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T Duprez

Publications and source records attributed to T Duprez.

At least 37 records · Page 2Linked to original sources
PubMed2000

Whole brain quantitative CBF, CBV, and MTT measurements using MRI bolus tracking: implementation and application to data acquired from hyperacute stroke patients.

A robust whole brain magnetic resonance (MR) bolus tracking technique based on indicator dilution theory, which could quantitatively calculate cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) on a regional basis, was developed and tested. T2*-weighted gradient-echo echoplanar imaging (EPI) volumes were acquired on 40 hyperacute stroke patients after gadolinium diethylene triamine pentaacetic acid (Gd-DTPA) bolus injection. The thalamus, white matter (WM), infarcted area, penumbra, and mirror infarcted and penumbra regions were analyzed. The calculation of the arterial input function (AIF) needed for absolute quantification of CBF, CBV, and MTT was shown to be user independent. The CBF values (ml/min/100 g units) and CBV values (% units, in parentheses) for the thalamus, WM, infarct, mirror infarct, penumbra, and mirror penumbra (averaged over all patients) were 69.8 +/- 22.2 (9.0 +/- 3.0 SD); 28.1 +/- 6.9 (3.9 +/- 1.2); 34.4 +/- 22.4 (7.1 +/- 2.7); 60.3 +/- 20.7 (8.2 +/- 2.3); 50.2 +/- 17.5 (10.4 +/- 2.4); and 64.2 +/- 17.0 (9.5 +/- 2.3), respectively, and the corresponding MTT values (in seconds) were 8.0 +/- 2.1; 8.6 +/- 3.0; 16.1 +/- 8.9; 8.6 +/- 2.9; 13.3 +/- 3.5; and 9.4 +/- 3.2. The infarct and penumbra CBV values were not significantly different from their corresponding mirror values, whereas the CBF and MTT values were (P < 0.01). Quantitative measurements of CBF, CBV, and MTT were calculated on a regional basis on data acquired from hyperacute stroke patients, and the CBF and MTT values showed greater sensitivity to areas with perfusion defects than the CBV values. J. Magn. Reson. Imaging 2000;12:400-410.

Blood Flow Velocity↗
PubMed2000

High signal in cerebrospinal fluid mimicking subarachnoid haemorrhage on FLAIR following acute stroke and intravenous contrast medium.

We describe five cases of high signal in the cerebrospinal fluid (CSF) on fast-FLAIR images 24-48 h after onset of stroke. All the patients had undergone perfusion-weighted MRI within 6 h of the onset of the symptoms. The CSF was far brighter than the cortical gyri. The high signal was diffusely around both cerebral hemispheres in two cases and around one hemisphere in two others; it was focal, around the acute ischaemic lesion, in one. CT was normal in all cases. The CSF high signal was transient, decreasing in extent and intensity with time and resolving completely within 3-6 days. It was not associated with worsening of the clinical state or poor outcome. Our explanation of this phenomena is hypothetical: we speculate that it could be due to disruption of the blood-brain barrier resulting in leakage of protein, gadolinium chelates, or both in to the subarachnoid space. It should not be confused with subarachnoid haemorrhage.

Aged↗
PubMed2000

Postcontrast magnetic resonance imaging assessment of porous polyethylene orbital implant (Medpor).

OBJECTIVE: To evaluate the fibrovascular ingrowth progression within the porous polyethylene orbital implant (Medpor) with serial magnetic resonance imaging (MRI). DESIGN: Prospective, nonrandomized, comparative (self-controlled) trial. PARTICIPANTS: Ten patients who underwent enucleation and implantation of a 20-mm porous polyethylene implant wrapped with heterologous sclera. METHODS: Serial precontrast and postcontrast T1-weighted MRI were obtained at 1.5, 3, 6, and 12 months after implantation. The percentage area of enhancement was calculated by use of manual planimetric contouring unenhanced areas at the equator of each sphere on axial and coronal planes. RESULTS: All the implants showed enhancing areas as early as 1.5 months after enucleation. In 8 of the 10 patients, the areas of enhancement at the equator of the implant consistently showed similar centripetal progression primarily during the first 6 months after enucleation. The presence of fibrovascular tissue at the equator was associated in all cases with enhancing zones at the anterior portion of the implant. None of the implants showed diffuse complete enhancement after 12 months. Two patients failed to demonstrate further enhancement progression 1.5 months after implantation. No histopathologic study to equate with the MRI findings was performed in this series. CONCLUSIONS: Postcontrast magnetic resonance studies seem to be the best-suited imaging modality for assessing the fibrovascular tissue progression into porous polyethylene spheres after enucleation and for identifying patients in whom failure of vascularization occurs. Incomplete vascularization at the equator of the porous polyethylene sphere does not prove an absence of fibrovascular ingrowth in the anterior region. Prior ocular surgery and coexisting arterial hypertension may slow the progression of fibrovascular ingrowth.

Adolescent↗
PubMed2000

Phase I/II study of 2-chloro-2'-deoxyadenosine with cyclophosphamide in patients with pretreated B cell chronic lymphocytic leukemia and indolent non-Hodgkin's lymphoma.

