Showing papers on "Perfusion scanning published in 1985"

Hypertension in acute ischemic strokes.

Abstract: Most patients with acute ischemic strokes are hypertensive 1 and pose an almost daily dilemma of whether to treat their blood pressure on admission or not. Yatsu and Zivin emphasize the dangers of decreasing brain perfusion further, producing watershed infarction and facilitating thrombus formation by treating hypertension acutely. Spence and Del Maestro agree, but they argue that these risks are outweighed by the hazards of not treating hypertension. In acute ischemic stroke the brain commonly loses the ability to regulate its own blood supply, cerebral perfusion varying with the systemic blood pressure. A high perfusion pressure promotes edema formation, increasing intracranial pressure and ischemia. Wallace and Levy 2 studied 334 patients with acute stroke, half of whom had a history of hypertension. During the first 24 hours after admission, 84% of the patients showed hypertension (supine blood pressure >150/90 mm Hg), whereas only one third of the patients remained hypertensive

Regional cerebrovascular transport of leucine as measured by the in situ brain perfusion technique

Abstract: Leucine influx into six brain regions was determined in anesthetized rats with the in situ brain perfusion technique using either saline or plasma perfusate. This technique has several advantages over other methods such as the brain uptake index (BUI) technique. The concentration dependence of l-leucine influx was best described by a model with a saturable and a nonsaturable component. For the saturable component, Vmax equaled 10.67 ± 0.21 × 10−4 μmol s−1 g−1 and Km equaled 0.0257 ± 0.0009 μmol ml−1, whereas the constant of nonsaturable diffusion (Kd) equaled 0.957 ± 0.067 × 10−4 s−1 in the parietal lobe during saline perfusion. Vmax was higher in the cortical lobes than in other brain areas, probably owing to a greater capillary surface area. There were no regional differences in Km or Kd. The apparent Km for l-leucine during plasma perfusion was 20 times greater than the Km during saline perfusion, and 3 to 4 times greater than the plasma leucine concentration, owing to competitive inhibition of leucine...

Imaging system and method using radiopaque microspheres for evaluation of organ tissue perfusion

Abstract: A radiologic imaging system and method (20) using radiopaque microspheres for evaluating organ tissue perfusion. Radiopaque microspheres are administered to organ tissue (22) which is then scanned using a computerized tomography (CT) scanner (24) which provides a visual CT image (26) and/or statistical report (28) providing an indication and/or measurement of organ tissue perfusion.

Thallium-201 myocardial perfusion imaging in myocarditis.

Abstract: TI-201 myocardial perfusion imaging was performed in six patients with clinically documented myocarditis. Each case manifested electrocardiographic abnormalities with elevation of serum cardiac enzymes and no significant stenosis of the coronary arteries observed on angiogram. Resting TI-201 images were visually assessed by three observers. Focal perfusion defects were observed in three cases (50%), among which two showed multiple perfusion defects. Emission computed tomography using TI-201 clearly delineated multifocal lesions in the first case. On the other hand, no significant perfusion defects were noted in the remaining three cases. Thus, myocarditis should be considered as one of the disease entities that may produce perfusion defects on TI-201 myocardial imaging.

The utility of SPECT for 99mTc-MAA hepatic arterial perfusion scintigraphy

Abstract: The utility of single-photon emission computed tomography (SPECT) for hepatic arterial perfusion scintigraphy was evaluated in 86 patients (91 studies). Previous reports have shown planar studies to be valuable for the clinical management of patients receiving intraarterial chemotherapy and more reliable than angiography in determining blood flow distribution. However, overlying areas of intra- and extrahepatic perfusion can sometimes make interpretation of these two-dimensional images difficult. Since SPECT has the potential to depict the three-dimensional distribution of perfusion, separate out overlying activity, and improve contrast resolution, SPECT Tc-MAA perfusion studies were compared to planar studies. Planar and SPECT studies both demonstrated the extent of hepatic and tumor perfusion, although occasionally SPECT added additional information. SPECT was most useful in confirming or excluding extrahepatic perfusion that was suspected but not definite on planar studies. Extrahepatic abdominal perfu...

