Showing papers on "Perfusion scanning published in 1996"
TL;DR: A theoretical framework and experimental methods to more accurately account for transit effects in quantitative human perfusion imaging using endogenous magnetic resonance imaging (MRI) contrast are presented and a novel method for measuring T1, which is fast, insensitive to contamination by cerebrospinal fluid, and compatible with the application of magnetization transfer saturation is presented.
Abstract: Herein, we present a theoretical framework and experimental methods to more accurately account for transit effects in quantitative human perfusion imaging using endogenous magnetic resonance imaging (MRI) contrast. The theoretical transit time sensitivities of both continuous and pulsed inversion spin tagging experiments are demonstrated. We propose introducing a delay following continuous labeling, and demonstrate theoretically that introduction of a delay dramatically reduces the transit time sensitivity of perfusion imaging. The effects of magnetization transfer saturation on this modified continuous labeling experiment are also derived, and the assumption that the perfusion signal resides entirely within tissue rather than the arterial microvasculature is examined. We present results demonstrating the implementation of the continuous tagging experiment with delay on an echoplanar scanner for measuring cerebral blood flow (CBF) in normal volunteers. By varying the delay, we estimate transit times in the arterial system, values that are necessary for assessing the accuracy of our quantification. The effect of uncertainties in the transit time from the tagging plane to the arterial microvasculature and the transit time to the tissue itself on the accuracy of perfusion quantification is discussed and found to be small in gray matter but still potentially significant in white matter. A novel method for measuring T1, which is fast, insensitive to contamination by cerebrospinal fluid, and compatible with the application of magnetization transfer saturation, is also presented. The methods are combined to produce quantitative maps of resting and hypercarbic CBF.
754 citations
TL;DR: The data indicate that accurate diagnosis of pulmonary embolism is possible by perfusion scanning alone, without ventilation imaging, and combined with perfusion-scan evaluation helps to restrict the need for angiography to a minority of patients with suspected pulmonary emblism.
Abstract: To assess the value of perfusion lung scan in the diagnosis of pulmonary embolism, we prospectively evaluated 890 consecutive patients with suspected pulmonary embolism. Prior to lung scanning, each patient was assigned a clinical probability of pulmonary embolism (very likely, possible, unlikely). Perfusion scans were independently classified as follows: (1) normal, (2) near-normal, (3) abnormal compatible with pulmonary embolism (PE+: single or multiple wedge-shaped perfusion defects), or (4) abnormal not compatible with pulmonary embolism (PE-: perfusion defects other than wedge-shaped). The study design required pulmonary angiography and clinical and scintigraphic follow-up in all patients with abnormal scans. Of 890 scans, 220 were classified as normal/or near-normal and 670 as abnormal. A definitive diagnosis was established in 563 (84%) patients with abnormal scans. The overall prevalence of pulmonary embolism was 39%. Most patients with angiographically proven pulmonary embolism had PE+ scans (sensitivity: 92%). Conversely, most patients without emboli on angiography had PE- scans (specificity: 87%). A PE+ scan associated with a very likely or possible clinical presentation of pulmonary embolism had positive predictive values of 99 and 92%, respectively. A PE- scan paired with an unlikely clinical presentation had a negative predictive value of 97%. Clinical assessment combined with perfusion-scan evaluation established or excluded pulmonary embolism in the majority of patients with abnormal scans. Our data indicate that accurate diagnosis of pulmonary embolism is possible by perfusion scanning alone, without ventilation imaging. Combining perfusion scanning with clinical assessment helps to restrict the need for angiography to a minority of patients with suspected pulmonary embolism.
343 citations
TL;DR: Early results indicate that transmyocardial laser revascularization is a simple operative technique that may improve myocardial perfusion and provide angina relief for patients in whom standard methods of rev vascularization is contraindicated.
222 citations
TL;DR: It is concluded that MRI of lung perfusion is feasible and with further development, perfusion MRI could eventually have a significant clinical role in the diagnostic evaluation of pulmonary embolism.
Abstract: The accurate assessment of pulmonary perfusion is especially important in the evaluation of patients with suspected pulmonary embolism, a common and potentially lethal disorder that can be treated by aggressive anticoagulation. In this study, we demonstrate for the first time the use of MR to image pulmonary perfusion in humans by using dynamic imaging after contrast administration. The technique, which uses an inversion recovery turbo FLASH sequence with ultrashort TE (1.4 ms) and 1-s temporal resolution, was tested in a series of eight healthy subjects and in a porcine model of pulmonary embolism. After the administration of gadopentetate dimeglumine in humans and animal models, there was serial enhancement of the systemic veins, right atrium, right ventricle, and pulmonary arteries. The pulmonary arterial tree was visualized beyond the segmental branches, followed by a gradual diffuse increase in signal intensity of the lung parenchyma over a period of 4.0-7.0 s. Pulmonary circulation times ranged from 3.0-3.4 s. Whereas a high dose (20 or 40 ml) of contrast agent tended to produce the most intense parenchymal enhancement, a low dose (5 ml) was best for showing recirculation. In the animal model, a perfusion defect due to a pulmonary embolus was clearly shown and confirmed by cine angiography. It is concluded that MRI of lung perfusion is feasible. With further development, perfusion MRI could eventually have a significant clinical role in the diagnostic evaluation of pulmonary embolism.
