Cerebrospinal Fluid Flow Artifacts Research Articles

Cerebrospinal Fluid CSF Flow Artifacts are Associated with Brain Pulsation in Patients with Severe Carotid Artery Stenoses.

We investigated the factors associated with cerebrospinal fluid (CSF) flow artifacts on fluid-attenuated inversion recovery imaging in patients with carotid artery (CA) stenosis. Each CSF artifact grade was defined by comparing the highest intensity in a given region of interest (ROI) to those in reference ROIs, as follows: higher than the intensity of normal white matter in the centrum semiovale = 2 points; equal to or less than the white matter, and higher than CSF = 1 point; and equal to CSF = 0. CSF flow scores in eight sites were measured and added to the total score (0 -16). The prevalences of each finding, specifically white matter lesions, CA stenoses and brain atrophy, were compared using multivariate logistic regression models. We evaluated the findings in 54 patients with CA stenosis treated by CA stenting (CAS) and 200 adults with no history of neurological disorders (control group). Adjusted by stroke risk factors, a CSF flow score ≤ 11 was positively associated with CA stenosis, heart rate > 70 / min, and brain atrophy, and negatively with the female gender. The score was 12.8 ± 1.8 in the control group and 12.0 ± 2.0 in CA stenosis group after CAS, which was significantly higher than before CAS (10.4 ± 2.8, p<0.001). The CSF flow score was associated with female gender, brain atrophy, heart rate, and severe CA stenosis, and was found to be elevated after revascularization.

The Value of Different Magnetic Resonance Imaging Sequences for the Detection of Intraventricular Hemorrhages*

The aim of this study was to determine the value of different magnetic resonance imaging (MRI) sequences for the diagnosis of intraventricular hemorrhages (IVHs). The study included 22 consecutive patients with computed tomography (CT) proven IVH in which an MR examination had been performed. Proton-density-(PD-), T2-, fluid-attenuated inversion-recovery (FLAIR), T1- and T2*-weighted images were evaluated retrospectively by two neuroradiologists regarding presence and anatomical distribution of IVH, and cerebrospinal fluid (CSF) flow artifacts. CT was used as gold standard. According to CT, IVH was located in the right/left lateral ventricles in 16/17 patients, in the third ventricle in seven and in the fourth ventricle in twelve cases. PD- and T2*-weighted images both showed a 100% sensitivity and specificity for the overall diagnosis of IVH, and a high sensitivity for the detection of IVH in all four ventricles. The sensitivity of T1-, T2- and FLAIR- weighted images for the overall presence of an IVH was 77%, 85%, and 93%, respectively, with specificities of 100%. CSF flow artifacts occurred predominantly in the third and fourth ventricles. While FLAIR- and T2-weighted sequences were especially prone to this phenomenon, T1-, T2*- and PD-weighted images showed a higher resistance to those artifacts. This study demonstrates a high sensitivity of PD- and T2*-weighted images in the detection of IVH. On the contrary, T2-, T1- and FLAIR-weighted sequences were not suitable for a reliable detection of IVH.

FLAIR imaging using nonselective inversion pulses combined with slice excitation order cycling and k-space reordering to reduce flow artifacts.

High-signal artifacts produced by cerebrospinal fluid (CSF) flow can adversely affect fluid-attenuated inversion recovery (FLAIR) imaging of the brain and spinal cord. This study explores the use of a nonslice-selective inversion pulse to eliminate CSF flow artifacts together with a technique called "K-space Reordered by Inversion-time for each Slice Position" (KRISP) to achieve constant contrast in a multislice acquisition. Theory shows that with this method the CSF point spread function (PSF) has a minimum at the center and attenuated side lobes, providing CSF suppression, but residual edge signals remain. The PSF for brain is only mildly attenuated and signals for extended regions are not attenuated. KRISP FLAIR sequences were assessed in 15 patients (10 brain and five spinal cord cases). The images showed reduced CSF and blood flow artifacts and higher conspicuity of the cortex, meninges, ventricular system, brainstem, and cerebellum when compared with conventional FLAIR sequences.

Contributions of an Adiabatic Initial Inversion Pulse and K-space Re-ordered by Inversion-time at each Slice Position (KRISP) to Control of CSF Artifacts and Visualization of the Brain in FLAIR Magnetic Resonance Imaging

