Ilana Idy-Peretti

Temporal and spatial assessment of normal cerebrospinal fluid dynamics with MR imaging

The purpose of this study was to measure normal cerebrospinal fluid (CSF) pulsations within the intracranial and upper cervical subarachnoid spaces and the ventricular system. Phase contrast cine MR sequences were performed in sagittal and axial planes on 13 volunteers with flow encoding in the craniocaudal direction. CSF pulsations displayed considerable variations in healthy subjects, depending both on measurements localization and subjects, with CSF peak velocities ranging from 0 to 7 cm/s. In the subarachnoid spaces, the highest velocities occurred in the anterior location and increased from the cerebellar pontine angle cisterns towards the lower cervical spaces. In the ventricular system, the highest velocities occurred through the aqueduct of Sylvius. CSF flow within the third ventricle seemed to reflect a circular motion. There was a caudal net CSF flow in the aqueduct whereas in the upper cervical spaces net CSF flow was caudal anteriorly and cranial laterally. Velocity profiles of CSF pulsations demonstrated arterial morphology. After the R wave, caudal systolic motion was first observed in the posterior subarachnoid spaces, soon after in the anterior subarachnoid spaces and later in the ventricular system. Considering the morphology of CSF pathways, three successively initiated phenomena may explain the temporal course of CSF motion: the systolic expansion of the main arteries at the base of the brain, the systolic expansion of the cerebrospinal axis and, finally, the systolic expansion of the choroid plexuses.

Standard and high resolution magnetic resonance imaging of glomus tumors of toes and fingertips

BACKGROUND High-resolution magnetic resonance imaging (MRI) of subungual glomus tumors has been recently reported. OBJECTIVE Our purpose was to compare high-resolution MRI and standard MRI for the diagnosis of 44 glomus tumors of the toes and fingertips. METHODS Glomus tumors (11 cases) were first examined by MRI with a commercial surface coil (set 1). Thirty-three other glomus tumors and one tumor from set 1 were then examined with a high-resolution module designed for skin imaging (set 2). RESULTS All 44 glomus tumors were identified with MRI. The limits of the tumors were detected in 54% of set 1 and 100% of set 2. A capsule was present in most cases, but was incomplete or absent in eight cases. Subtypes of glomus tumors were more easily differentiated in set 2. CONCLUSION Standard MRI was adequate to detect glomus tumors, but high-resolution MRI assessed tumor characteristics more accurately.

Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus.

Henry-Feugeas MC, Idy-Peretti I, Baledent O, et al. Cerebrospinal fluid flow waveforms: MR analysis in chronic adult hydrocephalus. Invest Radiol 2001;36:146–154. rationale and objectives. To analyze changes in cere-brospinal fluid (CSF) hydrodynamics in chronic adult hydrocephalus. methods.Phase-contrast cine-MR acquisitions were used to explore the ventricular system and the upper ventral cervical spaces of 16 patients. The aqueductal jet was explored in 32 control subjects. results.The duration of pulsatile caudal CSF flow (ie, CSF systole) was abnormally short in patients with active idiopathic and obstructive hydrocephalus. The duration of CSF cervical systole was normal in patients with stable hydrocephalus. The aqueductal stroke volume could be increased in stable communicating hydrocephalus. Patients who responded to shunting had shortened CSF systoles and hyperpulsatile ventricular patterns. Successful CSF diversion resulted in longer CSF systoles and CSF ventricular patterns that were no longer hyperpulsatile. conclusions.Magnetic resonance analysis of CSF flow can show craniospinal dissociation and limitation of CSF outflow from the ventricles in both obstructive and communicating hydrocephalus; it should help determine the response to shunting in communicating hydrocephalus.

Intracranial fluid dynamics in normal and hydrocephalic states: Systems analysis with phase-contrast magnetic resonance imaging

Objective: To present a novel magnetic resonance (MR) method of analysis of cerebrospinal fluid (CSF) flow dynamics. Methods: Fifty-one subjects were explored with phase-contrast cine MR imaging. There were 36 volunteers, 9 patients with normal pressure hydrocephalus (NPH), and 6 patients with asymptomatic ventricular dilation (VD). The transfer function XFRA/CSF from the arterial pulse waves (APWs) and the CSF pulse waves (CSFPWs) and the transfer function XFRCSF/SS from the CSF pulse waves (CSFPWs) and the sagittal sinus pulse waves (SSPWs) were studied separately. Results: There was a significant difference in the amplitude spectrum of the XFRA/CSF of patients with VD and volunteers (P < 0.05) and in that of patients with NPH and volunteers (P = 0.005). The amplitude of the fundamental frequency was higher in the NPH group than in the VD group (P = 0.02). In patients with NPH, the amplitude spectrum of XFRCSF/SS showed an attenuation of the pulse wave components that significantly differed from the observed amplification in healthy subjects (P = 0.009) and patients with VD (P = 0.012). Conclusion: This systems analysis method could help to detect increased venous compliance in VD and decreased venous compliance in NPH.

MR imaging of hemophilic arthropathy of the knee: Classification and evolution of the subchondral cysts

Magnetic resonance imaging was performed to assess the subchondral bone of the knee in 64 patients with severe hemophilia A. Using this method, subchondral cysts could be detected and evaluated. We separated the cysts into four classes (LL, LH, HH, C) depending on their signal intensities on T1- and T2-weighted images. Follow-up studies, performed on 25 patients during a period of 10-30 mo after the initial examination, suggest that these four classes of cysts correspond to four successive stages. Morphological changes within a class of cysts were also observed. Although histological confirmation was not possible, this study demonstrated that magnetic resonance imaging allows a better understanding of the pathophysiology and the natural evolution of the subchondral cysts in hemophilic arthropathy.

Study of brain white matter anisotropy

An in vitro study to detect brain white matter anisotropy is presented. Porcine cylindrical samples were compressed (0.5 mm/mn) in a testing apparatus composed of a testing machine combined with a precision balance. Two different types of samples were harvested: 1) cut in parallel and 2) perpendicular to axon fibers present in white matter. For an elongation of 0 to 25% white matter exhibited isotropy. For deformation superior to 25%, the load versus elongation curves diverged increasingly, just to a difference of 37% between the samples of the two perpendicular directions for 35% of elongation, respectively.

Numerical study of the cerebrospinal fluid (CSF) dynamics under quasistatic condition during a cardiac cycle

We present a method to perform a numerical simulation of the flow dynamics of cerebrospinal fluid (CSF) based on anatomical magnetic resonance images (MRI). The computational fluid dynamics (CFD) software, written in language C, integrates different numerical schemes to solve the governing equations. The time derivatives were discretized using the Crank-Nicolson scheme. The equation of continuity was modified by introducing an artificial compressibility and discretized by a finite difference scheme. The meshed boundary of the CSF was immersed in a marker-and-cell staggered grid to take into account the fluid-structure interactions. Equations of hydrodynamics were solved with an iterative method under different quasi-static conditions. The anatomical basis of our simulations was generated from individual MRI scans. The surface of the anatomical flow channels of interest was extracted by segmentation and triangulated. In parallel to the acquisition of the anatomical data, CSF flow has been measured by MRI. To characterize a whole cardiac cycle, sixteen equidistant velocity measurements have been performed. In addition, a home made software was implemented to visualize computed data (velocities, pressure).