Comparison of skull circumference and linear measurements with CSF volume MR measurements in hydrocephalus.

In children with hydrocephalus, accurate and reproducible estimation of the presence, severity, and course of the condition is of paramount importance for both clinical and scientific purposes. In this study, 30 hydrocephalic patients were assessed with a number of commonly used methods, such as occipitofrontal skull circumference (SC) measurements, Evans ratio (ER), and bicaudate index (BCI), as well as, for comparison, another ratio of linear measurements [ventricle-skull ratio (VSR)] and MR measurements of total intracranial CSF volume. In repeated CSF volume measurements in healthy volunteers, the MR method appeared to be accurate and reproducible. This technique was simpler and easier in application, requiring less interaction than comparable MR techniques described by others. The variation coefficients were within the same range. In increased CSF volumes, our technique can be recommended; in very small CSF volumes, another technique is more adequate. Direct assessment of CSF volume as a measure of hydrocephalus was preferable over derived estimations for scientific purposes and may function as a gold standard against which to evaluate other techniques that are easier to apply clinically. In comparison, SC measurements were poor; CSF volume changes were not reflected in SC changes. VSR was preferable over ER and BCI, because it correlated more closely with CSF volume.     

MRI evidence for preserved regulation of intracranial pressure in patients with cerebral arteriovenous malformations

Purpose

The purpose of this study was to investigate intracranial pressure and associated hemo- and hydrodynamic parameters in patients with cerebral arteriovenous malformations AVMs.

Methods

Thirty consecutive patients with arteriovenous malformations (median age 38.7 years, 27/30 previously treated with radiosurgery) and 30 age- and gender-matched healthy controls were investigated on a 3.0 T MR scanner. Nidus volume was quantified on dynamic MR angiography. Total arterial cerebral blood flow (tCBF), venous outflow as well as aqueductal and craniospinal stroke volumes were obtained using velocity-encoded cine-phase contrast MRI. Intracranial volume change during the cardiac cycle was calculated and intracranial pressure (ICP) was derived from systolic intracranial volume change (ICVC) and pulse pressure gradient.

Results

TCBF was significantly higher in AVM patients as compared to healthy controls (median 799 vs. 692 mL/min, p = 0.007). There was a trend for venous flow to be increased in both the ipsilateral internal jugular vein (IJV, 282 vs. 225 mL/min, p = 0.16), and in the contralateral IJV (322 vs. 285 mL/min, p = 0.09), but not in secondary veins. There was no significant difference in median ICP between AVM patients and control subjects (6.9 vs. 8.6 mmHg, p = 0.30) and ICP did not correlate with nidus volume in AVM patients (ρ = −0.06, p = 0.74). There was a significant positive correlation between tCBF and craniospinal CSF stroke volume (ρ = 0.69, p = 0.02).

Conclusions

The elevated cerebral blood flow in patients with AVMs is drained through an increased flow in IJVs but not secondary veins. ICP is maintained within ranges of normal and does not correlate with nidus volume.     

Paramagnetic effect of supplemental oxygen on CSF hyperintensity on fluid-attenuated inversion recovery MR images

BACKGROUND AND PURPOSE: Oxygen has a known paramagnetic effect and increases CSF signal intensity on fluid-attenuated inversion recovery (FLAIR) MR images. The purposes of this study were to investigate the effect of supplemental oxygen on CSF signal intensity and the arterial partial pressure of oxygen and to determine the possible synergistic effect of oxygen and albumin on T1 shortening effect in vitro. METHODS: Six healthy volunteers underwent FLAIR MR imaging of the brain before and during inhalation of 10 to 15 L/min of 100% oxygen for < or = 30 min. The signal intensity was measured in the subarachnoid spaces and various tissues and correlated with estimated arterial partial pressure of oxygen and arterial carbon dioxide pressure. In vitro measurements were also obtained by using two sets of saline-filled tubes with various concentrations of albumin, one of which was exposed to increased oxygen levels. In vitro T1 relaxation times were calculated to assess the possible synergistic effect of oxygen and albumin. RESULTS: FLAIR images of healthy volunteers showed increased CSF signal intensity within the basal cisterns and sulci along the cerebral convexities. The CSF hyperintensity was observed immediately after the initiation of supplemental oxygen and remained stable during the oxygen administration. There was approximately a 4- to 5.3-fold increase in signal intensity with supplemental oxygen. The phantom experiments showed a T1 shortening effect of oxygen. Albumin significantly altered T1 relaxation time only at high concentrations of albumin. CONCLUSION: Inhalation of increased levels of oxygen led to readily detectable CSF hyperintensity on FLAIR images of healthy volunteers. No significant synergetic effect of albumin and oxygen was noted.     