The aim of this study was to compare the performance of three fluid attenuated inversion recovery (FLAIR) pulse sequences for control of cerebrospinal fluid (CSF) and blood flow artifacts in imaging of the brain. The first of these sequences had an initial sinc inversion pulse which was followed by conventional k-space mapping. The second had an initial sinc inversion pulse followed by k-space re-ordered by inversion time at each slice position (KRISP) and the third had an adiabatic initial inversion pulse followed by KRISP. Ten patients with established disease were studied with all three pulse sequences. Seven were also studied with the adiabatic KRISP sequence after contrast enhancement. Their images were evaluated for patient motion artifact, CSF and blood flow artifact as well as conspicuity of the cortex, meninges, ventricular system, brainstem and cerebellum. The conspicuity of lesions and the degree of enhancement were also evaluated. Both the sinc and adiabatic KRISP FLAIR sequences showed better control of CSF and blood flow artifacts than the conventional FLAIR sequence. In addition the adiabatic KRISP FLAIR sequence showed better control of CSF artifact at the inferior aspect of the posterior fossa. The lesion conspicuity was similar for each of the FLAIR sequences as was the degree of contrast enhancement to that shown with a T(1)weighted spin echo sequence. The KRISP FLAIR sequence controls high signal artifacts from CSF flow and blood flow and the adiabatic pulse controls high signal artifacts due to inadequate inversion of the CSF magnetization at the periphery of the head transmitter coil. The KRISP FLAIR sequence also improves cortical and meningeal definition as a result of an edge enhancement effect. The effects are synergistic and can be usefully combined in a single pulse sequence. Curati, W. L.et al. (2001)Clinical Radiology56, 375-384

CSF flow artifact reduction using cardiac cycle ordered phase-encoding method

The flow effects appear as a change of phase as well as signal intensity in NMR imaging. Since the flow of blood and CSF (cerebrospinal fluid) is pulsatile due to the heart pumping, their velocities are not constant during NMR imaging. This type of velocity fluctuation such as the blood or CSF flow induces irregular flow-dependent phase shifts, which have been one of the main causes of flow artifacts in NMR imaging. In order to reduce the flow artifacts, especially the CSF flow artifacts, a new cardiac cycle ordered phase encoding method is proposed and has been studied. This proposed technique utilizes the cardiac cycle as a precursor for the phase encoding gradients similar to the ROPE (respiratory ordered phase encoding) technique which has been used for respiratory motion artifact reduction. The basic concept and its applications are discussed together with the experimental results obtained with human volunteers using the KAIS 2.0 2.0 T whole-body NMR imaging system.

The Motion Artifact Suppression Taechnique (MAST) in magnetic resonance imaging: Clinical results

The Motion Artifact Suppression Technique (MAST) is a method which uses a series of gradient echos that are computed to cancel velocity, acceleration and pulsatility components of involuntary motion in MR imaging. A total of 916 patient studies were performed over a nine month period using MAST sequences with a TE 40, 60, 80, 100, 120, and 26/112. There was considerable improvement in long TR, long TE images. Cerebrospinal fluid flow artifacts were reduced. Body and spine images had reduced flow and respiratory artifacts. Spin rephasing in blood vessels caused increase intraluminal signal. This might be useful for cardiovascular imaging.

CSF-gated MR imaging of the spine: theory and clinical implementation.

A spine phantom and cervical spines of seven volunteers were studied with cerebrospinal fluid (CSF)-gated magnetic resonance imaging to optimize acquisition factors reducing CSF flow artifacts. Peripheral gating was performed with either an infrared reflectance photoplethysmograph or peripheral arterial Doppler signal. The effects of effective repetition time, echo train, trigger delay, number of sections, and imaging plane on image quality were evaluated. Gated imaging of oscillatory CSF motion simulated constant-velocity flow and reduced CSF flow artifacts caused by cardiac-dependent temporal phase-shift effects. Velocity compensation on sagittal even-echo images with a symmetric short-echo time echo train reduced the remaining CSF flow artifacts caused by spatial phase-shift effects. Overall gated imaging time was not increased compared with nongated imaging and was reduced when improved image quality permitted the use of fewer excitations. These results suggest that the combination of CSF gating and flow compensation is clinically useful and efficient because it improves image quality without prolonging imaging time.

Optimizing conventional MR imaging of the spine.

With the use of conventional spin-echo pulse sequences with a long repetition time (TR), the echo time (TE) and the number of echoes were varied to minimize cerebrospinal fluid (CSF) flow artifacts in a spine phantom and in cervical spines of three volunteers. The following echo trains were compared in both axial and sagittal planes with a TR of 2,000 msec: TE of 25, 80 msec ("asymmetric"); TE of 40, 80 msec ("symmetric long TE"); and TE of 20, 40, 60, and 80 msec ("symmetric short TE"). Variable degrees of even-echo rephasing of CSF flow artifacts were observed during sagittal but not axial imaging, depending on the echo train used. Even-echo rephasing was most complete with the symmetric short-TE echo train, less complete with the symmetric long-TE echo train, and absent with the asymmetric echo train. Switching the orientation of the phase and frequency encoding gradients and slightly modifying TR on the basis of the heart rate further improved image quality. The results suggest that a symmetric short-TE echo train may be used to provide velocity compensation (similar to that observed with rephasing gradients) on even echoes of conventional spin-echo pulse sequences during spine imaging.