Showing papers on "Perfusion scanning published in 2000"

Thrombolytic reversal of acute human cerebral ischemic injury shown by diffusion/perfusion magnetic resonance imaging

Abstract: Diffusion magnetic resonance imaging provides an early marker of acute cerebral ischemic injury. Thrombolytic reversal of diffusion abnormalities has not previously been demonstrated in humans. Serial diffusion and perfusion imaging studies were acquired in patients experiencing acute hemispheric cerebral ischemia treated with intra-arterial thrombolytic therapy within 6 hours of symptom onset. Seven patients met inclusion criteria of prethrombolysis and postthrombolysis magnetic resonance studies, presence of large artery anterior circulation occlusion at angiography, and achievement of vessel recanalization. Mean diffusion-weighted imaging lesion volume at baseline was 23 cm3 (95% confidence interval [95% CI], 8-38 cm3) and decreased to 10 cm3 (95% CI, 3-17 cm3) 2.5 to 9.5 hours after thrombolysis. Mean apparent diffusion coefficient lesion volume decreased from 9 cm3 (95% CI, 2-16 cm3) at baseline to 1 cm3 (95% CI, 0.4-2 cm3) early after thrombolysis. A secondary increase in diffusion volumes was seen in 3 of 6 patients at day 7. In all 4 patients in whom perfusion imaging was obtained before and after treatment, complete resolution of the perfusion deficit was shown. Diffusion magnetic resonance signatures of early tissue ischemic injury can be reversed in humans by prompt thrombolytic vessel recanalization. The ischemic penumbra includes not only the region of diffusion/perfusion mismatch, but also portions of the region of initial diffusion abnormality.

Dynamic CT perfusion imaging of acute stroke.

Abstract: BACKGROUND AND PURPOSE: Because cerebral perfusion imaging for acute stroke is unavailable in most hospitals, we investigated the feasibility of a method of perfusion scanning that can be performed rapidly during standard cranial CT. Our aim was to identify the scanning parameters best suited to indicate tissue at risk and to measure a perfusion limit to predict infarction. METHODS: Seventy patients who had suffered stroke and had undergone cranial CT 0.5 to 12 hours (median, 3.75 hr) after the onset of symptoms participated in the study. While undergoing conventional CT, each patient received a bolus of iodinated contrast medium. Maps of time to peak (TTP), cerebral blood volume (CBV), and CBF were calculated from the resulting dynamically enhanced scans. These perfusion images were compared with follow-up CT scans or MR images showing the final infarctions. RESULTS: CBF maps predicted the extent of cerebral infarction with a sensitivity of 93% and a specificity of 98%. In contrast, CBV maps were less sensitive and TTP maps were less specific and also showed areas of collateral flow. Infarction occurred in all of the patients with CBF reduction of more than 70% and in half of the patients with CBF reduction of 40% to 70%. CONCLUSION: Dynamic CT perfusion imaging safely detects tissue at risk in cases of acute stroke and is a feasible method for any clinic with a third-generation CT scanner.

Frequency and Clinical Implications of Fluid Dynamically Significant Diffuse Coronary Artery Disease Manifest as Graded, Longitudinal, Base-to-Apex Myocardial Perfusion Abnormalities by Noninvasive Positron Emission Tomography

Abstract: Background—Diffuse coronary atherosclerosis is the substrate for plaque rupture and coronary events. Therefore, in patients with mild arteriographic coronary artery disease without significant segm...

Cerebral perfusion and arterial transit time changes during task activation determined with continuous arterial spin labeling.

Abstract: Perfusion imaging by arterial spin labeling (ASL) can be highly sensitive to the transit time from the labeling site to the tissue. We report the results of a study designed to separate the transit time and perfusion contributions to activation in ASL images accompanying motor and visual stimulation. Fractional transit time decreases were found to be comparable to fractional perfusion increases and the transit time change was found to be the greatest contributor to ASL signal change in ASL sequences without delayed acquisition. The implications for activation imaging with ASL and the arterial control of flow are discussed.