Diameter of the superior ophthalmic vein in relation to intracranial pressure

BACKGROUND AND PURPOSE: Bilateral engorged superior ophthalmic veins (SOV) have been reported in patients with diffuse brain swelling. We investigated the relationship between the diameter of the SOV on brain MR images and the intracranial pressure (ICP). METHODS: We reviewed the medical records of neurologic inpatients who had undergone both MR imaging of the brain and lumbar puncture. MR imaging had to have been performed before lumbar puncture, and the two studies had to have occurred within 2 days. The diameters of the SOV were measured on coronal contrast-enhanced fat-saturated T1-weighted MR images. For this, the image nearest the rear of the globe of the eye was chosen. RESULTS: Sixty-nine patients (32 male, 37 female; mean age, 46 years +/- 19) were included. The average diameters of the SOV and the ICP were positively correlated (r = 0.58, P <.001), if an SOV diameter of <1 mm was treated as 0.5 mm for calculations. In patients with increased ICP (CSF pressure >200 mm H(2)O), SOV diameters were larger than those of patients with a normal CSF pressure (3.0 vs 1.6 mm, P <.001). Frequencies of increased ICP were 3% among patients with an average SOV diameter of 0.5-1 mm, 15% for 1.5-2 mm, and 58% for 2.5-5 mm (P <.001). CONCLUSION: This study showed that the SOV diameter, determined on the basis on MR imaging, was positively correlated with ICP. Dilatation of the SOV should alert physicians to the possibility of increased ICP.     

Phase contrast MRI quantification of pulsatile volumes of brain arteries, veins, and cerebrospinal fluids compartments: repeatability and physiological interactions

Purpose:

To study measurement repeatability and physiological determinants on measurement stability for phase contrast MRI (PC‐MRI) measurements of cyclic volume changes (ΔV) of brain arteries, veins, and cerebrospinal fluid (CSF) compartments.

Materials and Methods:

Total cerebral blood flow (tCBF), total internal jugular flow (tJBF) and spinal CSF flow at C2–C3 level and CSF in the aqueduct was measured using five repetitions in 20 healthy subjects. After subtracting net flow, waveforms were integrated to calculate ΔV of arterial, venous, and cerebrospinal fluid compartments. The intraclass correlation coefficient (ICC) was used to measure repeatability. Systematic errors were investigated by a series of phantom measurements.

Results:

For ΔV calculated from tCBF, tJBF and both CSF waveforms, the ICC was ≥0.85. ΔV from the tCBF waveform decreased linearly between repetitions (P = 0.012). Summed CSF and venous volume being shifted out from the cranium was correlated with ΔV calculated from the tCBF waveform (r = 0.75; P < 0.001). Systematic errors increased at resolutions <4 pixels per diameter.

Conclusion:

Repeatability of ΔV calculated from tCBF, tJBF, and CSF waveforms allows useful interpretations. The subject's time in the MR system and imaging resolution should be considered when interpreting volume changes. Summed CSF and venous volume changes was associated with arterial volume changes. J. Magn. Reson. Imaging 2012;35:1055‐1062. © 2011 Wiley Periodicals, Inc.     

Cardiac-gated phase MR imaging of aqueductal CSF flow

The direction of CSF flow within the cerebral aqueduct was studied by cardiac-gated magnetic resonance (MR) phase images in five healthy volunteers and 10 patients with presumably normal cerebral CSF circulation. Caudal CSF flow was observed during systole and cranial flow during diastole. Using phantom based calibrations of the imager, aqueductal CSF velocities of 3-5 mm/s were calculated. Cardiac-gated phase MR is a potentially major tool for the investigation of the CSF circulation.     

