Abstract: AIMS: To study recovery of segmental wall thickening (SWT), ejection fraction (EF), and end-systolic volume (ESV) after acute myocardial infarction (AMI) in patients who underwent primary stenting with drug-eluting stents. Additionally, to evaluate the predictive value of magnetic resonance imaging (MRI)-based myocardial perfusion and delayed enhancement (DE) imaging. METHODS AND RESULTS: Twenty-two patients underwent cine-MRI, first-pass perfusion, and DE imaging 5 days after successful placement of a drug-eluting stent in the infarct-related coronary artery. Regional myocardial perfusion and the transmural extent of DE were evaluated. A per patient perfusion score was calculated and consisted of a summation of all segmental scores. Myocardial infarct size was quantified by measuring the volume of DE. At 5 months after AMI, cine-MRI was performed and SWT, EF, and ESV were quantified. EF increased from 48+/-11 to 55+/-9% (P<0.01). SWT at 5 months was inversely related to baseline segmental DE scores (P<0.001) and segmental perfusion scores (P<0.001). EF and ESV at 5 months were related to acute infarct size (R(2)=0.65; P<0.001 and R(2)=0.78; P<0.001, respectively) and the calculated perfusion score (R(2)=0.23; P=0.02 and R(2)=0.14; P=0.09, respectively) at baseline. CONCLUSION: Marked recovery of left ventricular function was observed in patients receiving a drug-eluting stent for AMI. DE imaging appears to be a better prognosticator than perfusion imaging.

Abstract: Brain perfusion SPECT is a functional neuroimaging technique that allows noninvasive study of physiologic and physiopathologic events in the human brain. With the appropriate technique and careful interpretation of the information provided, brain perfusion SPECT has proven potential for patient management. SPECT has clinical value in the diagnosis, therapeutic management, and follow-up of patients. The diversity of central nervous system diseases and the still incomplete knowledge of the mechanisms that underlie them have contributed to the success of brain perfusion SPECT as a research tool in neurosciences. This article provides fundamental knowledge on how and when to perform brain perfusion SPECT in clinical practice. A general overview of the clinical value of this technique is followed by relevant information on cerebral physiology for proper understanding of brain SPECT images. Practical considerations on quantification and interventional studies are also offered. Finally, step-by-step recommendations for interpreting and reporting brain perfusion SPECT images are provided to obtain the maximum clinical benefit from this technique.

Abstract: A quantitative analysis was undertaken to calibrate the perfusion quantification technique based on tracking the first pass of a bolus of a blood pool contrast agent. A complete simulation of the bolus passage, of the associated changes in the T2 and T* signals, and of the data processing was performed using the tracer dilution theory, an analytical theory of the MR signal from living tissues and numerical simulations. The noise was excluded in the simulation in order to analyze the ultimate accuracy of the method. It is demonstrated that the relationship between the contrast agent concentration and the associated changes in the transverse relaxation rate shows essentially different forms in studied tissue and in the reference artery. This effect results in systematic deviations of the measured blood flow, blood volume, and the residue function obtained with conventional processing from their true values. The error depends on the microvascular composition, the properties of the contrast agent, and the weights of the various compartments in the total signal. The results show that dynamic susceptibility contrast MRI can reach the goal of absolute perfusion quantification only with additional input from measurements of the microvascular architecture. Alternatively, the method can be used to provide such information if the perfusion is quantified by another modality. Magn Reson Med 46: 1113‐1122, 2001. © 2001 Wiley-Liss, Inc.

Abstract: positive ST2 responses because of the design of our study. Only a few studies have addressed the diagnostic or prognostic value of ischemic ST2 occurring solely during recovery after exercise. Nearly all have used coronary angiography as the “gold standard,” and 1 had evaluation of myocardial perfusion by nongated planar Tl-201 scintigraphy. In the present study, Tc99m sestamibi was used, yielding high-quality gated SPECT images permitting quantitative assessment of perfusion, regional function, and measurement of left ventricular ejection fraction. Gianrossi et al indicated that the sensitivity of the exercise electrocardiogram for CAD detection is lower when performed in conjunction with Tl-201 scintigraphy, because ST monitoring during recovery is sacrificed for expediency in Tl-201 imaging. With perfusion imaging studies using Tc-99m, image acquisition commences approximately 30 minutes after exercise, so that the imaging protocol does not interfere with recovery ST-segment monitoring.