211 citations
TL;DR: It is concluded that brain death importantly alters regional perfusion, with possible implications for donor organ function, probably due to the tremendous alterations in the activity of the sympathetic nervous system.
Abstract: Brain death can have an impact on donor organ function. This is often attributed to an altered hormonal, mainly thyroidal, status after brain death. A second possible explanation is that during the brain death process, blood flow is redistributed, causing ischemic damage in underperfused organs or regions. We investigated blood flow redistribution with colored microspheres in the rat early and late after brain death, induced by inflation of an intracranial balloon, and correlated this with the global hemodynamic situation and plasma catecholamine concentrations. Brain death was proven by the demonstration of lasting absence of brain perfusion in all animals. Myocardial blood flow closely followed the myocardial oxygen need as estimated by the rate-pressure product. The abdominal organs showed intense vasoconstriction early after brain death, which led to significantly decreased perfusion of these organs despite the highly increased perfusion pressure, followed by significant vasodilation. Total plasma catecholamine concentration was 57 times higher at 30 sec after brain death as compared with basal levels. Plasma noradrenaline concentration fell significantly below basal levels late after brain death. We conclude that brain death importantly alters regional perfusion, with possible implications for donor organ function. These changes are probably due to the tremendous alterations in the activity of the sympathetic nervous system.
175 citations
TL;DR: SVCT is a relatively noninvasive test for pulmonary embolism which is both sensitive and specific and which may serve as an alternative to ventilation scintigraphy and possibly to pulmonary angiography in the diagnostic strategy for pulmonaryembolism.
Abstract: BACKGROUND: A study was carried out to evaluate the potential place of spiral volumetric computed tomography (SVCT) in the diagnostic strategy for pulmonary embolism. METHODS: In a prospective study 249 patients with clinical suspicion of pulmonary embolism were evaluated with various imaging techniques. In all patients a ventilation/perfusion (V/Q) scan was performed. Seventy seven patients with an abnormal V/Q scan underwent SVCT. Pulmonary angiography was then performed in all 42 patients with a non-diagnostic V/Q scan and in three patients with a high probability V/Q scan without emboli on the SVCT scan. Patients with an abnormal perfusion scan also underwent ultrasonography of the legs for the detection of deep vein thrombosis. RESULTS: One hundred and seventy two patients (69%) had a normal V/Q scan. Forty two patients (17%) had a non-diagnostic V/Q scan, and in five of these patients pulmonary emboli were found both by SVCT and pulmonary angiography. In one patient, although SVCT showed no emboli, the angiogram was positive for pulmonary embolism. In one of the 42 patients the SVCT scan showed an embolus which was not confirmed by pulmonary angiography. The other 35 patients showed no sign of emboli. Thirty five patients (14%) had a high probability V/Q scan, and in 32 patients emboli were seen on SVCT images. Two patients had both a negative SVCT scan and a negative pulmonary angiogram. In one who had an inconclusive SVCT scan pulmonary angiography was positive. The sensitivity for pulmonary embolism was 95% and the specificity 97%; the positive and negative predicted values of SVCT were 97% and 97%, respectively. CONCLUSIONS: SVCT is a relatively noninvasive test for pulmonary embolism which is both sensitive and specific and which may serve as an alternative to ventilation scintigraphy and possibly to pulmonary angiography in the diagnostic strategy for pulmonary embolism.
145 citations
TL;DR: The diagnostic accuracy of thallium SPECT myocardial perfusion imaging is lower in women than in men, and it is proposed that the most likely cause is the relatively greater effect of imaging blurring on smaller hearts.
126 citations
TL;DR: This study demonstrates that previous treatment with radiotherapy resection of well perfused lung parenchyma and excessive fluid load are high risk factors for the development of non-cardiogenic pulmonary edema and that patients for whom these factors are relevant should be closely monitored in their postoperative course.
Abstract: Objective. To analyze the risk factors for postpneumonectomy pulmonary edema in 146 consecutive patients. Methods. In 1992, 146 consecutive patients, aged 60.5±9.4 years, under― went pneumonectomy, mostly for cancer (n=136). Pulmonary edema was defined clinically and radiologically in the absence of left ventricular dysfunction or infection. Several parameters, including preoperative functional respiratory values, pulmonary perfusion scan data and intraoperative data were analyzed. Two groups were determined according to the occurrence of pulmonary edema and differences were compared by univariate and multivariate analyses. Results. Twenty-two patients (15%) developed pulmonary edema within the 1st postoperative week. Most cases were mild or moderate. Severe pulmonary edema occurred in five (3.4%) patients requiring mechanical ventilation; among them, two died. Previous chemotherapy (P<0.01), radiotherapy (P<0.0001), predictive postoperative forced expiratory volume in the 1st second less than 45% (P<0.01), a remaining lung perfusion of 55% or less (P<0,05) and an intraoperative fluid load of 2000 ml fluid or more (P<0.01) were associated with pulmonary edema in the univariate analysis. Multivariate analysis identified prior radiotherapy, perfusion of the remaining lung of 55% or less and high intraoperative fluid load as independent and significant risk factors for pulmonary edema. Conclusions. This study demonstrates that previous treatment with radiotherapy resection of well perfused lung parenchyma and excessive fluid load are high risk factors for the development of non-cardiogenic pulmonary edema and that patients for whom these factors are relevant should be closely monitored in their postoperative course.