Venous filling and elastance in the calf positioned above and below heart level

INTRODUCTION: Limb venous compliance is a major factor in determining the extent of blood pooling during orthostatic stress. We measured the filling of the calf and of its major veins at different postures and quantified the venous contribution to the total volume shift of the calf. The results were also used to determine the venous elastance and to gain some information on the filling of the small veins. METHODS: Twelve healthy volunteers participated in the study. The calf volume was measured with strain gauge plethysmography and the veins were imaged with ultrasound in the following positions: supine, sitting with both legs horizontal, sitting with one leg suspended, and supine with one leg raised. Cross-sectional areas of the imaged veins were calculated from the measured diameters. Hydrostatic change in the venous pressure was assumed when calculating the venous elastance. RESULTS: The maximal increase in the calf area was up to 1 cm2. The large veins accounted for approximately 30% of the total volume shift of the calf except in cases where the subjects had one leg suspended. Then, the contribution of the large veins was less than 20%. The estimated elastance of the large veins was 80 +/- 14 mmHg, which may be regarded as substantial. CONCLUSIONS: The study suggests that there is a distinct difference in the filling of the small and the large leg veins. The small veins may be the principal contributors to the total compliance of the calf when the venous pressure is above 30 mmHg.     

Usefulness of MR imaging-derived thermometry and dosimetry in determining the threshold for tissue damage induced by thermal surgery in rabbits

PURPOSE: To investigate in vivo the feasibility of using magnetic resonance (MR) imaging-derived temperature and thermal dose measurements to find the threshold of thermal tissue damage. MATERIALS AND METHODS: Sonications were delivered in rabbit thigh muscles at varying powers. Temperature-sensitive MR images obtained during the sonications were used to estimate the temperature and thermal dose. The temperature, thermal dose, and applied power were then correlated to the occurrence of tissue damage observed on postsonication images. An eight-element phased-array transducer was used to produce spatially flat temperature profiles that allowed for averaging to reduce the effects of noise and the voxel size. RESULTS: The occurrence of tissue damage correlated well with the MR imaging-derived temperature and thermal dose measurements but not with the applied power. Tissue damage occurred at all locations with temperatures greater than 50.4 degrees C and thermal doses greater than 31.2 equivalent minutes at 43.0 degrees C. No tissue damage occurred when these values were less than 47.2 degrees C and 4.3 equivalent minutes. CONCLUSION: MR imaging thermometry and dosimetry provide an index to predict the threshold for tissue damage in vivo. This index offers improved online control over minimally invasive thermal treatments and should allow for more accurate target volume coagulation.     

Quantifying the effect of posture on intracranial physiology in humans by MRI flow studies

PURPOSE: To quantify the effect of posture on intracranial physiology in humans by MRI, and demonstrate the relationship between intracranial compliance (ICC) and pressure (ICP), and the pulsatility of blood and CSF flows. MATERIALS AND METHODS: Ten healthy volunteers (29+/-7 years old) were scanned in the supine and sitting positions using a vertical gap MRI scanner. Pulsatile blood and CSF flows into and out from the brain were visualized and quantified using time-of-flight (TOF) and cine phase-contrast techniques, respectively. The total cerebral blood flow (tCBF), venous outflow, ICC, and ICP for the two postures were then calculated from the arterial, venous, and CSF volumetric flow rate waveforms using a previously described method. RESULTS: In the upright posture, venous outflow is considerably less pulsatile (57%) and occurs predominantly through the vertebral plexus, while in the supine posture venous outflow occurs predominantly through the internal jugular veins. A slightly lower tCBF (12%), a considerably smaller CSF volume oscillating between the cranium and the spinal canal (48%), and a much larger ICC (2.8-fold) with a corresponding decrease in the MRI-derived ICP values were measured in the sitting position. CONCLUSION: The effect of posture on intracranial physiology can be quantified by MRI because posture-related changes in ICC and ICP strongly affect the dynamics of cerebral blood and CSF flows. This study provides important insight into the coupling that exists between arterial, venous, and CSF flow dynamics, and how it is affected by posture.     

实验性颅内高压诱发家兔自发脑电非线性特征的变化

目的观察实验性高颅压条件下家兔自发脑电非线性特征的变化,探讨在重力变化引起颅内压改变,进而影响脑功能变化的研究中应用脑电复杂性指标的可能性。方法以家免为实验对象,以灌注法改变颅内压,应用关联维和李亚普诺夫指数等参数估计不同颅内压条件下脑电信号的复杂性特征。结果加压前正常颅内压条件下,动物的自发脑电信号均具有正的李亚普诺夫指数和分数关联维,提示这种信号具有混沌性质。实验性高颅压条件下,李亚普诺夫指数在每例动物都明显降低,提示脑电活动的复杂性降低。颅内压恢复正常值,李亚普诺夫指数的变化具有良好的可逆性,提示有限的高颅压引起的脑电活动的复杂度的变化是可逆的。结论自发脑电信号的李亚普诺夫指数作为监测颅内压变化时脑功能变化的指标,具有一定的应用价值。     

