Cine PC-MRI Research Articles

Cerebral arterial flow dynamics during systole and diastole phases in young and older healthy adults

BackgroundSince arterial flow is the leading actor in neuro-fluids flow dynamics, it might be interesting to assess whether it is meaningful to study the arterial flow waveform in more detail and whether this provides new important information. Few studies have focused on determining the influence of heart rate variation over time on the arterial flow curve. Therefore, this study aimed to evaluate cerebral arterial flow waveforms at extracranial and intracranial compartments in young and elderly healthy adults, also considering systole and diastole phases.MethodsCine phase-contrast magnetic resonance imaging (CINE-PC MRI) was performed on twenty-eight healthy young volunteers (HYV) and twenty healthy elderly volunteers (HEV) to measure arterial blood flows at the extracranial and intracranial planes. A semi-automated protocol using MATLAB scripts was implemented to identify the main representative points in the arterial flow waveforms. Representative arterial profiles were estimated for each group. Moreover, the effects of age and sex on flow times, amplitude-related parameters, and parameters related to systole and diastole phases were evaluated at the extracranial and intracranial compartments. Student’s t-test or Wilcoxon’s test (depending on the normality of the distribution) was used to detect significant differences.ResultsIn HYVs, significant differences were observed between extracranial and intracranial levels in parameters related to the AP1 amplitude. Besides the detected differences in pulsatility index (extracranial: 0.92 ± 0.20 vs. 1.28 ± 0.33; intracranial: 0.79 ± 0.15 vs. 1.14 ± 0.18, p < .001) and average flow (715 ± 136 vs. 607 ± 125 ml/min, p = .008) between HYV and HEV, differences in the amplitude value of the arterial flow profile feature points were also noted. Contrary to systole duration (HYV: 360 ± 29 ms; HEV: 364 ± 47 ms), diastole duration presented higher inter-individual variability in both populations (HYV: 472 ± 145 ms; HEV: 456 ± 106 ms). Our results also showed that, with age, it is mainly the diastolic phase that changes. Although no significant differences in duration were observed between the two populations, the mean flow value in the diastolic phase was significantly lower in HEV (extracranial: 628 ± 128 vs. 457 ± 111 ml/min; intracranial: 599 ± 121 vs. 473 ± 100 ml/min, p < .001). No significant differences were observed in the arterial flow parameters evaluated between females and males in either HYV or HEV.ConclusionOur study provides a novel contribution on the influence of the cardiac cycle phases on cerebral arterial flow. The main contribution in this study concerns the identification of age-related alterations in cerebral blood flow, which occur mainly during the diastolic phase. Specifically, we observed that mean flow significantly decreases with age during diastole, whereas mean flow during systole is consistent.

Measuring respiratory and cardiac influences on blood and cerebrospinal fluid flow with real-time MRI

Background. A link between various pathological conditions and blood and cerebrospinal fluid (CSF) flow alterations has been suggested by numerous studies.1 The blood and CSF dynamics are influenced by many factors, such as posture,2 heart beating, and thoracic pressure changes during respiration.2,3 The blood/CSF can be estimated using phase-contrast (PC) – magnetic resonance imaging (MRI). However, the clinical cardiac-gated cine PC-MRI requires several heartbeats to form the time-resolved flow images covering the entire cardiac cycle, not allowing to assess beat-by-beat variability differences and respiratory-driven flow changes. To overcome these limitations, we recently used a real-time (RT)-PC prototype for the study of blood and CSF flow rate modulations, showing low-frequency oscillations (Mayer waves).4 With the same MRI technique, in the current study we focused on assessing the cardiac and respiratory modulations on the blood and CSF flow rates, and the effects of different respiration modes.&#x0D; Methods. Thirty healthy volunteers (21 females, median age=26 years old, age range= 19-57 years old) were examined with a 3 T scanner. RT-PC sequences (Figure 1) allowed for a quantification of the flow rates of internal carotid arteries (ICAs), internal jugular veins (IJVs), and CSF at the first cervical level. The superior sagittal sinus (SSS) was also studied in 16 subjects.5 The flow rates were estimated with a temporal resolution of 58.5 ms for the blood, and 94 ms for the CSF. Each RT-PC lasted 60 seconds and was repeated three times: while the subject breathed with free (F) breathing, at a constant rate with a normal (PN) or forced (PD) strength. The systolic, diastolic and average flow rates and their power spectral densities were computed. High and very-high frequency peaks were identified on the spectra. Frequencies associated to the identified peaks were compared to the respiratory and cardiac frequencies estimated by a thoracic band and a pulse oximeter. The area under the spectra, normalized by the flow rate variance, was computed in the respiratory and cardiac frequency ranges (0.5 Hz-wide ranges, centered on the cardiac or breathing frequency peaks, respectively).&#x0D; Results. The frequencies associated with the spectral peaks were not significantly different compared to the respiratory and cardiac frequencies, for all regions and breathing modes. The average blood flow rate and the diastolic CSF peak progressively decreased from F to PN to PD breathing, the flow rate variance remained stable, and only the ICAs cross-sectional area decreased. The respiratory modulation increased with PD breathing compared with F and PN, while the cardiac modulations were less predominant for all the structures of interest.&#x0D; Conclusions. Using the RT-PC sequence we showed that the blood and CSF flow rates were modulated at the respiratory and cardiac frequencies. The observed reduced blood flow rate during forced breathing in the arteries and consequently in the extra and intracranial veins are suggestive of compensatory vasoconstriction in response to decreased CO2 blood concentration. Breathing modulation of flow rates was observed both in the extracranial and intracranial compartments, and it was greater during forced breathing than free breathing, due to the greater thoracic pump effect on the flow rates.