Right-axis deviation and anterior wall thallium-201 defect in Becker's muscular dystrophy.

Abstract: Dilated cardiomyopathy has been shown to occur in families with X-linked recessive (Becker's) muscular dystrophy. 1 Pedigree members of such families frequently manifest various electrocardiographic anomalies, including infranodal blocks (for example, left bundle branch block and complete atrioventricular block), 2–4 left-axis deviation, small Q waves in leads I and aVL and loss of R-wave amplitude in lead V 2 and V 3 . Myocardial perfusion scanning in patients with early-onset, autosomal recessive muscular dystrophy has frequently shown posterobasal and lateral perfusion defects that may be a unique marker of that disorder in the heart. 5 Perfusion scanning in patients with late-onset muscular dystrophy has not been described.

A combined procedure for 99mTc aerosol ventilation and perfusion imaging.

Abstract: For several years, radioaerosols have been successfully used to provide detailed images of regional ventilation to aid in the differential diagnosis of pulmonary embolism. It has been widely advocated that the ventilation images should follow the perfusion scan and that the amount of aerosol deposited in the patient's lungs should be three times greater than the perfusion dose. We employed an alternative approach which avoided the deposition of an unpredictable amount of aerosol in individual patients. The aerosol study was performed first, and the activity of the microspheres used for the perfusion images was then tailored to the actual amount of aerosol which the patient had retained. This allowed a microsphere/aerosol activity ratio of 10:1 to be readily achieved, thus successfully masking the ventilation pattern by the perfusion activity. The faster biological clearance of 99mTc-DTPA aerosol from the lung fields, as compared to 99mTc-sulphur-colloid aerosol, allowed higher initial activities to be deposited in the lungs, thus enabling a high-resolution collimator to be used. When the perfusion study was delayed by 1 h (one effective half-life for the 99mTc-DTPA aerosol), it was not necessary to increase the perfusion activity required to mask the ventilation image.

Radioaerosol ventilation imaging in ventilator-dependent patients. Technical considerations.

Abstract: The differentiation of pulmonary embolism (PE) from regional ventilatory abnormalities accompanied by reduced perfusion requires contemporary perfusion and ventilation studies. Distinguishing these conditions in ventilator-dependent patients is aided by administering a Tc-99m aerosol to characterize regional ventilation, and by performing a conventional Tc-99m MAA perfusion study. The technique uses a simple "in-house" constructed apparatus. Simple photographic techniques suffice, but computer subtraction of perfusion from the combined perfusion-ventilation image renders interpretation easier if aerosol administration follows perfusion imaging. Multiple defects can be examined in a single study. Excluding normal or near-normal perfusion studies, PE was thought to be present in eight of 16 patients after perfusion imaging alone, but in only one of eight after added aerosol imaging. Angiography confirmed the diagnosis in that patient. Of the eight patients who had abnormal perfusion but were thought unlikely to have PE from the perfusion study alone, two had normal ventilation, and subsequently were shown to have PE by angiography. Because angiography was only performed on patients who were thought to have a high probability of PE on sequential perfusion-ventilation imaging, the true incidence of PE may have been higher. Aerosol ventilation imaging is a useful adjunct to perfusion imaging in patients on ventilators. It requires an efficient delivery system, particularly if aerosol administration follows perfusion imaging, as it does in this study. The major disadvantage of aerosol imaging compared to a gas in intubated patients is the significant bronchial deposition due to retained mucus secretions.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism underlying the absence of ischemic changes on the exercise electrocardiogram in patients with abnormal exercise thallium-201 imaging and coronary artery disease

