Showing papers on "Perfusion scanning published in 1998"
TL;DR: Combined early PI and DWI can define different acute infarct patterns, which may allow the selection of rational therapeutic strategies based on the presence or absence of potentially salvageable ischemic tissue.
Abstract: Objectives: We examined the utility of echoplanar magnetic resonance perfusion imaging and diffusion-weighted imaging (DWI) in predicting stroke evolution and outcome in 18 patients with acute hemispheric infarction. Methods: Patients were studied within 24 hours (mean, 12.2 hours), subacutely(mean, 4.7 days), and at outcome (mean, 84 days). Comparisons were made between infarction volumes as measured on perfusion imaging (PI) and isotropic DWI maps, clinical assessment scales (Canadian Neurological Scale, Barthel Index, and Rankin Scale), and final infarct volume (T2-weighted MRI). Results: Acute PI lesion volumes correlated with acute neurologic state, clinical outcome, and final infarct volume. Acute DWI lesions correlated less robustly with acute neurologic state, but correlated well with clinical outcome and final infarct volume. Three of six possible patterns of abnormalities were seen: PI lesion larger than DWI lesion (65%), PI lesion smaller than DWI lesion (12%), and DWI lesion but no PI lesion (23%). A pattern of a PI lesion larger than the DWI lesion predicted DWI expansion into surrounding hypoperfused tissue ( p Conclusions: Combined early PI and DWI can define different acute infarct patterns, which may allow the selection of rational therapeutic strategies based on the presence or absence of potentially salvageable ischemic tissue.
562 citations
TL;DR: In the investigation of ischemic stroke, conventional structural magnetic resonance techniques are valuable for the assessment of infarct extent and location beyond the first 12 to 24 hours after onset, but during the critical first 6 to 12 hours, the probable period of greatest therapeutic opportunity, these methods do not adequately assess the extent and severity of ischemia.
Abstract: In the investigation of ischemic stroke, conventional structural magnetic resonance (MR) techniques (eg, T1-weighted imaging, T2-weighted imaging, and proton density-weighted imaging) are valuable for the assessment of infarct extent and location beyond the first 12 to 24 hours after onset, and can be combined with MR angiography to noninvasively assess the intracranial and extracranial vasculature However, during the critical first 6 to 12 hours, the probable period of greatest therapeutic opportunity, these methods do not adequately assess the extent and severity of ischemia Recent developments in functional MR imaging are showing great promise for the detection of developing focal cerebral ischemic lesions within the first hours These include (1) diffusion-weighted imaging, which provides physiologic information about the self-diffusion of water, thereby detecting one of the first elements in the pathophysiologic cascade leading to ischemic injury; and (2) perfusion imaging The detection of acute intraparenchymal hemorrhagic stroke by susceptibility weighted MR has also been reported In combination with MR angiography, these methods may allow the detection of the site, extent, mechanism, and tissue viability of acute stroke lesions in one imaging study Imaging of cerebral metabolites with MR spectroscopy along with diffusion-weighted imaging and perfusion imaging may also provide new insights into ischemic stroke pathophysiology In light of these advances in structural and functional MR, their potential uses in the study of the cerebral ischemic pathophysiology and in clinical practice are described, along with their advantages and limitations
558 citations
TL;DR: Perfusion CT not only allows early detection of cerebral ischemia but also yields valuable information about the extent of perfusion disturbances in ischemic territories.
Abstract: PURPOSE: To determine the value of perfusion computed tomography (CT) in a clinical study of patients with stroke and compare the results with single photon emission CT (SPECT) findings. MATERIALS AND METHODS: Perfusion CT was performed within 6 hours of symptom onset in 32 patients with possible stroke. Cerebral blood volume (CBV), cerebral blood flow (CBF), and time to peak contrast material enhancement were calculated on the basis of the CT results. Cerebral SPECT was also performed in a subgroup of 18 patients. Perfusion CT and SPECT findings were compared in a lesion-by-lesion analysis. Perfusion CT results were compared with follow-up CT and magnetic resonance imaging findings. RESULTS: Areas of reduced CBF were detected with the aid of perfusion CT in 25 of 28 patients with a proved infarct (sensitivity, 89%). The results of the CBF maps corresponded well to SPECT findings in 13 (81%) of 16 patients, but ischemia was located outside the scanning level in the other three patients and was therefore m...
322 citations
TL;DR: A review of the literature showing the advantages of SPECT brain perfusion imaging in mild or moderate traumatic brain injury (TBI) over other morphologic imaging modalities such as x-ray CT or MRI showed that Tc-99m HMPAO is more stable in the brain with no washout over time.