Diffusion tensor tractography of the limbic system

BACKGROUND AND PURPOSE: The limbic system, relevant to memory and emotion, is an interesting subject of study in healthy and diseased individuals. It consists of a network of gray matter structures interconnected by white matter fibers. Although gray matter components of this system have been studied by using MR imaging, the connecting fibers have not been analyzed to the same degree. Cerebrospinal fluid (CSF) signal intensity contamination of the fornix and cingulum, the 2 major white matter tracts of the limbic system, can alter diffusion-tensor imaging (DTI) measurements and affect tractography. We investigated the effect of CSF signal intensity suppression on fiber tracking of the limbic connections and characterized the diffusion properties of these structures in healthy volunteers. METHODS: Nine healthy individuals were scanned with standard and CSF-suppressed DTI. Tractography of the fornix and cingulum was performed for both acquisition methods. We report mean diffusivity and fractional anisotropy measurements of the crus, body, and columns of the fornix, and descending, superior, and anterior portions of the cingulum. RESULTS: Diffusion measurements were improved and tractography was facilitated by using CSF-suppressed DTI. In particular, tract volume increased, whereas decreases of the mean diffusivity and increases of diffusion anisotropy more accurately represented the underlying tissue by minimizing deleterious partial volume averaging from CSF. This was particularly true for the fornix because it is in closest contact to CSF. Diffusion measurements throughout the limbic connections were consistent in healthy volunteers. CONCLUSION: We recommend the use of CSF suppression when performing diffusion-tensor tractography of the limbic system.     

Effect of arginine vasopressin, acetazolamide, and angiotensin II on CSF pressure at simulated altitude

To test the hypothesis that arginine vasopressin (AVP) in the cerebral spinal fluid (CSF) influences CSF dynamics at simulated altitudes, cannulae were bilaterally implanted into the lateral ventricles of rabbits and rats. Recordings of CSF pressures at ambient and at various reduced barometric pressures identified an increase in CSF pressure in animals at simulated altitudes. Samples of CSF collected before and immediately after altitude exposures and assayed for AVP did not show a significant change in AVP concentration. Brain water content did not change after 6-8 h of reduced barometric pressure. Intraarterial injections of acetazolamide reduced CSF pressures, whereas intraventricular injection had no effect. Intraventricular angiotensin II (AII) elevated CSF pressures both at ambient (744-755 mm Hg) and reduced barometric pressures. When AII was preceded by saralasin, an AII blocker, the rise in CSF pressure with AII injection was prevented. Indeed, saralasin given alone, reduced or prevented the rise in CSF pressure seen at simulated altitudes. Intraventricular AVP did not influence CSF pressures nor did prostaglandins E2 and F1 alpha and norepinephrine. In AVP-deficient (Brattleboro) rats, response to intraventricular AVP depended on barometric pressure; i.e. CSF pressure rose when the rat was exposed to reduced barometric pressures and fell when the rat was exposed to ambient pressure. We suggest that hypobaric stress could cause an increase in AII content of the central nervous system which, in turn, would lead to an increase in CSF pressure. The exact mechanism of CSF pressure increase after AII increase remains to be investigated.     

Calculation of left ventricle relative pressure distribution in MRI using acceleration data.

Measurements of pressure variations within the cardiac chambers could provide important information for clinical assessments of cardiovascular function. In this work an MRI method for evaluating spatial distributions of intracardiac relative pressure is presented. We first calculated pressure gradients from MR maps of blood acceleration by applying the NS equation. We then used an original algorithm to compute pressure distribution in a region of interest (ROI) by minimizing the pressure gradient curl so that the result in a given pixel is independent of the integration path. The method was assessed in five healthy volunteers by means of MR 2D maps of the blood acceleration in the left ventricle (LV) during ejection and filling phases. The pressure variations calculated from acceleration mapping fit the known physiological variations better than those based on velocity maps acquired in the same volunteers. Furthermore, the optimization algorithm presented here produced the same results as iterative algorithms proposed by other authors, but in much less time and without requiring adjustable parameters or boundary conditions.     