A mathematical framework for the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid

BackgroundShedding light on less-known aspects of intracranial fluid dynamics may be helpful to understand the hydrocephalus mechanism. The present study suggests a mathematical framework based on in vivo inputs to compare the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid (CSF) between the healthy subject and the hydrocephalus patient. MethodThe input data for the mathematical formulations was pulsatile blood velocity, which was measured using cine PC-MRI. Tube law was used to transfer the created deformation by blood pulsation in the vessel circumference to the brain domain. The pulsatile deformation of brain tissue with respect to time was calculated and considered to be inlet velocity in the CSF domain. The governing equations in all three domains were continuity, Navier-Stokes, and concentration. We used Darcy law with defined permeability and diffusivity values to define the material properties in the brain. ResultsWe validated the preciseness of the CSF velocity and pressure through the mathematical formulations with cine PC-MRI velocity, experimental ICP, and FSI simulated velocity and pressure. We used the analysis of dimensionless numbers including Reynolds, Womersley, Hartmann, and Peclet to evaluate the characteristics of the intracranial fluid flow. In the mid-systole phase of a cardiac cycle, CSF velocity had the maximum value and CSF pressure had the minimum value. The maximum and amplitude of CSF pressure, as well as CSF stroke volume, were calculated and compared between the healthy subject and the hydrocephalus patient. ConclusionThe present in vivo-based mathematical framework has the potential to gain insight into the less-known points in the physiological function of intracranial fluid dynamics and the hydrocephalus mechanism.

Cine phase-contrast magnetic resonance imaging evaluation of cerebrospinal fluid flow dynamics in healthy pediatric subjects.

ObjectiveTo evaluate cerebrospinal fluid dynamics, using cine phase-contrast magnetic resonance imaging (cine-PC MRI), in healthy pediatric subjects, determining the normal flow values in this population, as well as identifying differences related to age, sex, and body surface area.Materials and MethodsThis was a descriptive cross-sectional study involving 32 healthy children and adolescents, in whom the flow of cerebrospinal fluid through the cerebral aqueduct was evaluated quantitatively with cine-PC MRI. We used specialized software to analyze the images obtained with cine-PC MRI, drawing a region of interest on the aqueduct. A flow-time curve was obtained, as were automated measurements of the various parameters.ResultsThe following normal (mean) values were obtained: net flow, 1.10 ± 0.99 mL/m; stroke volume, 12.2 ± 10.1 µL/cycle; mean velocity, 0.72 ± 1.00 cm/s; peak systolic velocity, 5.28 ± 2.30 cm/s; peak diastolic velocity, 4.51 ± 1.77 cm/s. These values were not affected by age or sex. In addition, body surface area was not found to correlate significantly with mean velocity or stroke volume.ConclusionIn children and adolescents, the basic cerebrospinal fluid flow parameters, as determined by cine-PC MRI, appear to be independent of age and sex.

Fluid dynamics analyses of the intrahepatic portal vein tributaries using 7-T MRI.