Intrapericardial delivery of fibroblast growth factor-2 induces neovascularization in a porcine model of chronic myocardial ischemia.

Abstract: Therapeutic angiogenesis is a novel approach to the treatment of myocardial ischemia based on the use of proangiogenic growth factors to induce the growth of new blood vessels to supply the myocardium at risk. This study was designed to assess the safety and efficacy of a single intrapericardial injection of basic fibroblast growth factor (FGF-2) in a porcine model of chronic myocardial ischemia. Yorkshire pigs underwent ameroid placement around the left circumflex coronary artery. At 3 weeks, animals were randomized to receive a single intrapericardial injection of either saline (n = 10), 3 mg of heparin (n = 9), 3 mg of heparin + 30 microgram of FGF-2 (n = 10), 200 microgram of FGF-2 (n = 10), or 2 mg of FGF-2 (n = 10). Coronary angiography, microsphere flow, magnetic resonance functional, and perfusion imaging were performed before and 4 weeks after treatment, at which time histologic analysis was also performed on 3 animals in each group. In ischemic pigs, FGF-2 treatment resulted in significant increases in left-to-left angiographic collaterals and left circumflex coronary artery blood flow. These benefits were accompanied by improvements in myocardial perfusion and function in the ischemic territory, as well as histologic evidence of increased myocardial vascularity without any adverse effects. Not one of these benefits was seen in saline- or heparin-treated ischemic animals. A single intrapericardial injection of FGF-2 in a porcine model of chronic myocardial ischemia results in functionally significant myocardial angiogenesis, without any adverse outcomes. This mode of FGF-2 administration may prove to be a useful therapeutic strategy for the treatment of patients with ischemic heart disease.

Dobutamine stress echocardiography: safety in diagnosing coronary artery disease.

Abstract: Among exercise-independent stresses, the most popular are dobutamine and dipyridamole. Dobutamine is the prototype of pharmacological adrenergic or isotropic stresses, initially proposed in combination with perfusion imaging [1] and later with 2-D echocardiography [2, 3]. Other sympathomimetic agents have been proposed for stress echocardiography, including isoproterenol [4] and epinephrine [5], but arrhythmogenic side effects are frequent with these drugs. Dobutamine was first proposed in 1984 [1, 2] and later abandoned, mostly due to concern about induced arrhythmias [6]. In the past few years it has been extensively adopted as the most-used pharmacological stress — with an explosion triggered by the demonstration of low-dose dobutamine as a way to unmask myocardial viability by recruiting the inotropic reserve [7]. The main differences between physical and pharmacological stress echocardiography are summarized in Table 1.

Left Frontotemporal Hypoperfusion Is Associated With Aggression in Patients With Dementia

Abstract: Background Aggressive behavior is common in patients with dementia. Temporolimbic and prefrontal cortical lesions can produce pathological aggression; however, involvement of these structures has not been established in aggressive patients with dementia. Objective To study the relation between regional brain perfusion and aggressive behavior in patients with dementia. Methods We compared the pattern of regional cerebral perfusion determined with technetium Tc 99m–labeled hexamethylpropelene amineoxime single photon emission computed tomography in 2 groups of 10 patients with dementia with and without aggression, that were comparable for demographic factors, severity of cognitive impairments, and other behavioral symptoms as measured by the Neuropsychiatric Inventory. Results Patients with aggression revealed significant (P Conclusion These results indicated an association between aggression and decreased perfusion in the left anterior temporal cortex.

Non-invasive quantification of liver perfusion with dynamic computed tomography and a dual-input one-compartmental model.

