Utilidad práctica de la dinámica cuantitativa de LCR en la malformación de Chiari tipo I y la siringomielia. Reporte de 5 casos / Practical utility of quantitative CSF dynamics in type I Chiari malformation and syringomyelia. Report of 5 cases

Introducción: el tratamiento de la malformación de Chiari I (MCI) y/o la siringomielia (SM) es controversial. La dinámica cuantitativa del LCR a nivel cráneo espinal es una alternativa que podría orientar la terapéutica. El objetivo de esta publicación es describir 5 casos en donde la utilización de la dinámica de LCR permitió guiar el tratamiento. Material y método: se revisaron las historias clínicas de 5 casos (edad media: 39 años / 3 mujeres y 2 varones). Todos fueron estudiados con RM en contraste de fase. El diagnóstico fue de MCI (1 caso) y SM (3 casos) o solo SM (1 caso). Sólo 2 casos con MCI+SM fueron intervenidos (descompresión + plástica dural). Todos fueron seguidos entre 1,5 y 6 años. Resultados: caso 1 (MCI) la velocidad del LCR fue normal por lo que su cefalea fue tratada médicamente con buenos resultados; caso 2 (MCI+SM) la velocidad estuvo aumentada por lo que fue intervenida controlándose los síntomas y la SM; caso 3 (MCI +SM) la velocidad fue normal siendo su diagnóstico compatible con síndrome post-siringomiélico; caso 4 (SM) la velocidad estuvo aumentada a nivel C5-C6 siendo su diagnóstico compatible con una SM espinal primaria; caso 5 (CMI + SM) luego de la intervención se observó que las velocidades y la SM tardaron 16 meses en normalizarse. Conclusión: en los casos descriptos la dinámica de LCR permitió realizar el diagnóstico correcto, determinar la conveniencia de realizar la cirugía, encontrar la causa y controlar la evolución postoperatoria(AU)

Background: the treatment of Chiari malformation I (CMI) and/or syringomyelia (SM) is controversial. The quantitative dynamics of CSF at the craniospinal level is an alternative that could guide therapy. The objective of this publication is to describe 5 cases in which the use of CSF dynamics allowed guiding the treatment. Methods: the medical records of 5 cases (mean age: 39 years / 3 women and 2 men) were reviewed. All were studied with MRI in phase contrast. The diagnosis was CMI (1 case) and SM (3 cases) or only SM (1 case). Only 2 cases with CMI+SM underwent surgery (decompression + duraplasty). All were followed between 1.5 and 6 years. Results: case 1 (CMI) the velocity of the CSF was normal, so his headache was treated medically with good results; case 2 (CMI+SM) the velocity was increased so it was intervened controlling the symptoms and the SM; case 3 (CMI +SM) the velocity was normal, its diagnosis being compatible with post-syringomyelic syndrome; case 4 (SM) the velocity was increased at the C5-C6 level, its diagnosis being compatible with a primary spinal SM; case 5 (CMI + SM) after the intervention it was observed that the velocities and the SM took 16 months to normalize. Conclusion: in the cases described, the CSF dynamics allowed the correct diagnosis to be made, to determine the advisability of performing surgery, to find the cause and to control the postoperative evolution(AU)

4D flow MRI: impact of region of interest size, angulation and spatial resolution on aortic flow assessment.

Objectives.In cardiovascular magnetic resonance, the 3D time-resolved phase-contrast technique, also known as 4D flow, is gaining increasing attention due to applications that exploit three-directional velocity encoding throughout the cardiac cycle. Blood flow volume assessment usually requires an expert to draw regions of interest (ROI) around the vessel cross section, whereas the errors involved in this estimation have not been thoroughly investigated. Our objective is to quantify the influence of ROI sizing, angulation and spatial resolution of the reconstructed plane employed in blood flow measurements using 4D flow.Approach.Three circular ROIs were drawn around the ascending, arch and descending aorta of healthy volunteers (n= 27) and patients with a dilated ascending aorta or bicuspid valve (n= 37). We applied systematic changes of ROI diameter (up to ±10%), tilt angle (up to ±25°) and spatial resolution (from 0.25 to 2 mm) of the reconstructed oblique planes, calculating the effects on net, forward and backward blood flow volumes.Main results.Patients had a larger ascending aorta than healthy volunteers with similar ages and male sex proportion (60 ± 15 y.o. vs 58 ± 16 y.o. and 84% vs 70%, respectively). Higher forward and backward flow volumes were observed in the ascending aorta and the aortic arch of the patients with respect to controls (p< 0.001), whereas net volumes were similar: 74.0 ± 20.8 ml versus 75.7 ± 21.8 ml (p= 0.37), respectively. The ascending aorta was the most sensitive to ROI modifications. Changes of ±10% in the ROI diameter and ±25° in tilt angles produced flow volume differences of up to 9 ml (10%) and 18 ml (15%) in controls and patients, respectively. Modifying the reconstructed planes spatial resolution produced flow volume changes below 2 ml.Significance.Since the setting of the ROI size and plane angle could produce errors that represent up to 20% of the forward and/or backward aortic flow volume, a good standardization for vessel segmentation and plane positioning is desirable.

