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Biomedical subjects

L Picard

Publications and source records attributed to L Picard.

At least 19 recordsLinked to original sources
PubMed2006

[MRI findings in a case of prolonged status epilepticus].

We report the MR imaging findings in a 20 year old woman with status epilepticus of more than 3 months duration following an episode of lymphocytic meningitis. Repeated MR examinations showed progressive symmetrical cortical lesions, followed by subcortical and basal ganglia lesions which evolved to cortical laminar necrosis and hemorrhagic necrosis with eventual subcortical cerebral atrophy. This case has similarities with animal status epilepticus models. Biological investigations were all negative. This suggests that the brain lesions may be related to the prolonged status epilepticus.

Adult↗
PubMed2005

Model of a vascular C-arm for 3D augmented fluoroscopy in interventional radiology.

This paper deals with the modeling of a vascular C-arm to generate 3D augmented fluoroscopic images in an interventional radiology context. A methodology based on the use of a multi-image calibration is proposed to assess the physical behavior of the C-arm. From the knowledge of the main characteristics of the C-arm, realistic models of the acquisition geometry are proposed. Their accuracy was evaluated and experiments showed that the C-arm geometry can be predicted with a mean 2D reprojection error of 0.5 mm. The interest of 3D augmented fluoroscopy is also assessed on a clinical case.

Computer-Aided Design↗
PubMed2005

[Neuroimaging of hereditary hemorrhagic telangiectasia].

Hereditary Hemorrhagic telangiectasia is an autosomal dominant vascular disorder with high penetrance and variable expressivity. Most cases are caused by mutations in the endoglin gene on chromosome 9 (HHT type 1) or the activin receptor-like kinase 1 gene on chromosome 12 (HHT type 2). HHT is characterized by mucocutaneous telangiectases and visceral arteriovenous malformations (AVMs). Neurological complications occur in 8 to 10% of the patients. Brain ischemia or abscess are often associated with pulmonary arteriovenous fistula. Cerebral or spinal arteriovenous malformations are frequent but have a lower risk of haemorrhage than sporadic AVMs and routine screening should not be practiced in adult patients. Routine screening should be discussed for children with a familial history of cerebral haemorrhage and/or HHT type 1.

Brain Diseases↗
PubMed2005

[Risks and responsibilities in diagnostic and interventional radiology. Ethical and medicolegal considerations].

Medical risk management has one main purpose: to ensure the safety of care. The law of March 2002 has generated a true cultural revolution. The radiologist is involved with new and difficult areas of medical liability due to technical advances, the increasing number of imaging techniques, the increasing complexity of imaging techniques, their efficiency and the need for multidisciplinary approach. Imaging recommendations requiring increasing levels of technical and clinical skills. The radiologist is liable with regards to the indications of imaging studies, and also with regards to informed consent. The prevention of medicolegal problems is achieved by competency, which must be combined to good liability insurance and ongoing vigilance supported by appropriate continuous medical education.

France↗
PubMed2004

Contrast-enhanced transcranial Doppler sonography in the follow-up of intracranial aneurysms after endovascular treatment.

Two pilot studies on a small number of patients demonstrated the feasibility of transcranial Doppler ultrasound evaluation in the follow-up of intracranial aneurysms treated with detachable coils. This prospective study aimed to assess the sensitivity of contrast-enhanced transcranial echo-Doppler in detecting partial aneurysmal occlusion following endovascular treatment. Transcranial Doppler sonography (TCD) with contrast administration and magnetic resonance angiography (MRA) or angiography were carried out after endovascular treatment in 92 patients for 98 aneurysms of the anterior circulation. In 18% of cases, the quality of ultrasound exploration was deemed unsatisfactory for evaluation of the aneurysmal site. Results were concordant in 63% of patients (49/78). When occlusion appeared satisfactory at angiography or MRA, the result was concordant with TCD in 68% of cases (44/77). When a residual aneurysm was detected, TCD sensitivity was 38% (8/18). An analysis of subgroups failed to disclose anatomic or morphological aneurysm features in which transcranial echo-Doppler is sufficiently sensitive and specific to detect possible residual aneurysm or recanalisation. In our experience, even after contrast administration TCD is not sufficiently sensitive or specific in the detection of residual aneurysm to replace angiography or MRA.

Adult↗
PubMed2004

[Medicolegal aspects in neuroradiologic emergencies].

Naturally, neuroimaging emergencies are a component of the global subject of emergencies that have for several years been a frequent subject in the press. The current situation is the consequence of the evolution of ideas from contractual liability to the frequently discussed principle of precaution. Examples offered by the daily practice allow to emphasize the main difficulties: diagnosis of headaches, seizure episode on public roads, head trauma, stroke... The medical liability of the neuroradiologist is not the same for diagnostic or interventional neuroradiology; it can sometimes be shared with other physicians. This liability includes the indication, the quality of the diagnosis, the information of the patient and relatives, the communication of results with other physicians, the maintenance of the equipment... Knowledge of potential pitfalls allows preventive measures including competence of the neuroradiologist, informed patient consent, and written precise protocols are the most important. However, according to the evolution of our societies, it is likely that it will become increasingly difficult to achieve a professional neuroradiology career without being questioned; it is thus advisable to be prepared for such eventuality.