Assessing portal vein (PV) hemodynamics is an essential part of liver disease management/liver surgery, yet the optimal methods of assessing intrahepatic PV flow have not yet been established. This study investigated the usefulness of 7-Tesla MRI with hemodynamic analysis for detecting small flow changes within narrow intrahepatic PV branches. Flow data in the main PV was obtained by two methods, two-dimensional cine phase contrast-MRI (2D cine PC-MRI) and three-dimensional non-cine phase contrast-MRI (3D PC-MRI). Hemodynamic parameters, such as flow volume rate, flow velocity, and wall shear stress in intrahepatic PV branches were calculated before and after a meal challenge using 3D PC-MRI and hemodynamic analysis. The hemodynamic parameters obtained using 3D PC-MRI and 2D cine PC-MRI were similar. All intrahepatic PV branches were clearly depicted in eight planes, and significant changes in flow volume rate were seen in three planes. Average and maximum velocities, cross-sectional area, and wall shear stress were similar between before and after a meal challenge in all planes. 7-Tesla 3D PC-MRI combined with hemodynamic analysis is a promising tool for assessing intrahepatic PV flow and enables future studies in small animals to investigate PV hemodynamics associated with liver disease/postoperative liver recovery.

Endoscopic Third Ventriculostomy for Hydrocephalus in Paediatrics

Background: Abnormal CSF accumulation within ventricles of brain leading to raised intracranial pressure is a potentially life-threatening state that is commonly seen in neurosurgical patients. Aim of this study is to assess the efficacy of endoscopic third ventriculostomy (ETV) in treatment of pediatric hydrocephalus in pediatrics. Materials and Methods: A total of sixty-two patients were included in this prospective study. Patients were generally discharged from the hospital on the 2nd or 3rd postoperative day unless some complication arose. All the information was recorded in a pre-structured proforma, and data were analyzed by SPSS. Statistical significance was defined as p-value less than or equal to 0.05. Results: At follow up, clinical improvement and radiological findings did not necessarily correlate with each other, as ventricular size was reduced in only 42 (67.7%) out of 62 patients. Remaining 20 (32.3%) patients had no change in the size of ventricles. The difference was not statistically significant. However, as observed by cine PC MRI, CSF flow was observed in all the patients. Conclusion: In non-communicating hydrocephalus, ETV is a simple technique and safe and effective treatment if done by an expert surgeon correctly. It is a reasonable alternate of VPS due to its simplicity and effectiveness.

Fast Phase-Contrast Cine MRI for Assessing Intracranial Hemodynamics and Cerebrospinal Fluid Dynamics.

We propose fast phase-contrast cine magnetic resonance imaging (PC-cine MRI) to allow breath-hold acquisition, and we compared intracranial hemo- and hydrodynamic parameters obtained during breath holding between full inspiration and end expiration. On a 3.0 T MRI, using electrocardiogram (ECG)-synchronized fast PC-cine MRI with parallel imaging, rectangular field of view, and segmented k-space, we obtained velocity-mapped phase images at the mid-C2 level with different velocity encoding for transcranial blood flow and cerebrospinal-fluid (CSF) flow. Next, we calculated the peak-to-peak amplitudes of cerebral blood flow (ΔCBF), cerebral venous outflow, intracranial volume change, CSF pressure gradient (ΔPG), and intracranial compliance index. These parameters were compared between the proposed and conventional methods. Moreover, we compared these parameters between different utilized breath-hold maneuvers (inspiration, expiration, and free breathing). All parameters derived from the fast PC method agreed with those from the conventional method. The ΔPG was significantly higher during full inspiration breath holding than at the end of expiration and during free breathing. The proposed fast PC-cine MRI reduced scan time (within 30 s) with good agreement with conventional methods. The use of this method also makes it possible to assess the effects of respiration on intracranial hemo- and hydrodynamics.

Optimal Plane Selection for Measuring Post-prandial Blood Flow Increase within the Superior Mesenteric Artery: Analysis Using 4D Flow and Computational Fluid Dynamics.