Abstract: The purpose of this atlas is to present a review of the literature showing the advantages of SPECT brain perfusion imaging (BPI) in mild or moderate traumatic brain injury (TBI) over other morphologic imaging modalities such as x-ray CT or MRI. The authors also present the technical recommendations for SPECT brain perfusion currently practiced at their center. For the radiopharmaceutical of choice, a comparison between early and delayed images using Tc-99m HMPAO and Tc-99m ECD showed that Tc-99m HMPAO is more stable in the brain with no washout over time. Therefore, the authors feel that Tc-99m HMPAO is preferable to Tc-99m ECD. Recommendations regarding standardizing intravenous injection, the acquisition, processing parameters, and interpretation of scans using a ten grade color scale, and use of the cerebellum as the reference organ are presented. SPECT images of 228 patients (age range, 11 to 88; mean, 40.8 years) with mild or moderate TBI and no significant medical history that interfered with the results of the SPECT BP were reviewed. The etiology of the trauma was in the following order of frequency: motor vehicle accidents (45%) followed by blow to the head (36%) and a fall (19%). Frequency of the symptoms was headache (60.9%), memory problems (27.6%), dizziness (26.7%), and sleep disorders (8.7%). Comparison between patients imaged early ( 3 months) from the time of the accident, showed that early imaging detected more lesions (4.2 abnormal lesions per study compared to 2.7 in those imaged more than 3 months after the accident). Of 41 patients who had mild traumatic injury without loss of consciousness and had normal CT, 28 studies were abnormal. Focal areas of hypoperfusion were seen in 77% (176 patients, 612 lesions) of the group of 228 patients. The sites of abnormalities were in the following order: basal ganglia and thalami, 55.2%, frontal lobes, 23.8%, temporal lobes, 13%, parietal, 3.7%, insular and occipital lobes together, 4.6%.
176 citations
TL;DR: The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals.
Abstract: A method is presented for multislice measurements of quantitative cerebral perfusion based on magnetic labeling of arterial spins. The method combines a pulsed arterial inversion, known as the FAIR (Flow-sensitive Alternating Inversion Recovery) experiment, with a fast spiral scan image acquisition. The short duration (22 ms) of the spiral data collection allows simultaneous measurement of up to 10 slices per labeling period, thus dramatically increasing efficiency compared to current single slice acquisition protocols. Investigation of labeling efficiency, suppression of unwanted signals from stationary as well as intraarterial spins, and the FAIR signal change as a function of inversion delay are presented. The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals. CBF values measured on normal volunteers are consistent with results obtained from H2O15 positron emission tomography (PET) studies and other radioactive tracer approaches. In addition, the new method allows detection of activation-related perfusion changes in a finger-tapping experiment, with locations of activation corresponding well to those observed with blood oxygen level dependent (BOLD) fMRI.
157 citations
TL;DR: In this article, the effects of A-127722, a novel ETA-selective ET antagonist, on cerebral ischemic lesion size using 2,3,5-triphenyltetrazolium chloride (TTC) staining postmortem, on acute cerebral lesion development with DWI, and on the cerebral circulation using PI Methods.
Abstract: Background and Purpose—Endothelins (ETs) are potent vasoconstrictors Plasma ET levels increase during acute brain ischemia and may worsen the ischemic damage Diffusion-weighted MRI (DWI) and perfusion imaging (PI) are powerful tools for evaluation of acute cerebral ischemia We studied the effects of A-127722, a novel ETA-selective ET antagonist, on cerebral ischemic lesion size using 2,3,5-triphenyltetrazolium chloride (TTC) staining postmortem, on acute ischemic lesion development with DWI, and on the cerebral circulation using PI Methods—Twenty male Sprague-Dawley rats received either 5 mg/kg of A-127722 or vehicle (n=10 per group) intravenously 30 minutes and subcutaneously 4 hours after middle cerebral artery occlusion (MCAO) Whole-brain DWI and single-slice PI were done before initiation of treatment and repeated frequently thereafter up to 4 hours after MCAO The animals were reperfused in the MRI scanner 90 minutes after the onset of MCAO At 24 hours the animals were killed, and the brains we
150 citations
TL;DR: Electrical impedance tomography can be regarded as a promising technique to estimate the left-right division of pulmonary perfusion and ventilation in patients with lung cancer.
