Search results for " MRI."
showing 10 items of 211 documents
Quantitative study of cardiac wall motion from cine-MRI using frequency-based optical flow methods
2010
The aim of this thesis is to study parietal desynchronisation of the left ventricle from conventional cine-MRI. The first part of our work consisted in the quantification of the left ventricle wall motion of the heart directly from conventional retrospective SSFP type cine-MRI sequences used in the study of cardiac function. The developed methods for measuring displacements within the images are frequency-based optical flow methods. These techniques seem to be particularly adapted to MRI specificities. We have demonstrated their robustness in the event of Rician noise and pixel intensity variations as a function of time. These variations are often associated with the through-plane motion of…
MR imaging of entrapment neuropathies of the shoulder
2010
Learning objectives Background Imaging findings OR Procedure details Conclusion Personal Information References
Rectal cancer: Assessment of response to neoadjuvant chemoradiation by dynamic contrast-enhanced MRI
2012
Purpose To assess pretreatment functional and morphological tumor characteristics with magnetic resonance imaging (MRI) in advanced rectal carcinoma and to identify factors predicting response to neoadjuvant chemoradiation. Materials and Methods In a prospective study, 95 patients with rectal carcinoma underwent dynamic contrast-enhanced MRI before and after chemoradiation. Quantitative parameters were derived from a pharmacokinetic two-compartment model. Tumors were also characterized with regard to mucinous status at pretreatment high-resolution MRI as nonmucinous or mucinous. Response to treatment was defined as a downshift in the local tumor stage. Results The parameter k21 (contrast me…
Peritumoral perfusion and proton spectroscopic MR imaging in the differentiation of gliomas and solitary metastases
2015
Purpose: To asses the value of peritumoural perfusion-weighted and proton spectroscopic MR imaging in preoperative grading of gliomas and in differentiating between primary gliomas and solitary metastases. Methods and Materials: Ten low-grade gliomas, eight high-grade gliomas, and ten metastases were prospectively evaluated with MR imaging, dynamic susceptibility contrast-enhanced perfusion imaging, and single-voxel proton MR spectroscopy before surgical resection or stereotactic biopsy. Maximal rCBV values and maximal Cho/Cr ratios were calculated from peritumoural region surrounding the tumour. Tumour grade presumed with these values was compared to histopathologic grading. Differences in…
Imaging of Substantia Nigra in Parkinson's Disease: A Narrative Review.
2021
Parkinson’s disease (PD) is a progressive neurodegenerative disorder, characterized by motor and non-motor symptoms due to the degeneration of the pars compacta of the substantia nigra (SNc) with dopaminergic denervation of the striatum. Although the diagnosis of PD is principally based on a clinical assessment, great efforts have been expended over the past two decades to evaluate reliable biomarkers for PD. Among these biomarkers, magnetic resonance imaging (MRI)-based biomarkers may play a key role. Conventional MRI sequences are considered by many in the field to have low sensitivity, while advanced pulse sequences and ultra-high-field MRI techniques have brought many advantages, partic…
Widespread white matter microstructural abnormalities in bipolar disorder: evidence from mega- and meta-analyses across 3033 individuals
2019
Fronto-limbic white matter (WM) abnormalities are assumed to lie at the heart of the pathophysiology of bipolar disorder (BD);\ud however, diffusion tensor imaging (DTI) studies have reported heterogeneous results and it is not clear how the clinical\ud heterogeneity is related to the observed differences. This study aimed to identify WM abnormalities that differentiate patients with\ud BD from healthy controls (HC) in the largest DTI dataset of patients with BD to date, collected via the ENIGMA network. We gathered\ud individual tensor-derived regional metrics from 26 cohorts leading to a sample size of N = 3033 (1482 BD and 1551 HC). Mean\ud fractional anisotropy (FA) from 43 regions of i…
Dysembryoplastic Neuroepithelial Tumor of the Brainstem
2007
Dysembryoplastic neuroepithelial tumor (DNT) is a clinically benign stable lesion, most frequently located in the temporal and frontal lobes, often responsible for epilepsy in young adults. We describe an unusual case of DNT in the brainstem of a 45-year-old woman. Brain MRI showed a multicystic-like lesion localized in the left inferior pons, involving the ipsilateral cerebellar peduncle and partially dislocating the fourth ventricle. The specific pattern of MRI and CT appearance of DNT and its benign course (our patient is clinically stable with unchanged MRI images at two year follow-up) may help differentiate this tumor from other lesions, i.e. ganglioglio-mas and glioneural malformati…
Rectal cancer: Dynamic contrast-enhanced MRI correlates with lymph node status and epidermal growth factor receptor expression
2013
Purpose To evaluate correlations between dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and clinicopathologic data as well as immunostaining of the markers of angiogenesis epidermal growth factor receptor (EGFR) and CXC-motif chemokine receptor 4 (CXCR4) in patients with rectal cancer. Materials and Methods Presurgical DCE-MRI was performed in 41 patients according to a standardized protocol. Two quantitative parameters (k21, A) were derived from a pharmacokinetic two-compartment model, and one semiquantitative parameter (TTP) was assessed. Standardized surgery and histopathologic examinations were performed in all patients. Immunostaining for EGFR and CXCR4 was performed an…
Angiogenesis of cancer of the cervix. Contrast-enhanced dynamic MRT, histological quantification of capillary density and lymph system infiltration
1998
Purpose: It was the aim of this project to examine (i) the relationships between contrast-enhanced dynamic MR imaging derived characteristics and histologic microvessel density counts – a recognized surrogate of tumor angiogenesis – from tumors in patients with primary or recurrent cancer of the uterine cervix, and (ii) to correlate these parameters with lymphatic involvement (i. e. lymphatic channels) to assess tumorbiological aggressiveness in terms of lymphatic spread. Materials and methods: Pharmacokinetic MR imaging parameters (amplitude A, exchange rate constant k 21) were derived from contrast-enhanced dynamic MR imaging in thirty-three patients with biopsy proven cancer of the uteri…
A multicenter measurement of magnetization transfer ratio in normal white matter
1999
To assess the importance of intercenter variations when measuring magnetization transfer ratio (MTR) in the brain, six European centers measured MTR in normal white matter. MTR ranged from 9 to 51 percent units (25 sequences). The effective flip angle of the saturating pulse divided by the pulse repetition time (ENRsat degrees/msec) was a good predictor of MTR (MTR = 3.25 ENRsat).