Purpose:2D cine phase contrast (PC)-MRI is a standard velocimetry for the superior mesenteric artery (SMA); however, the optimal localization of the measurement plane has never been fully discussed previously. The purpose of this Institutional Review Board approved prospective and single arm study is to test whether flow velocimetry of the SMA with combined use of 2D cine PC-MRI and meal challenge is dependent on the localizations of the measurement planes and to seek optimal section for velocimetry.Methods:Seven healthy volunteers underwent cardiac phase resolved ECG gated 2D cine PC-MRI pre- and 30 min post-meal challenge at three measurement planes: proximal, curved mid section and distal straight section of the SMA at 3T. 4D Flow using 3D cine PC-MRI with vastly undersampled isotropic projection imaging (PC VIPR) was also performed right after 2D cine PC-MRI to delineate the flow dynamics within the SMA using streamline analysis. Two radiologists measured flow velocities, and rated the appearances of the abnormal flow in the SMA on streamlines derived from the 4D Flow and the computational fluid dynamics (CFD).Results:2D cine PC-MRI measured increased temporally averaged flow velocity (mm/s) after the meal challenge only in the proximal (129.3 vs. 97.8, P = 0.0313) and distal section (166.9 vs. 96.2, P = 0.0313), not in the curved mid section (113.1 vs. 85.5, P = 0.0625). The average velocities were highest and their standard errors (8.5–26.5) were smallest at the distal straight section both before and after the meal challenge as compared with other sections. The streamline analysis depicted more frequent appearances of vertical or helical flow in the curved mid section both on 4D Flow and CFD (κ: 0.27–0.68).Conclusion:SMA velocimetry with 2D cine PC-MRI was dependent on the localization of the measurement planes. Distal straight section, not in the curved mid section is recommended for MR velocimetry.

Assessing the Risk of Intracranial Aneurysm Rupture Using Morphological and Hemodynamic Biomarkers Evaluated from Magnetic Resonance Fluid Dynamics and Computational Fluid Dynamics.

Purpose:Evaluate in vivo hemodynamic and morphological biomarkers of intracranial aneurysms, using magnetic resonance fluid dynamics (MRFD) and MR-based patient specific computational fluid dynamics (CFD) in order to assess the risk of rupture.Methods:Forty-eight intracranial aneurysms (10 ruptured, 38 unruptured) were scrutinized for six morphological and 10 hemodynamic biomarkers. Morphological biomarkers were calculated based on 3D time-of-flight magnetic resonance angiography (3D TOF MRA) in MRFD analysis. Hemodynamic biomarkers were assessed using both MRFD and CFD analyses. MRFD was performed using 3D TOF MRA and 3D cine phase-contrast magnetic resonance imaging (3D cine PC MRI). CFD was performed utilizing patient specific inflow–outflow boundary conditions derived from 3D cine PC MRI. Univariate analysis was carried out to identify statistically significant biomarkers for aneurysm rupture and receiver operating characteristic (ROC) analysis was performed for the significant biomarkers. Binary logistic regression was performed to identify independent predictive biomarkers.Results:Morphological biomarker analysis revealed that aneurysm size [P = 0.021], volume [P = 0.035] and size ratio [P = 0.039] were statistically significantly different between the two groups. In hemodynamic biomarker analysis, MRFD results indicated that ruptured aneurysms had higher oscillatory shear index (OSI) [OSI.max, P = 0.037] and higher relative residence time (RRT) [RRT.ave, P = 0.035] compared with unruptured aneurysms. Correspondingly CFD analysis demonstrated significant differences for both average and maximum OSI [OSI.ave, P = 0.008; OSI.max, P = 0.01] and maximum RRT [RRT.max, P = 0.045]. ROC analysis revealed AUC values greater than 0.7 for all significant biomarkers. Aneurysm volume [AUC, 0.718; 95% CI, 0.491–0.946] and average OSI obtained from CFD [AUC, 0.774; 95% CI, 0.586–0.961] were retained in the respective logistic regression models.Conclusion:Both morphological and hemodynamic biomarkers have significant influence on intracranial aneurysm rupture. Aneurysm size, volume, size ratio, OSI and RRT could be potential biomarkers to assess aneurysm rupture risk.

Classification of Chiari I malformation based on various cerebrospinal fluid flow patterns at the cranial-vertebral junction and selection of surgical procedure