Abstract: Electrical impedance tomography (EIT) is a technique that makes it possible to measure ventilation and pulmonary perfusion in a volume that approximates to a 2D plane. The possibility of using EIT for measuring the left-right division of ventilation and perfusion was compared with that of radionuclide imaging. Following routine ventilation (81mKr) and perfusion scanning (99mTc-MAA), EIT measurements were performed at the third and the sixth intercostal level in 14 patients with lung cancer. A correlation (r = 0.98, p < 0.005) between the left-right division for the ventilation measured with EIT and that with 81mKr was found. For the left-right division of pulmonary perfusion a correlation of 0.95 (p < 0.005) was found between the two methods. The reliability coefficient (RC) was calculated for estimating the left-right division with EIT. The RC for the ventilation measurements was 94% and 96% for the perfusion measurements. The correlation analysis for reproducibility of the EIT measurements was 0.95 (p < 0.001) for the ventilation and 0.93 (p < 0.001) for the perfusion measurements. In conclusion, EIT can be regarded as a promising technique to estimate the left-right division of pulmonary perfusion and ventilation.
134 citations
TL;DR: The feasibility and reproducibility of the technique to map quantitatively myocardial perfusion in vivo in rats, based on the modification of the longitudinal relaxation time T1 induced by magnetic spin labeling of endogenous water protons, is evaluated.
Abstract: Measurement of myocardial perfusion is important for the functional assessment of heart in vivo. Our approach is based on the modification of the longitudinal relaxation time T1 induced by magnetic spin labeling of endogenous water protons. Labeling is performed by selectively inverting the magnetization within the detection slice, and longitudinal relaxation is measured using a fast gradient echo MRI technique. As a result of blood flow, nonexcited spins enter the detection slice, which leads to an acceleration of the relaxation rate. Incorporating this phenomenon in a mathematical model that describes tissue as two compartments yields a simple expression that allows the quantification of perfusion from a slice-selective and a global inversion recovery experiment. This model takes into account the difference between T1 in blood and T1 in tissue. Our purpose was to evaluate the feasibility and reproducibility of this technique to map quantitatively myocardial perfusion in vivo in rats. Quantitative maps of myocardial blood flow were obtained from nine rats, and the reproducibility of the technique was evaluated by repeating the whole perfusion experiment four times. Evaluation of regions of interest within the myocardium yielded a mean perfusion value of 3.6 ± .5 ml min−1 g-1 over all animals, which is in good agreement with previously reported literature values.
116 citations
TL;DR: In patients withMyocardial ischemia, LV mapping, compared with myocardial perfusion imaging, shows mild reduction of endocardial voltage potentials and LS in segments with reversible perfusion defects and profound electromechanical impairment in segment with fixed perfusion defect.
Abstract: Background —A novel 3-dimensional left ventricular (LV) mapping system uses low-intensity magnetic field energy to determine the location of sensor-tipped electrode catheters within the LV. Using this system, we sought to distinguish between infarcted, ischemic, and normal myocardium by comparing LV electromechanical mapping data with myocardial perfusion imaging studies.
Methods and Results —Unipolar voltage potentials and local endocardial shortening (LS) were measured in 18 patients (mean age, 58±12 years) with symptomatic chronic angina having reversible and/or fixed myocardial perfusion defects on single photon emission computed tomography imaging studies using 201Tl at rest and 99mTc-sestamibi after adenosine stress. Overall, a significant difference in voltage potentials and LS values was found between groups ( P <0.001 for each comparison by ANOVA). The average voltage potentials (14.0±2.0 mV) and LS values (12.5±2.8%) were highest when measured in myocardial segments (n=56) with normal perfusion and lowest (7.5±3.4 mV and 3.4±3.4%) when measured in myocardial segments with fixed perfusion defects (n=20) ( P <0.0001). Myocardial segments with reversible perfusion defects (n=66) had intermediate voltage amplitudes (12.0±2.8 mV, P =0.048 versus normal and P =0.005 versus fixed segments) and LS values (10.3±3.7%, P =0.067 versus normal and P =0.001 versus fixed segments).
Conclusions —In patients with myocardial ischemia, LV mapping, compared with myocardial perfusion imaging, shows (1) mild reduction of endocardial voltage potentials and LS in segments with reversible perfusion defects and (2) profound electromechanical impairment in segments with fixed perfusion defects. Thus, such an LV mapping procedure may allow the detection on-line of myocardial viability in the catheterization laboratory.
109 citations
TL;DR: In this article, the authors used the quantitative functional information and high spatial resolution of perfusion computed tomography to study neovascularization of hepatic metastases, and measured arterial and portal perfusion in a small rim of liver tissue immediately adjacent to the metastasis.
