Biomedical subjects

M Cercignani

Publications and source records attributed to M Cercignani.

24 records · Page 2Linked to original sources

PubMed2000

Reproducibility of magnetization transfer ratio histogram-derived measures of the brain in healthy volunteers.

Using two MR scanners, we evaluated the intraobserver, interobserver, image-reimage, and interimager variabilities in the assessment of magnetization transfer ratio (MTR) histograms obtained monthly on four occasions from five healthy volunteers. With multiple observers, the mean coefficients of variations ranged from 2.2% to 8.2% for "pure" image-reimage variability, from 1.2% to 4.9% for interobserver variability, and from 2.1% to 4.9% for image-reimage variability. The mean intraobserver coefficients of variations were always lower than 1%. The mean coefficients of variations ranged from 10.2% to 14.6% for pure interimager variability and from 8.6% to 14.3% for interimager variability with multiple observers. Interimager variability accounted for 96.0% of the overall variability of average MTR, for 96.7% of peak location, and for 41.1% of the peak height. The use of different MR scanners is the main source of variability when obtaining MTR histograms.

Adult↗

PubMed1999

An optimized pulse sequence for isotropically weighted diffusion imaging.

Single-shot echo-planar imaging is becoming the most widely used technique for magnetic resonance diffusion imaging, since it enables measurement of diffusion coefficients in human brain without motion artifacts. However, its reliability is limited by geometrical distortions due to eddy currents. In this report, an isotropically weighted echo-planar pulse sequence, optimized to give the maximum signal-to-noise ratio in the computed trace image and designed to produce inherently low distortions, is presented. It is also shown how the residual translational distortion can be easily characterized and removed by postprocessing. A full characterization of the distortion artifact involves a few measurements on a phantom, in order to estimate the distortion as a function of slice orientation, which can then be used to correct any slice orientation. Results of applying the image translation correction to data collected from a patient are presented.

Artifacts↗

PubMed1999

Diffusion-weighted imaging in multiple sclerosis.

Diffusion-weighted imaging (DWI) provides a unique form of magnetic resonance (MR) contrast that enables the diffusional motion of water molecules to be quantitatively measured. As a consequence, DWI provides information about the orientation, size and geometry of brain structures. Cellular structures in the central nervous system restrict water molecular motion, and the apparent diffusion coefficient (ADC) is reduced compared to diffusion in bulk water. Pathological processes that modify tissue integrity, thus removing some of the "restricting" barriers, can result in increased ADC. Preliminary studies in multiple sclerosis (MS) using DWI showed that the ADC is higher in macroscopic lesions than in the normal appearing white matter (NAWM). The ADC is also dependent on the direction in which diffusion is measured, thus making comparison of ADC values meaningless without taking into account the measurement direction. One measurement of diffusion that is independent of the orientation of structures is provided by measuring the ADC in three orthogonal directions, and then averaging the results to form the mean diffusivity, D. We obtained DW scans from 35 patients with relapsing-remitting MS and 24 healthy volunteers. D was measured inside T2-visible lesions and regions located in different areas of the NAWM. D histograms from a large portion of the brain were created. MS lesions had a significantly higher D than NAWM. T1-hypointense lesions had the highest diffusion values, consistent with more severe tissue disruption. D was higher in the NAWM from patients than in the white matter from healthy controls. We also found significant differences between D histogram-derived measures from patients and controls, confirming the presence of diffuse damage in the brain of patients with MS.

Body Water↗

PubMed1999

Relevance of hypointense lesions on fast fluid-attenuated inversion recovery MR images as a marker of disease severity in cases of multiple sclerosis.

BACKGROUND AND PURPOSE: Hypointense lesions can be visible on fast fluid-attenuated inversion recovery (FLAIR) MR images of the brain of patients with multiple sclerosis (MS), and they may be produced by severely damaged white matter. To test the role of these lesions as an MR marker of MS severity, we assessed their relationship with clinical findings and other MR measures. METHODS: Using a 1.5-T scanner, dual-echo rapid acquisition with relaxation enhancement, fast FLAIR, and T1-weighted MR images (24 axial, 5-mm-thick contiguous interleaved sections) were obtained from 50 patients (32 with relapsing-remitting and 18 with secondary progressive MS). RESULTS: Hypointense lesions were visible on the fast FLAIR images of 19 patients (mean number of lesions, 7.8; range 1-22); their median load was 1.4 mL (range, 0.05-12.6 mL). The median lesion load was significantly higher in patients with secondary progressive MS than in those with relapsing-remitting MS on the T1-weighted images. Both the number and the load of hypointense lesions shown by fast FLAIR imaging were significantly higher in patients with secondary progressive MS. Significant correlations were found between Expanded Disability Status Scale scores and MR lesion load. A multivariate analysis showed that only the presence of hypointense lesions on fast FLAIR images significantly separated cases of relapsing-remitting MS from cases of secondary progressive MS (relative risk, 7.1; 95% confidence interval, 2.0-25.9). CONCLUSION: The presence of hypointense lesions on fast FLAIR images was a strong predictor of disease severity in cases of MS, although the low sensitivity of this approach might limit its use for the assessment of MS evolution.