Normal brain development and aging: quantitative analysis at in vivo MR imaging in healthy volunteers

PURPOSE: To quantitate neuroanatomic parameters in healthy volunteers and to compare the values with normative values from postmortem studies. MATERIALS AND METHODS: Magnetic resonance (MR) images of 116 volunteers aged 19 months to 80 years were analyzed with semiautomated procedures validated by means of comparison with manual tracings. Volumes measured included intracranial space, whole brain, gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF). Results were compared with values from previous postmortem studies. RESULTS: Whole brain and intracranial space grew by 25%-27% between early childhood (mean age, 26 months; age range, 19-33 months) and adolescence (mean age, 14 years; age range, 12-15 years); thereafter, whole-brain volume decreased such that volunteers (age range, 71-80 years) had volumes similar to those of young children. GM increased 13% from early to later (6-9 years) childhood. Thereafter, GM increased more slowly and reached a plateau in the 4th decade; it decreased by 13% in the oldest volunteers. The GM-WM ratio decreased exponentially from early childhood through the 4th decade; thereafter, it gradually declined. In vivo patterns of change in the intracranial space, whole brain, and GM-WM ratio agreed with published postmortem data. CONCLUSION: MR images accurately depict normal patterns of age-related change in intracranial space, whole brain, GM, WM, and CSF. These quantitative MR imaging data can be used in research studies and clinical settings for the detection of abnormalities in fundamental neuroanatomic parameters.     

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.     

In vitro and in vivo comparison of three MR measurement methods for calculating vascular shear stress in the internal carotid artery

BACKGROUND AND PURPOSE: Vascular abnormalities, such as atherosclerosis and the growth and rupture of cerebral aneurysms, result from a derangement in tissue metabolism and injury that are, in part, regulated by hemodynamic stress. The purpose of this study was to establish the feasibility and accuracy of determining wall shear rate in the internal carotid artery from phase-contrast MR data. METHODS: Three algorithms were used to generate shear rate estimates from both ungated and cardiac-gated 2D phase-contrast data. These algorithms were linear extrapolation (LE), linear estimation with correction for wall position (LE*), and quadratic extrapolation (QE). In vitro experiments were conducted by using a phantom under conditions of both nonpulsatile and pulsatile flow. The findings from five healthy volunteers were also studied. MR imaging-derived shear rates were compared with values calculated by solving the fluid flow equations. RESULTS: Findings of in vitro constant-flow experiments indicated that at one or two excitations, QE has the advantage of good accuracy and low variance. Results of in vitro pulsatile flow experiments showed that neither LE* nor QE differed significantly from the predicted value of wall shear stress, despite errors of 17% and 22%, respectively. In vivo data showed that QE did not differ significantly from the predicted value, whereas LE and LE* did. The percentages of errors for QE, LE, and LE* in vivo measurements were 98.5%, 28.5%, and 36.1%, respectively. The average residual of QE was low because the residuals were both above and below baseline whereas, on average, LE* tended to be a more biased overestimator of the shear rate in volunteers. The average and peak wall shear force in five volunteers was approximately 8.10 dyne/cm2 and 13.2 dyne/cm2, respectively. CONCLUSION: Our findings show that LE consistently underestimates the shear rate. Although LE* and QE may be used to estimate shear rate, errors of up to 36% should be expected because of variance above and below the true value for individual measurements.     

Measurement of right and left ventricular volumes in healthy individuals with cine MR imaging

Cine magnetic resonance (MR) imaging is a new, rapid MR pulse sequence that acquires up to 32 images per cardiac cycle at up to four levels of the heart within 4 minutes. In this study, the whole heart was encompassed by contiguous 10-mm transverse sections. Ventricular volumes were calculated by adding luminal areas determined in each section at end-diastole and end-systole. The left ventricular volume index was 57 ml/m2 +/- 9 at end-diastole and 17 ml/m2 +/- 4 at end-systole. The right ventricular volume index was 63 ml/m2 +/- 9 at end-diastole and 22 ml/m2 +/- 6 at end-systole. The left to right ventricular stroke volume ratio was 0.97 +/- 0.06, which was not statistically different from the theoretically expected ratio of 1. Interobserver and intraobserver measurements were closely correlated. Volume measurements were validated with two-dimensional echocardiography in five volunteers. Cine MR imaging allows reproducible three-dimensional measurement of right and left ventricular volumes with short imaging time and good temporal resolution.     

