Interference In Steady State Sequence Research Articles

Capability of constructive interference in steady state sequence versus postcontrast T1-weighted imaging in cerebellopontine angle and internal auditory canal masses

Background: The tumor size is one of the main factors in the treatment of cerebellopontine angle (CPA) tumors, and magnetic resonance imaging (MRI) with gadolinium-based contrast agent (GBCA) provides the best evaluation. However, administration of the gadolinium is time consuming and increasing in cost. There is a risk of nephrogenic systemic fibrosis in patients with renal failure and liver or renal transplantation. Objective: The purpose of this study was to assess the capability of constructive interference in steady state (CISS) sequence in measuring the tumor size of the CPA and internal auditory canal (IAC) masses compared to postcontrast T1-weighted images (T1-WI). Materials and Methods: The 118 MR studies with both CISS sequence and postcontrast T1-WI of 45 patients with CPA and IAC masses were retrospectively reviewed. Results: There was no significant difference between CISS and postcontrast T1-WI in measuring size in transverse diameter of the masses (p = 0.051-0.06). The longitudinal diameter measurement revealed a significant difference (p < 0.001) and the measured size on postcontrast T1-WI was slightly larger than the CISS image. The difference in median measurement between two sequences was less than 0.9 mm. and Bland-Altman plots revealed that differences between the two sequences in longitudinal and transverse diameters of the masses were within the limits of agreement. Interobserver agreement showed excellent correlation (r = 0.994-0.999, p < 0.001 by Pearson's product-moment correlation). Conclusions: The CISS sequence may be sufficient for assessing the size of CPA and IAC masses, which can be used interchangeably with postcontrast T1-weighted image as a contrast-free option, especially in follow-up studies and vulnerable settings of gadolinium administration.

57-Year-Old Man With Headache, Vomiting, and Gait Instability

57-Year-Old Man With Headache, Vomiting, and Gait Instability

Signal Alteration of the Inner Ear on High-Resolution Three-Dimensional Constructive Interference in Steady State Sequence in Patients with Ménière’s Disease and Labyrinthitis

Introduction: The aim of this study is to evaluate signal alteration in the inner ear using three-dimensional (3D)-constructive interference in steady state (CISS) sequence in patients with Ménière’s disease and labyrinthitis and its correlation with clinical and audiological parameters. Methods: The medical records of the department of otorhinolaryngology were searched for patients with Ménière’s disease or labyrinthitis who underwent MRI with 3D-CISS sequence. Blinded analysis of these patients and of MRI from control subjects without middle or inner ear symptoms was performed to detect any signal asymmetry of the inner ear structures. The results were correlated with clinical symptoms and results of audiological and vestibular tests. Results: Fifty-eight patients with definite Ménière’s disease and 5 patients with labyrinthitis as well as 41 control exams were included. A separate analysis was performed for patients with probable Ménière’s disease (n = 68). A total of 172 3D-CISS sequences were analyzed by 2 blinded independent neuroradiologists. A CISS-hypointense signal of the inner ear structures was found in 3 patients with definite Ménière’s disease (5.2%), in 4 patients with probable Ménière’s disease (5.9%), and 2 patients with labyrinthitis (40%). No CISS hypointensity was found in the control group. Although no significant difference in symptoms or audiological test results was found between patients with and without this signal change, the side of hypointensity was frequently correlated with the symptomatic side and with hearing impairment. Discussion/Conclusion: CISS hypointensity of the inner ear structures was evident in patients with clinical conditions other than vestibular schwannoma – more frequently in labyrinthitis than in Ménière’s disease. This signal alteration was frequently encountered on the same symptomatic side as that of the pathological audiology tests, but it is not a predictor for hearing or vestibular impairment.

Association of Lymphatic Fluid Volume in the Inner Ear of Beagle Dogs with the Susceptibility to Motion Sickness.

