Is All “Communicating” Hydrocephalus Really Communicating? Prospective Study on the Value of 3D-Constructive Interference in Steady State Sequence at 3T

Use of magnetic resonance imaging (MRI) with Constructive Interference in Steady State (CISS) sequence and isometric voxels to demonstrate the anatomic variations of vertebral artery in C2 vertebra. To determine the transarticular screw trajectory on CISS MRI and to identify patients with anatomic variations of vertebral artery in C2 vertebra. Atlantoaxial transarticular screw fixation has been reported to be biomechanically superior to other posterior techniques for atlantoaxial arthrodesis. Vertebral artery injury can be associated with catastrophic sequelae. Anatomic variation of vertebral artery is well recognized and computed tomography scan is the traditional preoperative assessment. However, no report has evaluated the use of MRI in preoperative assessment for the screw trajectories and the anatomic variation of vertebral artery. The 3-dimensional (3D) CISS MRI with isometric voxels was performed in 30 local Chinese patients. The 3D reconstruction images were created to determine the proposed screw trajectories and their relationship with the vertebral arteries. In 12 patients (40%), the vertebral arteries were lying within the screw trajectories prohibiting transarticular screw fixation on at least one side. Bilateral variations with high risk of vertebral artery injuries were found in 6 patients. The remaining 6 patients had unilateral variations prohibiting the insertion of transarticular screws on one side. The 3D CISS MRI with isometric voxels is a safe and simple imaging technique to outline the vertebral arteries in C2. Reconstruction images are easily created and undistorted. It is one of the useful imaging in preoperative planning of transarticular screw fixation and determination of anatomy of vertebral artery.

Hypothalamic hamartomas are relatively rare, non-neoplastic congenital malformations. With conventional MR images alone, small hypothalamic hamartomas may be difficult to diagnose because of artifacts from cerebrospinal fluid. We present the usefulness of three-dimensional constructive interference in steady state sequence for evaluating small hypothalamic hamartomas in three pediatric patients.

Objective To investigate the value of combined 3D-constructive interference in steady state(3D-CISS) with phase-contrast MR(PC-MR) in diagnosis of hydrocephalus children. Methods We collected retrospectively 28 children with hydrocephalus who caused by obstructive membranes.They all underwent MR imaging examination with a 1.5 T consisting of 3D-CISS, conventional sequences and PC-MR. With the result of surgery and CT cisternography as gold standard,we analysised different sequence in the diagnosis of membranous obstruction. The results of obstructive were analysed by χ2 test between 3D-CISS combined with PC-MR and conventional sequences. Results The study included 28 children, of whom 16 showed obstructive membranes in CSF pathways of ventricle and 12 displayed obstructive membranes in CSF pathways of cistern. Conventional sequences diagnosed obstructive membranes of 15 children, and obstructive membranes of 11 children were consistent with gold standard, and 4 cases were false positive. The 3D-CISS diagnosed obstructive membranes of 40, and 12 cases were false positive.There were significant difference between 3D-CISS combined with PC-MR and conventional sequence about obstructive membranes diagnosis of CSF pathways(χ2=24.410, P=0.001). Conclusions Making use of jointing 3D-CISS sequence and PC-MR sequence successively, and we can diagnose the position of obstructive membrane for hydrocephalus, which can be helpful to select a perfect surgical approach. Key words: Hydrocephalus; Magnetic resonance imaging

O.013 Mathematical modelling of acqueductal CSF flow

Stereotactic radiosurgery (SRS) is an effective treatment for vestibular schwannoma (VS). Three-dimensional (3D) constructive interference in steady state (CISS) is the preferred magnetic resonance imaging (MRI) sequence for evaluating signal changes in the inner ear endolymph. Previous studies demonstrated acorrelation between pretreatment cochlear signal intensity in 3D-CISS and posttherapeutic hearing outcomes. The purpose of our study was to compare 3D-CISS sequences before and after primary SRS of unilateral VSs to evaluate the effect of radiosurgery on the 3D-CISS signal intensities of cochlea and sacculus/utriculus. We retrospectively reviewed 47patients with unilateral VS treated with SRS. The neuroradiological MRI datasets were analysed to evaluate the signal intensity of the inner ear structure, tumour size, Koos grade, tumour volume, and infiltration of the cochlear aperture before therapy and at follow-up. The differences in these signal intensities before SRS and at follow-up were correlated with clinical symptoms, cochlear radiation dose, tumour volume and infiltration of the cochlear aperture. No differences were found between signal intensities in cochlea and utriculus/sacculus before and after SRS and no correlation with clinical symptoms, cochlear radiation dose, tumour volume, Koos grade or infiltration of the cochlear aperture (all p > 0.05). Our study supports the theory of acomplex interaction causing alteration of the endolymph protein concentration and not adirect dependency on the SRS. Use of modern dosing schemes will have apositive impact on clinical outcome with preservation of hearing in patients with VS.

