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Y Berthezene

Publications and source records attributed to Y Berthezene.

18 recordsLinked to original sources
PubMed2001

Perfusion-based segmentation of the human brain using similarity mapping.

In this work, a method for segmenting human brain MR scans on the basis of perfusion is described. This technique uses a measure of similarity between the time-intensity curves obtained with dynamic susceptibility contrast-enhanced MRI and a modeled curve of reference to isolate a tissue of interest, such as white or gray matter. The aim of this study was to validate the method by performing segmentation of white and gray matter in six controls. The relative regional blood volume gray-to-white matter ratio was used as a criterion to assess the quality of segmentation. On average, this ratio was 2.1 +/- 0.2, which is in good agreement with the literature, thus suggesting reliable segmentation. In the case of abnormal perfusion, time-intensity curves are different in shape than that of normal tissue. Therefore, this approach might allow the segmentation of pathological regions, and combined with an indicator-dilution analysis might offer new possibilities for characterizing a brain pathology. Magn Reson Med 45:261-268, 2001.

Brain↗
PubMed2001

CT pulmonary angiography with a macromolecular contrast medium: a comparative study versus iobitridol in rabbits.

RATIONALE AND OBJECTIVES: To compare the pharmacokinetics of a new macromolecular iodinated contrast medium, prototype P743, with a standard contrast agent (iobitridol) for spiral computed tomography pulmonary angiography in rabbits. METHODS: Manual injection was first used to test the performance of P743 even in cases of nonoptimal bolus timing. Then a protocol was designed to compare vessel enhancement in both first-pass and delayed scans for the two contrast agents with the help of a power injector. RESULTS: With manual fast injection, the first pass of iobitridol was observed only on proximal scans. Conversely, opacification of vessels was maintained during three spiral scans with P743 under the same injection conditions. When optimal bolus timing was performed, higher vessel enhancement was observed during bolus first pass with iobitridol (iodine dosage 250 mg I/kg) compared with P743 (150 mg I/kg). However, during the postbolus phase, the decrease in attenuation values was markedly faster with iobitridol than with P743. CONCLUSIONS: This study confirmed that P743 remains more intravascular than iobitridol, which may have clinical implications for the diagnosis of pulmonary embolism, for example.

Angiography↗
PubMed2000

rtPA intravenous thrombolysis in anterior choroidal artery territory stroke.

OBJECTIVE: To study the possible specific response to recombinant tissue plasminogen activator (rtPA) thrombolysis of anterior choroidal artery (AChA) stroke. BACKGROUND: Outcome and response after rtPA thrombolysis are possibly better in small-vessel infarcts, but a specific study of AChA stroke has not yet been performed. METHODS: The authors proposed an open trial of IV rtPA within 7 hours in patients age 20 and 81 years with all types of internal carotid artery territory stroke if the baseline Scandinavian Stroke Scale (SSS) score was less than 48. A dose of rtPA 0.8 mg/kg was infused over 90 minutes. Of 114 consecutive patients, 9 patients (7.9%) exhibited hypodensity in the AChA territory on day 1 brain CT. RESULTS: Seven of nine patients with AChA infarct had a primary early recovery within 6 hours after the initiation of rtPA infusion. In addition, recovery was complete in five patients and partial in two patients. No intracerebral hematoma was observed. Three patients had a "reinfarct syndrome" at 12, 25, and 48 hours respectively. However, in the two latter patients treated with IV heparin, the deficit disappeared again with the increase of heparin dose in one patient and disappeared spontaneously in the other patient. The overall outcome at day 90 was six total recoveries in nine patients (66%). Patients with a final good outcome had a slight "unstructured" hypodensity in the AChA territory on day 1 brain CT, whereas patients with a bad outcome had the classic "structured" hypodensity of AChA territory stroke. CONCLUSION: These data support a specific quick response of AChA territory stroke to IV rtPA thrombolysis, probably due to the small size of the artery and of the "clot." The high frequency of the reinfarct syndrome is a clinical fact that is difficult to explain. Efficient heparin treatment after 24 hours may control the reinfarct syndrome in some patients.