Abstract: Neovascularization of tumours produces a high microvessel density. Although diagnostic imaging is unable to visualize microvessels directly, it is possible to demonstrate associated changes in tissue perfusion. The aim of this study was to use the quantitative functional information and high spatial resolution of perfusion computed tomography to study neovascularization of hepatic metastases. Perfusion CT was performed in 13 patients with hepatic metastases from various primary tumours. Arterial perfusion was measured in the metastasis; both arterial and portal perfusion were measured in a small rim of liver tissue immediately adjacent to the metastasis. Perfusion measurements were correlated against survival of the patient in nine cases. Arterial perfusion was increased above normal values, both in the metastasis (median: 0.62 ml min-1 ml-1; range: 0.26-3.05 ml min-1 ml-1) and in the adjacent liver (median: 0.51 ml min-1 ml-1; range: 0.14-1.60 ml min-1 ml-1). Portal perfusion of adjacent liver was highly...
96 citations
TL;DR: The results show that in ischemic areas PtiO2 is dependent on CPP suggesting both a derangement of pressure autoregulation and high regional cerebrovascular resistences (CVRs).
Abstract: Arterial hypertension is widely applied to improve regional cerebral blood flow (rCBF) We measured local brain tissue O2 pressure (PtiO2) in low density lesions at computerized tomography (CT) of the head before and after manipulation of mean arterial pressure (MAP) in order to increase cerebral perfusion pressure (CPP) Nine patients, 7 subarachnoid hemorrhage (SAH), 1 severe head injury, 1 meningeoma, were included in our study A flexible Polarographic microcatheter for PtiO2 measurement was placed at the border of the low density area found at CT PtiO2 was continuously measured for 615 hours Hypoperfusion in low density areas was detected by perfusional single photon emission computed tomography (SPECT) We recorded 22 episodes of induced or spontaneous increase of MAP Initial PtiO2 regularly improved after the CPP increase (r2 074 in induced episodes) Low PtiO2 showed a greater percent increase for unitary changes of CPP than normal-high PtiO2 Baseline PtiO2 below 20 mm Hg was associated with normal CPPs; 5 readings of PtiO2 below 20 mm Hg normalized when a higher CPP was obtained Our results show that in ischemic areas PtiO2 is dependent on CPP suggesting both a derangement of pressure autoregulation and high regional cerebrovascular resistences (CVRs) Low PtiO2 was associated with normal CPP, thus indicating that CPP could be an inadequate estimate of rCBF in focal ischemic areas Arterial hypertension, capable of increasing CPP above normal values, appeared useful in normalizing tissue oxygenation in ischemic areas
TL;DR: It is concluded that T2 reduction in acute ischemia can unambiguously identify regions at risk and potentially discriminate between reversible and irreversible hypoperfusion and is chemia.
Abstract: The hypothesis was tested that hypoperfused brain regions, such as the ischemic penumbra, are detectable by reductions in absolute transverse relaxation time constant (T2) using magnetic resonance imaging (MRI). To accomplish this, temporal evolution of T2 was measured in several models of hypoperfusion and focal cerebral ischemia in the rat at 9.4 T. Occurrence of acute ischemia was determined through the absolute diffusion constant Dav = 1/3Trace [double overline] D, while perfusion was assessed by dynamic contrast imaging. Three types of regions at risk of infarction could be distinguished: (1) areas with reduced T2 (4% to 15%, all figures relative to contralateral hemisphere) and normal Dav, corresponding to hypoperfusion without ischemia; (2) areas with both reduced T2 (4% to 12%) and Dav (22% to 49%), corresponding to early hypoperfusion with ischemia; (3) areas with increased T2 (2% to 9%) and reduced Dav (28% to 45%), corresponding to irreversible ischemia. In the first two groups, perfusion-defic...
TL;DR: The present study demonstrates for the first time that TRsHI produces accurate contrast in different brain areas and represents an ultrasonic tool related to brain perfusion.
Abstract: Background and Purpose—Gray-scale harmonic imaging is the first method to visualize blood perfusion and capillary blood flow with ultrasound after intravenous contrast agent application. The purpose of the present study was to evaluate the potential of transient response second harmonic imaging (TRsHI) to assess normal echo contrast characteristics in different brain areas by transcranial ultrasound. Methods—In 18 patients without cerebrovascular diseases, TRsHI examinations were performed bilaterally with the use of the transtemporal approach after application of 6.5 mL of a galactose-based microbubble suspension (400 mg/mL). The transmission rate was once every 4 cardiac cycles. Regional cerebral contrast was visually assessed and then quantified off-line with the use of time-intensity curves. In 4 different regions of interest (ROI) (posterior part of the thalamus [ROIa], anterior part of the thalamus [ROIb], lentiform nucleus [ROIc], and white matter [ROId]), the following parameters were evaluated: p...
TL;DR: It is demonstrated that adenosine myocardial perfusion SPECT added significant incremental prognostic information to clinical and physiologic variables in women after adjusting for prior myocardia infarction and diabetes mellitus.
