ICP Monitoring and Phase-Contrast MRI to Investigate Intracranial Compliance.

OBJECTIVE: The amplitude of intracranial pressure (ICP) can be measured by ICP monitoring. Phase-contrast magnetic resonance imaging (PCMRI) can quantify blood and cerebrospinal fluid (CSF) flows. The aim of this work was to investigate intracranial compliance at rest by combining baseline ICP monitoring and PCMRI in hydrocephalus patients. MATERIALS AND METHODS: ICP monitoring was performed before infusion testing to quantify ΔICP_rest at the basal condition in 33 suspected hydrocephalus patients (74 years). The day before, patients had had a PCMRI to assess total cerebral blood flow (tCBF), intracranial blood volume change (stroke volume SVblood), and cervical CSF volume change (the stroke volume CSV). Global (blood and CSF) intracranial volume change (ΔIVC) during each cardiac cycle (CC) was calculated. Finally, Compliance: C_rest = ΔIVC/ΔICP_rest was calculated. The data set was postprocessed by two operators according to blind analysis. RESULTS: Bland-Altman plots showed that measurements presented no significant difference between the two operators. ΔICP_rest = 2.41 ± 1.21 mmHg, tCBF = 469.89 ± 127.54 mL/min, SVblood = 0.82 ± 0.32 mL/cc, CSV = 0.50 ± 0.22 mL/cc, ΔIVC = 0.44 ± 0.22 mL, and C_rest = 0.23 ± 0.15 mL/mmHg. There are significant relations between SVblood and CSV and also SVblood and tCBF. CONCLUSIONS: During "basal" condition, the compliance amplitude of the intracranial compartment is heterogeneous in suspected hydrocephalus patients, and its value is lower than expected! This new parameter could represent new information, complementary to conventional infusion tests. We hope that this information can be applied to improve the selection of patients for shunt surgery.

Perfusion magnetic resonance imaging in pediatric brain tumors.

PURPOSE: The use of DSC-MR imaging in pediatric neuroradiology is gradually growing. However, the number of studies listed in the literature remains limited. We propose to assess the perfusion and permeability parameters in pediatric brain tumor grading. METHODS: Thirty children with a brain tumor having benefited from a DSC-MR perfusion sequence have been retrospectively explored. Relative CBF and CBV were computed on the ROI with the largest lesion coverage. Assessment of the lesion's permeability was also performed through the semi-quantitative PSR parameter and the K2 model-based parameter on the whole-lesion ROI and a reduced ROI drawn on the permeability maps. A statistical comparison of high- and low-grade groups (HG, LG) as well as a ROC analysis was performed on the histogram-based parameters. RESULTS: Our results showed a statistically significant difference between LG and HG groups for mean rCBV (p < 10-3), rCBF (p < 10-3), and for PSR (p = 0.03) but not for the K2 factor (p = 0.5). However, the ratio K2/PSR was shown to be a strong discriminating factor between the two groups of lesions (p < 10-3). For rCBV and rCBF indicators, high values of ROC AUC were obtained (> 0.9) and mean value thresholds were observed at 1.07 and 1.03, respectively. For K2/PSR in the reduced area, AUC was also superior to 0.9. CONCLUSIONS: The implementation of a dynamic T2* perfusion sequence provided reliable results using an objective whole-lesion ROI. Perfusion parameters as well as a new permeability indicator could efficiently discriminate high-grade from low-grade lesions in the pediatric population.

Impact of duration of symptoms on CSF dynamics in idiopathic normal pressure hydrocephalus.