Because of their substantial in vitro synergy, we conducted a dose-escalation study of cyclophosphamide (CP) added to 2-chloro-2'-deoxyadenosine (CdA) in patients with previously treated chronic lymphocytic leukemia and non-Hodgkin's lymphoma. CdA was given at a fixed dose (5.6 mg/m2/day) as a 2-h intravenous (i.v.) infusion, immediately followed by a 1-h i.v. infusion of CP, for 3 days. The initial daily CP dose was 200 mg/m2, and was escalated by 100 mg/m2 increments in successive cohorts of three to six patients to determine the maximum-tolerated dose (MTD). Additional patients were included at the MTD to extend toxicity and response analysis. Twenty-six patients received 68 cycles of chemotherapy. The MTD of CP after CdA 5.6 mg/m2, was 300 mg/m2. Acute neutropenia was the dose-limiting toxicity of this regimen, which was otherwise well tolerated. Delivery of repeated cycles was not feasible in eight patients (31%) because of prolonged thrombocytopenia. Severe infections were seen in three of 68 cycles (4%). The overall response rate was 58% (15 of 26; 95% CI, 36-76%), with 15% complete responses and 42% partial responses. These data show the feasibility of the association of CdA with CP. Given the response rate observed, further studies of this regimen are warranted in untreated patients, in particular with chronic lymphocytic leukemia and with Waldenström macroglobulinemia.

Adult↗
PubMed2000

[Thoracic myelopathy revealing a chronic ossificans arachnoiditis of the thoraco-lumbar spinal cord].

We report a case of chronic spinal, ossificans, thoraco-lumbar arachnoiditis, associated with an arachnoidal cyst at the level of TH7, and revealed by a rapidly progressive thoracic myelopathy. Two years ago, he had presented with a spinal intrathecal haemorrhage of unknown etiology. There was no evidence of spinal traumatism, arterial hypertension or coagulation disorder. The finding of several small cysts and angiomas in the liver of this patient lead us to suspect an associated spinal vascular malformation, not detected on the spinal magnetic resonance imaging. A partial neurologic improvement was observed after laminectomy and cysto-peritoneal derivation.

Aged↗
PubMed2000

[Diffusion- and perfusion-weighted MR imaging during the hyperacute phase of stroke].

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.

Aged↗
PubMed2000

[Degree of hemodynamic disturbance at the hyperacute phase of stroke: predictive value of 3D-TOF angiography and the T2 fast-FLAIR sequence].

GOAL: To define during the hyperacute phase of stroke the value of 3D-TOF MR angiography (MRA) and T2 fast-FLAIR sequence for predicting the volume of tissue presenting a hemodynamic disturbance. MATERIAL: and method: Thirty-five cases of hyperacute stroke located in following territories: middle cerebral artery (MCA) (n=29), anterior choroidal artery (AChoA) (n=5) and watershed (n=1) were retrospectively reviewed. The vascular abnormalities defined on MRA (vessel stenosis or occlusion) or FLAIR sequence (vessel hyperintensity) were classified into 3 groups: normal (I), distal abnormalities (II), abnormalities of the entire arterial territory (III). These results were compared with the volume of tissue showing a prolonged mean transit time (MTT) determined on relative MTT maps calculated from bolus tracking MR perfusion images. RESULTS: The abnormal volume measured on the MTT map was significantly correlated to the results of the MRA and FLAIR sequence. In the 12 cases of group III defined on the MRA (abnormality from M1), the volume of hemodynamic disturbance was always higher than 100 ml. For the MCA territory, it was not possible to predict the presence of a hemodynamic disturbance in any of the 3 groups defined on the FLAIR sequence and in the groups I and II defined on the MRA. For the AChoA territory, a hemodynamic disturbance was never observed in groups I and II defined either on MRA or FLAIR sequence. CONCLUSION: When there was no flow within the M1 segment on the MRA, there was always a hemodynamic disturbance larger than 100 ml on the MTT map. In the case of AChoA ischemic lesion, when no vascular abnormality was observed on the MRA or FLAIR images, the MTT map was always normal.

Acute Disease↗
PubMed2000

Results of cerebellopontine space imaging by magnetic resonance during one year.

The authors present the results of a retrospective study concerning 231 magnetic resonance imaging (MRI) of the cerellopontine space requested by the otologists of the department between September 1996 and September 1997. The motives of imaging were sensorineural hearing loss (44%), vertigo and unsteadiness (25.5%), tinnitus (16.5%) and other (13%). The MRI was abnormal in 18% of the cases and the diagnosis of acoustic schwannoma was made in 10% of the cases.

Belgium↗
PubMed1999

Fast FLAIR sequence for detecting major vascular abnormalities during the hyperacute phase of stroke: a comparison with MR angiography.

