Quadrature Head Coil Research Articles

Radiologic-pathologic correlation of lesions in resected liver specimens with an ex vivo MRI-compatible localization device.

Liver lesion characterization is limited by the lack of an established gold standard for precise correlation of radiologic characteristics with their histologic features. The objective of this study was to demonstrate the feasibility of using an ex vivo MRI-compatible sectioning device for radiologic-pathologic co-localization of lesions in resected liver specimens. In this prospective feasibility study, adults undergoing curative partial hepatectomy from February 2018 to January 2019 were enrolled. Gadoxetic acid was administered intraoperatively prior to hepatic vascular inflow ligation. Liver specimens were stabilized in an MRI-compatible acrylic lesion localization device (27 × 14 × 14 cm3) featuring slicing channels and a silicone gel 3D matrix. High-resolution 3D T1-weighted fast spoiled gradient echo and 3D T2-weighted fast-spin-echo images were acquired using a single channel quadrature head coil. Radiologic lesion coordinates guided pathologic sectioning. A final histopathologic diagnosis was prepared for all lesions. The proportion of successfully co-localized lesions was determined. A total of 57 lesions were identified radiologically and sectioned in liver specimens from 10 participants with liver metastases (n = 8), primary biliary mucinous cystic neoplasm (n = 1), and hepatic adenomatosis (n = 1). Of these, 38 lesions (67%) were < 1 cm. Overall, 52/57 (91%) of radiologically identified lesions were identified pathologically using the device. Of these, 5 lesions (10%) were not initially identified on gross examination but were confirmed histologically using MRI-guided localization. One lesion was identified grossly but not on MRI. We successfully demonstrated the feasibility of a clinical method for image-guided co-localization and histological characterization of liver lesions using an ex vivo MRI-compatible sectioning device. • The ex vivo MRI-compatible sectioning device provides a reliable method for radiologic-pathologic correlation of small (< 1 cm) liver lesions in human liver specimens. • The sectioning method can be feasibly implemented within a clinical practice setting and used in future efforts to study liver lesion characterization. • Intraoperative administration of gadoxetic acid results in enhancement in ex vivo MRI images of liver specimens hours later with excellent image quality.

Configuration-based electrical properties tomography.

To introduce phase-based conductivity mapping from a configuration space analysis. The frequency response function of balanced SSFP (bSSFP) is used to perform a configuration space analysis. It is shown that the transceive phase for conductivity mapping can be directly obtained by a simple fast Fourier transform of a series of phase-cycled bSSFP scans. For validation, transceive phase and off-resonance mapping with fast Fourier transform is compared with phase estimation using a recently proposed method, termed PLANET. Experiments were performed in phantoms and for in vivo brain imaging at 3 T using a quadrature head coil. For fast Fourier transform, aliasing can lead to systematic phase errors. This bias, however, decreases rapidly with increasing sampling points. Interestingly, Monte Carlo simulations revealed a lower uncertainty for the transceive phase and the off-resonance using fast Fourier transform as compared with PLANET. Both methods, however, essentially retrieve the same phase information from a set of phase-cycled bSSFP scans. As a result, configuration-based conductivity mapping was successfully performed using eight phase-cycled bSSFP scans in the phantoms and for brain tissues. Overall, the retrieved values were in good agreement with expectations. Conductivity estimation and mapping of the field inhomogeneities can therefore be performed in conjunction with the estimation of other quantitative parameters, such as relaxation, using configuration theory. Phase-based conductivity mapping can be estimated directly from a simple Fourier analysis, such as in conjunction with relaxometry, using a series of phase-cycled bSSFP scans.

3-Tesla MRI of deep brain stimulation patients: safety assessment of coils and pulse sequences.

Physicians are more frequently encountering patients who are treated with deep brain stimulation (DBS), yet many MRI centers do not routinely perform MRI in this population. This warrants a safety assessment to improve DBS patients' accessibility to MRI, thereby improving their care while simultaneously providing a new tool for neuromodulation research. A phantom simulating a patient with a DBS neuromodulation device (DBS lead model 3387 and IPG Activa PC model 37601) was constructed and used. Temperature changes at the most ventral DBS electrode contacts, implantable pulse generator (IPG) voltages, specific absorption rate (SAR), and B1+rms were recorded during 3-T MRI scanning. Safety data were acquired with a transmit body multi-array receive and quadrature transmit-receive head coil during various pulse sequences, using numerous DBS configurations from "the worst" to "the most common."In addition, 3-T MRI scanning (T1 and fMRI) was performed on 41 patients with fully internalized and active DBS using a quadrature transmit-receive head coil. MR images, neurological examination findings, and stability of the IPG impedances were assessed. In the phantom study, temperature rises at the DBS electrodes were less than 2°C for both coils during 3D SPGR, EPI, DTI, and SWI. Sequences with intense radiofrequency pulses such as T2-weighted sequences may cause higher heating (due to their higher SAR). The IPG did not power off and kept a constant firing rate, and its average voltage output was unchanged. The 41 DBS patients underwent 3-T MRI with no adverse event. Under the experimental conditions used in this study, 3-T MRI scanning of DBS patients with selected pulse sequences appears to be safe. Generally, T2-weighted sequences (using routine protocols) should be avoided in DBS patients. Complementary 3-T MRI phantom safety data suggest that imaging conditions that are less restrictive than those used in the patients in this study, such as using transmit body multi-array receive coils, may also be safe. Given the interplay between the implanted DBS neuromodulation device and the MRI system, these findings are specific to the experimental conditions in this study.