Accurate visualization of dental root canals is vital for the correct diagnosis and subsequent treatment. This work assesses the improvement of a dedicated new coil for dental magnetic resonance imaging (MRI) in comparison to conventional ones in terms of signal-to-noise ratio (SNR) and visibility. A newly developed intraoral flexible coil was used to display dental roots with MRI, and it provides improved sensitivity with a loop design and size adjusted to a single tooth anatomy. Ex vivo and in vivo measurements were performed on a 3 T clinical MR system, and results were compared with conventional head and surface coil images. Additional comparison was performed with a modified fast spin echo sequence and a constructive interference in steady-state sequence. Ex vivo, an SNR gain of 6.3 could be achieved with the intraoral flexible coil setup, and higher visibility down to 200 μm was possible, whereas the external loop coil is limited to 400 μm. In vivo measurements in a volunteer resulted in an SNR gain of up to 4.5 with an improved delineation of the root canals, especially for the branch tissue splitting of the mesial root canal into mesial-buccal and mesial-lingual. In summary, we showed the feasibility of implementing a wireless coil approach with readily available dental practice materials for sealing and placement. Highly improved MRI scans can be acquired within clinically feasible scan times, and this might provide additional medical findings to supplement available x-ray images.

The inner ears of 167 patients with vertigo and/or abnormal findings at vestibular testing were studied using magnetic resonance (MR). Pathology potentially explaining vertigo was found in 54 patients, and was detected in the posterior fossa (28%), the internal auditory canal (28%) and the membranous labyrinth (44%). The overall percentage of pathology and the percentage of pathology found in the membranous labyrinth was high and was probably influenced by the referral pattern in our hospital where high resolution MR of the inner ear (three dimensional Fourier transformation-constructive interference in steady state sequence; 3DFT-CISS sequence) is available. Unenhanced, and especially gadolinium (Gd)-enhanced T1-weighted spin-echo images, are needed to detect most of the pathology inside the internal auditory canal, and some of the lesions inside the membranous labyrinth. 3DFT-CISS images are the only images that can show fibrous obliteration of the intralabyrinthine fluid spaces, and are therefore necessary to recognise most of the intralabyrinthine pathology. Finally, T2-weighted spin-echo images are best suited to demonstrate cerebellar or brain stem infarction. An additional MR-angiography sequence (three dimensional Fourier transformation-fast imaging with steady precession; 3DFT-FISP) is used when vascular compression of the cochleovestibular nerve is suspected. MR is the method of choice to look for pathology in patients with vertigo, and allows detection of pathology that remains invisible with other imaging techniques. However, well adapted sequences are needed to detect these lesions.

Recurrent laryngeal nerve (RLN) preservation is critical in both parathyroid and thyroid surgery. RLN imaging can determine both the location and trajectory relative to key cervical structures. In this chapter, we present an overview of nerve imaging methods using Magnetic Resonance Imaging (MRI). We highlight key techniques that enable the resolution required to image small nerves, such as the facial and cranial nerves. Furthermore, we discuss the challenges involved in RLN imaging and present preliminary MRI results using a novel phase-navigated T2-Turbo Spin-Echo and Constructive Interference in Steady-State sequences. Ultimately, preoperative MRI images can guide surgical planning or be used with a navigation system during surgery to localize and preserve the RLN in real-time.