Objective To discuss about the classification of Chiari Ⅰ malformation based on different CSF (cerebrospinal fluid) flow patterns at the cranial-vertebral junction (CVJ) and to investigate its surgical strategies and outcomes. Methods A total of 126 patients with Chiari Ⅰ malformation were admitted to Department of Neurosurgery, Sanbo Brain Hospital, Capital Medical University from January 2008 to December 2015 and retrospectively enrolled into this study. According to the preoperative findings obtained by using cine phase-contrast MRI (cine PC-MRI) and based on the abnormal CSF flow dynamics at the CVJ, all those patients of Chiari Ⅰ malformation were classified into 3 patterns: type Ⅰ (36 cases), type Ⅱ (48 cases) and type Ⅲ (42 cases). Intraoperative ultrasound to detect cerebrospinal fluid again determined the surgical strategy. In type Ⅰ patients, 34 patients underwent subdural decompression, and the remaining 2 patients underwent subarachnoid decompression due to cerebrospinal fluid obstruction. In type Ⅱ patients, 36 patients underwent subarachnoid decompression and the remaining 12 cases underwent subdural decompression. In type Ⅲ patients, 40 cases underwent subarachnoid decompression, and the remaining 2 cases underwent subdural decompression due to unobstructed cerebrospinal fluid flow. Two weeks after surgery, the patients underwent an imaging review and assessment based on cervical spine modified Japanese Orthopaedic Association (mJOA) score. All patients underwent clinical follow-up. The follow-up included the use of the cervical spine mJOA score to assess the improvement of syringomyelia-related symptoms. The Chicago Chiari Outcome Scale (CCOS) was used to assess postoperative neurological recovery. Results All 126 patients had successful surgery. There were no cases of new neurological deficits after operation. Eight cases (6.3%) had fever, and 5 cases (4.0%) had cerebrospinal fluid leakage, which improved after symptomatic treatment. Two weeks after surgery, imaging examination showed that there was no significant improvement in syringomyelia in 2 patients (type Ⅲ, subarachnoid decompression). Further improvement of symptoms was observed after syringomyelia-thoracic shunt. The mJOA score was improved compared with preoperative conditions (12.7±2.0 vs. 10.7±1.6, P<0.01). The follow-up time of 126 patients was 24.8 ± 10.9 months (12 to 96 months). At the last follow-up, the cervial spine mJOA scores of 126 patients were significantly higher than those before surgery (12.8±1.9 vs. 10.7±1.6, P<0.01), but there was no significant difference when compared with two weeks after surgery (P=0.48). There was no significant difference in CCOS score compared with 2 weeks post surgery (14.7±1.5 vs. 14.4±1.5, P=0.576). Conclusions Chiari malformation type Ⅰ could be classified into 3 subtypes according to cerebrospinal fluid dynamic abnormalities in the cranial-cervical junction area. Type Ⅰ is suitable for subdural decompression and type Ⅲ for subarachnoid decompression. In type Ⅱ, specific decompression methods could be chosen based on intraoperative ultrasound through bone window after craniectomy. The postoperative results seem good. Key words: Arnold-Chiari malformation; Hydrodynamics; Neurosurgical procedures; Treatment outcome; Cerebrospinal fluid; Typing

The diagnosis of ventriculoperitoneal shunt malfunction by using phase-contrast cine magnetic resonance imaging

The ventriculoperitoneal (VP) shunt is a gold standard procedure to treat hydrocephalus. However, shunt malfunction is the common complications after surgery. In this study, we utilize phase-contrast cine magnetic resonance imaging (PC cine MRI) to improve the diagnosis of VP shunt malfunction. In in vitro and in vivo experiment results demonstrate the cerebrospinal fluid (CSF) flow velocities in the shunt tube are significantly decreased in the shunt malfunction group, which indicated PC cine MRI could evaluate the CSF flow dynamics of VP shunt effectively. This method is noninvasive and simple, also can improve the diagnosis of shunt malfunction.

Accuracy of the Flow Velocity and Three-directional Velocity Profile Measured with Three-dimensional Cine Phase-contrast MR Imaging: Verification on Scanners from Different Manufacturers.

Purpose:The accuracy of flow velocity and three-directional velocity components are important for the precise visualization of hemodynamics by 3D cine phase-contrast MRI (3D cine PC MRI, also referred to as 4D-flow). The aim of this study was to verify the accuracy of these measurements of prototype or commercially available 3D cine PC MRI obtained by three different manufactures’ MR scanners.Methods:The verification of the accuracy of flow velocity in 3D cine PC MRI was performed by circulating blood mimicking fluid through a straight-tube phantom in a slanting position, such that the three-directional velocity components were simultaneously measurable, using three 3T MR scanners from different manufacturers. The data obtained were processed by phase correction, and the velocity and three-directional velocity components in the center of the tube on the central cross section of a slab were calculated. The velocity profile in each three directions and the composite velocity profiles were compared with the calculated reference values, using the Hagen–Poiseuille equation. In addition, velocity profiles and the spatially time-averaged velocity perpendicular to the tube were compared with the theoretical values and measured values by a flowmeter, respectively.Results:An underestimation of the maximum velocity in the center of the tube and an overestimation of the velocity near the tube wall due to partial volume effects were observed in all three scanners. A roughening and flattening of profiles in the center of the tube were observed in one scanner, due, presumably, to the low signal-to-noise ratio. However, the spatially time-averaged velocities corresponded well with the measured values by the flowmeter in all three scanners.Conclusion:In this study, we have demonstrated that the accuracy of flow velocity and three-directional velocity components in 3D cine PC MRI was satisfactory in all three MR scanners.