Abstract: Various liver diseases lead to significant alterations of the hepatic microcirculation. Therefore, quantification of hepatic perfusion has the potential to improve the assessment and management of liver diseases. Most methods used to quantify liver perfusion are invasive or controversial. This paper describes and validates a non-invasive method for the quantification of liver perfusion using computed tomography (CT). Dynamic single-section CT of the liver was performed after intravenous bolus administration of a low-molecular-mass iodinated contrast agent. Hepatic, aortic and portal-venous time-density curves were fitted with a dual-input one-compartmental model to calculate liver perfusion. Validation studies consisted of simultaneous measurements of hepatic perfusion with CT and with radiolabelled microspheres in rabbits at rest and after adenosine infusion. The feasibility and reproducibility of the CT method in humans was assessed by three observers in 10 patients without liver disease. In rabbits, significant correlations were observed between perfusion measurements obtained with CT and with microspheres (r=0.92 for total liver perfusion, r=0.81 for arterial perfusion and r=0.85 for portal perfusion). In patients, total liver plasma perfusion measured with CT was 112+/-28 ml.min(-1).100 ml(-1), arterial plasma perfusion was 18+/-12 ml.min(-1).100 ml(-1) and portal plasma perfusion was 93+/-31 ml.min(-1).100 ml(-1). The measurements obtained by the three observers were not significantly different from each other (P>0.1). Our results indicate that dynamic CT combined with a dual-input one-compartmental model provides a valid and reliable method for the non-invasive quantification of perfusion in the normal liver.

Transit time, trailing time, and cerebral blood flow during brain activation: Measurement using multislice, pulsed spin-labeling perfusion imaging

Abstract: Transit time and trailing time in pulsed spin-labeling perfusion imaging are likely to be modulated by local blood flow changes, such as those accompanying brain activation. The majority of transit/trailing time is due to the passage of the tagged blood bolus through the arteriole/capillary regions, because of lower blood flow velocity in these regions. Changes of transit/trailing time during activation could affect the quantification of CBF in functional neuroimaging studies, and are therefore important to characterize. In this work, the measurement of transit and trailing times and CBF during sensorimotor activation using multislice perfusion imaging with pulsed arterial spin-labeling is described. While CBF elevated dramatically (∼80.7%) during the sensorimotor activation, sizable reductions of transit time (∼0.11 sec) and trailing time (∼0.26 sec) were observed. Transit and trailing times were dependent on the distances from the leading and trailing edges of the tagged blood bolus to the location of the imaging slices. The effects of transit/trailing time changes on CBF quantification during brain activation were analyzed by simulation studies. Significant errors can be caused in the estimation of CBF if such changes of transit/trailing time are not taken into account. Magn Reson Med 44:680–685, 2000. © 2000 Wiley-Liss, Inc.

Systematic review of diffusion and perfusion imaging in acute ischemic stroke.

Abstract: Background and Purpose—Recent advances in neuroimaging have raised hopes of early and accurate identification of ischemic brain and the discrimination of dead from salvageable tissue. We sought to determine whether the data published so far are enough to establish the roles of these techniques in everyday clinical practice. Methods—A systematic review of studies of MR diffusion-weighted imaging (DWI), perfusion imaging (PI), or a combination of the two, in human stroke, excluding abstracts and case reports. One reviewer extracted information on the size of each study, its main purpose, methodological details, and results. Results—We identified 47 studies of DWI, 18 studies of MR PI alone or in combination with another advanced imaging modality, and 19 studies of DWI and PI together. Although high proportions of the studies were prospective and gave good details of the imaging sequences used, the majority gave very limited details on patient selection and clinical characteristics or blinded imaging assessm...

Comparison of blood-brain barrier permeability in mice and rats using in situ brain perfusion technique.

Abstract: Here we present a method for measuring the permeability coefficient-surface area product (PS) values at the blood-brain barrier in mice, using the in situ brain perfusion technique originally developed for rats by Takasato et al. (Am J Physiol Heart Circ Physiol 247: H484-H493, 1984). Retrograde infusion into the right external carotid artery increased the carotid perfusion pressure in proportion to the perfusion rate. Intravascular volume and cerebral perfusion fluid flow at a perfusion rate of 1.0 ml/min in mice were similar to those in rats. In addition, the contribution of systemic blood to total flow in the hemisphere was small (only 3. 2%). These findings indicated that this perfusion rate is suitable for mice. The PS values of more than 20 different compounds were determined in mice by using the in situ brain perfusion technique, and comparisons were made with data from rats. There was a close relationship (1:1) between the PS values in mice and rats, indicating that brain capillary permeabilities are similar in mice and rats.