Abstract: Adenosine myocardial perfusion single-photon emission computed tomography (SPECT) is now increasingly used for risk stratification of patients with known or suspected coronary artery disease. However, the incremental prognostic value of this test over clinical and historical information in a large series of women has not been examined. Thus, we studied 923 consecutive women who underwent adenosine technetium (Tc)-99m sestamibi myocardial perfusion SPECT and were followed-up for a mean period of 26 ± 8 months. During the follow-up period, 77 hard events (46 cardiac deaths and 31 nonfatal myocardial infarctions) occurred. The results of the perfusion scan significantly risk stratified the population; patients with normal scans had a low rate of nonfatal myocardial infarction and cardiac death (
TL;DR: It is concluded that the quantitative measurement of renal cortical perfusion by MRI with arterial spin-labeling could provide a non-invasive diagnostic method for monitoring the status of renal transplants without requiring the administration of a contrast agent.
TL;DR: It is suggested that alterations in regional brain perfusion may accompany conversion symptoms and functional imaging may offer a means of elucidating the neural correlates of conversion disorder.
Abstract: We evaluated regional cerebral blood flow in five patients with conversion disorder (three females, two males, mean age±S.D.: 29.8±9.5 years) with astasia-abasia. The patients underwent single photon emission computed tomography after the injection of 555 MBq of [ 99m Tc]hexamethylpropyleneamine oxime. Uptake ratios between areas of decreased perfusion and normal brain regions were considered significantly decreased when there was a change ≥10%. Four of the five patients had left temporal and one patient had left parietal perfusion decreases. Uptake ratios ranged from 0.72 to 0.88 (mean±S.D.: 0.81±0.08). Our findings suggest that alterations in regional brain perfusion may accompany conversion symptoms. Functional imaging may therefore offer a means of elucidating the neural correlates of conversion disorder.
TL;DR: The present results suggest brain perfusion abnormalities during heroin withdrawal in heroin-dependent patients, which are not due to the conditions of withdrawal.
Abstract: The aims of the present study were to investigate regional cerebral blood flow (rCBF) in heroin-dependent patients during withdrawal and to assess the relation between these changes and duration of heroin consumption and withdrawal data. The rCBF was measured using brain SPECT with 99mTc-HMPAO in 16 heroin-dependent patients during heroin withdrawal. Thirteen patients received levomethadone at the time of the SPECT scans. The images were analyzed both visually and quantitatively. A total of 21 hypoperfused brain regions were observed in 11 of the 16 patients. The temporal lobes were the most affected area, hypoperfusions of the right and left temporal lobe were observed in 5 and 5 patients, respectively. Three of the patients had a hypoperfusion of the right frontal lobe, 2 patients showed perfusion defects in the left frontal lobe, right parietal lobe and left parietal lobe. The results of the quantitative assessments of the rCBF were consistent with the results of the qualitative findings. The stepwise regression analysis showed a significant positive correlation (r = 0.54) between the dose of levomethadone at the time of the SPECT scan and the rCBF of the right parietal lobe. Other significant correlations between clinical data and rCBF were not found. The present results suggest brain perfusion abnormalities during heroin withdrawal in heroin-dependent patients, which are not due to the conditions of withdrawal.
11 Oct 1998
TL;DR: This technique was successful in eliminating or attenuating the false increases in perfusion shown in probable Alzheimer’s patients in over 90% of cases, and in enhancing the sensitivity of detection of degenerative changes by Statistical Parametric Mapping.
Abstract: Functional imaging of the brain can aid in the diagnosis of Alzheimer’s disease. Tc-HMPAO SPECT is widely available and relatively inexpensive to use. Combined with computer-based analysis of images, SPECT is a powerful tool in detecting decreases in brain perfusion caused by Alzheimer’s disease. However, analysis can falsely elevate the perfusion of normal areas and diminish the perfusion of atrophic areas in the Alzheimer’s brain when used with conventional scaling methods. In this paper, we present a technique for scaling images that overcomes the problems associated with conventional scaling methods. Our technique was successful in eliminating or attenuating the false increases in perfusion shown in probable Alzheimer’s patients in over 90% of cases (n=17), and in enhancing the sensitivity of detection of degenerative changes by Statistical Parametric Mapping.
TL;DR: It is concluded that changes in frontal and in cerebellar function are relevant to the pathophysiology of EPD and suggest that EPD represents a paroxysmal movment disorder rather than epilepsy.
