Biomedical subjects
Publications and source records attributed to D Ducreux.
Functional MRI is a technique of imaging which is developing fast as it allows non-aggressive evaluation of brain functions. Diffusion, perfusion and activation are each used to study brain responsiveness to a given task. As a pretherapeutic routine investigation, in brain tumours, it can be helpful as an additional tool to morphological MRI in evaluating the prognosis of patients.
OBJECTIVES: To illustrate the value of diffusion tensor imaging and tractography in the diagnosis and follow-up of central pontine myelinolysis. CASE REPORT: We report a case of central pontine myelinolysis in a 29 year old woman, also anorexic, studied using MR Diffusion Tensor Imaging (DTI) and Fibre Tracking (FT) focused on the pons, and compared with the studies of 5 normal volunteers. Tractography showed a swollen aspect of the right corticospinal fiber tract correlating with mild left lower extremity deficit at clinical evaluation. The pontine fibers were posteriorly displaced but intact. The sensory tracts were also intact. Apparent Diffusion Coefficient values were increased and Fractional Anisotropy was decreased in the lesions. Follow up imaging showed persistent abnormal ADC and FA values in the pons although the left cortico-spinal tract returned to normal, consistent with the clinical outcome. CONCLUSION: Diffusion Tensor Imaging MR and Fiber tractography are a new method to analyse white matter tracts. It can be used to prospectively evaluate the location of white matter tract lesions at the acute phase of central pontine myelinolysis and follow up.
Spinal cord astrocytomas are rare neoplasms that can result in alteration of the spinal cord structural integrity, which can be assessed by using diffusion tensor imaging methods. Our objective was to visualize the deformation of the posterior spinal cord lemniscal and corticospinal tracts in 5 patients with low-grade astrocytomas compared with 10 healthy volunteers by using 3D fiber-tracking reconstructions.
BACKGROUND AND PURPOSE: Brain hypervascular diseases are complex and induce hemodynamic disturbances on brain parenchyma, which are difficult to accurately evaluate by using perfusion-weighted (PWI) MR imaging. Our purpose was to test and to assess the best AIF estimation method among 4 patients with brain hypervascular disease and healthy volunteers. METHODS: Thirty-three patients and 10 healthy volunteers underwent brain perfusion studies by using a 1.5T MR imaging scanner with gadolinium-chelate bolus injection. PWI was performed with the indicator dilution method. AIF estimation methods were performed with local, regional, regional scaled, and global estimated arterial input function (AIF), and PWI measurements (cerebral blood volume [CBV] and cerebral blood flow [CBF]) were performed with regions of interest drawn on the thalami and centrum semiovale in all subjects, remote from the brain hypervascular disease nidus. Abnormal PWI results were assessed by using Z Score, and evaluation of the best AIF estimation method was performed by using a no gold standard evaluation method. RESULTS: From 88% to 97% of patients had overall abnormal perfusion areas of hypo- (decreased CBV and CBF) and/or hyperperfusion (increased CBV and CBF) and/or venous congestion (increased CBV, normal or decreased CBF), depending on the AIF estimation method used for PWI computations. No gold standard evaluation of the 4 AIF estimates found the regional and the regional scaled methods to be the most accurate. CONCLUSION: Brain hypervascular disease induces remote brain perfusion abnormalities that can be better detected by using PWI with regional or regional scaled AIF estimation methods.
PURPOSE: Our aim was to study the fractional anisotropy (FA) variations and the fiber tracking (FT) patterns observed in patients with myelitis. MATERIAL AND METHODS: Fifteen patients with symptomatic myelitis and 11 healthy subjects were prospectively selected. We performed T2-weighted and diffusion tensor imaging on a 1.5T MR scanner. FA and apparent diffusion coefficient maps were computed in both healthy subjects and patients. In each patient, we performed FT to study pathologic aspects on this imaging method. FA data were analyzed by using z-scores. RESULTS: For the healthy subjects, averaged FA values ranged from 0.745 to 0.751. All abnormal areas seen on T2-weighted imaging had a significantly decreased FA value. In 9 patients (60%), FA maps showed decreased FA areas, whereas T2-weighted imaging findings were normal. These areas matched the neurologic deficit in 33%. Eighty percent of patients had multiple decreased FA areas. Five patients (33%) had increased FA values in normal T2-weighted areas. CONCLUSION: We observed specific FA and FT pattern variations in patients with myelitis.