Automatic correction of background phase offset in 4D-flow of great vessels and of the heart in MRI using a third-order surface model.

OBJECTIVE: To evaluate an automatic correction method for velocity offset errors in cardiac 4D-flow acquisitions. MATERIALS AND METHODS: Velocity offset correction was done in a plane-by-plane scheme and compared to a volumetric approach. Stationary regions were automatically detected. In vitro experiments were conducted in a phantom using two orientations and two encoding velocities (Venc). First- to third-order models were fit to the time-averaged images of the three velocity components. In vivo experiments included realistic ROIs in a volunteer superimposed to a phantom. In 15 volunteers, blood flow volume of the proximal and distal descending aorta, of the pulmonary artery (Qp) and the ascending aorta (Qs) was compared. RESULTS: Offset errors were reduced after correction with a third-order model, yielding residual phantom velocities below 0.6 cm/s and 0.4% of Venc. The plane-by-plane correction method was more effective than the volumetric approach. Mean velocities through superimposed ROIs of a volunteer vs phantom were highly correlated (r2 = 0.96). The significant difference between proximal and distal descending aortic flows was decreased after correction from 8.1 to - 1.4 ml (p < 0.001) and Qp/Qs reduced from 1.08 ± 0.09 to 1.01 ± 0.05. DISCUSSION: An automatic third-order model corrected velocity offset errors in 4D-flow acquisitions, achieving acceptable levels for clinical applications.

Aqueductal Cerebrospinal Fluid Stroke Volume Flow in a Rodent Model of Chronic Communicating Hydrocephalus: Establishing a Homogeneous Study Population for Cerebrospinal Fluid Dynamics Exploration.

BACKGROUND: Idiopathic normal pressure hydrocephalus (iNPH) is a cause of dementia that can be reversed when treated timely with cerebrospinal fluid (CSF) diversion. Understanding CSF dynamics throughout the development of hydrocephalus is crucial to identify prognostic markers to estimate benefit/risk to shunts. OBJECTIVE: To explore the cerebral aqueduct CSF flow dynamics with phase-contrast magnetic resonance imaging (MRI) in a novel rodent model of adult chronic communicating hydrocephalus. METHODS: Kaolin was injected into the subarachnoid space at the convexities in Sprague-Dawley adult rats. 11.7-T Bruker MRI was used to acquire T2-weighted images for anatomic identification and phase-contrast MRI at the cerebral aqueduct. Aqueductal stroke volume (ASV) results were compared with the ventricular volume (VV) at 15, 60, 90, and 120 days. RESULTS: Significant ventricular enlargement was found in kaolin-injected animals at all times (P < 0.001). ASV differed between cases and controls/shams at every time point (P = 0.004, 0.001, 0.001, and <0.001 at 15, 60, 90, and 120 days, respectively). After correlation between the ASV and the VV, there was a significant correlation at 15 (P = 0.015), 60 (P = 0.001), 90 (P < 0.001), and 120 days. Moreover, there was a significant positive correlation between the VV expansion and the aqueductal CSF stroke between 15 and 60 days. CONCLUSIONS: An initial active phase of rapid ventricular enlargement shows a strong correlation between the expansion of the VV and the increment in the ASV during the first 60 days, followed by a second phase with less ventricular enlargement and heterogeneous behavior in the ASV. Further correlation with complementary data from intracranial pressure and histologic/microstructural brain parenchyma assessments are needed to better understand the ASV variations after 60 days.

Relative pressure estimation from velocity measurements in blood flows: State-of-the-art and new approaches.

The relative pressure difference across stenotic blood vessels serves as an important clinical index for the diagnosis of many cardiovascular diseases. While the clinical gold standard for relative pressure difference measurements is invasive catheterization, Phase-Contrast Magnetic Resonance Imaging has emerged as a promising tool for enabling a noninvasive quantification, by linking highly spatially resolved velocity measurements with relative pressures via the incompressible Navier-Stokes equations. In this work, we provide a review and analysis of current methods for relative pressure estimation and propose 3 additional techniques. Methods are compared using synthetic data from numerical examples, and sensitivity to subsampling and noise was explored. Through our analysis, we verify that the newly proposed approaches are more robust with respect to spatial subsampling and less sensitive to noise and therefore provide improved means for estimating relative pressure differences noninvasively.