125 citations
TL;DR: Experimental CVT is characterized by early cytotoxic edema closely followed by vasogenic edema, which encourages the use of cytoprotective drugs in addition to anticoagulant or thrombolytic therapy.
Abstract: Diffusion-weighted (DWI), dynamic contrast-enhanced (perfusion imaging), and conventional spin-echo magnetic resonance imaging (MRI) were applied to characterize the pathophysiology of cerebral venous thrombosis (CVT) in the rat. We induced CVT by rostral and caudal ligation of the superior sagittal sinus (SSS) and injection of a thrombogenic cephalin suspension. The resulting pathology was monitored in an acute and long-term study group. Evans blue and hematoxylin-eosin staining was performed for comparison with MRI data. A subgroup of animals was treated with i.v. tissue plasminogen activator (t-PA). Successful thrombosis of the SSS was confirmed by macropathology or histopathology in all rats. Parenchymal lesions as shown by MRI, however, were present only in animals with additional involvement of cortical cerebral veins (11 of 18 rats). The early pathology was clearly detected with the DWI. The apparent diffusion coefficient declined to 56 +/- 7% of control value at 0.5 h and slowly increased to 84 +/- 8% by 48 h. Perfusion imaging showed parasagittal perfusion deficits. Treatment with t-PA partially resolved the hyperintensity on DWI. Evidence of blood-brain-barrier disruption was observed 2 to 3 h after induction of CVT. In conclusion, experimental CVT is characterized by early cytotoxic edema closely followed by vasogenic edema. The t-PA treatment partially reversed the DWI signal changes consistent with regional tissue recovery, as shown by histopathology. These results encourage the use of cytoprotective drugs in addition to anticoagulant or thrombolytic therapy.
124 citations
Book•
01 Jan 1996
TL;DR: In this article, the authors discuss the use of contrast agents in the diagnosis of Cardiac Imaging. But they do not discuss the application of Contrast Echocardiography in other medical applications.
Abstract: (Volume I) Part I: Introduction. Goals of Cardiac Imaging. Principles of Myocardial Perfusion. Principles of Ventricular Function. Principles of Myocardial Metabolism. Principles of Valvar Function. Quantitative Methods in Cardiac Imaging: An Introduction to Digital Image Processing. Perceptual Aspects of Cardiac Imaging. A Clinician's Perspective: The Place of Imaging in Cardiac Diagnosis. Part II: Integrated Clinical Approach to Diagnosis Using Imaging Methods. Coronary Artery Disease. Valvular Heart Disease. Myocarditis and Cardiomyopathy. Congenital Heart Disease. Pericardial Disease. Cardiovascular Trauma. Diseases of the Great Vessels. Part III: Conventional Radiography and Angiography. Principles of Instrumentation for Radiography. The Chest Radiograph in the Adult Patient. Radiographic Contrast Agents. Principles and Practice of Contrast Ventriculography. Applications of Contrast Ventriculography. Role of Aortography in the Age of Imaging. Pulmonary Angiography. Principles and Practice of Coronary Angiography. Digital Angiography. Part IV: Echocardiography. Echocardiography: Physics and Instrumentation. Principles and Instrumentation for Doppler. Echocardiographic Assessment of Ventricular Systolic Function. Assessment of Systolic Function with Doppler Echocardiography. Doppler-Echocardiographic Evaluation of Diastolic Function. Valvular Heart Disease. Cardiomyopathies. Echocardiography in Pericardial Diseases. Two-Dimensional and Doppler Echocardiography in the Evaluation of Congenital Heart Disease. Cardiac and Extracardiac Masses: Echocardiographic Evaluation. Myocardial Perfusion and Other Applications of Contrast Echocardiography. Stress Echocardiography. Echocardiography in Coronary Artery Disease: Myocardial Ischemia and Infarction. Transesophageal Echocardiography. Intraoperative Echocardiography. Intravascular Ultrasound. Ultrasonic Characterizationof Cardiovascular Tissue. (Volume II) Part V: Magnetic Resonance Imaging. Principles of Nuclear Magnetic Resonance Relaxation. Principles and Instrumentation for Cardiac Magnetic Resonance Imaging. Contrast Agents for Cardiac Magnetic Resonance Imaging. Integrated Cardiac Magnetic Resonance Examination. Congenital Heart Disease Assessed with Magnetic Resonance Techniques. Imaging of the Valves and Great Vessels. Magnetic Resonance Imaging Assessment of Ischemic Heart Disease. Cardiomyopathies, Cardiac Masses, And Pericardial Disease: Value of Magnetic Resonance in Diagnosis and Management. Quantitative Magnetic Resonance Imaging of the Heart. Cardiac Magnetic Resonance Spectroscopy: Principles and Applications. Part VI: Fast Computed Tomography. Ultrafast Computed Tomography: Principles and Instrumentation. Evaluation of Cardiovascular Structure and Function with Electron-Beam Computed Tomography. Evaluation of Coronary Artery Disease By