Adult↗

PubMedDate not supplied

A comparison of MR imaging with fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences in the assessment of patients with multiple sclerosis.

BACKGROUND AND PURPOSE: Fast fluid-attenuated inversion-recovery (FLAIR) sequences are sensitive for detecting lesions in patients with multiple sclerosis (MS). More rapid fast-FLAIR imaging of the brain can be achieved by the concomitant use of half-Fourier acquisition single-shot turbo spin-echo (HASTE-FLAIR) and echo-planar imaging (EPI-FLAIR). The present study was performed in a large cohort of subjects to assess and compare the number and volume of brain lesions detected by the fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences in patients with MS. METHODS: Fast-FLAIR, HASTE-FLAIR, and EPI-FLAIR sequences were obtained from 46 consecutive MS patients. Lesions seen on each type of sequence were counted and classified by consensus by two observers. Lesion volumes were measured using a semiautomated segmentation technique based on local thresholding. RESULTS: The quality of the fast-FLAIR images was significantly better than that of HASTE-FLAIR and EPI-FLAIR images. Fast-FLAIR revealed significantly more lesions and higher lesion volumes than did HASTE-FLAIR and EPI-FLAIR. A similar number of large lesions was detected by the three sequences, but HASTE-FLAIR and EPI-FLAIR showed significantly fewer small and intermediate lesions than did fast-FLAIR. The number of lesions seen on HASTE-FLAIR and EPI-FLAIR images was similar. CONCLUSION: HASTE-FLAIR and EPI-FLAIR sequences revealed as many large MS lesions as fast-FLAIR. Because their acquisition times are only a fraction of that needed for fast-FLAIR sequences, they may be useful for making a rapid diagnosis of MS in uncooperative patients. Their reduced ability to detect smaller lesions indicates that they should not be used as a routine approach to imaging patients with MS.

Adult↗

PubMedDate not supplied

Hypercoagulable state in hypercholesterolemic subjects assessed by platelet-dependent thrombin generation: in vitro effect of cerivastatin.

BACKGROUND: Hypercholesterolemia is an important risk factor to develop acute thrombotic complications of atherosclerosis like to myocardial infarction and ischemic stroke. Platelets and coagulation factors are strictly involved in the genesis of such thrombotic events and their hyperactivity in hypercholesterolemic patients has been previously reported. Moreover some cholesterol-lowering molecules (statins) seem to be able of reducing platelet activity. METHODS: We performed platelet-dependent thrombin generation (colorimetric method) to assess the coagulative potential of 40 caucasian hypercholesterolemic subjects with respect to normal controls and to the grade of hypercholesterolemia. Moreover we observed the effect of platelets from hypercholesterolemics on thrombin generation in plasma from normal subjects. The effect of Cerivastatin on thrombin generation was evaluated too. RESULTS: Our data show an increased thrombin generation both in mild and high hypercholesterolemic subjects with respect to controls (424.6+/-30.5 vs. 197.1+/-27.4 mIU/ml). No significant difference in the amount of thrombin generation was found between mild and high hypercholesterolemics (399.6+/-20.7 vs. 440.2+/-21.4 mIU/ml). Platelets directly influence thrombin generation and they present an intrinsic hyperactivity that can be modulated by Cerivastatin (223.6+/-24.8 vs. 424.6+/-30.5 mIU/ml). CONCLUSIONS: Mild hypercholesterolemia is associated with an increased thrombinic potential that may be considered an added risk factor to develop thrombotic events. Platelets directly influences this hypercoagulative state and Cerivastatin is able to reduce thrombin generation by way of a direct interaction with platelets.

Blood Coagulation Disorders↗