Background:This study aimed to quantify total lymphatic fluid spaces of the inner ears volumetrically in the dog in order to find a correlation between the lymphatic volume of the inner ears and motion sickness susceptibility.Methods:A total of 16 healthy adult Beagle dogs were used to delineate the lymphatic fluid spaces of inner ears by magnetic resonance imaging with a 3-dimensional-constructive interference steady-state sequence. Manual segmentation was applied for 3-dimensional reconstruction and volumetric quantification of total lymphatic space. The susceptibility of Beagle dogs to motion sickness was judged by latency of vomiting during rotatory stimulus.Results:The volume range of total fluid space in the vestibule and cochlea of Beagle dogs is 55.07 ± 6.2 mm3. There is no significant difference in the total lymphatic volume of bilateral inner ears between 2 different motion sickness susceptibility groups (i.e., sensitive group and insensitive group), but the difference of lymphatic volume in the cochlea and vestibule between bilateral inner ears in insensitive group is greater than that of sensitive group. Moreover, a significant positive correlation was found between bilateral inner ear difference in lymphatic volume and vomiting latency.Conclusion:Magnetic resonance imaging could be used as a method to evaluate the inner ear lymphatic fluid volume of Beagle dogs with different susceptibilities to motion sickness, through which we found that motion sickness susceptibility is related to the difference in lymphatic volume in the vestibule and cochlea between bilateral inner ears, and the larger the volume difference, the lower the susceptibility.

Reproducibility and postacquisition correction methods for quantitative magnetic resonance imaging of the anterior cruciate ligament (ACL).

Quantitative magnetic resonance imaging has been used to evaluate the structural integrity of knee joint structures. However, variations in acquisition parameters between scanners pose significant challenges. Understanding the effect of small differences in acquisition parameters for quantitative sequences is vital to the validity of cross-institutional studies, and for the harmonization of large, heterogeneous datasets to train machine learning models. The study objective was to assess the reproducibility of T2 * relaxometry and the constructive interference in steady-state sequence (CISS) across scanners, with minimal hardware-necessitated changes to acquisition parameters. It was hypothesized that there would be no significant differences between scanners in anterior cruciate ligament T2 * relaxation times and CISS signal intensities (SI). Secondarily, it was hypothesized that differences could be corrected by rescaling the SI distribution to harmonize between scanners. Seven volunteers were scanned on 3T Prisma and Tim Trio scanners (Siemens). Three correction methods were evaluated for T2 *: inverse echo time scaling, z-scoring, and Nyúl histogram matching. For CISS, scans were normalized to cortical bone, scaled by the background noise ratio, and log-transformed. Before correction, significant mean differences of 6.0 ± 3.2 ms (71.8%;p = 0.02) and 0.49 ± 0.15 units (40.7%; p = 0.02) for T2 * and CISS across scanners were observed, respectively. After rescaling, T2 * differences decreased to 2.6 ± 2.7 ms (23.9%;p = 0.03), 1.3 ± 2.5 ms (10.9%;p = 0.13), and 1.27 ± 3.0 ms (19.6%;p = 0.40) for inverse echo time, z-scoring, and Nyúl, respectively, while CISS decreased to 0.01 ± 0.11 units (4.0%; p = 0.87). These findings suggest that small acquisition parameter differences may lead to large changes in T2 * and SI values that must be reconciled to compare data across magnets.

Inductively Coupled Intraoral Flexible Coil for Increased Visibility of Dental Root Canals in Magnetic Resonance Imaging.

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.

A transfer learning approach for automatic segmentation of the surgically treated anterior cruciate ligament.