OBJECTIVE: Cerebrospinal fluid (CSF) pressure-volume compensation may change over time as part of normal ageing, where the resistance to CSF outflow increases and the formation of CSF decreases with age. Is CSF compensation dependent on duration of symptoms in idiopathic normal pressure hydrocephalus (iNPH)? METHODS: We investigated 92 patients presenting with iNPH. Mean age was 73 (range 47-86). There were 60 men and 32 women. They all presented with gait disturbance and ventricular dilatation. Memory deficit occurred in 72% and urinary incontinence in 52% of patients. All patients underwent computerized CSF infusion tests. Sixty-four shunted patients were available for follow-up, and their improvement was expressed using the NPH score. RESULTS: Mean intracranial pressure (ICP) was 10.1±5.1 mmHg, and mean resistance to CSF outflow was 17.3±5.2 mmHg/(ml/min). Mean duration of symptoms was 24±19 months (range from 2 weeks to 86 months). Baseline ICP, magnitude of ICP pulse waveform, brain compliance and improvement after shunting (72% of patients improved) did not exhibit any dependency on the duration of symptoms. The resistance to CSF outflow showed a strong tendency to decrease in time with the duration of symptoms beyond 2 years (R= -0.702; P<0.005). CONCLUSION: This is a preliminary observation, and it suggests that for patients with duration of symptoms longer than 2-3 years, the threshold for normal resistance to CSF outflow should be duration-adjusted.

Role of flow magnetic resonance imaging in the monitoring of facial allotransplantations: preliminary results on graft vasculopathy.

Chronic vascular rejection characterized by the myointimal proliferation of smooth muscle cells that progressively obstruct the arterial graft lumen may become the main cause of long-term graft loss in vascularized composite allotransplantation (VCA), as observed in solid organ transplantation. As such, new diagnostic tools are required. The objective of this study was to evaluate the usefulness of flow magnetic resonance imaging (MRI) in the qualitative and quantitative monitoring of VCA in three patients transplanted between 2005 and 2012. Seven flow MRI acquisitions were performed concurrently with standardized clinical and histological monitoring between 2015 and 2017. A progressive reduction in the average flow rate and intraluminal diameter of the arterial pedicle of the grafts was demonstrated. During follow-up, two patients developed chronic vascular rejection requiring partial resection of the graft. For these patients, flow MRI acquisitions were characterized by a significant reduction in vascular signal, with a reduction in intravascular flow prior to anatomical injury. The results of this study confirm the feasibility of reproducible, non-invasive, and non-operator-dependent morphometric and haemodynamic radiological analysis, providing clinicians with new information on the vascular status of VCA over time and offering the prospect of an imaging technique specific to vascular outflow.

Biomechanical response of the CNS is associated with frailty in NPH-suspected patients.

Frailty is known to predict dementia. However, its link with neurodegenerative alterations of the central nervous system (CNS) is not well understood at present. We investigated the association between the biomechanical response of the CNS and frailty in older adults suspected of normal pressure hydrocephalus (NPH) presenting with markers of multiple co-existing pathologies. The biomechanical response of the CNS was characterized by the CNS elastance coefficient inferred from phase contrast magnetic resonance imaging and intracranial pressure monitoring during a lumbar infusion test. Frailty was assessed with an index of health deficit accumulation. We found a significant association between the CNS elastance coefficient and frailty, with an effect size comparable to that between frailty and age, the latter being the strongest known risk factor for frailty. Results were independent of CSF dynamics, showing that they are not specific to the NPH neuropathological condition. The CNS biomechanical characterization may help to understand how frailty is related to neurodegeneration and detect the shift from normal to pathological brain ageing.

[Acute CSF changes in the mesencephalon aqueduct after subarachnoid hemorrhage as measured by PC-MRI]. / Caractérisation des perturbations du flux de LCS dans l'aqueduc du mésencéphale par IRM-CP à la phase aiguë de l'hémorragie méningée.

PURPOSE: Determining acute intracranial hydrodynamic changes after subarachnoid hemorrhage through an analysis of the CSF stroke volume (SV) as measured by phase-contrast MRI (PC-MRI) in the mesencephalon aqueduct. METHOD: A prospective study was performed in 33 patients with subarachnoid hemorrhage. A PC-MRI imaging study was performed n the acute phase (< 48 hours). CSF flow was measured in the aqueduct. The appearance of acute hydrocephalus (HCA) was then compared with data on CSF flow, and the location of the intraventricular and perimesencephalic bleeding. RESULTS: CSF analysis was performed on 27 patients, 11 of whom presented with an acute HCA. All 11 patients had an abnormal SV in the aqueduct: patients with a communicating HCA had an increased SV (n=8); and patients with a noncommunicating HCA had a nil SV (n=3). Patients with a normal SV in the aqueduct did not develop an acute HCA. Intraventricular bleeding significantly led to HCA (P=0.02), which was of the communicating type in 70% of cases. CONCLUSION: Subarachnoid hemorrhage leads to intracranial CSF hydrodynamic modifications in the aqueduct in the majority of patients. CSF flow can help us to understand the mechanism of the appearance of acute HCA. Indeed, hydrocephalus occurred - of the communicating type in most cases - even in the presence of intraventricular bleeding.