Electron-Beam Computed Tomography. Measurement of Myocardial Perfusion Using Electron-Beam (Ultrafast) Computed Tomography. The Great Vessels: Imaging By Electron-Beam Computed Tomography. Cardiac Masses and Pericardial Disease: Imaging By Electron-Beam Computed Tomography. Ultrafast Computed Tomography Evaluation of Congenital Cardiovascular Disease in Children and Adults. Part VII: Radionuclide Imaging. Principles and Instrumentation. First-Pass Radionuclide Angiography. Equilibrium Radionuclide Angiography. Single-Photon Emitting Tracersfor Imaging Myocardial Perfusion and Cell Membrane Integrity. Myocardial Perfusion Imaging for the Detection and Evaluation of Coronary Artery Disease. Imaging Acute Myocardial Necrosis. Metabolic Imaging with Single-Photon Emitting Tracers. Thrombosis Imaging with Indium-111-Labeled Platelets. Imaging the Cardiac Autonomic Nervous System. Part VIII: Positron Emission Tomography. Principles of Positron Emission Tomography. Evaluation of Myocardial Blood Flow in Cardiac Disease. Evaluation of Myocardial Substrate Metabolism in Ischemic Heart Disease. Assessment of Myocardial Perfusion and Metabolism in the Cardiomyopathies. Positron Emission Tomography: Evaluation of Cardiac Receptors and Neuronal Function.
124 citations
TL;DR: The results of this preliminary study suggest that the chronic use of opiates results in perfusion abnormalities without corresponding abnormalities on imaging studies of cerebral anatomy and morphology, and that these perfusion defects are partially reversible with short-term abstinence.
Abstract: The purpose of this study was to determine if cerebral blood flow (CBF) alterations are associated with discontinuation of heroin in chronic heroin users, and whether these alterations are reversible during abstinence. Ten physically healthy opioid-dependent males, hospitalized on an inpatient drug rehabilitation unit, were studied. Each patient had an initial single photon emission computed tomographic (SPECT) scan with the radiotracer technetium-99m-d,l-hexamethylpropyleneamine oxime (99mTc-HMPAO) 1 week after opiate discontinuation and a repeat scan 2 weeks later. The initial scans in 9 of the 10 subjects demonstrated significant, often discrete, perfusion defects, especially in the frontal, parietal, and temporal cortices. Two weeks later, repeat brain perfusion SPECT scans showed improvement in all nine subjects who had abnormal scans. Comparisons of the first scan with the second scan showed an increase in cortical uptake on the repeat SPECT study. All subjects had normal computed tomographic or magnetic resonance imaging scans. The results of this preliminary study suggest that the chronic use of opiates, like chronic use of cocaine, results in perfusion abnormalities without corresponding abnormalities on imaging studies of cerebral anatomy and morphology. This study also documents that these perfusion defects are partially reversible with short-term abstinence.
TL;DR: In patients with typical angina and a normal or nondiagnostic electrocardiogram, initial SPECT scintigraphy allows early accurate risk stratification and the previously observed excellent inpatient prognosis of patients with a normal scintigram appears to extend for at least 90 days of follow-up.
TL;DR: Visual brain perfusion patterns correlate with the extent, severity, and short-term outcome of hemispheric stroke and HMPAO SPECT may improve the prognostic value of clinical examination if performed during the first 72 hours of stroke.
Abstract: Background and Purpose Single-photon emission computed tomography (SPECT) is used in patients with acute stroke but as yet is of controversial value. We investigated an association of brain perfusion changes in stroke patients with stroke severity, volume of brain damage, and recovery. Methods Consecutive patients with hemispheric stroke were studied prospectively with serial neurological examinations using the Canadian Neurological Scale (CNS), CT, and 99m Tc–hexamethylpropyleneamine oxime (HMPAO) SPECT. Visual SPECT patterns of brain perfusion (normal, high, mixed, low, and absent) were correlated with the severity of stroke, lesion volume, and short-term outcome. Results SPECT studies were performed in a total of 458 consecutive acute stroke patients within 2 weeks after the onset (mean time, 5 days; range, 1 to 12 days). SPECT perfusion patterns correlated with stroke severity (CNS score) during the first 2 weeks ( P P P =.0001). SPECT had its own prognostic value independent of clinical judgment ( P =.03). SPECT statistically improved predictive power of the CNS score (+1% receiver operating characteristic curve area, [χ 2 ] 2 =20, P Conclusions Visual brain perfusion patterns correlate with the extent, severity, and short-term outcome of hemispheric stroke. HMPAO SPECT may improve the prognostic value of clinical examination if performed during the first 72 hours of stroke.
