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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this review, the clinical utility of echoplanar techniques in MRI of the brain is discussed. Comparison of high-resolution EPI with SE/turbo-SE shows high image quality of EPI in the supratentorial brain. In the infratentorial region, however, susceptibility artifacts limit image quality. For the assessment of neuronal brain activation utilizing the intrinsic contrast of blood (BOLD), EPI has definite advantages over other techniques of functional MRI. Due to its superior temporal resolution and multislice capabilities, EPI allows for analysis of complex neuronal activation patterns. Diffusion imaging benefits from the lack of bulk motion artifacts and serves primarily to detect early stroke. Three methods of perfusion imaging (rel. blood volume, rel. blood flow) are discussed: the susceptibility artifact method (T2*), the relaxitivity method (T1), and the signal-labelling technique (STAR). Perfusion imaging may have a clinical impact in the assessment of brain tumors and cerebral ischemia.
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PMID:[Echo-planar imaging of the brain]. 858 33

Rapid changes in the apparent diffusion coefficient of water following brain ischemia have been extensively studied using echo planar diffusion imaging at low fields (2.0 T). There is a desire to perform these studies at higher fields (> 3.0 T) where the benefits of improved signal-to-noise can be exploited. Unfortunately, EPI diffusion is technically difficult to implement at high fields because of large magnetic susceptibility effects. This article demonstrates the feasibility of employing a line-scan diffusion protocol for ADCw measurements in stroke. The technique was applied on a 4.0 T system to monitor the decline in ADCw following the induction of focal cerebral ischemia in rat. ADCw data were acquired every 15 s with 10 b-values or every 22.5 s with 15 b-values, with a cubic spatial resolution of 1.5 mm. The results demonstrate that estimates of ADCw can be acquired with coefficients of variation under 3.0%, and with a combination of spatial and temporal resolution comparable to that previously reported for EPI.
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PMID:The application of diffusion-weighted line-scanning for the rapid assessment of water ADC changes in stroke at high magnetic fields. 926 65

We have prospectively studied all cholecystectomies performed in one year in our clinic in two groups: 190 cases performed laparoscopically and 98 open. We used standardized records and the EPI 5 program on an IBM compatible computer. There were no significant differences between groups regarding weight, sex and proportion of cases with acute cholecystitis. There were however major differences regarding age, type of habitat, ASA score and association with acute pancreatitis, obstructive jaundice and angiocholitis. Conversion of laparoscopic cholecystectomy to open procedure was imposed in 17 cases (not included in statistical analysis) due to technical difficulties (12 cases), haemorrhagic accidents (6 cases), injury of the common bile duct (1 case), stones lost in the abdominal cavity (3 cases), local peritonitis (5 cases). Laparoscopic cholecystectomy lasted a mean of 74 minutes. We encountered 3 specific complications: one CBD injury recognized intraoperatively and managed by Kehr's procedure (one CBD injury in the open cholecystectomy group), one small bowel perforation and one of biloma. Mortality averaged 0.5% in the LC group (one case of late postoperative stroke considered not related to the procedure) and 1% in the open cholecystectomy group. The hospital admission period was significantly reduced in the LC group (5 days vs. 12 days). LC appears as a safe procedure with a low complication rate. Conversion to open procedure is not a complication. Our study recommend LC as the method of choice in the treatment of gallbladder lithiasis.
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PMID:[The value of laparoscopic cholecystectomy in the treatment of gallbladder pathologies]. 945 51