Quantitative magnetic resonance imaging enables quantitative assessment of the healing anterior cruciate ligament or graft post-surgery, but its use is constrained by the need for time consuming manual image segmentation. The goal of this study was to validate a deep learning model for automatic segmentation of repaired and reconstructed anterior cruciate ligaments. We hypothesized that (1) a deep learning model would segment repaired ligaments and grafts with comparable anatomical similarity to intact ligaments, and (2) automatically derived quantitative features (i.e., signal intensity and volume) would not be significantly different from those obtained by manual segmentation. Constructive Interference in Steady State sequences were acquired of ACL repairs (n = 238) and grafts (n = 120). A previously validated model for intact ACLs was retrained on both surgical groups using transfer learning. Anatomical performance was measured with Dice coefficient, sensitivity, and precision. Quantitative features were compared to ground truth manual segmentation. Automatic segmentation of both surgical groups resulted in decreased anatomical performance compared to intact ACL automatic segmentation (repairs/grafts: Dice coefficient = .80/.78, precision = .79/.78, sensitivity = .82/.80), but neither decrease was statistically significant (Kruskal-Wallis: Dice coefficient p = .02, precision p = .09, sensitivity p = .17; Dunn post-hoc test for Dice coefficient: repairs/grafts p = .054/.051). There were no significant differences in quantitative features between the ground truth and automatic segmentation of repairs/grafts (0.82/2.7% signal intensity difference, p = .57/.26; 1.7/2.7% volume difference, p = .68/.72). The anatomical similarity performance and statistical similarities of quantitative features supports the use of this automated segmentation model in quantitative magnetic resonance imaging pipelines, which will accelerate research and provide a step towards clinical applicability.

Feasibility of three-dimensional constructive interference in steady state sequences for evaluating the anterolateral ligament

The purpose of the study was to determine the feasibility of three-dimensional (3D) constructive interference in steady state (CISS) sequences for evaluating the anterolateral ligament (ALL). Magnetic resonance imaging (MRI) of the right knee joint in 30 healthy volunteers was performed using a 3 T MRI machine. Axial T2-weighted imaging with fat saturation (T2WI-FS), coronal proton-density-weighted imaging with fat saturation (PDWI-FS), and 3D-CISS were included in the protocol. Multiplanar reconstruction (MPR) and rotating stretched curved planar reconstructions (CPRs) of the ALL at 30°, 60°, 90°, 120°, and 150° were generated from the 3D-CISS images. The visibility of the femoral part, meniscal part, tibial part, meniscal insertion, femoral footprint, and tibial footprint of the ALL on the imaging of all sequences was recorded. Based on the CPR of 3D-CISS MRI, the presence of tibial and femoral footprints of the ALL was rated superior to MPR and PDWI-FS (96.67% and 96.67%, respectively; p<0.017). Rotating CPR of 3D-CISS MRI imaging was rated superior to PDWI-FS with respect to the tibial part, meniscal part, and meniscal insertion of the ALL (96.67%, 83.33%, and 83.33%, respectively; p<0.05). Rotating CPR of 3D-CISS MRI was rated superior to PDWI-FS with respect to the femoral part of the ALL, but the difference was not statistically significant (p=0.095). The angle between the ALL and lateral collateral ligament (LCL) on the oblique sagittal image was 18.34±1.88°. The MRI 3D-CISS sequences significantly enhanced the ability to identify the ALL compared to the 2D MRI sequences.

A Classification for the Anterior Inferior Cerebellar Artery-Subarcuate Artery Complex Based on the Embryological Development.

Objective To hierarchize the anterior inferior cerebellar artery (AICA)-subarcuate artery (SAA) complex's variations in the surgical field. Background The AICA's "subarcuate loop" (SL) presents multiple variations, closely related to the SAA. AICA-SAA complex's variations may represent major issues in cerebellopontine angle (CPA) surgery. As the spectrum of configurations is originated during the development, a systematized classification was proposed based on the interaction between the petrosal bone and the AICA in the embryonic period. Methods The variations were defined as follow: Grade 0: free, purely cisternal AICA, unidentifiable or absent SAA; Grade 1: purely cisternal AICA, loose SL, SAA > 3 mm; Grade 2: AICA near the subarcuate fossa, pronounced SL, SAA <3 mm; Grade 3: "duralized" AICA, unidentifiable SAA, or included in the petromastoid canal (PMC); and Grade 4: intraosseous AICA, unidentifiable SAA, or included in the PMC. The classification was applied to a series of patients assessed by magnetic resonance constructive interference in steady state sequence. Surgical examples were also provided. Results Eighty-four patients were evaluated, including 161 CPA. The proportions found in the gradation remained within the range of previous publications (Grade 0: 42.2%; Grade 1: 11.2%; Grade 2: 35.4%; Grade 3: 10.6%; and Grade 4: 0.6%). Moreover, the degrees of the classification were related to the complexity of the anatomical relationships and, therefore, to the difficulty of the maneuvers required to overcome them. Conclusion The proposed AICA-SAA complex classification allowed to distinguish and objectify pre- and intraoperatively the spectrum of variations, to thoroughly plan the required actions and instrumentation.