Imaging of the entire cerebrospinal fluid volume with a multistation 3D SPACE MR sequence: feasibility study in patients with hydrocephalus

Objectives

To evaluate the feasibility of imaging the entire cerebrospinal fluid (CSF) volume using the SPACE MR sequence.

Methods

The SPACE sequence encompassing the brain and spine was performed at 1.5 T in 12 healthy volunteers and 26 consecutive patients with hydrocephalus. Image contrast was estimated using difference ratios in signal intensity between CSF and its background. Segmentation of CSF was performed using geometrical features and a topological assumption of CSF shapes. Subarachnoid and ventricular CSF space volumes were assessed in volunteers and patients and linear discriminant analysis was performed.

Results

Image contrast was 0.94 between the CSF and the brain and 0.90 between the CSF and the spinal cord. According to the phantom study, the accuracy of CSF volume measurement was 98.5 %. A clear distinction between patients and healthy volunteers was obtained using the linear discriminant analysis. Significant linear regression was found in healthy volunteers between ventricular (Vv) and the whole subarachnoid CSF volume (Vs) with Vv?=?0.083 Vs.

Conclusions

Imaging of the entire CSF volume is feasible in healthy volunteers and patients with hydrocephalus. CSF volume can be obtained on a whole-body scale. This approach may be of use for the diagnosis and follow-up of patients with hydrocephalus.

Key Points

? MRI assessment of CSF volume is feasible in healthy volunteers/hydrocephalus patients. ? CSF volume can be obtained on a whole-body scale. ? The ratio of subarachnoid and ventricular CSF is constant in healthy volunteers. ? CSF linear discriminant analysis can distinguish between patients and healthy volunteers. ? Entire CSF volume imaging is useful for diagnosing and following hydrocephalus.     

Noninvasive MRI assessment of intracranial compliance in idiopathic normal pressure hydrocephalus

PURPOSE: To assess the state and dynamics of the intracranial system in idiopathic normal-pressure hydrocephalus (I-NPH), we determined intracranial compliance using magnetic resonance imaging (MRI). MATERIALS AND METHODS: The intracranial compliance index (ICCI), which was defined as the ratio of the peak-to-peak intracranial volume change (ICVC(p-p)) to the peak-to-peak cerebrospinal fluid (CSF) pressure gradient (PG(p-p)) during the cardiac cycle, was obtained from the net transcranial blood and CSF flow measured with phase-contrast (PC) cine MRI. ICCI was determined in patients with I-NPH (N = 7), brain atrophy, or asymptomatic ventricular dilation (VD) (N = 6), and in healthy volunteers (control group; N = 11). The changes in ICCI indices were also analyzed after a CSF tap test (N = 2). RESULTS: The ICCI in the I-NPH group was significantly lower than in the control and VD groups, whereas no difference was found between the control and VD groups. The ICVC(p-p) was also lower than in the control and VD groups. However, no significant difference was found in the PG(p-p) between groups. The ICCI increased after the tap test. CONCLUSION: Intracranial compliance analysis with MRI makes it possible to noninvasively obtain more detailed information of intracranial biomechanics in the I-NPH and to assist in the diagnosis of I-NPH.     

A quantitative index of intracranial cerebrospinal fluid distribution in normal pressure hydrocephalus using an MRI-based processing technique

Our purpose was to quantify the intracranial cerebrospinal fluid (CSF) volume components using an original MRI-based segmentation technique and to investigate whether a CSF volume index is useful for diagnosis of normal pressure hydrocephalus (NPH). We studied 59 subjects: 16 patients with NPH, 14 young and 13 elderly normal volunteers, and 16 patients with cerebrovascular disease. Images were acquired on a 1.5-T system, using a 3D-fast asymmetrical spin- echo (FASE) method. A region-growing method (RGM) was used to extract the CSF spaces from the FASE images. Ventricular volume (VV) and intracranial CSF volume (ICV) were measured, and a VV/ICV ratio was calculated. Mean VV and VV/ICV ratio were higher in the NPH group than in the other groups, and the differences were statistically significant, whereas the mean ICV value in the NPH group was not significantly increased. Of the 16 patients in the NPH group, 13 had VV/ICV ratios above 30 %. In contrast, no subject in the other groups had a VV/ICV ratios higher than 30 %. We conclude that these CSF volume parameters, especially the VV/ICV ratio, are useful for the diagnosis of NPH. Received: 17 June 1999/Accepted: 12 October 1999