Abstract: A new CT perfusion technique providing extended anatomic coverage was evaluated in 12 patients with suspected acute middle cerebral artery ischemia. With a multidetector CT scanner, scans were obtained in an alternating fashion at two distinct "toggling" table positions (two 1-cm sections each) during a 40-mL contrast agent bolus (approximately 5 seconds per image), and perfusion parameter maps were created. The CT perfusion results were compared with follow-up images. Nine patients showed focal perfusion abnormalities in at least one section, most commonly on mean transit time maps. Using a single table location would have underestimated or missed the involved tissue in most cases. In three of 12 patients, perfusion maps failed to delineate any abnormality. In two patients, perfusion and diffusion MR imaging confirmed the absence of perfusion abnormality and tissue injury, respectively. In one case, a small ischemic injury was revealed by diffusion MR imaging. By using the toggling-table approach, perfusion images can be obtained over an extended anatomic area and, thus, reveal the presence and the extent of presumed tissue injury.

Abstract: Background Echocardiographic contrast media have been used to assess myocardial perfusion and to enhance endocardial definition for improved assessment of left ventricular (LV) function. These methodologies, however, have been qualitative or have required extensive offline image analysis. Power modulation is a recently developed imaging technique that provides selective enhancement of microbubble-generated reflections. Our goal was to test the feasibility of using power modulation for combined quantitative assessment of myocardial perfusion and regional LV function in an animal model of acute ischemia. Methods and Results Coronary balloon occlusions were performed in 18 anesthetized pigs. Transthoracic power modulation images (Agilent 5500) were obtained during continuous intravenous infusion of the contrast agent Definity (DuPont) at baseline and during brief coronary occlusion and reperfusion and were analyzed with custom software. At each phase, myocardial perfusion was assessed by calculation, in 6 my...

Abstract: Background Occlusive disease of the posterior circulation represents a heterogeneous group of strokes that differ in etiology, clinical presentation, and prognosis. Computed tomography provides suboptimal visualization of posterior-circulation infarcts. Anatomic definition of traditional magnetic resonance imaging sequences has been used for clinicoradiologic correlation in patients with posterior-circulation disease. These studies focused on the subacute rather than the acute phase of ischemia. Lesion volumes on diffusion-weighted imaging (DWI) and perfusion imaging were found to have a good correlation with 24-hour National Institutes of Health stroke scale (NIHSS) score in ischemia of the anterior circulation. Correlation between NIHSS score and lesion volume in posterior-circulation infarcts is unknown. Objectives To investigate whether DWI is useful for clinicoradiologic correlation of posterior-circulation ischemia within 24 hours after symptom onset and whether NIHSS score correlates with lesion volumes in patients with posterior-circulation stroke. Patients and methods In a database analysis of 631 patients with stroke from June 26, 1996, to July 30, 1999, 115 patients (18%) had symptoms of posterior-circulation ischemia by imaging and clinical criteria. Among these 115, we included all patients (n = 40) who underwent DWI within 24 hours from symptom onset (mean, 9.7 +/- 7.1 hours). All 40 patients also underwent magnetic resonance angiography and T2-weighted imaging. Seventy-five did not meet inclusion criteria: in 45, magnetic resonance imaging was performed more than 24 hours after symptom onset; 12 did not have DWI; in 11 patients, symptoms resolved within 24 hours; 6 had hemorrhages; and 1 had a border zone infarct. Results An acute lesion on DWI corresponding to the patient's symptoms was detected in all 40 patients, 16 (40%) of whom had detectable acute lesions on T2-weighted images. The lesions on DWI were larger in 11 of the 16 patients with positive T2-weighted images. Acute lesion volume did not correlate with NIHSS score (n = 40; rho = 0.30; P =.06, Spearman rank) also when DWI lesion volumes were divided by cause and territory. Conclusions Diffusion-weighted imaging is more effective than T2-weighted imaging in patients with acute posterior-circulation strokes. The DWI lesion volume did not significantly correlate with NIHSS score, suggesting that NIHSS is more weighted toward anterior-circulation stroke symptoms.