Contribution of flow MRI in the therapeutic management of middle face high flow arteriovenous malformation: A case report.

BACKROUND: The radiosurgical management of high flow arteriovenous malformations (HFAVM) in the "destructive" stage requires a precise hemodynamic and anatomical assessment. PATIENT AND METHODS/CASE REPORT: We report the case of a 32 years-old patient with a large ulcerated face HFAVM, on which Doppler ultrasound was impossible to perform. We show that, by combining 3D PCA and 2D CINE PC-MRI sequences, magnetic resonance imaging is capable to provide a complete morphometric and velocimetric mapping of the nidus and feeding arteries of the HFAVM. CONCLUSION: Although Doppler ultrasound is the reference examination in the HFAVM, Flow MRI without contrast agent provides an advantageous alternative to assess vascular pathologies and choose the therapeutic strategy.

Does Phase-Contrast Imaging through the Cerebral Aqueduct Predict the Outcome of Lumbar CSF Drainage or Shunt Surgery in Patients with Suspected Adult Hydrocephalus?

BACKGROUND AND PURPOSE: Radiologic imaging plays a key role in diagnosing chronic adult hydrocephalus, but its role in predicting prognosis is still controversial. We sought to evaluate the effectiveness of cardiac-gated phase-contrast MR imaging through the cerebral aqueduct in predicting the clinical response to diagnostic lumbar puncture/lumbar drainage and shunt surgery in suspected adult hydrocephalus. MATERIALS AND METHODS: In this retrospective study, the phase-contrast MR imaging of 185 patients with suspected chronic adult hydrocephalus was evaluated using the CSF Flow software package. Decision-making for shunt placement was performed in this cohort on the basis of clinical assessment alone without the availability of quantitative phase-contrast MR imaging results. We recorded the response to lumbar puncture or lumbar drainage and shunt surgery using quantitative tests such as the Tinetti Test, the Timed Up and Go, and the Mini-Mental State Examination and qualitative measures of gait, urinary, and cognitive symptom improvement before and after lumbar puncture/lumbar drainage and shunt surgery. Quantitative analysis of phase-contrast MR imaging was compared with clinical outcome measures. RESULTS: Both CSF stroke volume and flow rate overlapped between lumbar puncture/lumbar drainage responders and nonresponders. There was also a significant overlap between shunt responders and nonresponders. Aqueductal stroke volume or flow rate alone was a poor predictor of lumbar puncture/lumbar drainage and shunt surgery response. Quantitative clinical measures after lumbar puncture/lumbar drainage were better predictors of shunt response. CONCLUSIONS: This study suggests that the results of phase-contrast MR imaging through the cerebral aqueduct alone should not be used to select patients for diagnostic or therapeutic CSF diversion.

Use of Phase-Contrast MRA to Assess Intracranial Venous Sinus Resistance to Drainage in Healthy Individuals.

BACKGROUND AND PURPOSE: Resistance to blood flow in the cerebral drainage system may affect cerebral hemodynamics. The objective of the present study was to use phase-contrast MRA to quantify resistance to drainage of blood across branches of the venous sinus tree and to determine whether the resistance to drainage values correlated with internal jugular vein outflows. MATERIALS AND METHODS: We performed whole-head phase-contrast MRA and 2D phase-contrast MR imaging in 31 healthy volunteers. Vascular segmentation was applied to the angiograms, and the internal jugular vein velocities were quantified from the flow images. Resistance to drainage across branches of the venous sinus tree was calculated from the segmented angiograms, by using the Poiseuille equation for laminar flow. Correlations between the values of resistance to drainage and internal jugular vein outflow measurements were assessed by using the Spearman ρ. RESULTS: The overall mean resistance to drainage of the venous sinus tree was 24 ± 7 Pa s/cm3. The mean resistance to drainage of the right side of the venous sinus tree was 42% lower than that of the left side (P < .001). There were negative correlations between the values of resistance to drainage and internal jugular vein outflows on both the left side of the venous sinus tree (R = -0.551, P = .002) and the right side (R = -0.662, P < .001). CONCLUSIONS: Phase-contrast MRA is a noninvasive means of calculating the resistance to drainage of blood across the venous sinus tree. Our approach for resistance to drainage quantification may be of value in understanding alterations in the cerebral venous sinus drainage system.