Abstract: The clinical features of exercise-induced paroxysmal dystonia (EPD) are delineated in a pedigree including two affected members (both male) showing an autosomal-dominant inheritance trait. Gait analysis using kinematic electromyography during the motor attacks revealed coactivation of antagonistic calf muscles characteristic of dystonia. In the interval, impaired muscular alternation was observed. To characterize further the pathophysiological basis of the condition, ictal and interictal cerebral perfusion SPECT studies using technetium 99m-ethyl cysteinate dimer (ECD) were performed to establish whether cortical hyperactivity indicative of epilepsy is present during the motor attacks and to identify regional changes in the ictal perfusion pattern that could indicate an anatomic structure relevant to the disease. During the motor attacks, decreased ictal perfusion of the frontal cortex was found in both patients. In contrast, increased cerebellar perfusion was observed. The perfusion of the basal ganglia also decreased. No cortical hyperperfusion indicative of an epileptic nature was seen. Cerebellar hyperactivity in connection with prominent frontal hypoactivity has also been described in both the idiopathic and the symptomatic forms of dystonia. Our findings therefore suggest that EPD represents a paroxysmal movement disorder rather than epilepsy. It is concluded that changes in frontal and in cerebellar function are relevant to the pathophysiology of EPD.
TL;DR: It is concluded that brain perfusion SPECT examination is useful in identifying post-infectious cerebellitis and in monitoring its clinical course, and IVIg may be helpful in treating this condition.
Abstract: A 19 year-old man presented with pharyngitis and cervical lymphadenopathy, followed by vomiting and acute cerebellar ataxia. Serologic studies were consistent with a recent Epstein-Barr virus infection. Although contrast-enhanced brain computed tomography and MRI scans were normal, brain perfusion single photon emission tomography (SPECT) examination using 99mTc-HMPAO, performed on the 15th day of illness, showed marked cerebellar hyperperfusion, suggesting a diagnosis of acute post-infectious cerebellitis. After treatment with intravenous human immunoglobulin (IVIg, 2 g kg-1 over three days), progressive neurologic improvement occurred over two weeks. A brain SPECT study repeated after two additional weeks demonstrated a normal perfusion pattern. We conclude that brain perfusion SPECT examination is useful in identifying post-infectious cerebellitis and in monitoring its clinical course. In addition, IVIg may be helpful in treating this condition.
TL;DR: Dynamic susceptibility contrast-enhanced MR imaging can enable measurement of relative hemodynamic changes in patients with ICA occlusions, with the advantage that gray and white matter perfusion can be distinguished.
Abstract: PURPOSE: To determine, with dynamic susceptibility contrast-enhanced magnetic resonance (MR) imaging, changes in gray matter and white matter perfusion in patients with internal carotid artery (ICA) occlusions. MATERIALS AND METHODS: Regional cerebral blood volume (CBV), mean transit time, arrival time (time for contrast material to arrive in the brain), and peak time (time to highest contrast material concentration in the brain) were determined in 44 patients and 33 control subjects. Patients were divided into three groups: patients with a unilateral ICA occlusion, patients with a unilateral ICA occlusion and a contralateral severe stenosis (> 70%), and patients with bilateral ICA occlusions. RESULTS: Compared with control subjects, patients with unilateral ICA occlusions had hemodynamic changes in the ipsilateral hemisphere: Mean transit time, arrival time, and peak time were increased in white and gray matter (P < .001), and regional CBV was significantly increased in white matter only (P < .01). Hemod...
TL;DR: The use of a FOCI inversion pulse is shown to significantly minimize static signal subtraction errors that are common with conventional HS pulses, and the suitability of the pulse for perfusion studies is demonstrated, in vivo, on rat brain.
Abstract: Pulsed arterial spin-tagging techniques for perfusion measurements (e.g., echo planar MR imaging and signal targeting with alternating radiofrequency (EPISTAR), flow-sensitive alternating inversion recovery (FAIR), quantitative imaging of perfusion using a single subtraction (QUIPPS), uninverted FAIR (UNFAIR)) generally use hyperbolic secant (HS) pulses for spin inversion. The performance of these techniques depends on the inversion efficiency, as well as the sharpness of the slice profiles. Frequency offset corrected inversion (FOCI) pulses, a recently proposed HS variant, can provide slice profiles with edges that can be up to 10 times sharper than those obtained with conventional HS pulses. In this communication, the implementation and application of the C-shape FOCI pulse for perfusion imaging in rat brain with the FAIR technique is summarized. Despite providing a more rectangular slice profile than a conventional HS pulse, it is demonstrated both theoretically and experimentally that the FAIR perfusion signal is not increased by using a FOCI tagging pulse. However, the use of a FOCI inversion pulse is shown to significantly minimize static signal subtraction errors that are common with conventional HS pulses. Finally, the suitability of the pulse for perfusion studies is demonstrated, in vivo, on rat brain.