Abstract: Lung scintigraphy is the primary tool for diagnostics of pulmonary embolism. A perfusion study is often complemented by a ventilation study. Intermediate probability scans are frequent. Our goal was to develop a fast method for tomographic ventilation and perfusion scintigraphy to improve the diagnostic value of lung scintigraphy. METHODS: SPECT was performed with a dual-head gamma camera. Acquisition parameters were determined using a thorax phantom. Ventilation tomography after inhalation of 30 MBq (99m)Tc-diethylenetriaminepentaacetate (DTPA) aerosol was, without patient movement, followed by perfusion tomography after an intravenous injection of 100 MBq (99m)Tc-labeled macroaggregated albumin (MAA). Total SPECT acquisition time was 20 min. (99m)Tc-DTPA clearance, calculated from initial and final SPECT projections, was used for correction of the ventilation projection set before iterative reconstruction of ventilation and perfusion. The ventilation background was subtracted from the perfusion tomograms. A normalized ventilation/perfusion quotient (V/P quotient) image set was calculated. The method was evaluated on a trial group of 15 patients. RESULTS: Ventilation and perfusion images had adequate quality and showed ventilation/perfusion (V/Q quotient) relationships more clearly than did planar images. Frontal and sagittal slices were superior to planar scintigraphy for characterization of embolized areas. The V/Q quotient was supportive, particularly in the patients with chronic obstructive pulmonary disease. CONCLUSION: Fast, high-quality, ventilation/perfusion SPECT with standard isotopes doses is feasible and may contribute to higher objectivity in evaluating lung embolism as well as other lung diseases. The costs for the procedure and patient care until diagnosis are low because of the comprehensive system for the study and, particularly, the short time for its completion.

Abstract: The contributions of individual components of blood to brain [14C]palmitate uptake and incorporation were studied with the in situ brain perfusion technique in the pentobarbital-anesthetized rat. With whole-blood perfusate, brain unacylated [14C]palmitate uptake was linear with time and extrapolated to zero at T=0 s of perfusion. Tracer accumulated in brain with a blood-to-brain transfer coefficient of 1.8 ± 0.1 × 10−4 mL/s/g (whole cerebral hemisphere). Incorporation into brain lipids was rapid such that ∼40% of tracer in brain at 45 s of perfusion was in cerebral phospholipids and neutral lipids. Similar rates of uptake were obtained during unacylated [14C]palmitate perfusion in whole rat plasma, serum, or artificial saline containing 2–3% albumin, suggesting that albumin has a key role in determining [14C]palmitate uptake in brain. The excellent match in brain uptake rates between whole blood and albumin-containing saline fluid suggests that the perfusion technique will be useful method for quantifying the individual contributions of blood constituents and albumin binding on brain [14C]palmitate uptake.

Abstract: An original MRI contrast agent, called P792, is described. P792 is a gadolinium macrocyclic compound based on a Gd-DOTA structure substituted by hydrophilic arms. The chemical structure of P792 has been optimized in order to provide (1) a high r1 relaxivity in the clinical field for MRI: 29 mM−1 x s−1 at 60 MHz. (2) a high biocompatibility profile and (3) a high molecular volume: the apparent hydrodynamic volume of P792 is 125 times greater than that of Gd-DOTA. As a result of this high molecular volume, P792 presents an unusual pharmacokinetic profile, as it is a Rapid Clearance Blood Pool Agent (RCBPA) characterized by limited diffusion across the normal endothelium. The original pharmacokinetic properties of this RCBPA are expected to be well suited to MR coronary angiography, angiography, perfusion imaging (stress and rest), and permeability imaging (detection of ischemia and tumor grading). Further experimental imaging studies are ongoing to define the clinical value of this compound.