Value of phase contrast magnetic resonance imaging for investigation of cerebral hydrodynamics.

OBJECTIVE: Phase Contrast Magnetic Resonance Imaging (PCMRI) is a noninvasive technique that can be used to quantify variations of flow during the cardiac cycle. PCMRI allows investigations of blood flow dynamics in the main arteries and veins of the brain but also the dynamics of cerebrospinal fluid. These cerebral flow investigations provide a description of the regulation mechanisms of intracranial pressure during the cardiac cycle. The objective of this paper is to describe the contribution of this technique in diseases related to disorders of cerebral hydrodynamics in the light of 5 clinical cases. METHOD: Flow measurements were performed using PCMRI sequences on a 1.5 Tesla MR imager in 4 patients with symptomatic ventricular dilation and 1 patient with a syringomyelic cavity. RESULTS: Flow quantification in these 5 patients, representative of the diseases mainly concerned by cerebral hydrodynamics, is useful to guide the indication for ventricular shunting in patients with hydrocephalus, to demonstrate obstruction of the cerebral aqueduct, to demonstrate recirculation of ventricular CSF after ventriculostomy and to characterize the dynamic features of CSF inside a spinal cavity. CONCLUSION: PCMRI, now available to neurosurgeons, is complementary to morphological MR and provides quantitative information on cerebral hydrodynamics. This information is mainly used to confirm alteration of CSF flow in the cerebral and spinal compartments. PCMRI is also a functional tool to better understand the pathophysiology of hydrocephalus and syringomyelia.

[Cerebrospinal fluid flow imaging in the meningeal hemorrhage]. / Imagerie de l'hydrodynamique cérébrale dans les hémorragies méningées.

BACKGROUND AND PURPOSES: Cerebrospinal fluid (CSF) flow oscillations are synchronized with cerebral blood flow and are also involved in the control of variations of intracranial pressure during the cardiac cycle. The aim of this study was to investigate the possible alterations of CSF flow dynamics during the acute phase of meningeal hemorrhage (MH). METHODS: Eleven patients with MH confirmed by computed tomography (CT) scan were examined by MR imaging, which comprised morphological sequences and flow dynamic sequences for quantification of CSF oscillations and cerebral blood flow rates. CSF oscillations were recorded at the cerebral aqueduct and C2-C3 subarachnoid space (SAS), where a vascular sequence was also performed to quantify artery blood flow. These results were compared to oscillations of a population of 44 control subjects and a difference of at least two standard deviation was used to define a hyperdynamic or hypodynamic appearance of CSF flow. Dilatation of the ventricular system was determined on radiographs by two neuroradiologists and a neurosurgeon. RESULTS: Only four patients presented normal ventricular CSF flow, one patient presented hypodynamic flow and five patients presented hyperdynamic flow. Five patients had normal cervical CSF flow and five patients presented hyperdynamic flow. The two patients with ventricular dilatation both presented hyperdynamic ventricular CSF flow associated with normal cervical CSF flow. One patient was excluded. CONCLUSION: Abnormal CSF flow dynamics were shown suggesting the hypothesis that bleeding increases intracranial volume and induces a reduction of cerebral compliance and an increase of intracranial pressure. The increased oscillations in the ventricular system would therefore predispose to dilatation.

Ventricular dilation as an instability of intracranial dynamics.