Abstract: Patients with coronary artery disease may have reversible abnormalities on a thallium myocardial perfusion study without simultaneous ischemic changes on the exercise electrocardiogram, but the mechanisms responsible for this disparity have not been fully elucidated. A group of 37 patients with angiographically demonstrated coronary artery disease and abnormal thallium perfusion imaging were divided into two groups on the basis of their exercise electrocardiographic ST segment response. Thirteen patients (Group A) had no significant electrocardiographic changes with exercise, while 24 patients (Group B) had ST changes consistent with ischemia during the test. There were no significant differences in clinical or angiographic characteristics between the two groups. Stress test results showed a similar mean duration of exercise in the two groups (6.2 +/- 1.8 versus 6.7 +/- 2.5 min, p = NS), but the patients in Group A achieved a significantly lower mean maximal heart rate (117 +/- 26 versus 132 +/- 21 beats/min, p less than 0.05) and mean maximal double product (19,650 +/- 5116 versus 22,650 +/- 4871, p less than 0.05). There was no consistent pattern of thallium perfusion abnormality noted in Group A to suggest that a particular region of electrically silent myocardium was responsible for ischemia in the absence of electrocardiographic changes. These results suggest that exercise thallium-electrocardiogram discordance is mediated by the level of myocardial workload achieved. An abnormal perfusion scan accompanying an exercise electrocardiogram which does not demonstrate any ischemic ST change may occur when there is sufficient increase in myocardial oxygen demand to result in differential augmentation of myocardial blood flow, but insufficient imbalance of supply and demand to result in signs of ischemia on the surface electrocardiogram.

Non-invasive assessment of pulmonary blood supply after staged repair of pulmonary atresia.

Abstract: Radionuclide studies were performed to determine pulmonary blood flow in six children who had undergone surgery for pulmonary atresia, ventricular septal defect, and hypoplastic pulmonary arteries with or without major aortopulmonary collateral arteries. Lung blood flow was assessed from both particle perfusion lung scans and the pulmonary and systemic phase of a radionuclide dynamic flow study. Five patients had perfusion defects identified on the particle perfusion lung scan. In three of these, abnormal areas were perfused only during the systemic phase of the flow study, a combination of findings that indicate the presence of perfusion by collateral arteries. In one patient no systemic perfusion was noted and in one an initial particle perfusion study indicated the presence of a lung segment perfused by a collateral artery. In this last patient the particle perfusion scan after total correction showed a reduction in the size of the lung perfusion defect and no evidence of lung perfusion during the systemic phase of the flow study. The particle perfusion lung scan in the sixth patient showed pronounced asymmetry in blood flow to the lungs with no segmental perfusion defect on the particle perfusion scan and no abnormalities on the systemic flow study. It is concluded that radionuclide lung perfusion and flow studies provide useful information on lung perfusion and merit further evaluation to define their role in the management of these patients.

A stochastic interpretation of thallium myocardial perfusion scintigraphy.

Abstract: A method is presented for the quantitative interpretation of Thallium-201 myocardial perfusion studies. The data are planar images collected immediately following the stress injection, and four to six hours later. Data analysis consists of preprocessing, including thresholding of the original data, and data reduction using a variant of the circumferential profile methods.

99mTc particle perfusion/99mTc aerosol ventilation imaging using a subtraction technique in suspected pulmonary embolism.

Abstract: It is generally acknowledged that ventilation-perfusion mismatch is diagnostic of pulmonary embolism. Lung ventilation imaging with radioactive gases is a good method for the detection of pulmonary embolism, but it is not in widespread use because of the limited availability of 81mKr gas and the poor physical properties of 133Xe. Aerosols have been proposed, instead of gases for use in lung ventilation imaging. As perfusion and ventilation distributions may change very rapidly, the two imaging procedures should be done in rapid succession. The cheapest way to perform the combined perfusion-ventilation (Q/V) imaging is to use 99mTc-labelled macroaggregates and aerosols. In our method the perfusion imaging was done first, immediately followed by the ventilation imaging with 99mTc-labelled aerosols. A computer program was used to subtract the contribution of the perfusion from the combined Q/V image so that the pure ventilation image alone was obtained. The method was tested in 41 patients with suspected pulmonary embolism.

Cerebral Blood Flow in Patients with Extracranial Cerebrovascular Disease as Measured by Stable Xenon CT

Abstract: Advanced atherosclerotic disease of extracranial cerebral arteries in patients with no or negligible neurologic deficit and no brain damage on CT have been identified by new noninvasive test batteries [1]. The correct therapy for these patients sometimes poses a problem, because even an optimal assessment of their vascular disease does not predict their hemodynamic effect on brain perfusion. For such cases a clinically applicable, noninvasive, local, and quantitative method to measure brain blood flow is desirable.