We report here two cases of diffuse axonal injury (DAI) studied by MR diffusion tensor imaging (DTI) and fibre tracking (FT) focused on the corpus callosum. In one case, DTI and FT pattern matched the diagnosis of broken white matter tracts. In the other case there was a discrepancy between DTI and FT data that showed unaltered white matter tracts with the presence of intra-cellular oedema. These data suggested that DTI and FT are able to differentiate between traumatic cytotoxic oedema and broken fibres in the case of DAI.
Seizures, which may be the main expression of cerebral arteriovenous malformations (CAVM) can be difficult to control medically. Our goal was to use perfusion-weighted imaging (PWI) in correlation with clinical data to detect abnormal areas of the cerebrum related to a particular type of CAVM (proliferative angiopathy) and to study the pathophysiology. We use PWI, with a bolus injection of contrast medium, to investigate seven patients with proliferative angiopathy and fits producing language disturbance. Perfusion parameters were calculated using the first-pass moment theory. Five patients had perimalformative and/or contralateral abnormal areas with relative hyperperfusion (cerebral blood volume +20.7+/-16.2%, blood flow 92.5+/-68.8 ml/min/100 g). Areas of hypoperfusion and venous congestion were detected in two patients. One patient who underwent MRI after a severe focal deficit had no significant haemodynamic abnormality.
We report the MRI findings in an adult with epiglottitis. There was thickening of the epiglottis and left aryepiglottic fold. Management of this life-threatening condition requires imaging only when the diagnosis is uncertain or when an abscess or other complication is suspected.
The management of Brain Arteriovenous Malformations continues to be challenged by a lack of understanding and control of pathophysiological processes implied in the clinical symptoms. New data from functional MRI with diffusion-weighted, perfusion-weighted and neuronal activation highlight abnormal brain areas near or remote to the AVM nidus. Moreover, these techniques are able to show hemodynamic and neuronal adaptative phenomena involved in brain plasticity. They reflect the instantaneous hemodynamic brain conditions that may help to correlate the clinical symptoms with the anatomical and functional substratum and to influence any invasive therapy.
PURPOSE: MR based first-pass method can be utilized to obtain hemodynamic information in the head and neck region. The purpose of this study was to estimate the regional relative blood volume (rBV) in head and neck tumors, which is useful for tumor staging and tumor biopsy. METHODS: Eighteen patients with head and neck tumors (17 squamous cell carcinomas, 1 hemangiopericytoma) were studied on a 1.5-T system. Conventional T1-weighted MR images and T2-weighted images and sequential T2*-weighted images were obtained. During repetitive image sequence acquisition, a bolus (0.2 mmol/kg) of gadopentetate dimeglumine was mechanically injected. Image processing of the dynamic raw data was performed on a pixel-by-pixel basis. RESULTS: Regional relative blood volume maps of the head and neck were successfully reconstructed in all (18/18) patients. The regional relative blood volume values within the tumor area of squamous cell carcinoma were 7.0 +/- 2.8, normalized on muscle, whereas the rBV of a single hemangiopericytoma was 11.6. The difference of rBV values of tumor and muscle was highly significant at statistical evaluation (p < 0.001). CONCLUSIONS: Relative blood volume imaging of head and neck tumors is valid using MR-based first-pass method. This method provides hemodynamic information which is not available from conventional MR imaging and is promising for further characterization of head and neck tumors
Magnetic resonance imaging is the method of choice for the evaluation of brachial plexopathy. Knowledge of the anatomy and normal imaging appearance is required. High-resolution imaging technique is necessary with the use of adequate coils. Evaluation of the brachial plexus requires T1 weighted sequences in three plans, T2 weighted sequences with fat suppression and if necessary the study is completed with gadolinium injection sequences with fat suppression. A CISS sequence is used if a nerve root avulsion is suspected. The spatial resolution must be optimized with the use of adapted parameters. We illustrate a variety of pathologies that can involve the brachial plexus. The pathology includes trauma, primary (neurogenic tumors, lymphomatosis) or secondary tumors, radiation plexopathy or inflammatory polyneuropathy.