Aged↗
PubMed1998

Can cerebrovascular reactivity be assessed by dynamic susceptibility contrast-enhanced MRI?

The acetazolamide (ACZ) test is performed to evaluate the decrease in cerebral perfusion pressure (CPP) by investigation of vasomotor reactivity (VMR). Our aim was to study cerebral blood flow and blood volume changes induced by the ACZ test in healthy control subjects using dynamic susceptibility contrast-enhanced gradient-echo MRI (DSC-MRI). A FLASH sequence was used to produce susceptibility-weighted images during an intravenous injection of 0.1 mmol/kg gadopentetate dimeglumine (Gd-DTPA). After the first dynamic study, 1 g acetazolamide was given intravenously and 10 min later a second bolus of Gd-DTPA was injected. Using the indicator-dilution theory, relative cerebral blood volume and relative cerebral blood flow were estimated. In healthy subjects the ACZ test induced a significant increase in relative blood volume (from 80.5 +/- 10.7 to 113.4 +/- 11.9) and relative blood flow (from 5.73 +/- 0.96 to 7.5 +/- 0.97), symmetrically in the cerebral hemispheres. This approach might be promising in the understanding of cerebral haemodynamics in patients with vascular disorders.

Acetazolamide↗
PubMed1997

Assessment of cerebrovascular reactivity by dynamic susceptibility contrast-enhanced MR imaging.

In patients with cerebrovascular disease the acetazolamide (ACZ) test is performed to evaluate the decrease in cerebral perfusion pressure (CPP) through the investigation of the vasomotor reactivity (VMR). This latter is currently assessed with ACZ with several methods. Recently, magnetic resonance imaging (MRI) techniques have been developed that are sensitive to stimulus-induced changes in blood flow. Dynamic susceptibility contrast material-enhanced gradient-echo MRI techniques (DSC-MRI) might be an attractive tool to assess VMR. We aimed to test the ability of DSC-MRI in the assessment of VMR. Relative hemodynamic parameters rCBV, MTT, and rCBF were evaluated at baseline after the first injection of gadopentetate dimeglumine and 10 min after the intravenous administration of ACZ (1 g) with a second bolus of contrast agent. Assessment of hemodynamic parameters was performed over the whole hemisphere and also within regions of interest. The significances of the mean differences, before and after ACZ, were assessed with repeated-measures ANOVA with two within factors: laterality (right-left) and ACZ. DSC-MRI with ACZ test was performed in ten healthy controls (aged 51.4+/-16.2 years). The cerebral hemispheric ratio for the three parameters (cerebral blood volume (CBV), mean transit time (MTT), and cerebral blood flow (CBF)) ranged between 1.01 and 1.03. The mean gray matter-to-white matter ratio for CBV, CBF and MTT were 2.44, 2.41 and 1.05, respectively. As the laterality effect was not significant, left and right hemispheric values were averaged. A significant increase of all hemodynamic parameters was observed after ACZ (P<0.01-0.001). The same changes for CBV, CBF and MTT were observed after ACZ according to the regions of interest (P<0.006-0.015). DSC-MRI is a non-invasive method which enables the assessment of VMR. This technique may be added to any conventional MRI in order to detect a hemodynamic impact of an ICA stenosis. Therefore, it might be useful in determining the appropriate management when the indication for surgical versus medical therapy is in question.

Acetazolamide↗
PubMed1997

Definition of liver tumors in the presence of diffuse liver disease: comparison of findings at MR imaging with positive and negative contrast agents.