Dynamic contrast-enhanced brain perfusion imaging: technique and clinical applications.

Abstract: Magnetic resonance (MR) and computed tomographic (CT) perfusion imaging are evolving noninvasive imaging techniques that, unlike conventional MR and CT angiographic methods, can be used to evaluate capillary level tissue perfusion. These techniques can provide early, highly accurate delineation of ischemic tissue, allowing the underlying hemodynamic disturbances of disorders such as stroke and vasospasm to be further analyzed, as well as defining abnormal regions of blood pool in brain tumors. Because MR perfusion (MRP) and CT perfusion (CTP) imaging can assess physiologic parameters such as cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT), they offer additional data that can be useful in the detection and characterization of entities such as tumor, infection, inflammation, and infarction, which all can have similar appearances on both contrast and noncontrast enhanced conventional CT and MR images. They can also facilitate the further evaluation of processes such as early dementia, psychiatric illnesses, and migraine headaches, which may appear normal on routine CT and MR imaging. MRP and CTP might also be of value in distinguishing residual or recurrent tumor from treatment effects such as radiation-induced necrosis. This article reviews the background principles, scanning techniques, and clinical applications of noninvasive cerebral perfusion imaging.

Harmonic Imaging of the Human Brain Visualization of Brain Perfusion With Ultrasound

Abstract: Background and Purpose—Through harmonic gray-scale imaging, it is possible to analyze brain tissue perfusion with different ultrasound methods. Methods—In 12 healthy volunteers, 2 doses (0.5 and 1.5 mL) of Optison, a perfluoropropane-containing contrast agent, were injected intravenously and produced a strong increase of brightness in the brain parenchyma. We used harmonic imaging for quantification of ultrasound intensity in the thalamus, ipsilateral temporoparietal white matter (TPWM), and ipsilateral lateral fissure at both sides. Time-intensity curves were calculated, and peak increase (PI) of intensity and the area under the time-intensity curve (AUC) from baseline were compared. Results—We found a significant dose dependence of the AUC in all regions at both sides. PI only showed a significant dose dependence in the TPWM but not in the ipsilateral thalamus and lateral fissure. No side differences for AUC and PI were detected in all regions and doses used. We found a significantly higher value of the...

Dynamic susceptibility contrast MR imaging of plaque development in multiple sclerosis: application of an extended blood-brain barrier leakage correction.

Abstract: Since the pathogenesis of multiple sclerosis (MS) lesions is not yet fully understood, we investigated the potential of dynamic susceptibility contrast (DSC) magnetic resonance (MR) perfusion imaging for a better characterization of lesion pathology. Twenty-five MS patients were examined on a 1.5 T scanner. A single dose of gadolinium (Gd)-DOTA contrast agent was injected, and echoplanar images were acquired every 0.5 seconds for 1 minute. From the signal intensity-versus-time curves, the relative cerebral blood volume (rCBV) was evaluated for regions in plaques and in gray and white matter. The rCBV calculated for acute, Gd-enhancing plaques was corrected for the effects of blood-brain barrier leakage, using a new correction algorithm. Acute plaques had significantly higher blood volumes than normal-appearing white matter (P < = 0.01). Chronic plaques that appeared hypointense on T(1)-weighted images had lower rCBV than T(1)-isointense plaques (P < = 0.03). Our results indicate that the acute phase in MS is accompanied by vasodilation. In later stages of gliosis, the perfusion decreases with increasing axonal injury. Although the DSC technique is less sensitive than conventional MR imaging, the information provided is essentially different from that obtained with any other MR method.

Perfusion MRI of the human brain with dynamic susceptibility contrast: gradient-echo versus spin-echo techniques.