Clinical Competence↗
PubMed2004

[Primary spinal melanoma: a case report].

Intra spinal primary melanoma is a rare entity. We report a new case, atypical in relation to its primary radicular location, and to its early metastatic intradural and extra-medullary location, six months later. MRI is the more valuable examination, showing a spontaneously hyper-intense lesion on T1-weighted MR images, intense enhancement after gadolinium administration, and decreased signal on T2-weighted MR images, thus suggesting a diagnosis of melanocytic or hemorrhagic lesion. Signal abnormalities are not specific and definitive diagnosis is established after histological analysis.

Adult↗
PubMed2001

Transcriptional induction of repair genes during slowing of replication in irradiated Saccharomyces cerevisiae.

We investigated the inhibition of cell-cycle progression and replication and the induction of the transcriptional response in diploid budding yeast populations exposed to two different doses of gamma-rays resulting in 15 and 85% survival respectively. We studied the kinetics of the cellular response to ionizing treatment during the period required for all of the surviving cells to achieve at least one cell division. The length of these periods increased with the dose. Irradiated populations arrested as large-budded cells containing partially replicated chromosomes. The extent of the S-phase was proportional to the amount of damage and lasted 3 or 7h depending on the irradiation dose. In parallel to the division study, we carried out a kinetic analysis of the expression of 126 selected genes by use of dedicated microarrays. About 26 genes were induced by irradiation and displayed various pattern of expression. Interestingly, 10 repair genes (RAD51, RAD54, CDC8, MSH2, RFA2, RFA3, UBC5, SRS2, SPO12 and TOP1), involved in recombination and DNA synthesis, display similar regulation of expression in the two irradiated populations. Their pattern of expression were confirmed by Northern analysis. At the two doses, the expression of this group of genes closely followed the extended replication period, and their expression resumed when replication restarted. These results suggest that the damage-induced response and DNA synthesis are closely regulated during repair. The analysis of the promoter regions indicates a high occurrence of the three MCB, HAP and UASH regulatory boxes in the promoters of this group of genes. The association of the three boxes could confer an irradiation-replication specific regulation.

Blotting, Northern↗
PubMed2001

Intracranial aneurysms: clinical value of 3D digital subtraction angiography in the therapeutic decision and endovascular treatment.

PURPOSE: To evaluate three-dimensional (3D) digital subtraction angiography (DSA) as a supplement to two-dimensional (2D) DSA in the endovascular treatment (EVT) of intracranial aneurysms. MATERIALS AND METHODS: In 22 ruptured aneurysms, neck visualization, aneurysm shape, and EVT feasibility were analyzed at 2D DSA (anteroposterior, lateral, and rotational views) and at maximum intensity projection (MIP) and surface shaded display (SSD) 3D DSA. The possibility of obtaining a working view for EVT at 3D DSA and the relevance of measurements in choosing the first coil also were assessed. RESULTS: Two-dimensional DSA images clearly depicted the aneurysm neck in four of 22 aneurysms; MIP images, in 10; and SSD images, in 21, but SSD led to overestimation of the neck size in one aneurysm. Aneurysm shape was precisely demonstrated in five of 22 aneurysms at 2D DSA, in eight at MIP, and in all cases at SSD. In two of 22 aneurysms, EVT seemed to be nonfeasible at 2D DSA; however, SSD demonstrated feasibility and EVT was successfully performed. In one aneurysm, only SSD demonstrated the extension of the neck to a parent vessel, which was proved at surgery. Working views for EVT were deduced from 3D DSA findings in 20 of 21 aneurysms. The choice of the first coil was correct in 19 of 21 aneurysms. CONCLUSION: Three-dimensional DSA is valuable for evaluating the potential for EVT, finding a working view, and performing accurate measurements.