PURPOSE: The potential to define liver tumors at magnetic resonance (MR) imaging was compared with a positive and a negative contrast agent (gadoxetic acid disodium, or gadolinium EOB-DTPA [a hepatocyte-directed agent], and ferumoxides, or superpara-magnetic iron oxide particles [a Kupffer cell-directed agent], respectively) in normal rats and in rats with induced acute hepatitis, fatty liver, or cirrhosis. MATERIALS AND METHODS: Rats with implanted liver adenocarcinomas were divided into four groups: no diffuse liver disease ("normal" [n = 6]) and diffuse liver diseases (induced acute hepatitis [n = 6], fatty liver [n = 6], or cirrhosis [n = 6]). Rats first received gadoxetic acid disodium (50 mumol/kg) and then, 45 minutes later, ferumoxides (10 mumol/kg). Liver signal intensity enhancement and tumor-to-liver contrast-to-noise ratio (C/N) were measured in each group. RESULTS: Mean liver signal intensity enhancement values with gadoxetic acid disodium and ferumoxides were excellent in the normal liver model (176% and -62%, respectively; P < .01) but were significantly reduced in the acute hepatitis model (82% and -36%, respectively). In the fatty livers compared with the normal livers, enhancement with gadoxetic acid disodium was reduced (57%) but with ferumoxides was excellent (-55%). In the cirrhotic livers compared with the normal livers, enhancement with gadoxetic acid disodium (174%) was virtually the same but was impaired with ferumoxides (-43%). CONCLUSION: Hepatic enhancement and tumor-to-liver C/N with either positive or negative liver-enhancing agents can be impaired by the presence of underlying liver disease. Prior knowledge of the type of diffuse liver disease may influence the choice of contrast agent for tumor detection.

Acute Disease↗
PubMed1997

[Painful ophthalmoplegia disclosing dural fistula of the anterior cranial fossa].

We report the case of a 54-year-old man without previous medical history who presented with sudden vertical diplopia and frontal headache. Clinical examination and Lancaster's test were consistent with superior rectus muscle palsy. Brain CT scan, MRI and CSF examination were normal. Cerebral angiography revealed a dural arteriovenous fistula at the base of the anterior cranial fossa with bilateral arterial supply from small branches of the ophthalmic artery. The causal relationship, the pathophysiology and the therapeutic approaches are discussed.

Arteriovenous Fistula↗
PubMed1996

Hemodynamic parameter assessment with dynamic susceptibility contrast magnetic resonance imaging in unilateral symptomatic internal carotid artery occlusion.

BACKGROUND AND PURPOSE: Hemodynamic parameters such as regional cerebral blood volume (rCBV), mean transit time (MTT), and regional cerebral blood flow (rCBF) can be assessed by dynamic susceptibility contrast MRI. The aim of the present study was to apply this method in patients who had symptomatic unilateral internal carotid artery occlusion. METHODS: Relative hemodynamic parameters (rCBV, MTT, and rCBF) were evaluated on the occluded side and thus compared with contralateral hemispheric values. We also attempted to detect any relationship between collateral flow and the hemodynamic parameters. RESULTS: Although rCBV was clearly increased in five patients over the whole hemisphere, we did not observe a statistically significant difference regarding the whole sample between sides (mean rCBV, 14.1 +/- 4.58 on the occluded side versus 11.8 +/- 2.99 on the contralateral side, P>.10). MTT was clearly increased on the occluded side (mean MTT, 4.29 +/- 0.83 on the lesion side versus 3.14 +/- 0.81 on the contralateral side, P<.010). A statistically significant decrease of rCBF on the occluded side was observed (mean rCBF, 3.27 +/- 0.73 versus 3.93 +/- 1.03 on the contralateral side; P<.01). CONCLUSIONS: A significant hemodynamic compromise in patients who had unilateral symptomatic carotid occlusion was observed according to CBF and MTT values. This approach might be promising in the understanding of cerebral hemodynamics in patients with vascular disorders.

Aged↗
PubMed1996

[Diagnosis of a post-thrombophlebitic dural fistula using MR angiography].