TL;DR: Differences in cerebral perfusion in the areas compressed secondary to the fused cranial suture both before and after cranial reconstructive surgery in patients with simple craniosynostosis supports early surgical intervention to prevent any potential central nervous system compromise secondary to abnormal blood flow.
Abstract: Premature fusion of multiple cranial sutures has been associated with increased intracranial pressure and the potential for mental impairment. Isolated craniosynostosis, however, has been thought to be a benign condition primarily reconstructed for aesthetic purposes. On the basis of subjective developmental improvement postoperatively, an objective radiographic analysis (single positron emission computed tomography [SPECT] was used to assess differences in cerebral perfusion in the areas compressed secondary to the fused cranial suture both before and after cranial reconstructive surgery in patients with simple craniosynostosis. Seven children with craniosynostosis, six boys and one girl (age age, 3-28 months), were enrolled in this prospective study. Six of the seven had cranial asymmetry on preoperative cranial computed tomographic scans, and one had a symmetric defect and was used as a control. Each subject had a preoperative SPECT scan approximately 3 to 5 days before the cranial reconstruction procedure and a follow-up scan 6 to 10 weeks postoperatively. Preoperative asymmetries in cerebral perfusion ranged from 0 to 30% (mean, 13%) the areas compressed secondary to the premature suture fusion. In five patients cerebral blood flow, which was asymmetric before surgery, became symmetric after craniofacial reconstruction, and no new perfusion defects were documented. The control patient and one another patient had symmetric perfusion both pre- and postoperatively. Craniosynostosis may be associated with decreased cerebral blood flow as a result of the constriction of the brain from the prematurely fused suture. The correction of asymmetric cranial single-suture synostosis is more than a cosmetic procedure in that it allows for normalization of cerebral blood flow. This difference in blood flow supports early surgical intervention to prevent any potential central nervous system compromise secondary to abnormal blood flow.
TL;DR: The cerebral blood flow images contain two types of artifact, probably due to arterial and venous blood volume contributions, which must be overcome before the arterial spin tagging approach can be used for routine clinical studies.
Abstract: Single-shot echo planar imaging (EPI) techniques have been applied, in conjunction with arterial spin tagging approaches, to obtain images of cerebral blood flow in a single axial slice in the human brain. Serial studies demonstrate that cerebral blood flow images acquired in 8 min are reproducible, with a statistical precision of approximately +/-10 cc/100 g/min. The average value of cerebral blood flow in the slice is 51 +/- 11 cc/100 g/min for six normal subjects. The cerebral blood flow images contain two types of artifact, probably due to arterial and venous blood volume contributions, which must be overcome before the arterial spin tagging approach can be used for routine clinical studies.
Journal Article•
TL;DR: Patients with symmetric cerebral perfusion measured by 99mTc-HMPAO SPECT may still have a high long-term complication rate following carotid sacrifice, although most of them had good surgical outcomes.
Abstract: The main objective of this study was to assess whether 99m Tc-HMPAO brain SPECT imaging can identify patients at high risk of developing an infarct following permanent carotid occlusion in the course of brain surgery. Methods : Test balloon occlusion of the internal carotid artery was performed in 44 patients with a variety of head and neck tumors or aneurysms. Technetium-99m-HMPAO was injected intravenously while the balloon was inflated and a SPECT study was obtained 30 min later. Follow-up CT scans were obtained routinely for all patients at 2 wk and 1 mo following surgery, or earlier when necessary. Thirty patients and five normal volunteers had semiquantitative analysis of cerebral perfusion. Results : Twenty-six patients demonstrated ipsilateral perfusion abnormalities during trial occlusion. Eight patients in this group underwent bypass grafting prior to sacrifice of the artery : two resulting in infarcts. Eighteen patients had symmetric cerebral perfusion during occlusion and four of these patients underwent permanent therapeutic carotid occlusion ; three patients had subsequent infarcts and the fourth patient had an impending stroke. Conclusion : Patients with symmetric cerebral perfusion measured by 99m Tc-HMPAO SPECT may still have a high long-term complication rate following carotid sacrifice. The scan findings in these patients were not predictive of the outcome. Patients with asymmetric cerebral perfusion had alternative therapeutic approach to carotid sacrifice and most of them had good surgical outcomes.
TL;DR: It is concluded that normal dobutamine-atropine technetium-99m sestamibi SPECT perfusion imaging in women with chest pain implies an excellent prognosis, even in womenwith high pretest likelihood of coronary disease.