Abstract: In this study, spin-echo and gradient-echo-based perfusion magnetic resonance imaging (MRI) techniques are systematically compared with respect to their application in the human brain. Six healthy subjects were evaluated with both techniques consecutively and injected twice with a gadolinium-based contrast agent. In accordance with theoretical predictions and with previous animal experiments, the spin-echo-based technique shows a markedly reduced appearance of large vessels. The intersubject standard deviations of the two methods are similar but smaller for the spin-echo technique in small regions adjacent to large vessels. Therefore, the sensitivity of the two acquisition methods for evaluating pathologic abnormalities may be similar despite the higher contrast-to-noise ratio of the gradient-echo-based technique. The gray-to-white matter ratio of the regional cerebral blood flow of the spin-echo method is closer to previous nuclear medicine measurements than that of the gradient-echo method. Our measurements indicate that spin-echo-based perfusion MRI is more representative of capillary perfusion than gradient-echo measurements. J. Magn. Reson. Imaging 2000;12:381-387.

Breast lesions: evaluation with dynamic contrast-enhanced T1-weighted MR imaging and with T2*-weighted first-pass perfusion MR imaging

Abstract: PURPOSE: To evaluate the diagnostic value of an imaging protocol that combines dynamic contrast-enhanced T1-weighted magnetic resonance (MR) imaging and T2*-weighted first-pass perfusion imaging in patients with breast tumors and to determine if T2*-weighted imaging can provide additional diagnostic information to that obtained with T1-weighted imaging. MATERIALS AND METHODS: One hundred thirty patients with breast tumors underwent MR imaging with dynamic contrast-enhanced T1-weighted imaging of the entire breast, which was followed immediately with single-section, T2*-weighted imaging of the tumor. RESULTS: With T2*-weighted perfusion imaging, 57 of 72 carcinomas but only four of 58 benign lesions had a signal intensity loss of 20% or more during the first pass, for a sensitivity of 79% and a specificity of 93%. With dynamic contrast-enhanced T1-weighted imaging, 64 carcinomas and 19 benign lesions showed a signal intensity increase of 90% or more in the first image obtained after the administration of c...

Cerebral MR perfusion imaging : principles and current applications

Abstract: This small book contains a tremendous amount of well-written information. It is divided into two large sections. The first section contains technical information about perfusion MR imaging; the second contains information about its clinical uses. There is an excellent reference section, including suggested readings for further detail on methods, clinical applications to stroke and neoplasm, and animal studies. A CD-ROM supplements the book with video clips of cine presentation of image data from patient perfusion studies and postprocessing software tools. The section on technical aspects of perfusion MR imaging is very detailed but is thoughtfully organized and easy to read. Basic cerebral hemodynamic physiology is reviewed, followed by a discussion of the physical basis of contrast material–induced susceptibility effects. This leads into a detailed discussion of all of the practical aspects of performing perfusion studies, including contrast material dose and bolus administration, imaging techniques, and postprocessing. Each step is explained in sufficient detail to allow anyone wishing to perform perfusion studies to do so. Imaging techniques are discussed for echo-planar and non–echo-planar systems and for spin-echo and gradient-echo echo-planar imaging, and tables give specific recommendations for pulse sequence parameters. Most recommendations include the rationale for the recommendation and information on trade-offs involved in selection of parameters and different techniques, allowing the reader to customize them for particular equipment or clinical situations. Numerous well-reproduced graphs and clinical images aid in the explanation of these sometimes difficult concepts. The section on perfusion imaging in clinical practice is equally well presented. The advantages and disadvantages of MR perfusion imaging compared with positron emission tomography and xenon computed tomography are discussed, and this is followed by discussion of use of perfusion MR imaging in the clinical setting of cerebrovascular disease and cerebral neoplasms. Short subsections with mostly preliminary, but interesting, information about perfusion MR in dementia, vasospasm, head trauma, migraine, and epilepsy are also included. Each section is illustrated with high-quality clinical images. The sections on stroke and tumors are more detailed, with background information on the rationale for perfusion imaging, the vascular pathophysiology, and practical clinical uses. The included CD-ROM contains the text and illustrations of the book in digital form, supplementary video clips of perfusion imaging data from clinical images, and a selection of software tools for performing postprocessing on a Unix (LINUX or Solaris) workstation. The video clips do aid the understanding of the technical aspects discussed in the text, but they are certainly not necessary (for those not interested or those who are reading the book away from a computer). I have not used the software tools yet, but I plan to. The authors warn that they are not “user-friendly, commercial-quality” software. The authors and publishers should be very proud of this excellent work. The writing is clear and concise, the illustrations are well chosen and well reproduced, the content is up to date, and the layout and type are perfect. The video clips and software tools are a valuable bonus. Anyone interested in perfusion MR imaging will want this book.