We report a case in which MRA made it possible to diagnose a dural arteriovenous fistula and thrombophlebitis in a 23-year old woman. 2D TOF MRA is the usual technique in the diagnosis of thrombophlebitis. Our experience shows the limits of 2D TOF since the increased signal intensity in the sinus could simulate a normal flow, and we describe the advantages of MR subtraction angiography. In our study, 3D TOF MRA showed the dural arteriovenous fistula, its location near the right transverse sinus and some of the feeding vessels: tentorial branch of the internal carotid artery and meningeal branch of the right occipital artery. 3D TOF MRA provides the diagnosis of dural arteriovenous fistula, but it cannot replace the plain angiography performed before endovascular or surgical treatment.

Adult↗
PubMed1993

Acute fracture of the femoral neck: assessment of femoral head perfusion with gadopentetate dimeglumine-enhanced MR imaging.

OBJECTIVE: Evaluation of the perfusion and viability of the femoral head after fracture of the femoral neck is important because the outcome of conservative treatment or joint-preserving surgery is adversely affected by the development of capital osteonecrosis. We evaluated the use of MR imaging, before and after IV administration of gadopentetate dimeglumine, for assessing perfusion of the femoral head in 13 patients with acute fracture of the femoral neck. SUBJECTS AND METHODS: Multiecho (1600/30-240 [TR/TE]) MR images were obtained before contrast administration and gradient-echo (315/14, 90 degrees flip angle) MR images were obtained both before and after contrast administration. MR findings were correlated with findings on superselective digital subtraction angiograms of the vessels supplying the femoral head and with clinical-radiographic follow-up for at least 12 months. RESULTS: Digital subtraction angiography showed impaired blood supply to the femoral head in five patients. On contrast-enhanced MR images of these patients, the femoral head did not enhance and was lower in signal intensity than were the enhancing femoral shaft and neck distal to the fracture and the enhancing femoral head on the unaffected side. In the patients with persistent perfusion, contrast-enhanced MR images showed a uniform increase in signal intensity in the femoral shaft and neck as well as the femoral head; the femoral head on the fractured side showed contrast enhancement similar to that on the healthy side. CONCLUSION: These preliminary results indicate that contrast-enhanced MR imaging may be useful for noninvasive evaluation of femoral head perfusion after fracture of the femoral neck. MR findings also may aid the clinician in deciding between joint-preserving therapy and hip arthroplasty.

Acute Disease↗
PubMed1992

[Residual and reconverted hematopoietic bone marrow in the distal femur. Spin-echo and opposed-phase gradient-echo MRT].

The distal femur contains usually only fatty marrow in the adult. We investigated the incidence of areas of residual and reconverted hematopoietic marrow in the distal femur in a series of 50 adult patients using conventional spin-echo and opposed-phase gradient-echo MR images. Zones with intermediate to low signal intensity in both sequences representing hematopoietic marrow within high signal intensity fatty marrow were observed in 17 of the 50 patients. Opposed-phase gradient-echo sequences demonstrated significantly greater red-yellow marrow contrast than conventional spin-echo sequences. Residual red marrow may represent a biologic variation of the normal adult pattern of red-yellow marrow distribution in women of menstruating age. Reconverted red marrow appears to be related to increased erythrocyte demand. It should not be mistaken for bone marrow malignancy. Absence of epiphyseal involvement, cortical destruction and soft-tissue mass in residual and reconverted hematopoietic marrow are helpful differential criteria.

Adult↗
PubMed1991

Differentiation of capillary leak and hydrostatic pulmonary edema with a macromolecular MR imaging contrast agent.

The ability of a macromolecular contrast agent (polylysine-[gadopentetate dimeglumine]40) to allow distinction of pulmonary capillary leak from hydrostatic pulmonary edema was investigated. Capillary leak edema was induced in 12 rats by means of venous injection of oleic acid; hydrostatic pulmonary edema was induced in 10 rats by means of continuous infusion of 0.9% sodium chloride. In the oleic acid pulmonary edema model, the signal intensity continued to increase for 12 minutes after administration of contrast material, indicating a leak of paramagnetic molecules from the intravascular to the extravascular spaces. Conversely, lung enhancement remained virtually constant after injection of contrast material in the hydrostatic edema model, as would be expected in the absence of endothelial damage. Hydrostatic edema tended to be distributed homogeneously throughout the lung, while capillary leak edema tended to occur predominantly in the peripheral portions of the lung. These findings indicate that macromolecular contrast agents can facilitate differentiation between edema caused by elevated intravascular pressure and edema induced by abnormal capillary permeability.