Quantitative assessment of the flow distribution in the branches of the external carotid by non-injected flow MRI

Owing to the lack of databases of blood flow distributions in the external carotid branches, surgeons currently rely on per-operative imaging and on their experience to choose the recipient vessels for microsurgical facial reconstructions. But, thanks to three-dimensional phase contrast angiography (PCA) and kinematic CINE phase contrast (PC) sequences, MRI technologies have the potential to provide quantitative anatomical and hemodynamic information without injection of contrast agent. Having developed and optimized PC-MRI sequences for the small facial vessels, our objective was to investigate the haemodynamic and blood flow distribution in the external carotid branches. We included 31 healthy volunteers in an MRI prospective study. Two-dimensional CINE PC-MRI sequences (average duration time of 2 min40 s ± 24 s) were performed in the external carotid collaterals (n = 290). A statistical analysis of the flow measurements showed that, despite large interpersonal variabilities, a general flow distribution pattern was obtained by dividing the vessel flow rates by the external carotid artery one (providing local percentages of the incoming flow). The vessels could then be classified in three haemodynamic groups (p < 0.05 Student's test): "low flow" group (lingual artery-12.5±5% of incoming flow), "intermediate flow" group (superior thyroid artery-16.5±10%, internal maxillary artery-20.5±11%, superficial temporal artery-18.4±6%), "high flow" group (facial artery -26.6±10%). Thanks to this general flow distribution mapping, it is now possible to estimate the flow rates in the distal branches of any individual from a single blood flow measurement in the external carotid artery.

Evaluation of the patency of endoscopic third ventriculostomy using phase contrast MRI-CSF flowmetry as diagnostic approach

PurposeThe aim is to assess the usefulness of cine phase-contrast MRI for evaluation of patency of endoscopic third ventriculostomy operation and correlation with clinical state postoperatively. Material & methodsProspective study performed upon 20 patients who underwent ETV operation, concerned on obstructive hydrocephalus (age range, 4–63 years; 11 male & 9 Female). Cine PC-MRI CSF flowmetry technique was applied for qualitative and quantitative assessment of CSF flow dynamics through ETV stoma to assess its patency. ResultsThe patency of ETV stoma was evaluated according to overall flow amplitude (OFA) as it was the most effective variable to predict the response to surgery, we found that when OFA value is ≥75 μL, the sensitivity and specificity of our technique to determine patient improvement were 71.4% and 76.9%, respectively.According to OFA, we classified the state of ETV stoma into three subcategories: patent stoma with adequate flow; OFA value ≥75 μL (10 patients), patent stoma with low flow; OFA value from 25 up to <75 μL (4 patients) and obstructed stoma with impaired flow; OFA value <25 μL (6 patients). ConclusionCine phase-contrast MR imaging is an effective and reliable method for evaluation and follow up of the ETV patients postoperatively.

Cerebrospinal fluid flowmetry using phase-contrast MRI technique and its clinical applications

Background and aim and aim Cine phase-contrast (PC) MRI is a useful noninvasive imaging technique in evaluating the dynamics of cerebrospinal fluid (CSF) in the evaluation, follow-up, surgical decision, and postoperative survey of certain disease processes, such as normal pressure hydrocephalus, aqueduct stenosis (AS), postendoscopic third ventriculostomy, and arachnoid cysts cases. The aim of this study was to determine the value of cardiac-gated cine-PC-MRI in characterizing CSF flow in patients with CSF flow disorders. Patients and methods The study included 30 patients with 10 persons as the control group and 20 patients who were suspected to have CSF flow abnormalities. Two imaging techniques were applied: the axial plane for flow quantification and the sagittal plane for a qualitative assessment. Results Among the 30 patients, quantitative analysis revealed the mean value to be 22 μl as the average aqueductal stroke volume in the control group. In the normal pressure hydrocephalus group, systolic velocities as well as stroke volume values were higher than those of the controls. In the AS group, lack of significant aqueductal CSF flow was noticeable. Both peak systolic and diastolic velocities were found to be statistically significantly lower in patients with AS than in the control group. In arachnoid cyst cases, CSF flow study with cine PC-MRI enables visualization of flow communication between cysts and neighboring CSF compartments. Two cases were assigned as communicating cysts and four cases were noncommunicating. Conclusion Assessment of CSF flow indicates the potentials of using PC-MRI adjunct to routine MR for the clinical study of CSF-related diseases.