Abnormalities within the spinal arachnoid space are often treated surgically, but they can be challenging to detect with conventional magnetic resonance imaging (MRI) sequences. 3D-CISS sequences are considered superior in evaluating structures surrounded by cerebrospinal fluid (CSF) due to the high signal-to-noise ratio, high contrast-to-noise ratio and intrinsic insensitivity to motion with minimal signal loss due to CSF pulsations. Our objective was to describe findings and advantages in adding 3D-CISS sequences to routine MRI in patients affected by spinal arachnoid diverticula (SAD) or arachnoid adhesions. This article is a retrospective review of medical records of 19 dogs admitted at Fitzpatrick Referrals between 2013 and 2017 that were diagnosed with SAD and confirmed surgically. Inclusion criterions were the presence of clinical signs compatible with compressive myelopathy and an MRI diagnosis, which included the 3D-CISS sequence. Our database was searched for additional 19 dogs diagnosed with other spinal lesions other than SAD that had the same MR sequences. All MR images were anonymized and evaluated by two assessors. 3D-CISS sequence appears to improve confidence in diagnosing and surgical planning (Mann-Whitney U-test: p < 0.0005), delineating SAD from other changes associated with abnormal CSF hydrodynamics and providing more anatomical details than conventional MRI sequences. The clinical data in combination with imaging findings would limit over interpretation, when concurrent pathology within the arachnoid space is present.

Purpose : To assess the value of 3D CISS (constructive interference in steady state) MR sequence in imaging the cervical spine. Materials and Methods : MR images of cervical spine were prospectively obtained with both conventional (sagittal TSE and axial 2D FLASH) and CISS sequences in 20 patients suspected of having cervical spinal diseases. MR technique was performed on a 1.5T MR machine. Axial, oblique coronal, and curved coronal images were reformatted with the 3D raw datas of CISS sequence which were obtained in cornal plane. The findings of CISS sequence were compared with those of the conventional sequence in terms of visualization of the neural foramen and nerve roots, detection and differentiation of herniated disc, conspicuity of the intramedullary lesion, contrast between the CSF and spinal cord and between the gray and white matters within the cord. Results : In 17 cases including traumatic root avulsions, 3D CISS sequence demonstrated the intradural nerve roots with excellent contrast especially in coronal plane. Reformatted oblique coronal images of CISS sequence offered better visualization of entire neural foramen beyond the region of interest. CISS sequence was superior to the conventional sequence in demonstration of disease extent and correlation to the clinical symptoms in 4.5 cases of foraminal stenosis and in contrast between the CSF and spinal cord (n=15). CISS sequence was almost equal to the conventional sequence in detection of herniated disc (n=15). CISS was inferior to the conventional sequence in differentiation of herniated disc (n=7), delineation of intramedullary lesion (n=4) and in contrast between the gray and white matter within the cord in all patients. Conclusion : The 3D CISS sequence gives better information than the conventional sequence especially in the evaluation of the nerve roots and neural foramens but worse contrast of intramedullary lesion. It may well be used as a supplementary sequence in assessment of foraminal stenosis and nerve root injury.

To evaluate three-dimensional (3D) constructive interference in steady-state (CISS) magnetic resonance (MR) imaging and MR angiography with multiplanar reconstruction (MPR) for detection of neurovascular compression (NVC) in patients with trigeminal neuralgia and to evaluate the relationship between clinical symptoms related to trigeminal branches and those related to the site of trigeminal nerve compression. Fifty-four consecutive patients with trigeminal neuralgia were examined at 3D CISS imaging and MR angiography with a 1.5-T MR system. Original transverse and four reformatted images were used for image interpretation. Vascular contact with the trigeminal nerve at the root entry zone (REZ) was determined, and the nature of the involved vessels was identified. The position of the blood vessel compressing the nerve was classified into cranial, caudal, medial, or lateral sites. Statistical analysis was performed with the chi2 test or the Fisher exact test between two groups and with the chi2 test among more than two groups. In 12 of 15 patients who underwent surgery, the artery that was considered a responsible vessel at 3D CISS imaging and MR angiography was confirmed as such. In the other three patients, the vein was the responsible vessel, which was detected only at 3D CISS imaging. Sixteen (89%) of 18 patients with symptoms related to the maxillary division had NVC at the medial site of the REZ, while 16 (76%) of 21 patients with symptoms related to the mandibular division had NVC at the lateral site (P <.001, chi2 test). 3D CISS MR imaging with MPR is useful in the detection of NVC in patients with trigeminal neuralgia, compared with MR angiography. A close relationship was found between the region of neuralgic manifestation and the site of trigeminal nerve compression.