We address the question of the ventricles' dilation as a possible instability of the intracranial dynamics. The ventricular system is shown to be governed by a dynamical equation derived from first principles. This general nonlinear scheme is linearized around a well-defined steady state which is mapped onto a pressure-volume model with an algebraic effective compliance depending on the ventricles' geometry, the ependyma's elasticity, and the cerebrospinal fluid (CSF) surface tension. Instabilities of different natures are then evidenced. A first type of structural instability results from the compelling effects of the CSF surface tension and the elastic properties of the ependyma. A second type of dynamical instability occurs for low enough values of the aqueduct's conductance. This last case is then shown to be accompanied by a spontaneous ventricle's dilation. A strong correlation with some active hydrocephalus is evidenced and discussed. The transfer function of the ventricles, compared to a low-pass filter, are calculated in both the stable and unstable regimes and appear to be very different.

Cerebrospinal fluid dynamics and relation with blood flow: a magnetic resonance study with semiautomated cerebrospinal fluid segmentation.

RATIONALE AND OBJECTIVES: To investigate and measure temporal and amplitude aspects of blood and cerebrospinal fluid (CSF) flow waveform relations. METHODS: A cine phase-contrast magnetic resonance imaging pulse sequence was used to measure blood and CSF flow in 16 healthy subjects aged 27 +/- 4 years. A semiautomated segmentation algorithm was developed to study CSF flow. RESULTS: Standard deviations of the aqueductal and cervical flow measurements carried out by five observers were 1% and 4%, respectively. The peak systolic arterial flow was 1087 +/- 169 mL/min, and the peak cervical CSF flush (173 +/- 59 mL/min) occurred at 5% +/- 3% of the cardiac cycle after the internal carotid systolic peak flow. Peak aqueductal flush flow (13 +/- 5 mL/min) occurred at 21% +/- 7% of the cardiac cycle after the internal carotid systolic peak flow. CONCLUSIONS: The CSF segmentation algorithm is reproducible. Brain expansion was quickly regulated by a major extracerebral CSF flush flow, whereas ventricular CSF made only a very small contribution.

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

UNLABELLED: 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 cerebrospinal 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.

Origin of subarachnoid cerebrospinal fluid pulsations: a phase-contrast MR analysis.

Cerebrospinal fluid (CSF) pulsations result from change of blood volume in the closed craniospinal cavity. We used cine phase contrast MR analysis to determine whether spinal CSF pulsations result from spinal vascular pulsations or intracranial subarachnoid pulsations, whether intracranial CSF pulsations result from intracranial large arteries pulsations or cerebrovascular bed changes. We performed a quantified physiological mapping of CSF velocity waveforms along the craniospinal axis. Thirty-six volunteers participated in the study. MR acquisitions were obtained at the intracranial level, the upper, midcervical, cervicothoracic, mid thoracic, and/or the thoracolumbar levels. The temporal velocity information were plotted as wave form and key temporal parameters were determined and analyzed; intervals from the R wave to the onset of CSF systole, to CSF systolic peak, to the end of systole, as well as duration of systole. Three kinds of dynamic channels could be differentiated along the spinal axis, the lateral, medioventral and mediodorsal channels. Lateral spinal CSF pulse waves show significant craniocaudal propagation. No such significant progression was detected through the medial channels along the spine. Through the medial channels, a cephalic progression was observed from the upper cervical level to the intracranial level. At the craniocervical junction, mediodorsal CSF systole appeared the earliest one whereas in the anterior intracranial basal cistern, CSF systole appeared delayed. In conclusion, spinal CSF pulsations seem to result mainly from intracranial pulsations in the lateral channels, whereas local vascular pulsations could modify CSF pulse wave mainly in the medial channels. At the craniocervical junction, our results suggest that blood volume change in the richly vascularised cerebellar tonsils is the main initiating factor of CSF systole; and that spinal vascular pulsations could be considered as an additional early and variable CSF pump.

[Imaging of tumors of the third ventricle]. / Imagerie des tumeurs du troisième ventricule.

MR imaging now appears as the best tool for diagnosis and pre-therapeutic assessment of tumors arising in the third ventricle (V3), as MR images can be obtained in the axial, coronal, and sagittal planes. MRI makes certain the location of the tumor in the V3 and delineates the anatomical landmarks in order to plan the surgical approach. It also allows the evaluation of associated hydrocephalus. Colloid cysts, choroid plexus papillomas, cavernomas, subependymal giant cell astrocytomas and germ-cell tumors may exhibit specific radiological features.