Three-dimensional quantification of vorticity and helicity from 3D cine PC-MRI using finite-element interpolations.

We propose a 3D finite-element method for the quantification of vorticity and helicity density from 3D cine phase-contrast (PC) MRI. By using a 3D finite-element method, we seamlessly estimate velocity gradients in 3D. The robustness and convergence were analyzed using a combined Poiseuille and Lamb-Ossen equation. A computational fluid dynamics simulation was used to compared our method with others available in the literature. Additionally, we computed 3D maps for different 3D cine PC-MRI data sets: phantom without and with coarctation (18 healthy volunteers and 3 patients). We found a good agreement between our method and both the analytical solution of the combined Poiseuille and Lamb-Ossen. The computational fluid dynamics results showed that our method outperforms current approaches to estimate vorticity and helicity values. In the in silico model, we observed that for a tetrahedral element of 2 mm of characteristic length, we underestimated the vorticity in less than 5% with respect to the analytical solution. In patients, we found higher values of helicity density in comparison to healthy volunteers, associated with vortices in the lumen of the vessels. We proposed a novel method that provides entire 3D vorticity and helicity density maps, avoiding the used of reformatted 2D planes from 3D cine PC-MRI. Magn Reson Med 79:541-553, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Surgical management of Chiari I malformation based on different cerebrospinal fluid flow patterns at the cranial-vertebral junction

Chiari I malformation has been shown to present different cerebrospinal fluid (CSF) flow patterns at the cranial-vertebral junction (CVJ). Posterior fossa decompression is the first-line treatment for symptomatic Chiari I malformation. However, there is still controversy on the indication and selection of decompression procedures. This research aims to investigate the clinical indications, outcomes, and complications of the decompression procedures as alternative treatments for Chiari I malformation, based on the different CSF flow patterns at the cranial-vertebral junction. In this study, 126 Chiari I malformation patients treated with the two decompression procedures were analyzed. According to the preoperative findings obtained by using cine phase-contrast MRI (cine PC-MRI), the abnormal CSF flow dynamics at the CVJ in Chiari I malformation was classified into three patterns. After a preoperative evaluation and an intraoperative ultrasound after craniectomy, the two procedures were alternatively selected to treat the Chiari I malformation. The indication and selection of the two surgical procedures, as well as their outcomes and complications, are reported in detail in this work. Forty-eight patients underwent subdural decompression (SDD), and 78 received subarachnoid manipulation (SAM). Ninety patients were diagnosed as having Chiari I malformation with a syrinx. Two weeks after the operation, the modified Japanese Orthopedic Association (mJOA) scores increased from the preoperative value of 10.67±1.61 to 12.74±2.01 (P<0.01). The mean duration of follow-up was 24.8months; the mJOA scores increased from the postoperative value of 12.74±2.01 to 12.79±1.91 at the end of follow-up (P=0.48). More complications occurred in the patients who underwent SAM than in those who received SDD (SAM 11 of 78 (9.5%) vs SDD 2 of 48 (3.5%)). The abnormal CSF flow dynamics at the CVJ in Chiari I malformation can be classified into three patterns. A SAM procedure is more feasible in Chiari I malformation (CM1) patients with pattern III CSF flow dynamics, whereas a SDD procedure is more suitable for CM1 patients with pattern I CSF flow dynamics. In CM1 patients with pattern II CSF flow dynamics, an intraoperative ultrasound after craniectomy could play an important role in the selection of an effective decompression procedure.