Diffusion-weighted (DWI) echo-planar (EPI) MRI has been used for imaging acute ischaemic stroke. We used DWI and conventional spin-echo (SE) MRI to study the dynamics of ischaemic human stroke. We examined 30 patients (mean age 57.5 years, range 27-82 years, median 57 years) with a diagnosis of stroke. They were examined in the acute (120 min to 47 h, mean 15.3 h), subacute (8 days) and chronic (2-3 months) stages of ischaemia using clinical scores and MRI. Imaging was performed on an 1.5-T imager. Anisotropic DWI with diffusion gradients in all three axes, an isotropic tensor trace pulse DWI sequence and SE MRI were used. In all patients both DWI sequences showed a decrease in the apparent diffusion coefficient (ADC) in the acute stage, even when SE images did not reveal signal abnormalities. Clinical features correlated with lesion site but not size. The ADC was initially 19.6-43% less than that of nonischaemic tissue and increased to normal after 7 days in conventionally treated patients and after 2-5 days in patients who underwent intra-arterial fibrinolysis. In the chronic stage the ADC rose by up to 254.4 %. In patients who did not undergo fibrinolysis DWI changes correlated with the final infarct size (P<0.05). It was possible to differentiate acute from chronic ischaemic lesions. We conclude that DWI is a sensitive and practicable tool for detecting early cerebral ischaemia. It is possible to predict in the acute stage the final size of an infarct. DWI may be helpful for clinical decisions and for monitoring therapy.
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PMID:Diffusion-weighted imaging in ischaemic stroke: a follow-up study. 1077 39

The sensitivity of diffusion-weighted MR imaging to detect a lesion within 6 hours of stroke onset was approximately 90%. The false negative results were usually small lesions (1 ml), were seen early, and were usually located in the brain stem. The specificity of this technique was nearly 100% when it was used correctly. The volume and the value of the apparent diffusion coefficient of the detected lesions provided prognostic information. After injection of a contrast agent (perfusion imaging), a time series of volumes were obtained using a T2* sensitive gradient echo EPI sequence. Hemodynamic perturbations of the cerebral parenchyma could be detected as well as the type of perturbation in the lesion. A map representing the mean transit time for each voxel was used to define the maximum volume of the perturbation. A hemodynamic penumbra was defined to be when this volume was larger than the volume detected on the diffusion images. The quantitative measure of cerebral blood flow could predict the irreversibility of the lesions when the value was below 18 ml/min/100g, and the extension of the ischemia in the penumbra zone when the value was below a threshold of 30 ml/min/100g.
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PMID:[Diffusion- and perfusion-weighted MR imaging during the hyperacute phase of stroke]. 1091 3

The preliminary results of MR echoplanar diffusion-weighted imaging (EPI DWI) in patients with stroke are presented. Twelve patients (5 females, 7 males) aged 36-78 years (mean 63.8) were examined by 2T system. No focal lesions were found in the acute phase of stroke on T1-weighted images. Narrowing of sulci in the region of stroke was the only abnormal finding. Focal hyperintense lesions were shown on PD and T2-weighted images in 50% of patients in the acute phase, 7 hours after the onset of clinical symptoms. On EPI diffusion-weighted images focal decrease of apparent diffusion coefficient (ADC) was observed in all cases of the acute phase of stroke after 3 hours. EPI DWI allows for earliest detection of ischaemic lesions in brain tissue. The method is especially useful in characterisation of the acute phase of stroke and shows its evolution thanks to the use of ADC.
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PMID:[The usefulness of the method of planar diffusion echo imaging (EPI DWI) in the diagnosis of cerebral ischemia]. 1096 19

Diffusion-weighted imaging(DWI) has been demonstrated to be valuable for assessment of ischemic stroke patients. The aim of this study is to evaluate clinical usefulness of DWI in the diagnosis of transient ischemic attack(TIA). Nineteen patients with symptoms of TIA were studied. DWI was taken with 1.5 Tesla MRI system using spin echo EPI sequence. Seven patients revealed areas of hyperintensity (brightness) on DWI and of hypointensity on apparent diffusion coefficient(ADC) maps relative to normal brain. As the duration of TIA symptom elongated, the percentage of patients with DWI abnormalities became higher. DWI enabled to detect areas of hyperintense lesion in all three patients as early as 3 hours after the onset, while conventional T2 weighted imaging showed in one. All the DWI abnormalities were irreversible in spite of the complete recovery from TIA. DWI is an useful technique for the detection of responsible lesions in TIA. However, TIA cannot be ruled out even if DWI does not demonstrate any abnormal signals.
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PMID:[Usefulness of diffusion-weighted MRI in the diagnosis of transient ischemic attacks]. 1107 Sep 24