Phase-contrast MR imaging support for the diagnosis of aqueductal stenosis.

BACKGROUND AND PURPOSE: Patients with aqueductal stenosis (AS) present with various clinical and radiologic features. Conventional MR imaging provides useful information in AS but depends on a subjective evaluation by the neuroradiologist. The purpose of this study was to evaluate the support of the phase-contrast MR imaging (PC-MR imaging) technique (sensitive to CSF flows) for the diagnosis of AS. MATERIALS AND METHODS: We retrospectively considered 17 patients who underwent PC-MR imaging to explore hydrocephalus, with the absence of CSF flow at the aqueductal level. We analyzed their clinical and morphologic MR imaging data. RESULTS: None of the usually reported direct or indirect signs of aqueductal obstruction were seen in 7 patients in whom the clinical suggestion of AS was confirmed by PC-MR imaging results. Seven patients in this population had a third ventriculostomy, and 5 of them were among those in whom conventional MR imaging failed to reveal signs of aqueductal obstruction. All of these 7 patients had a positive postsurgical outcomes. The analysis of CSF and vascular dynamic data in this population was compared with an aged-matched population, and these data were found similar except for the fourth ventricular CSF flush flow latency. CONCLUSIONS: PC-MR imaging supports the diagnosis of CSF flow blockage at the aqueductal level in a reliable, reproducible, and rapid way, which aids in the diagnosis of AS in patients with clinical and/or radiologic suggestion of obstructive hydrocephalus. We, therefore, suggest using this technique in the current evaluation of hydrocephalus.

Segmentación deiimágenes de resonancia magnétic en contraste de fase para el eestudio de la dinámica del líquido cefalorraquídeo perimedular / Segmentation of Phase Contrast Magnetic Resonance Imaging to Study the Dynamic of Perimedullary Cerebrospinal Fluid

La imagen de resonancia magnética en contraste de fase permite estudiar la dinámica del líquido cefalorraquídeo (LCR) perimedular de manera cuantitativa. Sin embargo la anatomía propia del espacio subaracnoideo dificulta la segmentación del LCR debido a la presencia de estructuras vasculares y nervios raquídeos. El objetivo de este trabajo es describir un método de segmentación semiautomático para el estudio de la dinámica del LCR perimedular. El proceso se inicializa con un punto semilla dentro de la región a analizar. El algoritmo crea un mapa de correlación, calcula un valor de umbral y clasifica píxeles de LCR combinando diversas características temporales del comportamiento del flujo como atributos de entrada a un algoritmo k-medias. Un observador llevó a cabo diez veces la segmentación en cinco sujetos sanos y se calculó el volumen por ciclo y el área en el espacio perimedular C2C3. Las variaciones de las medidas fueron evaluadas como una estimación de la reproducibilidad del método. Para esto se calculó el coeficiente de variación. La variabilidad de las medidas fue menor del 5%. El método facilita la cuantificación del LCR perimedular. En 16 sujetos sanos se cuantificó el volumen por ciclo de LCR y el área en el espacio C2C3 y cisterna prepontina.

Phase contrast magnetic resonance imaging allows studying quantitatively the perimedullary cerebrospinal fluid (CSF) dynamics. However, the anatomy of the subarachnoid space difficults the segmentation of CSF due to the presence of vascular structures and spinal nerves. The aim of this paper is to describe a semiautomatic segmentation method for the study of the perimedullary CSF dynamics. The process is started with a seed point within the region to analyze. The algorithm creates a correlation map, calculates a threshold value and classifies pixels of CSF combining different temporal characteristics of flow behavior as input attributes to a k-means algorithm. One observer carried out ten times the segmentation of the cervical images in 5 healthy subjects; stroke volume and area were calculated. The variability of the obtained measurements was evaluated as an estimation of the reproducibility of the method. For this the coefficient of variation was calculated. The variability of the measurements was less than 5%. The method facilitates the quantification of perimedullary CSF. Stroke volume and the area at C2C3 space and prepontine cistern were measured in 16 healthy subjects.