Abstract: To evaluate the prognostic value of normal dobutamine-atropine technetium-99m sestamibi single-photon emission computed tomography (SPECT) perfusion imaging in women with chest pain and inability to perform an adequate exercise test, 80 women with a normal scintigram were followed up for 23 ± 13 months. Heart age of the patients was 61 ± 12 years. Nine patients (11%) had a low probability ( 80%) of disease (including 19 patients with known coronary artery disease). During follow-up, no major cardiac events (cardiac death or nonfatal myocardial infarction) occurred. One patient with known coronary disease underwent coronary bypass surgery after 3 months, and 1 patient with a 91% pretest likelihood of coronary disease underwent coronary angioplasty after 7 months. Thus, the overall incidence of (soft) cardiac events during the follow-up period was 2 of 80 patients, or 1.3%/ year. It is concluded that normal dobutamine-atropine technetium-99m sestamibi SPECT perfusion imaging in women with chest pain implies an excellent prognosis, even in women with high pretest likelihood of coronary disease.
TL;DR: The pathophysiology of stroke is discussed as a basis for understanding the neuroimaging findings and newer MR stroke imaging techniques such as perfusion imaging and diffusion‐weighted imaging are presented.
Abstract: A review of the CT and MRI features of stroke imaging is presented. The pathophysiology of stroke is discussed as a basis for understanding the neuroimaging findings. Neuroimaging is divided according to the time interval between ictus and imaging: hyperacute, acute, subacute, and chronic. Newer MR stroke imaging techniques such as perfusion imaging and diffusion-weighted imaging are presented.
TL;DR: Preliminary data suggest that patients with low ejection fractions, multivessel CAD, and preserved viability who undergo CABG have a lower perioperative mortality and morbidity and a greater long-term survival rate than patients with a comparable degree of LV dysfunction and angiographic extent of CAD who undergo surgery but who manifest poor myocardial viability preoperatively.
Abstract: Noninvasive assessment of myocardial viability has proved clinically useful to distinguish hibernating or stunned myocardium from irreversibly injured myocardium in patients with chronic CAD or recent myocardial infarction who exhibit severe regional and global LV dysfunction. A variety of noninvasive methodologies are undergoing investigation and validation for determination of accuracy in the detection of preserved viability in akinetic and severely hypokinetic myocardium. These techniques include SPECT perfusion imaging with 201Tl or one of the new 99mTc-labeled agents, such as 99mTc sestamibi; SPECT imaging of 123I-labeled fatty acid analogs; PET imaging of regional flow and 18F-labeled FDG uptake; and assessment of inotropic reserve by use of dobutamine echocardiography. A major clinical objective when one of these techniques is used in CAD patients with ischemic cardiomyopathy is to identify those who will benefit most from coronary revascularization with respect to postoperative improvement in regional and global LV function, heart failure symptoms, functional capacity, and enhanced long-term survival.
Several observational studies1 2 3 4 showed substantial survival benefit with revascularization compared with medical therapy in patients whose low ejection fraction was primarily due to viable but hibernating myocardium. Similarly, preliminary data5 suggest that patients with low ejection fractions, multivessel CAD, and preserved viability who undergo CABG have a lower perioperative mortality and morbidity and a greater long-term survival rate than patients with a comparable degree of LV dysfunction and angiographic extent of CAD who undergo surgery but who manifest poor myocardial viability preoperatively. Gioia et al1 reported a 13% annual mortality rate in CAD patients with LV dysfunction and presence of viability by 201Tl criteria who were treated medically compared with 6% for those with comparable viability who underwent revascularization. DiCarli et al2 reporteda 50% mortality rate at 1 year in patients with …
TL;DR: The diffusion-weighted MRI findings suggest a potential delayed therapeutic effect of bFGF, and the perfusion imaging findings imply that the effect is not due to increased blood flow to the ischemic region.
Abstract: Background and Purpose Basic fibroblast growth factor (bFGF) has documented neuroprotective properties. This study was performed to evaluate the effects of bFGF on infarct size when administered 30 minutes after induction of focal cerebral ischemia in rats. Diffusion-weighted and perfusion MRI were used during the drug infusion.
Methods We blindly randomized 20 Sprague-Dawley rats to receive either drug (n=10) or vehicle (n=10). The animals underwent middle cerebral artery (MCA) occlusion using the suture model. Diffusion-weighted MRI was initiated 30 minutes after induction of ischemia and repeated frequently for 3.5 hours. Drug (45 μg/kg per hour) or vehicle (saline) infusion began 30 minutes after MCA occlusion and continued for 3 hours. Perfusion images were made at 25, 90, and 150 minutes after MCA occlusion. The animals were killed after 24 hours of permanent MCA occlusion, and brains were stained with 2,3,5-triphenyltetrazolium chloride (TTC).