Acute stroke is one of the three major causes of death and disability in the United States. Now that new, and possibly effective therapy is becoming available, accurate, rapid diagnosis is important to provide timely treatment, while avoiding the risk of complications from unnecessary intervention. Our objective was to test the hypothesis that use of echo-planar (EPI) diffusion-weighted imaging (DWI) is more accurate than conventional T2 weighted MRI in predicting progression to stroke in patients with acute ischemic neurologic deficits. We studied 134 patients presenting with acute neurologic deficits to a community hospital emergency room with both conventional MRI and DWI within 72 h of the onset of the acute deficit. We found DWI significantly more sensitive to permanent neurologic deficit at discharge (sensitivity 0.81) than conventional MRI (sensitivity 0.41). When available, DWI should be considered for routine use in patients being imaged for acute stroke.
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PMID:The value of diffusion-weighted imaging for prediction of lasting deficit in acute stroke: an analysis of 134 patients with acute neurologic deficits. 1146 53

Diffusion-weighted single-shot EPI (sshEPI) is one of the most important tools for the diagnostic assessment of stroke patients, but it suffers from well known artifacts. Therefore, sshEPI was combined with SENSitivity Encoding (SENSE) to further increase EPI's potential for stroke imaging. Eight healthy volunteers and a consecutive series of patients (N = 8) with suspected stroke were examined with diffusion-weighted SENSE-sshEPI using different reduction factors (1.0 < or = R < or = 3.0). Additionally, a high-resolution diffusion-weighted SENSE-sshEPI scan was included. All examinations were diagnostic and of better quality than conventional sshEPI. No ghostings or aliasing artifacts were discernible, and EPI-related image distortions were markedly diminished. Chemical shift artifacts and eddy current-induced image warping were still present, although to a markedly smaller extent. Measured direction-dependent diffusion-coefficients and isotropic diffusion values were comparable to previous findings but showed less fluctuation. We have demonstrated the technical feasibility and clinical applicability of diffusion-weighted SENSE-sshEPI in patients with subacute stroke. Because of the faster k-space traversal, this novel technique is able to reduce typical EPI artifacts and increase spatial resolution while simultaneously remaining insensitive to bulk motion.
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PMID:Improved diffusion-weighted single-shot echo-planar imaging (EPI) in stroke using sensitivity encoding (SENSE). 1155 Feb 48

Diffusion-weighted MR imaging (DWI) is particularly sensitive for the detection of acute stoke. Until recently, DWI was performed with EPI technology. We compared 18 patients with clinical suspicion of acute stroke on a standard 1.5T unit and an open low-field MR scanner. Eighteen patients with 20 lesions of acute stroke were studied retrospectively with DWI and ADC mapping on both systems. The technique used was a rotating fast-spin echo T2 at low-field and an EPI sequence at 1.5T. Both examinations were performed within 24 hours and analyzed by two neuroradiologists. We obtained the same results on DWI sequences on both systems, regarding high intensity lesions on DWI. Interpretation of the ADC maps proved to be difficult on low-field MR near the lateral ventricles (3/18). We experienced the same difficulty of interpretation at low and high field in the cerebellum, in the temporal fossa and in cortex situated near bone, due to susceptibility artifacts. Chronic lesions were better visualized at low than at high field. In our opinion, DWI on a low-field open MR scanner is a good technique to evaluate subacute stroke and was as reliable as when performed on a 1.5T MR system.
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PMID:Diffusion weighted MR imaging on a low-field open magnet. Comparison with findings at 1.5T in 18 patients with cerebral ischemia. 1262 88


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