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Since conventional MRI fails to distinguish between the common neoplasm involving the corpus callosum, we explored the utility of diffusion weighted imaging and single-voxel proton spectroscopy in a case of corpus callosum lymphoma.
Our aim is to illustrate the contribution of MRI to diagnosis of lesions of the lower-limb nerve trunks. We report six patients who had clinical and electrophysiological examination for a peroneal or tibial nerve palsy. MRI of the knee showed in three cases a nonenhancing cystic lesion of the peroneal nerve suggesting an intraneural ganglion cyst, confirmed by histological study in one case. One patient with known neurofibromatosis had an enhancing nodular lesion of the peroneal nerve compatible with a neurofibroma. Two patients had diffuse hypertrophy with high signal on T2-weighted images, without contrast enhancement of the sciatic nerve or its branches. These lesions were compatible with localised hypertrophic neuropathy. In one case, biopsy of the superficial branch of the peroneal nerve showed insignificant axonal degeneration. MRI can provide information about the size and site of the abnormal segment of a nerve before treatment and can be used to distinguish different patterns of focal lesion.
PURPOSE: to explore with functional MRI cerebral areas involved in musical and lyrical sounds signal processing with the mental imagery method. MATERIAL: and METHODS: nine volunteers (mean age: 27 years old) underwent functional MRI with BOLD contrast at 1.5 T. Box-car paradigms of partial recollections of musical or lyrical memories tasks were performed. Statistical correlations mappings were calculated and superimposed on previously realigned anatomical reference imaging to observe activated cerebral areas. RESULTS: all except one subjects had activation areas in primary and secondary auditive cortices in the temporal Heschl gyrus and the Planum Temporale, unilaterally (n=2) or bilaterally (n=6) during both mental tasks. Contralateral activation improvement was observed in 4 cases when the lyrical tasks were performed. Temporal and insular regions involved in language processing were observed in eight of nine subjects. CONCLUSION: auditive mental imagery can show in functional MRI cerebral areas involved in auditive functions and some of the areas involved in language processing.
Seizures, the main expression of cerebral arteriovenous malformations (AVMs) can be difficult to control medically. We studied fMRI in correlation with clinical findings cerebral activation clusters patterns in relation with singular AVMs (proliferative angiopathy). We carried out blood oxygen-level dependent functional MRI (fMRI) in seven patients with language problems due to capillary ectasia with verbal fluency and repetition language tasks in box-car paradigms. fMRI maps were calculated with cross-correlation coefficients and superimposed on brain anatomy. Five patients had perimalformative and/or contralateral areas of ipsi- and contralateral activation clusters redistribution. One patient who underwent fMRI after a severe focal post-ictal deficit had total hemisphere contralateral activation clusters redistribution.
Proliferative angiopathy is an uncommon type of cerebral arteriovenous shunt characterized by an extensive capillary network with normal brain intermingled and few clinical symptoms (mostly seizures and headaches). This case report depicts an extensive proliferative angiopathy located in the right hemisphere. Its hemodynamic disturbances were studied with MR perfusion imaging (local or remote areas of increased time to peak, decrease ratio of signal, and relative regional cerebral blood volume values).
In a chronic alcoholic patient with progressive confusion, which was consistent with the clinical diagnosis of Wernicke encephalopathy, T2-weighted, FLAIR and diffusion weighted (DWI) MR imaging depicted brain abnormalities located in both medial thalamic nuclei. Apparent Diffusion Coefficient (ADC) measurements in these regions shown unexpected normal values, referring to Wernicke pathological findings and DWI data. DWI may be helpful to diagnose early basal nuclei abnormalities, but may fail to compute ADC values in these locations.