Significance of the Cerebellopontine Cistern Cross-Sectional Area and Trigeminal Nerve Anatomy in Trigeminal Neuralgia: An Anatomical Study Using Magnetic Resonance Imaging.

To evaluate the relationship between trigeminal neuralgia (TN) and potential magnetic resonance imaging (MRI)-related measurements in patients with TN. Retrospective analysis of 104 patients with TN was performed. MRI studies of 98 healthy controls were included in the study to compare the parameters with TN patients’ measurements. MRI measurements of cerebellopontine cistern (CPC) cross-sectional area, trigeminal-pontine angle (TPA) width, and trigeminal nerve cisternal segment length and thickness were assessed on both symptomatic and asymptomatic sides using 1.5T MRI with constructive interference in steady-state sequences. The images were interpreted by two radiologists blinded to the affected sides of the patients. There were significant differences between the symptomatic and asymptomatic sides in terms of mean trigeminal nerve length (8.8 ± 2.34 mm vs. 9.39 ± 2.29 mm; respectively, p=0.001) and thickness (20.9 ± 9.6 mm2 vs. 25 ± 9.98 mm2, respectively; p < 0.001). The median cerebellopontine cistern cross-sectional area was considerably lower on the symptomatic side compared with the asymptomatic side [201 mm2 (interquartile range=93) vs. 224.5 mm2 (interquartile range=77), respectively; p < 0.001]. There were no significant differences between the trigeminal-pontine angle width on either side (38.32 ± 10.38 vs. 38.78 ± 10.9, respectively; p=0.679). There were no statistically significant differences between the right and left sides regarding these parameters in the control group. Smaller CPC cross-sectional area, trigeminal nerve length, and trigeminal nerve thickness on MRI were demonstrated to commonly exist on the symptomatic side in patients with TN. We suggest that this narrow space may increase the risk of vascular compression on the nerve.

Agreement between transverse T2-weighted and three-dimensional constructive interference in steady state sequences in the evaluation of spinal cord disease in dogs

The constructive interference in steady state (CISS) sequence has been widely used in human neuroimaging. It has been shown to be advantageous in the evaluation of intra-axial and extra-axial cystic...

The value of MRI 3D-CISS sequence in trigeminal neuralgia-related diseases

Objective To explore 3D constructive interference insteady state sequence value of related diseases in trigeminal neuralgia. Methods A retrospective analysis of 62 cases of trigeminal neuralgia as the main symptoms of patients with brain magnetic resonance imaging (MRI) routine scan and 3D constructive interference insteady state (3D-CISS) sequence images, of which 12 cases were enhanced scan, comparative analysis of MRI 3D-CISS sequence and conventional sequence of trigeminal nerve. The lesion showed the condition and was compared with the outcome of the operation. Trigeminal neuralgia-related lesions mainly included the trigeminal nerve brain pool around the vascular compression or transition, solid tumors and tumor-like lesions. Results Preoperative MRI 3D-CISS sequence was used to diagnose the vascular compression or metastasis of the trigeminal nerve pool segment in 46 cases. Forty-five patients were found to be responsible blood vessels. The 3D-CISS sequence showed 95.83% coincidence with surgical exploration. The routine sequence could not show the trigeminal The brain around the brain was forced or pushed. 3D-CISS sequence showed eight cases of solid tumors, routine scan showed six cases of solid tumors. Tumor-like lesions were shown in 6 cases of MRI3D-CISS sequences and routine plain scan sequences. The sensitivity of 3D-CISS sequence to trigeminal neuralgia-related disease was 96.77%, and the sensitivity of MRI routine scan to trigeminal neuralgia was only 19.35%. There was significant difference in the sensitivity of 3D-CISS sequence and conventional plain scan sequence to trigeminal neuralgia-related diseases (P<0.01). Conclusions MRI 3D-CISS sequence has a significant advantage in trigeminal neuralgia-related disease, and patients with trigeminal neuralgia should routinely use 3D-CISS sequences. Key words: Magnetic resonance imaging; Trigeminal neuralgia/CO/DI