Abstract: Objective—The direct calculation of cerebral perfusion pressure (CPP) as the difference between mean arterial pressure and intracranial pressure (ICP) produces a number which does not always adequately describe conditions for brain perfusion. A non-invasive method of CPP measurement has previously been reported based on waveform analysis of blood flow velocity measured in the middle cerebral artery (MCA) by transcranial Doppler. This study describes the results of clinical tests of the prototype bilateral transcranial Doppler based apparatus for non-invasive CPP measurement (nCPP). Methods—Twenty five consecutive, paralysed, sedated, and ventilated patients with head injury were studied. Intracranial pressure (ICP) and arterial blood pressure (ABP) were monitored continuously. The left and right MCAs were insonated daily (108 measurements) using a purpose built transcranial Doppler monitor (Neuro Q TM , Deltex Ltd, Chichester, UK) with software capable of the noninvasive estimation of CPP. Time averaged values of mean and diastolic flow velocities (FVm, FVd) and ABP were calculated. nCPP was then computed as: ABP×FVd/FVm+14. Results—The absolute diVerence between real CPP and nCPP (daily averages) was less than 10 mm Hg in 89% of measurements and less than 13 mm Hg in 92% of measurements. The 95% confidence range for predictors was no wider than ±12 mm Hg (n=25) for the CPP, varying from 70 to 95 mm Hg. The absolute value of side to side diVerences in nCPP was significantly greater (p<0.05) when CT based evidence of brain swelling was present and was also positively correlated (p<0.05) with mean ICP. Conclusion—The device is of potential benefit for intermittent or continuous monitoring of brain perfusion pressure in situations where the direct measurement is not available or its reliability is in question. (J Neurol Neurosurg Psychiatry 2001;70:198‐204)

Abstract: Neurological complications are common in sickle cell disease (SCD). However, it is often difficult to relate the clinical presentation to conventional neuroimaging, because subclinical infarction is common and stroke has been described in the absence of large-vessel disease. We studied 48 patients with SCD aged 4-34 (median 13) years with T2-weighted, diffusion and perfusion magnetic resonance imaging (MRI) and with MR angiography. Forty-four underwent transcranial Doppler (TCD). Abnormalities on perfusion imaging were seen in 25 cases, 24 of whom had been symptomatic. The remaining patient had evidence of executive dysfunction and reduced perfusion in the frontal lobes. The perfusion abnormality was larger than the area of infarction in 9 patients and was seen in an arterial distribution with no infarction in a further 9. In 3 patients with transient ischemic attacks, perfusion abnormalities were demonstrated in the absence of any other neuroimaging abnormalities, and perfusion changes were seen in 3 others despite normal MR angiography and TCD. Perfusion abnormalities are associated with neurological symptoms in patients with SCD, whether or not MRI, MR angiography, and TCD are abnormal. It is likely that this technique will guide management in individual patients.

Abstract: The ability to demonstrate regions of abnormal cerebral blood flow in the setting of acute stroke is of diagnostic and prognostic importance. It may also influence therapeutic strategies. The advantage of CT perfusion imaging is its ability to give quantifiable measurements of cerebral blood flow on any modern CT machine without the need to buy specialized equipment. The aim was to assess day-to-day variability of values of cerebral blood volume obtained with this technique. Seven patients with cerebral gliomas were studied using dynamic CT perfusion imaging on two occasions, approximately 24 h apart to reduce variability from diurnal variations. Regions of interest were produced in predominately middle cerebral artery locations in both hemispheres on the first and second CT perfusion studies. Absolute values for cerebral blood flow were produced for these regions and were correlated with flows obtained in the same regions of interest on the follow-up study. The Pearson correlation coefficient obtained was 0.884. CT perfusion imaging is easily performed on conventional modern CT equipment and demonstrates little variability in measures of absolute cerebral blood flow within individuals when studied on two occasions within 24 h.