Adult↗
PubMed2001

Vasospasm after subarachnoid hemorrhage: interest in diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE: Vasospasm secondary to subarachnoid hemorrhage (SAH) is responsible for severe ischemic complications. Although effective, angioplasty must be performed at a very early stage to produce any clinical recovery. Diagnostic investigations to assess arterial narrowing (transcranial Doppler, angiography) or cerebral perfusion (xenon CT, single-photon emission CT) do not provide evidence of the extent of parenchymal ischemia. In stroke, diffusion-weighted MR imaging (DWI) appears to be the most sensitive procedure to detect cerebral ischemia. We studied asymptomatic vasospasm in patients with aneurysmal SAH to assess whether DWI provides predictive markers of silent ischemic lesions and/or progression toward symptomatic ischemia. METHODS: Seven asymptomatic vasospasm patients (average blood velocity rates >120 cm/s), 3 patients with symptomatic vasospasm, and 4 patients with SAH but without vasospasm were studied at regular intervals by DWI, and their apparent diffusion coefficients (ADCs) were calculated. RESULTS: All patients with vasospasm including those without symptoms presented abnormalities on DWI with a reduction of the ADC prevalently in the white matter. No such abnormalities were observed in patients without vasospasm. The abnormalities on DWI resolved completely in 4 of the 7 patients, with no parenchymal lesion. Resolution was partial in 3 patients whose white matter still presented residual round, focal ischemic lesions. CONCLUSIONS: Being able to correlate abnormalities on DWI with parenchymal involvement in asymptomatic patients would be of considerable clinical significance. It is hoped that larger studies will be undertaken to determine whether the ADC has a reversibility threshold, because this would facilitate patient management.

Adult↗
PubMed2001

Relevance of diffusion and perfusion weighted mri for endovascular treatment of vasospasm in subarachnoid hemorrhage.

The endovascular treatment of vasospasm is effective when implemented rapidly. However its indication often proves difficult on account of the lack of diagnostic arguments or the difficulties in obtaining them in daily practice. We report a case that highlights the relevance of MRI in the decision-making process. A 37-year-old patient presented with symptomatic vasospasm of the middle cerebral artery and was subjected to morphological, diffusion- and perfusion-weighted MRI. These investigations confirmed the presence of significant oligemia in the MCA territory and revealed onsetting diffusion disorders. Angioplasty was immediately performed, resulting in normal diffusion and hemodynamic parameters and complete regression of clinical signs. This case highlights the relevance of MRI when assessing vasospasm before treatment. Coupled with transcranial Doppler, it should help teams quickly select patients most likely to benefit from angioplasty.

Adult↗
PubMed2001

Acute spontaneous hemorrhage after embolization of brain arteriovenous malformation with N-butyl cyanoacrylate.

PURPOSE: To investigate factors predisposing to spontaneous hemorrhage in the early period after embolization of brain arteriovenous malformations (AVMs). METHODS: The authors report 15 cases of spontaneous hemorrhage in a consecutive series of 492 brain AVMs totally or partially treated with intranidal injections of a polymerizing mixture, from 1984 to June 1998. Retrospective analysis of the records was performed with special attention to the angio-architectural features before embolization, details of embolization procedures and induced angiographic modifications. RESULTS: Pre-embolization features of greater incidence were the presence of steal phenomena (87%), multiple feeding arteries (100%), a compact aspect of the nidus (93%), and lobar topography (87%). In most cases the volume of injected glue exceeded 1 ml (80%), venous embolization was significant (67%) and immediate angiographic control showed venous stagnation in and/or around the nidus (80%). Four patients were asymptomatic (incidental discovery on systematic CT at day 3). Among the remaining 11 symptomatic patients, 6 were operated to evacuate an intracerebral hematoma, outcome was good for 4, 5 were left with sequelae and 2 died. CONCLUSION: Spontaneous hemorrhagic complications affected 3.04% of embolized patients. The combination of certain angio-architectural features, significant venous embolization and persistent venous stagnation within the nidus seem to have some predictive value of high risk hemorrhage. In light of this, additional preventive measures must be taken and a neurosurgical team systematically kept on standby.

Acute Disease↗
PubMed2000

Ligand-binding affinity of the type 1 and 2 inositol 1,4,5-trisphosphate receptors: effect of the membrane environment.

The inositol 1,4,5-trisphosphate (InsP3) receptor is essential for Ca2+ release from intracellular stores. There are three InsP3 receptor types which are targets for several types of regulation. Ca2+, phosphorylation, and protein-protein interactions may contribute to the complex pattern of the Ca2+ signal in stimulated cells. Furthermore, the 3 receptor types could have different affinities for InsP3. We compared the affinities of the type 1 receptor from the cerebellum with the liver type 2 receptor both in their membrane environment and after isolation by immunoprecipitation. Measurements of [3H]InsP3 binding in a cytosol-like medium revealed that the Kd of the liver receptor (45 +/- 5 nM, N = 14) was higher than the Kd of the cerebellar receptor (28 +/- 3 nM, N = 9). Solubilization and immunopurification of the liver InsP3 receptor resulted in a 10-fold increase in its affinity for InsP3. The affinity of the cerebellar receptor did not change under these conditions. Therefore, the extraction of the liver and the cerebellar receptors from their membrane environments induced an inversion of their relative affinities. Treatment of liver membranes with low concentrations of detergents also increased the affinity for InsP3 binding. These data indicate that the type 1 and the type 2 InsP3 receptors have different affinities for InsP3 and that the properties of the type 2 receptor are strongly regulated by hydrophobic interactions within its membrane environment.

Animals↗