Analogous Three-Dimensional Constructive Interference in Steady State Sequences Enhance the Utility of Three-Dimensional Time of Flight Magnetic Resonance Angiography in Delineating Lenticulostriate Arteries in Insular Gliomas: Evidence from a Prospective Clinicoradiologic Analysis of 48 Patients

Three-dimensional (3D) time of flight (TOF) imaging is the current gold standard for noninvasive, preoperative localization of lenticulostriate arteries (LSAs) in insular gliomas; however, the utility of this modality depends on tumor intensity. Over a 3-year period, 48 consecutive patients with insular gliomas were prospectively evaluated. Location of LSAs and their relationship with the tumor were determined using a combination of contrast-enhanced coronal 3D TOF magnetic resonance angiography and coronal 3D constructive interference in steady state (CISS) sequences. These findings were analyzed with respect to extent of tumor resection and early postoperative motor outcome. Tumor was clearly visualized in 29 (60.4%) patients with T1-hypointense tumors using 3D TOF and in all patients using CISS sequences. Using combined 3D TOF and CISS, LSA-tumor interface was well seen in 47 patients, including all patients with T1-heterointense or T1-isointense tumors. Extent of resection was higher in the LSA-pushed group compared with the LSA-encased group. In the LSA-encased group, 6 (12.5%) patients developed postoperative hemiparesis; 2 (4.2%) cases were attributed to LSA injury. Contrast-enhanced 3D TOF can delineate LSAs in almost all insular gliomas but is limited in identifying the LSA-tumor interface. This limitation can be overcome by addition of analogous CISS sequences that delineate the LSA-tumor interface regardless of tumor intensity. Combined 3D TOF and 3D CISS is a useful tool for surgical planning and safer resections of insular tumors and may have added surgical relevance when included as an intraoperative adjunct.

Three-Dimensional Constructive Interference in Steady State Sequences and Phase-Contrast Magnetic Resonance Imaging of Arrested Hydrocephalus

To evaluate the role of three-dimensional constructive interference in steady state (3D-CISS) sequences and phase-contrast magnetic resonance imaging (PC-MRI) in patients with arrested hydrocephalus. A prospective study of 20 patients with arrested hydrocephalus was carried out. All patients underwent PC-MRI and 3D-CISS for assessment of the aqueduct. Axial (through-plane), sagittal (in-plane) PC-MRI, and sagittal 3D-CISS were applied to assess the cerebral aqueduct and the spontaneous third ventriculostomy if present. Aqueductal patency was graded using 3D-CISS and PC-MRI. Quantitative analysis of flow through the aqueduct was performed using PC-MRI. The causes of obstruction were aqueductal obstruction in 75% (n= 15), third ventricular obstruction in 5% (n= 1), and fourth ventricular obstruction in 20% (n= 4). The cause of arrest of hydrocephalus was spontaneous third ventriculostomy in 65% (n= 13), endoscopic third ventriculostomy in 10% (n= 2), and ventriculoperitoneal shunt in 5% (n= 1), and no cause could be detected in 20% of patients (n= 4). There is a positive correlation (r= 0.80) and moderate agreement (κ= 0.509) of grading with PC-MRI and 3D-CISS sequences. The mean peak systolic velocity of cerebrospinal fluid was 1.86 ± 2.48 cm/second, the stroke volume was 6.43 ± 13.81 μL/cycle, and the mean flow was 0.21 ± 0.32 mL/minute. We concluded that 3D-CISS and PC-MRI are noninvasive sequences for diagnosis of the level and cause of arrested hydrocephalus.