Hemodynamic assessment of acute stroke using dynamic single-slice computed tomographic perfusion imaging.

Abstract: Background Stroke management would benefit from a broadly available imaging tool that detects perfusion deficits in patients with acute stroke. Objective To determine the role of dynamic, single-slice computed tomographic (CT) perfusion imaging (CTP) in the assessment of acute middle cerebral artery stroke. Design and Patients Imaging with CTP and CT within the first 6 hours of symptom onset and before the start of treatment in a consecutive clinical series of 22 patients (mean age, 68.3 years; 14 women; studied within 143 ± 96 minutes of stroke onset). Setting A stroke unit in a university hospital. Main Outcome Measures Area of the perfusion deficit (nAP 0 ) from time-to-peak maps, hemispheric lesion area from follow-up CT (HLA F ), final infarct volume, and stroke recovery (National Institutes of Health Stroke Scale scores). Results Eighteen patients had perfusion deficits in the middle cerebral artery territory and corresponding hypoattenuation in follow-up CT. Three patients with normal CTP findings showed lacunar infarctions or normal findings on follow-up CT. In 1 patient, CTP did not reveal a territorial deficit above the imaging slice. The overall sensitivity and specificity of CTP for the detection of perfusion deficits in patients with proven territorial infarction (n = 18) on follow-up CT were 95% and 100%, respectively. The nAP 0 was significantly correlated with the National Institutes of Health Stroke Scale score at admission ( P F ( P 0 >HLA F ; n = 6), (2) initial perfusion deficit and nonnutritional reperfusion (nAP 0 ≥HLA F ; n = 2), and (3) initial perfusion deficit without reperfusion (nAP 0 ≥HLA F ; n = 2). Conclusions Computed tomographic perfusion imaging detects major perfusion deficits in the middle cerebral artery territory. Because CTP is broadly available, it may play a role in acute stroke management.

Magnetic resonance imaging of regional myocardial perfusion in patients with single-vessel coronary artery disease: quantitative comparison with (201)Thallium-SPECT and coronary angiography.

Abstract: The clinical value of magnetic resonance perfusion imaging (MRI) was investigated by quantitative comparison with 201thallium-single-photon emission computed tomography (201TI-SPECT) and quantitative coronary angiography (QCA). Short-axis imaging was performed during dipyridamole administration in 13 patients with single-vessel coronary artery disease. Using inner and outer contours, the myocardium was divided into 30 contiguous, radial regions. Defining a perfusion defect as a region with less than 90% of maximum 201TI intensity, nine patients had a matching perfusion defect, two had no defect on both 201TI-SPECT or MRI, and one had a defect on 201TI-SPECT but not on MRI. One patient had a defect on both modalities but with inaccurate localization. Three perfusion parameters were investigated: a) maximum contrast enhancement (MCE); b) slope of the signal intensity versus time curve; and c) inverse mean transit time (1/MTT). The sensitivity and specificity of MCE in the detection of perfusion abnormalities with TI-SPECT as the reference method were 71% and 71%, respectively (slope 77% and 61%, 1/MTT 44% and 70%). Furthermore, correlations were calculated per patient for the entire circumference of the short-axis myocardium. Median correlations were as follows: MCE 0.92, slope 0.91, and 1/MTT 0.40. Mismatches between 201TI defects and defects on MRI resulted in low mean correlations (MCE 0.45, slope 0.46, and 1/MTT 0.26). There was a trend between severity of perfusion defects on MRI (using MCE) and QCA stenosis area (r = −0.56, P = 0.06). Thus, MRI and 201TI-SPECT demonstrate fair agreement in the assessment of perfusion defects but show moderate correlation when the entire short-axis myocardium is correlated. J. Magn. Reson. Imaging 2000;11:607–615. © 2000 Wiley-Liss, Inc.