In the hyperacute phase of stroke, occluded vessels can be seen as high signal on fast-FLAIR images or as absence of flow-related enhancement in maximum-intensity projection (MIP) MR angiography (MRA). To compare these techniques, we examined 53 patients within 6 h of a stroke, using a standardised MRI protocol including fast-FLAIR and 3D time-of-flight TOF MR to detect vessel occlusion or reduced flow corresponding to the suspected ischaemic territory. Brain infarcts were confirmed on MRI after 1-5 days in 41 cases (77%). The overall accuracy of 3D-TOF MRA was 68% and sensitivity, specificity, positive and negative predictive values were 67%, 71%, 87%, and 43% respectively. Values for the fast-FLAIR sequence were: 65%, 85%, 93% and 44%, with an overall accuracy of 70%. The fast-FLAIR sequence was thus able to show occluded vessels or reduced flow with about the same accuracy as 3D-TOF MRA and enabled better prediction of the ischaemic area.

Adult↗
PubMed1999

Diffusion-weighted MRI postoperative assessment of an epidermoid tumour in the cerebellopontine angle.

Cerebellopontine angle epidermoid tumour generally has a typical appearance with conventional MRI sequences. The lesion is irregular in shape and gives slightly higher signal than cerebrospinal fluid on T1- and T2-weighted images, with a characteristic marbled inner pattern on T1-weighted images. Diffusion-weighted imaging (DWI) can be useful for the diagnosis of an atypical epidermoid tumour. Our case report illustrates the usefulness of DWI for postoperative assessment of residual foci of tumour. The specific appearance of an epidermoid tumour is illustrated, with emphasis on apparent diffusion coefficient (ADC) measurements.

Adult↗
PubMed1999

Clinical and MRI long term evolution of intracavernous and carotid ophtalmic artery aneurysms, treated by common carotid ligation.

In four large, 15-25 mm, internal carotid artery aneurysms (3 intracavernous and 1 carotid ophthalmic), treatment by common carotid ligation was preferred. Pre- and postoperative MRI were obtained, at a delay between 5 to 9 years. Recovery of the ocular and visual symptomatology was a function of the role played by mechanical and/or ischaemic factors. No early or late consequences, ascribable to the common carotid ligation, were observed. Aneurysmal thrombosis occurred in the first postoperative week, but retraction of the thrombosed aneurysms was only obvious and maximal after several months. For this reason, rapid clinical recovery could be due, in the first instance, to the loss of aneurysmal pulsatility. Complete disappearance of the aneurysm was observed in two cases. In the other two, a small remnant of the initial lesion, without any unfavourable consequences, was revealed, respectively 6 and 9 years after the intervention, by current, modern-days, MRA.

Carotid Artery Diseases↗
PubMed1999

Congenital muscular dystrophy with central and peripheral nervous system involvement in a Belgian patient.

We report a patient with congenital muscular dystrophy (CMD), developmental brain defects, and peripheral neuropathy. Marked hypotonia and plagiocephaly were noted at birth. Failure to thrive, generalized muscle weakness and wasting, absent deep tendon reflexes, partial seizures, and secondary microcephaly developed. Brain MRI showed a large area of cortical dysplasia, a thin but complete corpus callosum, and diffuse ventriculomegaly. Nerve conduction velocities were slow and creatine kinase levels only mildly elevated. Muscle biopsy showed dystrophic features with normal merosin, sarcoglycan, and dystrophin immunostaining. The Japanese Fukuyama CMD founder mutation was not detected. This is the first report of a patient with merosin-positive CMD, cobblestone lissencephaly, and demyelinating peripheral neuropathy.

Atrophy↗
PubMed1999

Sequestrum-like appearance of a multiple sclerosis brain lesion on serial magnetic resonance images.

Using serial magnetic resonance imaging, we monitored an unique lesion of the brain in a 15-year-old girl with clinically definite and laboratory-supported remitting-relapsing multiple sclerosis. During initial phases of the disease course, cystic necrosis around the plaque was observed. Later, remyelination of the central core of the lesion was speculated, as similarities in signal intensity between the core and the normal appearing white matter were partially recovered both on the T1- and the T2-weighted images.

Adolescent↗
PubMed1998

Physostigmine results in an increased decrement in brain glucose consumption in Alzheimer's disease.

The responsibility of cerebral cholinergic lesions for the weak clinical response to cholinergic neurotransmission enhancement of Alzheimer's disease (AD) was studied by measuring the effects of physostigmine on glucose consumption and neuropsychological tests. Ten AD and ten aged normals (AN) were examined twice, under placebo and under maximal tolerated dose of physostigmine, in randomized order and blind fashion. Under physostigmine, both groups showed better performances in tests measuring attention (P < 0.05-0.001) but not long-term memory, and cerebral glucose consumption was regionally modified (P < 0.0001). We observed a regional decrease in AD and in AN which was larger in AD, where each patient exhibited a mean metabolic decrease. With normalized values, AD and AN showed a similar decrease in the metabolic values of prefrontal cortex and striatum (P = 0.0003). These findings suggest that cholinergic neurotransmission enhancement depresses glucose consumption and increases selective attention in similar ways in both groups, but to a larger extent in AD. This suggests that brain metabolism in AD over-responds to enhancement of cholinergic neurotransmission. The observed weak response of clinical symptomatology to anticholinesterase agents does not appear to be due to the failure to enhance the activity of the cholinergic system in AD.

Aged↗