Visualization of the olfactory nerve using constructive interference in steady state magnetic resonance imaging.

The olfactory nerve (OlfN) is a small neural structure with inconsistent visualization on neuroimages. The aim of this study was to delineate the intracranial course of the OlfN using constructive interference in steady state magnetic resonance (MR) imaging. A total of 168 patients were enrolled in this study. Following initial examinations with conventional MR sequences, constructive interference in steady-state sequence (CISS) was performed in coronal and axial sections. On coronal sections, the OlfN was entirely visualized in 90% of patients on the right and 92% on the left, coursing along the olfactory sulcus. Complete visualization of the OlfN occurred in 100% of patients on serial axial images. The OlfN was classified into four portions based on the topographical differences and surrounding structures. The olfactory fossa exhibited considerable variability at the midlevel of the olfactory bulb on coronal images. Characteristic appearance of the OlfN with respect to age range or gender was not observed. The OlfN follows a highly consistent course along the olfactory sulcus. Thin-sliced, CISS sequences are useful for consistent visualization of the OlfN.

The cisternal segments of the oculomotor nerve: a magnetic resonance imaging study.

The cisternal segments of the oculomotor nerve (OMN), which courses through the interpeduncular and oculomotor cisterns (OMC) have not been well delineated on neuroimages. The present study aimed to explore the cisternal segments of the OMN using magnetic resonance (MR) imaging. A total of 92 patients were enrolled in this study. A constructive interference in steady-state sequence was performed in coronal and axial sections. On coronal images, cisternal portions of the OMN were entirely delineated in 97% on the right and in 98.5% on the left. Most of the OMCs were of a round shape, with a centrally located OMN, while 9% were ectatic with the OMN located eccentrically. In 5.3% of cases, fetal-type posterior communicating arteries (PCoAs), which coursed adjacent to the superior surfaces of the OMNs at the oculomotor triangle (OMT), were observed. On axial images, cisternal portions of the OMN were identified in all cases. The OMN segment passing through the OMT showed medial, central, and lateral courses. The PCoAs and P2 segments of the posterior cerebral artery (PCA) were adjacent to the OMNs in 17 and 19% of cases, respectively. The OMN most frequently courses in the medial part of the OMT and enters into the OMC. These findings indicate that OMN paresis can be caused by vascular compression at any site of the interpeduncular cistern and OMT.

Arteriovenous malformation: a rare cause of trigeminal neuralgia identified by magnetic resonance imaging with constructive interference in steady state sequences

A 64-year-old female presented with a 4-year history of right-sided facial pain. She described an ‘electric shock-type’ pain starting on the right side of her chin that radiated along the lower lip, upper lip and into the lower cheek, in the mandibular division of the trigeminal nerve. The pain was triggered by speaking, eating, drinking, brushing her teeth or touching her chin. These attacks occurred daily and lasted for 3 months before resolving spontaneously, consistent with classical trigeminal neuralgia (TN). Systemic and neurological examinations were normal. In particular, trigeminal sensation was intact bilaterally and trigeminal reflexes were normal. A diagnosis of right-sided, mandibular division TN was made. She had four similar episodes of pain over the following 4 years, each lasting ∼3 months, with each episode becoming more severe. She did not want any analgesic medication for the first two episodes. However, during the most recent episode, carbamazepine (300 mg twice a day) and, subsequently, adjunctive amitriptyline (10 mg at night) were prescribed, although these failed to control the symptoms. Therefore the patient underwent investigation to assess for a structural cause amenable to neurosurgical intervention. The patient underwent a cranial MRI with constructive interference in steady state (CISS) sequences, which demonstrated several small blood vessels surrounding the right trigeminal nerve and a very large mass, thought likely to be a venous aneurysm, lying just behind the root entry zone into the trigeminal nerve (Figure 1). A contrast-enhanced computed tomography angiogram (CTA) confirmed the previous MRI findings and was highly suggestive of an underlying arteriovenous malformation (AVM) (Figure 2). For the pre-surgical work-up a digital subtraction angiogram was organized. This demonstrated a definite AVM during contrast injection in the right vertebral artery with rapid filling of the straight sinus during the early arterial phase (Figure …