Regional tidal volume assessed by gated lung imaging.

Abstract: We have measured regional lung tidal volumes and functional residual capacities by accumulating and framing iso-volumic images while the patient rebreathes 127Xe. As the lung changes shape during ventilation corrections for changes in geometry were obtained by simultaneous collection of 99Tcm counts from the gated perfusion scan. Regions of interest were made to vary throughout the respiratory cycle so that a region had always the same value of 99Tcm counts. From the corrected 127Xe counts regional tidal volumes (TVr) and functional residual capacities (FRCr) were derived. In patients with established chronic bronchitis and emphysema FRCr were greater and the ratio TVr/FRCr decreased compared with patients with relatively normal static and dynamic lung volumes. Preliminary studies suggest that this ratio was a better discriminator between normal and abnormal regional function than estimates of regional xenon washout. Studies with xenon-133 have contributed to our understanding of the physiology of ventilation but have contributed somewhat less to routine clinical practice. This results in part from the unsatisfactory physical properties of xenon-133. Its relatively low gamma ray energy of 80 keV results in significant self-absorption losses and the activity which may be administered is limited by the radiation dose from the associated beta particles so that relatively poor counting statistics are obtained. With inhaled technetium-99m (99Tcm) microspheres imaging conditions are greatly improved but the distribution of these particles may not equate with the distribution of ventilation particularly if wet particles are used. Moreover, simultaneous microsphere perfusion scans with technetium-99m as a label are impossible. Krypton-81m gas has a suitable energy but the short half-life of the rubidium-81m generator (4.7 h) makes supply difficult and the ultrashort half-life of the krypton-81m gas (13 s) leads to problems in calculating the indices of ventilation. Xenon-127 (127Xe) gas has a more favourable dosimetry profile than xenon-133 because it does not have associated beta particles. Further it has an energy (203 keV) suitable for modern gamma cameras and may be used in the presence of injected 99Tcm microspheres to provide simultaneous ventilation/perfusion imaging. Conventional techniques have assumed that a static image of a dynamic process is adequate. As the lungs move during imaging, some account of this respiratory movement should be made.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial perfusion assessed by digital subtraction angiography.

Abstract: Perfusion of each myocardial portion in ischemic heart disease was assessed by digital subtraction angiography (DSA). There were 45 cases of ischemic heart disease and five normal controls. The contrast medium was 40 ml 76% Urografin which was injected into the central vein at a rate of 16 ml/sec using a 5F thin-wall catheter. A myocardial image was extracted, and a time-density curve for the corresponding portion was obtained. In the normal controls, the density was maximum in systole with a gradual decrease in diastole. In all myocardial infarction cases, the wave pattern disappeared. In the group whose infarcted areas were small (26 of the 45 cases), 22 (85% of of the 26 cases) exhibited slowly increasing pattern. In the group whose infarcted areas were large (19 of the 45 cases) 15 cases (79%) had plateau type pattern. Observations of the perfusion of the myocardium using DSA facilitated quantitative diagnoses of the infarcted areas and forecasts of myocardial viability.

Intrahepatic arterial flow distribution after ligation of a right replaced hepatic artery. A case report.

Abstract: A basic requirement for arterial chemotherapy of liver tumors is complete catheter perfusion of the liver. In cases with atypical anatomy of the hepatic artery, it is frequently impossible to obtain this goal by means of a single catheter. In a patient with a right replaced hepatic artery, the aberrant vessel was ligated and the left hepatic artery was perfused through a catheter inserted into the gastroduodenal artery. Perfusion scans performed through the catheter 14 and 135 days after arterial ligation showed a fall in the arterial flow to the right liver (right/left ratio 0.43 and 0.60). In contrast, a nearly complete perfusion of the liver (0.91 right/left ratio) was obtained 28 days after ligation, when the perfusion scan was performed immediately after catheter infusion of 90,000,000 degradable starch microspheres (DSM: diameter = 40 m). DSM administration is supposed to increase back pressure in the lobe receiving native circulation, thus activating intrahepatic collateral flow to the ischemic lobe. As regards regional treatment of liver tumors, obvious conclusions are to be drawn.