Abstract: Recently, a technique based on arterial spin labeling, called dynamic arterial spin labeling (DASL (Magn Reson Med 1999;41:299‐ 308)), has been introduced to measure simultaneously the transit time of the labeled blood from the labeling plane to the exchange site, the longitudinal relaxation time of the tissue, and the perfusion of the tissue. This technique relies on the measurement of the tissue magnetization response to a time varying labeling function. The analysis of the characteristics of the tissue magnetization response (transit time, filling time constant, and perfusion) allows for quantification of the tissue perfusion and for transit time map computations. In the present work, the DASL scheme is used in conjuction with echo planar imaging at 4.7 T to produce brain maps of perfusion and transit time in the anesthetized rat, under graded hypercapnia. The data obtained show the variation of perfusion and transit time as a function of arterial pCO2. Based on the data, CO2 reactivity maps are computed. Magn Reson Med 45:1021‐1029, 2001. Published 2001 Wiley-Liss, Inc. †

Abstract: PURPOSE To investigate brain perfusion at single photon emission computed tomography (SPECT) as a function of age and sex in healthy adult volunteers and to correlate perfusion with gray matter concentration determined by using voxel-based morphometry (VBM). MATERIALS AND METHODS Eighty-one healthy volunteers underwent both technetium 99m ethylene cysteine dimer SPECT and three-dimensional magnetization preparation rapid acquisition gradient-echo magnetic resonance (MR) imaging. Statistical parametric mapping was used to conduct VBM analysis of the morphologic data, which were compared voxel by voxel with the results of a similar analysis of the perfusion data and more specifically in brain areas showing significant perfusion changes. RESULTS VBM data, as compared with perfusion changes, indicated a more symmetric age-related gray matter volume decrease along the Sylvian fissure and in subcortical regions (P < .001). The combination of functional and structural changes indicated a relatively lower functional decrease with aging, as compared with the structural atrophy in the visual, parietal, sensorimotor, and right prefrontal cortices. Significant relative morphologic sex-based differences were found in the cerebellar and temporal cortices, but the comparison did not reveal significant differences between the functional and morphometric data. CONCLUSION Age-related perfusion changes are paralleled by similar more symmetric changes in gray matter concentration, which are more prominent than the perfusion changes in some regions. No sex-based differences between perfusion and gray matter concentration were found.

Abstract: PURPOSE: To investigate brain perfusion at single photon emission computed tomography (SPECT) as a function of age and sex in healthy adult volunteers and to correlate perfusion with gray matter concentration determined by using voxel-based morphometry (VBM). MATERIALS AND METHODS: Eighty-one healthy volunteers underwent both technetium 99m ethylene cysteine dimer SPECT and three-dimensional magnetization preparation rapid acquisition gradient-echo magnetic resonance (MR) imaging. Statistical parametric mapping was used to conduct VBM analysis of the morphologic data, which were compared voxel by voxel with the results of a similar analysis of the perfusion data and more specifically in brain areas showing significant perfusion changes. RESULTS: VBM data, as compared with perfusion changes, indicated a more symmetric age-related gray matter volume decrease along the Sylvian fissure and in subcortical regions (P < .001). The combination of functional and structural changes indicated a relatively lower func...

Abstract: Important advances in rapid magnetic resonance (MR) imaging technology and its application to cardiovascular imaging have been made during the past decade. High-field-strength clinical magnets, high-performance gradient hardware, and ultrafast pulse sequence technology are rapidly making the vision of a comprehensive “one-stop shop” cardiac MR imaging examination a reality. This examination is poised to have a significant effect on the management of coronary artery disease by means of assessment of wall motion with tagging and pharmacologic stress testing, evaluation of the coronary microvasculature with perfusion imaging, and direct visualization of the coronary arteries with MR coronary angiography. This article reviews current state-of-the-art pulse sequence technology and its application to the evaluation of ischemic heart disease by means of MR tagging with dobutamine stress testing, MR perfusion imaging, and MR coronary angiography. Cutting edge areas of research in coil design and exciting new area...