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TL;DR: Echo-planar imaging provides functional and anatomical information beyond pixel brightness of classical magnetic resonance imaging, which is essential for early stroke and tumor detection, as well as neuronal fiber tracking in the brain and spinal cord.
Abstract: Single shot echo-planar imaging is the fastest magnetic resonance imaging method existing on every human MRI scanner. This is one of the reasons why it is so heavily used in functional magnetic resonance imaging as it allows acquiring images of an entire brain in a matter of a few seconds. Another reason is that echo-planar imaging easily allows susceptibility weighting, the key to measure the blood oxygenation level-dependent signal, the essence for performing functional magnetic resonance imaging. MR perfusion imaging, in brain tumors for example, is another method benefitting enormously from echo-planar imaging. Quantitative blood flow measurement can be exploited also with echo-planar imaging. Due to its fast acquisition scheme EPI is also the key to measure diffusion of spins, which is essential for early stroke and tumor detection, as well as neuronal fiber tracking in the brain and spinal cord. In the last 5–10 years methods to further accelerate Echo-planar imaging acquisition time have been developed allowing scanning the entire brain in a time shorter than a second. This is especially helpful for resting state functional magnetic resonance imaging and high resolution fiber tracking using diffusion imaging. Echo-planar imaging therefore provides functional and anatomical information beyond pixel brightness of classical magnetic resonance imaging.
Journal Article•
TL;DR: Perfusion abnormalities in SLE may represent reversible lesions or subclinical CNS involvement in juvenile systemic lupus erythematosus, and SPECT imaging appears to be useful in detecting and monitoring CNS involvementIn SLE.
Abstract: Objective. Using single photon emission computed tomography (SPECT) we evaluated the presence and evolution of changes in brain perfusion in juvenile systemic lupus erythematosus (JSLE). Methods. SPECT was performed in 14 patients with active JSLE divided in 2 groups: the first included 7 patients without central nervous system (CNS) involvement and the second 7 patients with minor neuropsychiatric symptoms (headache, reactive depression, cognitive impairment, mood swing). SPECT findings were compared to seroimmunological and magnetic resonance imaging (MRI) data. After 6 month followup, a second SPECT scan was performed in 12 of 14 patients. Results. At baseline, SPECT showed perfusion defects in 2 patients without neuropsychiatric symptoms and in 5 patients with CNS involvement. In one of the 7 patients with altered SPECT, MRI showed focal hyperintensities. MRI alterations were observed in another patient who had a normal SPECT scan. Cortical atrophy was present in 5 of 14 patients. Correlation between neuropsychiatric manifestations and SPECT findings was not clearly evident because the major part of JSLE patients with CNS involvement and with SPECT alterations had multiple symptoms, but showed focal hypoperfusion on SPECT imaging. No significant association was found between seroimmunological data and SPECT findings. At followup, improvement of perfusion alterations was observed in 6 of 7 patients with altered SPECT and, in 3 of them, findings might be attributed to changes in steroid treatment. Conclusion. Perfusion abnormalities in SLE may represent reversible lesions or subclinical CNS involvement. Moreover, SPECT imaging appears to be useful in detecting and monitoring CNS involvement in SLE.
Journal Article•
TL;DR: This case demonstrates the possibility of discordance between brain perfusion and glucose uptake in acute mild traumatic brain injury.
Abstract: A 28-yr-old woman who sustained a mild traumatic brain injury had an 18 F-fluorodeoxyglucose (FDG) PET brain study using coincidence imaging performed on a dual-head gamma camera (MCD version; ADAC, Milpitas, CA) followed 24 hr later by 99m Tc-hexamethyl propyleneamine oxime SPECT brain perfusion imaging using a triple-head gamma camera (TRIONIX, Twinsburg, OH). The results of the SPECT brain perfusion study demonstrated decreased frontoparietal cortical brain perfusion, whereas 18 F-FDG cerebral uptake was normal. Neuropsychological evaluation suggested frontal lobe involvement. This case demonstrates the possibility of discordance between brain perfusion and glucose uptake in acute mild traumatic brain injury.
TL;DR: The findings implicate dysfunction of the frontal and temporal cortex in clinically depressed patients before specific drug treatment and reflect the treatment effect on mood-related rCBF changes.
