertex view. The algorithm and preliminary results in normal brain and in different stages of cerebral perfusion abnormality (ischemia, stroke, migraine, tumor, abscess) are demonstrated. In contrast to the traditional methods using fixed, a priori defined regions of interest this type of mapping of the relative regional cerebral perfusion shows more clearly the irregular outlines of the disturbance. Right to left activity ratios in the arterial part of the time-activity curves showed significant correlation with the mean transit time ratios (Qt = 1.185 - 0.192 Qa, n = 38, r = 0.716, P less than 0.001).

The usefulness of chest radiographs obtained after a demonstrated perfusion scan defect in the diagnosis of pulmonary emboli.

Abstract: The chest radiographs obtained within seven days of scintigraphic lung studies in 38 patients clinically suspected of having a pulmonary embolus were reviewed. Twenty-two of these patients also had pulmonary angiograms. Lung densities in areas of perfusion defects not present at the time of the scan studies were sought. Densities were observed in ten patients. These appeared 4 hours to five days later (mean 1.8 days). This sequence of events strongly supports the diagnosis of pulmonary embolism. Chest radiographs are recommended one day and, if normal, again three days after an abnormal perfusion lung scan, even if the pulmonary angiogram is normal. The delayed appearance of these lung densities will eliminate some non-emboli causes and thereby strengthen the diagnosis of embolism. If such densities are seen following a "normal" angiogram, it should be critically reviewed.

Measurement of regional changes in myocardial perfusion using dynamic computed tomography and contrast medium.

Abstract: Changes in regional myocardial perfusion were measured using rapid sequence dynamic transmission tomography to detect differences in the initial distribution of contrast medium injected as an intravenous bolus. The experiments were carried out on 8 mongrel dogs instrumented with flow probes and vascular occluders around the coronary arteries. Flow reductions of 50 per cent or more were detected as regions of myocardium with less contrast enhancement than those with normal perfusion. Reactive hyperemia induced by transient ischemia was detected as areas of relatively increased contrast enhancement. These changes could be demonstrated on the images and quantitated using data depicting changes in HU (Hounsfield units) with time to develop an index of perfusion. The images obtained were of satisfactory quality and differences between the underperfused and normal myocardium were made more prominent by using dipyridamole infusions.

Pancreatic grafts. Nuclear perfusion imaging to detect vascular complications and rejection crises.

Abstract: Perfusion studies with 99m-Tc-DTPA were used routinely to investigate renal grafts. Efforts were made to employ this technique in monitoring the perfusion of pancreatic grafts. A total perfusion failure is as reliably detectable as in renal grafts. Smaller perfusion alterations could be demonstrated by follow up studies. It appears to be feasible to differentiate the salivary edema, well known from animal experiments, from a rejection reaction with the help of other parameters (e.g. creatinine). Further clinical studies, however, are necessary to confirm these results.

Parametric imaging of regional cerebral blood flow with the short-lived isotope 195mAu.

Abstract: The use of the short-lived (30 s) isotope 195mAu in brain perfusion studies has been tested on 40 patients and 8 volunteers. The activity of the eluate from the 195mHg/195Au generator was high enough to give good image statistics of brain perfusion after a single bolus injection. The examinations can be repeated after 3 min giving the same quality and without significant background. The use of a low-energy photon peak at 68 keV (Au−Kα) allows the imaging of brain perfusion in both lateral views with almost no look-through effect. With a modified height-over-area formula for the calculation of regional cerebral blood flow parametric images were obtained of high diagnostic value. The sensitivity and reproducibility, of the method has been demonstrated by mental stimulation tests on eight volunteers: after optical stimulation a clear increase of blood flow could be shown in the visual cortex.

Mean transit time image - A new method of analyzing brain perfusion studies

Abstract: Point-by-point calculation of the mean transit time based on gamma fit was used to analyze brain perfusion studies in a vertex view. The algorithm and preliminary results in normal brain and in different stages of cerebral perfusion abnormality (ischemia, stroke, migraine, tumor, abscess) are demonstrated. In contrast to the traditional methods using fixed, a priori defined regions of interest this type of mapping of the relative regional cerebral perfusion shows more clearly the irregular outlines of the disturbance. Right to left activity ratios in the arterial part of the time-activity curves showed significant correlation with the mean transit time ratios (Qt = 1.185 - 0.192 Qa, n = 38, r = 0.716, P less than 0.001).