Animals↗
PubMedDate not supplied

Subacute coronary artery thrombosis: MRI findings.

The article presents a case of subacute coronary artery thrombosis investigated by classic methods, coronary angiography, and MRI. T1- and T2-weighted images showed high signal intensity within the lumen of the right coronary artery corresponding to the methemoglobin content of the thrombus. Dynamic sequence images with intravenous gadolinium contrast agent displayed lack of right coronary artery enhancement, confirming coronary occlusion. The coronarography revealed the same finding. MRI appears to be a promising method of coronary thrombosis assessment.

Coronary Angiography↗
PubMedDate not supplied

Effects of subcortical cerebrovascular lesions on cortical hemodynamic parameters assessed by perfusion magnetic resonance imaging.

A simultaneous decrease of cerebral blood volume (CBV) and cerebral blood flow (CBF) has been described after subcortical stroke with positron emission tomography. However, this imaging modality cannot be applied routinely to stroke patients. Dynamic susceptibility contrast-enhanced MRI techniques (DSC-MRI) might be interesting in the assessment of these effects. Dynamic T2-weighted echo planar imaging was used to produce DSC-MR images during an intravenous bolus injection of gadopentetate dimeglumine in 9 patients who experienced a subcortical stroke involving thalamus or basal ganglia and in 8 control subjects. A series of 50 consecutive images at 1-second intervals was acquired at the anatomic level of the centrum semiovale quite distant from the subcortical lesion, rCBF and rCBV were determined over frontal and parietal regions of interest and through the entire cortical mantle. DSC-MRI enabled the detection of hemodynamic changes induced by subcortical stroke. Analysis of rCBV and rCBF values showed that the hemodynamic parameters were significantly decreased on the affected side. In controls mean rCBF and rCBV values recorded over the whole cortical mantle of each hemisphere showed no significant interhemispheric asymmetry.

Adult↗
PubMedDate not supplied

Hyperacute diffusion-weighted MRI in basilar occlusion treated with intra-arterial t-PA.

Basilar artery thrombosis should be diagnosed immediately, as intra-arterial thrombolysis might improve the outcome. Diffusion-weighted (DWI)-MRI and three-dimensional time-of-flight MR angiography (3D TOF Turbo MRA) may provide additional insight into the extent of ischemia and the level of the occlusion. These methods could be helpful in the early classification of vertebrobasilar stroke, thus reserving the use of conventional angiography and possible intra-arterial thrombolysis for patients who had a severe clinical picture explained by preliminary assessments. We report the case of a 74-year-old woman who experienced a basilar artery occlusion; DWI-MRI and 3D TOF Turbo MRA provided noninvasive information concerning the level of arterial occlusion and its parenchymal ischemic impact, this leading to an intra-arterial thrombolytic therapy. These data suggest the feasibility of a noninvasive urgent diagnostic and prognostic approach with DWI-MRI and 3D TOF Turbo MRA in basilar occlusion.

Aged↗
PubMedDate not supplied

Diffusion-weighted MRI in acute mutism.

Mutism defined as a complete loss of speech may be related to psychiatric or neurologic disorders. The ischemic stroke origins of mutism are often difficult to assess at the acute stage. Accordingly, the search for the underlying mechanism as the localization of the damages may be difficult by conventional radiological techniques. Diffusion-weighted (DWI) MRI may accurately identify patients with acute ischemic stroke and distinguish them from those who mimic acute stroke better than clinical and conventional neuroradiological methods. This report aims to demonstrate the utility of DWI-MRI in the diagnosis of acute mutism.

Acute Disease↗