MRI of the lumbar spine at 7 Tesla in healthy volunteers and a patient with congenital malformations

The aim of this study was to evaluate sequences that are established at lower magnetic field strengths for lumbar spine imaging at 7 Tesla (7T) MR imaging. The lumbar spine of five healthy volunteers and a patient with spina bifida and meningocele were evaluated at 7T. The examination included a T2-TSE (turbo spin echo), a 3D-DESS (double-echo steady-state sequence), a 3D-CISS (constructive interference in steady-state sequence), and a 3D-VIBE (volumetric interpolated breath hold examination) sequence. Imaging quality was evaluated by two raters on a three-level scale. The assessment included visualization of intraforaminal structures, the cauda equina, facet joints, and any abnormalities. Contrast ratios for intervertebral discs/vertebral bodies, vertebral bodies/cerebrospinal fluid (CSF) and CSF/spinal cord were calculated. The 3D-VIBE sequence provided best differentiation between intraforaminal structures. Visualization of the facet joints was reliable with VIBE, DESS, and CISS. Individual nerve roots of the cauda equina could only be delineated with the 3D-CISS sequence. CISS and DESS provided good contrast between vertebral bodies and intervertebral discs. Contrast between CSF and vertebral bodies was most pronounced for the T2-TSE sequence. Sufficient contrast between CSF and the spinal cord was only achieved with the T2-TSE sequence. VIBE and DESS sequences demonstrated best the bony malformations. Visualization of the meningocele was only possible with the 3D-CISS sequence. At 7T most structures of the lumbar spine were visualized with a combination of sequences. At present, imaging quality is not superior to 1.5T or 3T, precluding routine clinical use.

Fractional Anisotropy Levels Derived From Diffusion Tensor Imaging in Cervical Syringomyelia

Syringomyelia can result in major functional disability. Conventional imaging techniques frequently fail to detect the underlying cause of syringomyelia. The prediction as to whether syringomyelia might lead to neurological deficits is still challenging. We hypothesized that fractional anisotropy (FA) derived from diffusion tensor imaging (DTI) is a parameter to detect dynamic forms of syringomyelia. Six patients with cervical syringomyelia, all comparable in size, shape, and location, were examined, along with 2 volunteers. Patients underwent electrophysiological recordings (somatosensory evoked potentials, motor evoked potentials, silent periods). Magnetic resonance imaging (1.5 T) was performed with a 6-element spine coil. Anatomic images were acquired with a 3-dimensional, constructive interference in steady-state sequence, and DTI with an echo-planar imaging sequence (5-mm thickness, b value 800 s/mm) using the generalized autocalibrating partially parallel acquisitions technique. The positions were centered on the syrinx in the volunteers between the C2 and Th1. DTI data were interpolated to a spatial resolution of 0.5 mm. After calculation of a diffusion tensor in each pixel, an FA map was calculated and profiles of the FA values across the spinal cord were calculated in all slices. FA values were lower at the level of all examined syrinxes and reached normal values beyond them. Electrophysiological results correlated with the decrease in FA value. There were no presyrinx changes in the white matter tracts in terms of signs of FA changes beneath the syrinx. DTI of syringomyelia can demonstrate white matter fiber tracts around and beyond the syrinx consistent with electrophysiological values. DTI of the cervical spine can provide quantitative information about the pathological characteristics beyond the abnormalities visible on magnetic resonance imaging.

Study of the Anatomical Variations of Vertebral Artery in C2 Vertebra With Magnetic Resonance Imaging and Its Application in the C1–C2 Transarticular Screw Fixation

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.