Carotid Perfusion and Field Loss

Abstract: Forty patients with known open angle glaucoma were examined by ophthalmodynamometry and Doppler ultrasound to evaluate their carotid flow. The common internal and external carotids were examined at the bifurcation by the A.T.L. 5 MHz real time Duplex Scanner. This provides information on the disturbance and percentage reduction in flow in the affected vessels.

Evaluation of the post-coronary artery bypass patient by myocardial perfusion scintigraphy and computed tomography.

Abstract: The clinical utility of 201Tl scintigraphy and of computed tomography for the noninvasive assessment of graft patency and regional myocardial perfusion was evaluated in 24 patients who had undergone aortocoronary bypass surgery. Perfusion defects on 201Tl scintigraphy (reversible or new, fixed) correlated (100% sensitivity, 78% specificity) with occlusion or stenosis of a graft or significant new native vessel disease. Graft occlusion was accurately demonstrated by dynamic computed tomography (100% sensitivity, 96% specificity) but did not uniformly correlate with regional perfusion. Perfusion defects in the distribution of patent grafts resulted from progressive native vessel disease or graft stenosis without complete occlusion. The absence of exercise-induced perfusion defects in regions of occluded grafts was attributed to suboptimal exercise, collateralization, or noncritical native vessel stenosis. The two studies provide complementary anatomic and physiologic information in the evaluation of the postbypass patient.

Quantitative lung perfusion scintigraphy in lung function diagnosis

Abstract: A new method is described for quantitative evaluation in lung perfusion scintigraphy, which allows to conclude from the increased perfusion of normal lung-tissue to a virtual total lung perfusion. The relationship between this and the real total lung perfusion leads to the pulmonary perfusion defects in per cent. The findings of a comparison of 40 patients between the perfusion scan method and the lung function tests is presented, which proves the validity of the new method. It is shown that restrictive lung diseases have a good and obstructive have a bad correlation. It is demonstrated furthermore that the perfusion defects of bronchogenic carcinoma can be quantified very well by the method.

Clinical utilization of perfusion lung scans in the diagnosis of pulmonary emboli.

Abstract: To study the utilization of perfusion lung scans, the records of 116 consecutive patients who had "pulmonary embolus" (PE) as a discharge diagnosis were reviewed. The PE group was identical to the control group in the percent of male patients and of white patients. However, the PE group was older (60.4 versus 47.5 years), had a higher percentage of smokers (53.1 versus 34), and had a higher proportion of obese individuals (39.6 versus 25) than controls. Mortality was significantly greater in the PE patients (9.5% versus 1%) as was the length of hospital stay (21 versus 9 days). The PE group had more chest x-rays than did controls (6.1 versus 1.8) and had a higher percentage of lung scans (95.7 versus 5). While 95.7% of the patients diagnosed as having PE were studied by perfusion lung scans, 4.3% had none. Further, 18.1% had only one lung scan. Of 111 patients with perfusion lung scans, 3.6% were discharged with a diagnosis of PE despite a negative study. While clinical acceptance of perfusion lung scans is high, some patients diagnosed as having pulmonary emboli did not have a scan but underwent other diagnostic tests, while a small group of others were assigned the diagnosis despite a negative lung scan. This points to the need for better communication with referring clinicians.

Renal Perfusion Studies by Means of CT

Abstract: Sequential CT is a simple extension of conventional CT investigations for registering and evaluating the phenomena of contrast enhancement by repeating scans in the same sectional plane as quickly as possible after an intravenous bolus injection of contrast medium. Most of the presently used CT units have scan intervals of 10–15 s; the newest units have a higher scan rate intervals of 2–5 s. The parameter is the absorption value, which is directly observed and densitometrically detected by a software program and indicated in Hounsfield units (HU).