Results The TTC-derived, corrected infarct volume postmortem in the bFGF-treated group was significantly smaller than that in controls (126.6±51.9 versus 180.2±54.9 mm3, mean±SD, P =.038). Diffusion imaging showed essentially equal lesion volumes 3 hours after MCA occlusion (195.4±61 mm3 in the drug-treated group and 194.4±65 mm3 in controls). At 4 hours, ischemic lesion size was 182.1±56.9 mm3 in treated animals and 222.9±88.7 mm3 in the controls ( P =.24, NS). Perfusion imaging did not show a change of cerebral perfusion within ischemic brain regions in the bFGF group during the infusion. No behavioral or physiological side effects were observed.
Conclusions bFGF is a safe and effective treatment for focal cerebral ischemia in rats. We observed a modest delayed difference of ischemic lesion size in vivo with diffusion MRI. The diffusion-weighted MRI findings suggest a potential delayed therapeutic effect of bFGF, and the perfusion imaging findings imply that the effect is not due to increased blood flow to the ischemic region.
TL;DR: The results show that tumor vascularity can be assessed qualitatively by using EPISTAR without the need for contrast medium injection and high-grade astrocytomas demonstrated elevated EPISTar signal with marked regional heterogeneity.
Abstract: A total of 17 patients with histologically proven diagnoses of low-grade astrocytoma (n = 4), high-grade astrocytoma (n = 8), lymphoma (n = 3), and meningioma (n = 2) were examined by using EPISTAR MR imaging. Meningiomas had the highest EPISTAR tumor/white matter contrast and low-grade astrocytomas and lymphomas the lowest. High-grade astrocytomas demonstrated elevated EPISTAR signal with marked regional heterogeneity. There was agreement between tumor vascularity by SPECT and EPISTAR in the five cases where both were done. Our results show that tumor vascularity can be assessed qualitatively by using EPISTAR without the need for contrast medium injection.
TL;DR: A reduced uptake of N-13 ammonia is shown which is indicative of a reduction in myocardial perfusion in DMD and BMD, where both groups demonstrated significant regional perfusion/metabolism mismatches.
TL;DR: This spin-labeling method provides quantitative estimates of myocardial arterial perfusion in this model and may hold promise for clinical applications.
Abstract: PURPOSE: To quantitate myocardial arterial perfusion with a noninvasive magnetic resonance (MR) imaging technique that exploits the geometry of coronary vessel anatomy. MATERIALS AND METHODS: MR imaging was performed with a spin-labeling method in six arrested rabbit hearts at 4.7 T. Selective inversion of magnetization in the short-axis imaging section along with all myocardium apical to that section produces signal enhancement from arterial perfusion. A linescan protocol was used for validation of flow enhancement. Flow was quantitated from two images and validated with spin-echo (SE) imaging. Regional perfusion defects were created by means of coronary artery ligation and delineated with gadolinium-enhanced imaging. RESULTS: Linescan estimates of T1 obtained at physiologic flows agreed with model predictions. Flow-induced signal enhancement measured on SE images also agreed with expected values. Finally, perfusion abnormalities created by means of coronary artery ligation were detected. CONCLUSION: Thi...
TL;DR: Dobutamine myocardial perfusion perfusion imaging is a safe diagnostic test, although side effects are common, and should be done with the necessary caution.
TL;DR: Pacing caused a decrease of resting left ventricular myocardial blood flow and blood flow during pharmacologically induced coronary vasodilatation, which resulted in a reduction of anginal complaints and a reduction in intraventricular pressure gradient.
Abstract: OBJECTIVE: Angina and the presence of myocardial ischaemia are common in hypertrophic cardiomyopathy. Dual chamber pacing results in clinical improvement in these patients. This study evaluates the effects of permanent dual chamber pacing on absolute regional myocardial perfusion and perfusion reserve. SETTING: University hospital. PATIENTS AND DESIGN: Six patients with hypertrophic cardiomyopathy and severe symptoms of angina received a dual chamber pacemaker. Absolute myocardial regional perfusion and perfusion reserve (dipyridamole 0.56 mg/kg) were measured by dynamic positron emission tomography with 13N-ammonia both during sinus rhythm and 3 months after pacemaker insertion. Results were compared with those from 28 healthy volunteers. RESULTS: Pacing resulted in a reduction of anginal complaints and a reduction in intraventricular pressure gradient from 65 (SD 30) mm Hg to 19 (10) mm Hg. During sinus rhythm, baseline perfusion was higher in patients with hypertrophic cardiomyopathy than controls (184 (31) v 106 (26) ml/min/100 g, P < 0.01), and perfusion reserve was lower (1.6 (0.4) v 2.8 (1.0), P < 0.05). During pacing myocardial perfusion decreased to 130 (27) ml/min/100 g (P < 0.05), with variable responses in terms of perfusion reserve. Pacing caused a redistribution of myocardial stress perfusion and perfusion reserve. The coefficient of regional variation of myocardial stress perfusion decreased from 19.7 (7.0)% to 14.6 (3.9)% during pacing (12.9 (3.8)% in controls, P < 0.01). The coefficient of regional variation of perfusion reserve decreased from 16.7 (6.6)% to 11.4 (2.6)% during pacing (9.8 (4.1)% in controls, P < 0.01). CONCLUSIONS: Pacing caused a decrease of resting left ventricular myocardial blood flow and blood flow during pharmacologically induced coronary vasodilatation. Although global perfusion reserve remained unchanged, myocardial perfusion reserve became more homogeneously distributed.