Abstract: Summary: Purpose: To elucidate uncoupling of perfusion and metabolism and its significance in epilepsy, 15O water and 18F fluorodeoxyglucose (FDG) positron emission tomography (PET) and Tc-99m hexamethyl-propyleneamine-oxime (HMPAO) single-photon emission computed tomography (SPECT) were examined by SPM (statistical parametric mapping) and quantitation by using SPAM (statistical probabilistic anatomic map). Methods: [15O]water and [18F]FDG-PET, and [99mTc]-HMPAO SPECT were performed in 25 patients (SPECT in 17 of 25) with medial temporal lobe epilepsy. For volume of interest (VOI) count analysis, the normalized counts using VOI based on SPAM templates of PET and SPECT were compared with those of the normal controls. Perfusion or metabolism was found abnormal if the Z score was >2 for each VOI. For SPM analysis, the differences between each patient's image and a group of normal control images (t statistic for p < 0.01) on a voxel-by-voxel basis were examined to find significant decreases in perfusion or metabolism. Results: With SPAM VOI count analysis, areas of hypoperfusion were found in 13 patients in the epileptogenic temporal lobes by [15O]water PET and areas of hypometabolism in 21 patients by [18F]FDG-PET. With voxel-based SPM analysis, the epileptogenic zones were localized in 15 by [15O]water PET and in 23 patients by [18F]FDG-PET. The localization by [15O]water PET was concordant with that of [18F]FDG-PET. The areas of hypoperfusion on [15O]water PET were absent or smaller than the areas of hypometabolism on [18F]FDG-PET. Interictal [99mTc]-HMPAO SPECT revealed the hypoperfused zones in seven of 17 patients on visual assessment. Conclusions: SPAM VOI count and SPM analysis of [15O]water and [18F]FDG-PET and [99mTc]-HMPAO SPECT revealed that in the same patients, the areas of hypoperfusion were concordant with but smaller than the areas of hypometabolism. Discordance of perfusion and metabolic abnormalities represents an uncoupling of perfusion and metabolism in the epileptogenic zones, and this might explain the lower diagnostic accuracy of perfusion imaging in temporal lobe epilepsy.

Abstract: BACKGROUND AND PURPOSE: The development of thrombolytic agents for use with compromised cerebral blood flow has made it critical to quickly identify those patients to best treat. We hypothesized that combined diffusion and perfusion MR imaging adds vital diagnostic value for patients for whom the greatest potential benefits exist and far exceeds the diagnostic value of diffusion MR imaging alone. METHODS: The cases of patients with neurologic symptoms of acute ischemic stroke who underwent ultra-fast emergent MR imaging within 6 hours were reviewed. In all cases, automatic processing yielded isotropic diffusion images and perfusion time-to-peak maps. Images with large vessel distribution ischemia and with mismatched perfusion abnormalities were correlated with patient records. All follow-up images were reviewed and compared with outcomes resulting from hyperacute therapies. RESULTS: For 16 (26%) of 62 patients, hypoperfusion was the best MR imaging evidence of disease distribution, and for 15 of the 16, hypoperfusion (not abnormal diffusion) comprised the only imaging evidence for disease involving large vessels. For seven patients, diffusion imaging findings were entirely normal, and for nine, diffusion imaging delineated abnormal signal in either small vessel distributions or in a notably smaller cortical branch in one case. In all cases, perfusion maps were predictive of eventual lesions, as confirmed by angiography, CT, or subsequent MR imaging. CONCLUSION: If only diffusion MR imaging is used in assessing patients with hyperacute stroke, nearly one quarter of the cases may be incorrectly categorized with respect to the distribution of ischemic at-risk tissue. Addition of perfusion information further enables better categorizing of vascular distribution to allow the best selection among therapeutic options and to improve patient outcomes.