Evaluating the effect of hydrocephalus cause on the manner of changes in the effective parameters and clinical symptoms of the disease

In the present study, the heads of 11 normal subjects and 21 patients affected by hydrocephalus due to three different causes were simulated using fluid–structure interaction (FSI). To validate the results, the calculated diagram of CSF velocity in aqueduct of Sylvius (AS) was compared with the similar velocity diagram measured using Cine PC-MRI for the same subject. After ensuring the agreement of results, other outputs such as CSF pressure were calculated non-invasively using FSI. The intracranial pressure and CSF pressure in AS and behind the optic nerve sheath were in patients 5–5.3 times the value in normal subjects and the ventricular system volume in patients was 10.2–11.1 times the value in normal subjects. However, the difference between the coefficient of variation and the maximum value of pressure and volume in different types of hydrocephalus was small. Furthermore, the difference between CSF stroke volumes in various types of hydrocephalus patients was less than 4.4%. Results showed that the intensity of clinical symptoms was similar in patients with similar CSF pressure and the cause of the hydrocephalus disease didn’t have any significant effect on the intensity of patients’ clinical symptoms and the manner of changes in effective parameters on disease. It was also found that the relation of CSF pressure and volume was 16.7% greater in patients with non-communicating hydrocephalus than in patients with communicating hydrocephalus. These results enhance the insight into hydrocephalus bio-mechanism and can help to choose the proper treatment method for hydrocephalus patients.

3D Quantification of Wall Shear Stress and Oscillatory Shear Index Using a Finite-Element Method in 3D CINE PC-MRI Data of the Thoracic Aorta.

Several 2D methods have been proposed to estimate WSS and OSI from PC-MRI, neglecting the longitudinal velocity gradients that typically arise in cardiovascular flow, particularly on vessel geometries whose cross section and centerline orientation strongly vary in the axial direction. Thus, the contribution of longitudinal velocity gradients remains understudied. In this work, we propose a 3D finite-element method for the quantification of WSS and OSI from 3D-CINE PC-MRI that accounts for both in-plane and longitudinal velocity gradients. We demonstrate the convergence and robustness of the method on cylindrical geometries using a synthetic phantom based on the Poiseuille flow equation. We also show that, in the presence of noise, the method is both stable and accurate. Using computational fluid dynamics simulations, we show that the proposed 3D method results in more accurate WSS estimates than those obtained from a 2D analysis not considering out-of-plane velocity gradients. Further, we conclude that for irregular geometries the accurate prediction of WSS requires the consideration of longitudinal gradients in the velocity field. Additionally, we compute 3D maps of WSS and OSI for 3D-CINE PC-MRI data sets from an aortic phantom and sixteen healthy volunteers and two patients. The OSI values show a greater dispersion than WSS, which is strongly dependent on the PC-MRI resolution. We envision that the proposed 3D method will improve the estimation of WSS and OSI from 3D-CINE PC-MRI images, allowing for more accurate estimates in vessels with pathologies that induce high longitudinal velocity gradients, such as coarctations and aneurisms.

Quantitative Analysis of Wall Shear Stress for Human Carotid Bifurcation at Cardiac Phases by the Use of Phase Contrast Cine Magnetic Resonance Imaging: Computational Fluid Dynamics Study

Detailed strategy for regional hemodynamics is significant for knowledge of plaque development on vascular diseases such as atherosclerosis. The aim of this study was to derive relation between atherosclerosis and hemodynamics at human carotid bifurcation by the use of computational fluid dynamics (CFD), and to provide more accurate hemodynamic information. Blood velocity datasets at common carotid artery were obtained by phase-contrast cine magnetic resonance imaging (PC cine MRI). Carotid bifurcation model was computed for systolic, mid-diastolic, and end-diastolic phase. Comparison of wall shear stress (WSS) was performed for each cardiac phase. PC cine MRI provided velocity measurement for common carotid artery with various cardiac phases. The blood velocity had acute variation from 0.21 m/s to 1.07 m/s at systolic phase. The variation of WSS during cardiac phase was presented at carotid bifurcation model. High shear stress area was observed at dividing wall for all cardiac phases. The systole-diastole WSS ratio was 10.15 at internal carotid side of bifurcation. And low shear stress (<0.5 Pa) was observed at internal carotid side of bifurcation. Bifurcation area represented low shear stress and changed significantly WSS. The specific area with significant change in shear stress and low shear stress had good agreement with predilection sites of atherosclerosis. The result suggested that hemodynamics was related to atherosclerosis, and CFD analysis with various cardiac phases that were provided by PC cine MRI was allowed to determine an accurate analysis condition. This led to the representation of hemodynamics in vivo.