The role of DCE-MR imaging in the study of bone marrow perfusion is only partially developed, though potential applications for routine use in the clinical setting are beginning to be described. We hypothesize that DCE-MR imaging can be used to discriminate between hypervascular and hypovascular metastases based on measured perfusion variables. We conducted a retrospective study of 26 patients using conventional MR imaging and DCE-MR imaging. Patients were assigned to a hypervascular or hypovascular group based on tumor pathology. ROIs were drawn around normal-appearing bone marrow (internal controls) and enhancing tumor areas. Average wash-in enhancement slope, average peak enhancement signal percentage change, and average peak enhancement signal percentage change in areas of highest wash-in enhancement slope were calculated. Indices were compared among control, hypervascular, and hypovascular groups. Conventional imaging was assessed by calculating pre- to postgadolinium signal percentage changes in hypervascular and hypovascular lesions. Hypervascular and hypovascular tumors differed significantly with regard to wash-in enhancement slope (P < .01; hypervascular 95% CI, 22.5-26.5 AU/s; hypovascular 95% CI, 14.1-20.9 AU/s) and peak enhancement signal percentage change in areas of highest wash-in enhancement slope (P < .01; hypervascular 95% CI, 174.1-323.3%; hypovascular 95% CI, 39.5-150.5%). Peak enhancement signal percentage change over all voxels was not significant (P = .62). Areas of normal-appearing marrow showed no appreciable contrast enhancement. Conventional contrast-enhanced MR imaging was unable to differentiate between hypervascular and hypovascular tumors (P = .58). Our data demonstrate that, unlike conventional MR imaging sequences, DCE-MR imaging may be a more accurate technique in discriminating hypervascular from hypovascular spinal metastases.

3D-constructive interference into steady state (3D-CISS) labyrinth signal alteration in patients with vestibular schwannoma

Compressed sensing-sensitivity encoding is a promising MR imaging acceleration technique. This study compares the image quality of compressed sensing-sensitivity encoding accelerated imaging with conventional MR imaging sequences. Patients with known, treated, or suspected brain tumors underwent compressed sensing-sensitivity encoding accelerated 3D T1-echo-spoiled gradient echo or 3D T2-FLAIR sequences in addition to the corresponding conventional acquisition as part of their clinical brain MR imaging. Two neuroradiologists blinded to sequence and patient information independently evaluated both the accelerated and corresponding conventional acquisitions. The sequences were evaluated on 4- or 5-point Likert scales for overall image quality, SNR, extent/severity of artifacts, and gray-white junction and lesion boundary sharpness. SNR and contrast-to-noise ratio values were compared. Sixty-six patients were included in the study. For T1-echo-spoiled gradient echo, image quality in all 5 metrics was slightly better for compressed sensing-sensitivity encoding than conventional images on average, though it was not statistically significant, and the lower bounds of the 95% confidence intervals indicated that compressed sensing-sensitivity encoding image quality was within 10% of conventional imaging. For T2-FLAIR, image quality of the compressed sensing-sensitivity encoding images was within 10% of the conventional images on average for 3 of 5 metrics. The compressed sensing-sensitivity encoding images had somewhat more artifacts (P = .068) and less gray-white matter sharpness (P = .36) than the conventional images, though neither difference was significant. There was no significant difference in the SNR and contrast-to-noise ratio. There was 25% and 35% scan-time reduction with compressed sensing-sensitivity encoding for FLAIR and echo-spoiled gradient echo sequences, respectively. Compressed sensing-sensitivity encoding accelerated 3D T1-echo-spoiled gradient echo and T2-FLAIR sequences of the brain show image quality similar to that of standard acquisitions with reduced scan time. Compressed sensing-sensitivity encoding may reduce scan time without sacrificing image quality.

Evaluation of giant arachnoid granulations with high-resolution 3D-volumetric MR sequences at 3T