Abstract: Depression is one of the most common psychiatric illnesses. Its influence on brain perfusion has been demonstrated, but conflicting data exist on follow-up after drug treatment. The aim of our study was to evaluate the effects of antidepressant drugs on regional cerebral blood flow (rCBF) in patients with depression after 3 weeks and 6 months of drug therapy. Clinical criteria for depression without psychosis were met according to psychiatric evaluation. Severity of depression was evaluated with the Hamilton Depression Rating Scale (HAMD) before every scintigraphic study. rCBF was assessed using technetium-99m bicisate (Neurolite) brain single-photon emission tomography in nine patients with severe depression before the beginning of antidepressant drug therapy and 3 weeks and six months after initiation of therapy. Only patients with no change in antidepressant medication during the study were included. No antipsychotic drugs were used. Cerebellum was used as the reference region. rCBF was evaluated for eight regions in each study in three consecutive transversal slices. Follow-up studies were compared with the baseline study. The mean HAMD score was 25.5 points initially, 16 at the second examination and 8.8 after 6 months. Global CBF was decreased compared with the reference region in drug-free patients. Perfusion of left frontal and temporal regions was significantly lower (P<0.005) in comparison with the contralateral side. After therapy, a moderate decrease in perfusion was seen in the right frontal region (P<0.05). Perfusion decreased further after 6 months in the right frontal (P<0.005) and temporal regions (P<0.01). The highly significant asymmetry in perfusion between the left and right frontal and temporal lobes almost disappeared during treatment. Our findings implicate dysfunction of the frontal and temporal cortex in clinically depressed patients before specific drug treatment. Clinical improvement and decreases in HAMD score after 3 weeks and after 6 months reflect the treatment effect on mood-related rCBF changes.
TL;DR: Agreement between echocardiography and perfusion imaging with technetium-99m sestamibi is high when used in patients in the emergency department with possible myocardial ischemia.
TL;DR: The ability of BMIPP imaging at 1 week post AMI to identify areas at risk is similar to that of tetrofosmin perfusion imaging in the acute phase, which may be due to the impairment of fatty acid uptake and metabolism reflecting prior severe ischaemic insult.
Abstract: Previous studies have indicated that iodine-123 labelled β-methyliodophenyl pentadecanoic acid (BMIPP), an iodinated fatty acid analogue, can identify persistent alteration of fatty acid metabolism after restoration of blood flow. To assess whether fatty acid imaging can delineate areas at risk following successful revascularization in patients with acute myocardial infarction (AMI), BMIPP findings at 1 week post AMI were compared with perfusion imaging before and after revascularization therapy. Sixty-five patients with AMI underwent technetium-99m tetrofosmin single-photon emission tomography (SPET) before m (TF0) and 1 week (TF1) after successful revascularization therapy. BMIPP SPET was also performed under a fasting state at 1 week (BM1) post AMI. The extent scores were calculated from the defect scores in 20 segments. The BM1 score (7.7±3.9) was similar to the TF0 score (8.8±4.2) (r=0.86, P<0.0001), but significantly higher than the TF1 score (5.8±3.9) (P<0.0001). A significant correlation was observed between the BM1 score and TF0 score (r=0.86, P<0.0001). Among a total of 1300 segments, the BM1 score was identical to the TF0 score in 1156 (88.9%). These data indicate that the ability of BMIPP imaging at 1 week post AMI to identify areas at risk is similar to that of tetrofosmin perfusion imaging in the acute phase. This may be due to the impairment of fatty acid uptake and metabolism reflecting prior severe ischaemic insult which persists at least 1 week after recovery of perfusion in the acute phase of AMI.
TL;DR: It is demonstrated that brain perfusion in the right parietal lobe is a significant predictor of survival in patients with AD even when other predictors are taken into consideration, which suggests that SPECT perfusion imaging may provide additional useful information on disease prognosis in AD.
Abstract: Article abstract-Background: The variability of disease course in patients diagnosed with AD makes prediction of survival difficult, despite the identification of numerous predictors to date. This study evaluated the predictive utility of measurements of regional cerebral blood flow (rCBF) obtained with SPECT in a group of AD patients. Methods: Fifty AD patients were studied with SPECT and followed longitudinally. SPECT measures of relative rCBF were calculated by measuring radioactivity densities in dorsolateral frontal, orbitofrontal, temporal, and parietal cortex normalized to occipital cortical radioactivity density. Subjects were classified into three tertiles of rCBF ratios for each region. These rCBF ratios were used as predictors of survival in life-table and proportional hazard models to predict survival. Results: Right parietal rCBF was a significant predictor of survival in the life-table analysis, with subjects in the lowest tertile having shortest survivals. No other brain region was a significant predictor of survival. In a proportional hazards model when a variety of other potential predictors were accounted for, right parietal rCBF ratio remained a significant predictor. Conclusions: These results demonstrate that brain perfusion in the right parietal lobe is a significant predictor of survival in patients with AD even when other predictors are taken into consideration. This suggests that SPECT perfusion imaging may provide additional useful information on disease prognosis in AD.