TL;DR: Tc-99m MAA total-body imaging can be used for the diagnosis of intrapulmonary right-to-left shunts, as well as for the evaluation of postshunt therapy.
Abstract: The appearance of radiotracer in the systemic circulation to document the visualization of the brain, kidneys, and spleen after intravenous administration of Tc-99m MAA indicates right-to-left shunts because MAA particles (20-60 microns) are supposedly trapped in the pulmonary bed (less than 15 microns). Six hypoxemia patients (1 male, 5 females; age range, 12-52 years) with intrapulmonary right-to-left shunts were evaluated by Tc-99m MAA dynamic perfusion imaging and total-body scans. Tc-99m MAA total-body imaging of the six patients with intrapulmonary right-to-left shunts (3 patients with chronic liver disease/cirrhosis of the liver and 3 patients with pulmonary arteriovenous fistulae) revealed significant radiotracer uptake in extrapulmonary organs such as the brain, kidneys, and spleen; a shunt ratio, estimated by a semiquantitative method, ranged from 17.8% to 52%. All dynamic pulmonary perfusion scans showed a normal sequence of cardiopulmonary flow without intracardiac shunts. Three patients with pulmonary arteriovenous fistulae underwent a second Tc-99m MAA total-body imaging after embolization therapy (2 patients) or lobectomy (1 patient). The result in lobectomized patients were negative for uptake in extrapulmonary organs; the two patients who underwent embolization therapy demonstrated only mild improvement. As a consequence of these findings, the authors conclude that Tc-99m MAA total-body imaging can be used for the diagnosis of intrapulmonary right-to-left shunts, as well as for the evaluation of postshunt therapy.
TL;DR: Interictal brain perfusion studies, together with proton magnetic resonance spectroscopy, may play an important role in detecting anatomic substrate in developmental disorders of the neocortex.
Abstract: Single-photon emission computed tomography (SPECT) is being increasingly used in the investigation of children with epilepsy and may provide insights into congenital malformations. We analyzed the interictal 99Tc-HMPAO-SPECT in a series of seven children with developmental disorders of the neocortex, each of them representing a prototype of cerebral dysgenesis, such as lissencephaly, pachygyria, opercular dysplasia, polymicrogyria, nodular heterotopia and band heterotopia. The patients studied were selected among 22 epileptic children with neuronal migrational disorders (NMDs). Interictal SPECT hypoperfusion was observed in the area homologous to MRI findings in all the examined children. In three patients low perfusion was also present in the opposite hemisphere, probably due to functional involvement or related to an underlying microdysgenesis, not revealed by structural imaging. EEG features were in agreement with low perfusion areas, both anatomically and functionally, in all children. In one patient hypoperfusion area differed from that revealed by MRI and EEG. Ictal SPECT has been considered a useful tool for accurately locating the epileptic focus. Nevertheless, interictal brain perfusion studies, together with proton magnetic resonance spectroscopy, may play an important role in detecting anatomic substrate in developmental disorders of the neocortex.
TL;DR: The pH after the retrograde brain perfusion was significantly higher than the pH after circulatory arrest in the entire brain and the spinal cord, concluding that the brain is protected when perfused retrogradely beyond the venous valves with a driving pressure above 20 mm Hg.
TL;DR: Exercise and pharmacologic stress myocardial perfusion imaging abnormalities reflect diminished post-stenotic coronary flow to a greater degree than transstenotic pressure gradients.
Abstract: The functional significance of coronary stenoses is frequently determined by adjunctive noninvasive myocardial perfusion imaging. Poststenotic coronary flow velocity and pressure can be measured directly during routine cardiac catheterization. The aim of this study was to correlate poststenotic (distal) flow velocity and pressure with stress perfusion imaging in patients. Quantitative angiography, basal and hyperemic transstenotic coronary flow velocities, and pressure gradients were measured in 50 patients within 1 week of exercise (n = 29) or of pharmacologic (n = 21) stress perfusion imaging. Twenty-two of 25 patients (88%) with reversible perfusion abnormalities had diminished distal coronary flow velocity reserves (CFVR) of ≤2.0 × baseline, whereas 22 of 25 (88%) with normal perfusion imaging studies had a normal distal CFVR of > 2.0 (p = 0.0001). Thirteen of 25 patients (52%) with reversible perfusion abnormalities had transstenotic gradients ≥ 20 mm Hg, whereas 20 of 25 (80%) with normal perfusion studies had gradients
TL;DR: The study shows that moderate hypothermic circulatory arrest at 28 degrees C with antegrade brain perfusion duringcirculatory arrest protects the brain but that retrograde cerebral perfusion at 28degree C does not protect the brain.