Ultrasonic evaluation of pathological brain perfusion in acute stroke using second harmonic imaging

Abstract: OBJECTIVE To evaluate the use of transient response second harmonic imaging (HI) by means of ultrasound to assess abnormalities of cerebral echo contrast agent enhancement in patients with acute stroke. METHODS The study comprised 25 patients with acute onset of hemispheric stroke ( RESULTS Adequate cerebral contrast enhancement could be seen in 21 subjects. In seven, a large hemispheric deficit of contrast enhancement affecting the entire middle cerebral artery (MCA) territory was detectable; the lentiform nucleus was affected in three subjects. Assessment of cerebral contrast abnormalities was possible in two patients with superficial MCA infarctions but in none of the patients with lacunar ischaemias. None of the control persons had focal deficits of cerebral echo contrast enhancement. In all patients with complete MCA infarction and striatocapsular infarction, presumed ischaemic areas in HI examinations correlated with final CT findings. Overall sensitivity and specifity of HI examinations for predicting size and localisation of the infarction were 75 and 100%, respectively. During follow up, reappearance of contrast enhancement was determined in three patients, in two patients circulatory arrest due to malignant brain oedema with missing contrast enhancement in the entire cerebral hemisphere could be seen. Extent of contrast enhancement deficits significantly correlated with the clinical status on admission and after 1 week (p CONCLUSIONS Second harmonic imaging is the first ultrasonic technique that enables visualisation of pathological cerebral echo contrast enhancement. Because this method identifies deficits of focal contrast enhancement in patients with acute stroke and allows estimation of the final infarct size and clinical prognosis, it may help to select and monitor patients for invasive therapies.

Assessment of quantitative computed tomographic cerebral perfusion imaging with (H2O)-O-15 positron emission tomography

Abstract: Assessment of quantitative cerebral blood flow on a conventional fast CT machine without the use of specialized equipment may be valuable in the investigation of acute stroke and head injury. We aimed to compare a single slice CT perfusion sequence with H2150 positron emission tomography using the sagittal sinus as an input function, a method that avoids unnecessary orbital irradiation. Eight patients were studied, two patients with gliomas, and six with arteriovenous malformations. The dynamic CT perfusion sequence was performed by acquiring the same 7 0 mm slice 10 times over 30 sec during a 50 ml bolus of intravenous contrast medium given at a rate of 7.5 ml sec~^ using a power injector. The CT perfusion studies were completed without complication. Co-registration was sub-optimal in one patient. Overall the correlation between the two methodologies was encouraging with an average r2 value of0.524 for individual analyses. When two patients with high flow arteriovenous malformations were excluded...

Magnetic resonance first-pass myocardial perfusion imaging.

Abstract: Magnetic resonance first-pass perfusion imaging has developed considerably over the past decade. It is possible to acquire 7-8 imaging planes every heartbeat at rest and in two heartbeats during stress using high-performance gradients and hybrid echoplanar methods. T1 weighting can be achieved with volumetric saturation pulses or selective "notch" pulses. First-pass studies can be quantified, but it also is possible to directly visualize myocardial perfusion abnormalities as subendocardial defects with less contrast enhancement than surrounding myocardium. It is feasible to detect stress-induced perfusion abnormalities in patients with coronary artery disease. Magnetic resonance imaging (MRI) perfusion abnormalities associated with myocardial infarction have significantly different characteristics from those seen on nuclear methods such as thallium, where the final appearance of images represents a combination of perfusion, viability, and wall thickness. Infarcted myocardium enhances during the first-pass MRI study unless there is microvascular or epicardial obstruction. Microvascular obstruction after myocardial infarction is easily detected and has adverse prognostic significance. Stress-induced perfusion abnormalities are not synonymous with coronary artery disease, as they can be detected in hypertrophic cardiomyopathy. MRI perfusion methods appear promising as long as physicians interpret the results in accordance of the physiology portrayed in the images.