Abstract: A method is presented for measurement of perfusion changes during brain activation using a single-shot pulsed spin labeling technique By employing a double-inversion labeling strategy, stationary tissue (background) signal was suppressed while minimally affecting perfusion sensitivity This allowed omission of the otherwise required reference scan, resulting in twofoldimproved temporal resolution The method was applied to visual and motor cortex activation studies in humans, and compared to standard FAIR-type perfusion labeling techniques Experiments performed at 15T and 30T indicate a close to 90% suppression of background signal, at a cost of an 11% and 9%, respectively, reduction in perfusion signal Combined with the twofold increase in signal averaging, and a reduction in background signal fluctuations, this resulted in a 64% (15T, N 5 3) and a 128% (3T, N 5 4) overall improvement in sensitivity for the detection of activation-related perfusion changes Magn Reson Med 46:88 ‐94, 2001 Published 2001 Wiley-Liss, Inc †

Abstract: OBJECTIVE. We attempt to determine whether angiography is indicated in patients with suspected central nervous system (CNS) vasculitis who present with negative findings on MR imaging studies.CONCLUSION. MR imaging findings may be negative in the setting of CNS vasculitis confirmed on angiography, indicating that advanced imaging techniques tailored to detect infarction (i.e., fluid-attenuated inversion recovery, diffusion-weighted, and perfusion imaging) may be necessary to enhance the sensitivity of an MR study and that despite the high sensitivity of MR imaging for CNS vasculitis, angiography may still be required to render an accurate diagnosis.

Abstract: Magnetic resonance ventilation-perfusion (V/Q) imaging has been demonstrated using oxygen and arterial spin labeling techniques. Inhaled oxygen is used as a paramagnetic contrast agent in ventilation imaging using a multiple inversion recovery (MIR) approach. Pulmonary perfusion imaging is conducted using a flow-sensitive alternating inversion recovery with an extra radiofrequency pulse (FAIRER) technique. A half Fourier single-short turbo spin echo (HASTE) sequence is used for data acquisition in both techniques. V/Q imaging was performed in ten of the twenty volunteers, while either ventilation or perfusion was imaged in the other ten. This V/Q imaging scheme is completely noninvasive, does not involve ionized radiation, and shows promising potential for clinical use in the diagnosis of lung diseases such as pulmonary embolism.

Abstract: OBJECTIVES Many different stress echocardiographic and radionuclide perfusion imaging tests have been proposed for detecting epicardial coronary artery disease (CAD) in hypertensive patients Their relative diagnostic and prognostic value has not been exactly established BACKGROUND A positive exercise electrocardiography test has a low diagnostic specificity in hypertensive patients and warrants for a complementary imaging test to confirm the diagnosis of coronary artery disease METHODS Hypertensive patients (n = 53), (29 males, aged 58 +/- 10 years) with normal left ventricular function detected by echocardiography and previous positive exercise test ( > or = 015 mV of ST segment depression on 12 lead electrocardiogram) underwent dipyridamole-atropine stress echocardiography (DASE) and thallium-201 stress/ rest myocardial single-photon emission computed tomography (SPECT) All patients had coronary angiography within 15 days and independently of imaging test results RESULTS Coronary angiogram showed significant ( > or = 50% qualitatively assessed diameter reduction) epicardial coronary artery disease in 23 (43%) patients Sensitivity for detection of coronary artery disease was significantly higher for scintigraphy (DASE = 78% versus SPECT = 100%, P < 005) while specificity was higher for echo (DASE = 100% versus SPECT = 47%, P < 000001) Diagnostic accuracy was also higher for echo (DASE = 91% versus SPECT = 70%, P < 001) CONCLUSION In patients with exercise-nduced ST segment depression, dipyridamole stress echo and SPECT perfusion scintigraphy are both good diagnostic options, with DASE characterized by higher specificity, lower sensitivity, and at least comparable diagnostic accuracy than SPECT