Dynamic magnetic resonance imaging of carbogen challenge on awake rabbit brain at 1.5T.

Anesthesia may alter the cellular components contributing to the magnetic resonance imaging (MRI) signal intensities. Developing awake animal models to evaluate cerebral function has grown in importance. To investigate a noninvasive strategy for dynamic MRI (dMRI) of awake rabbits during carbogen challenge. A nonmetallic assistive device with a self-adhering wrap secure procedure was developed for the head fixation of awake rabbits. Multi-shot gradient echo echo-planar imaging sequence was applied for the dMRI on a 1.5 T clinical MRI scanner with a quadrature head coil. The carbogen challenge pattern was applied in a sequence of air - carbogen - air - carbogen - air. Twelve scans were performed for each block of carbogen challenge. T2-weighted fast-spin echo and T1-weighted gradient echo sequences were performed before and after dMRI to evaluate the head position shifts. The whole dMRI scan time was about 30 minutes. The position shift of 8 rabbits in the x-and y-direction was less than 3%. The average MRI signal intensities (SI) from the 8 rabbits during carbogen challenge was fitted well using exponential growth and decay functions. The average MRI SI increase due to carbogen inhaling was 1.51%. The proposed strategy for head dMRI on an awake rabbit during carbogen challenge is feasible.

Accurate determination of brain metabolite concentrations using ERETIC as external reference.

Magnetic Resonance Spectroscopy (MRS) can provide in vivo metabolite concentrations in standard concentration units if a reliable reference signal is available. For 1 H MRS in the human brain, typically the signal from the tissue water is used as the (internal) reference signal. However, a concentration determination based on the tissue water signal most often requires a reliable estimate of the water concentration present in the investigated tissue. Especially in clinically interesting cases, this estimation might be difficult. To avoid assumptions about the water in the investigated tissue, the Electric REference To access In vivo Concentrations (ERETIC) method has been proposed. In this approach, the metabolite signal is compared with a reference signal acquired in a phantom and potential coil-loading differences are corrected using a synthetic reference signal. The aim of this study, conducted with a transceiver quadrature head coil, was to increase the accuracy of the ERETIC method by correcting the influence of spatial B1 inhomogeneities and to simplify the quantification with ERETIC by incorporating an automatic phase correction for the ERETIC signal. Transmit field ( B1+) differences are minimized with a volume-selective power optimization, whereas reception sensitivity changes are corrected using contrast-minimized images of the brain and by adapting the voxel location in the phantom measurement closely to the position measured in vivo. By applying the proposed B1 correction scheme, the mean metabolite concentrations determined with ERETIC in 21 healthy subjects at three different positions agree with concentrations derived with the tissue water signal as reference. In addition, brain water concentrations determined with ERETIC were in agreement with estimations derived using tissue segmentation and literature values for relative water densities. Based on the results, the ERETIC method presented here is a valid tool to derive in vivo metabolite concentration, with potential advantages compared with internal water referencing in diseased tissue.

Breath-holding during the Calibration Scan Improves the Reproducibility of Parallel Transmission at 7T for Human Brain.

Purpose:The B0 and B1+ maps required for calculation of the radiofrequency (RF) pulse of parallel transmission (pTx) are obtained in calibration scans; however, they may be affected by respiratory motion. We aimed to compare the reproducibility of B0 and B1+ maps and gradient echo (GRE) images of the brain scanned with pTx at 7T between free-breathing (FB) and breath-holding (BH) conditions during the calibration scan.Methods:Nine healthy volunteers were scanned by 7T MRI using a two-channel quadrature head coil. In the pTx calibration scans performed with FB and BH, the B0 map was obtained from two different TE images and the B1+ map was calculated by the Bloch-Siegert method. A GRE image (gradient-recalled-acquisition in steady state) was also obtained with RF shimming and RF design of pTx with spoke method, as well as quadrature transmission (qTx). All the scans were repeated over five sessions. The reproducibility of the B0 and B1+ maps and GRE image was evaluated with region-of-interest measurements using inter-session standard deviation (SD) and coefficient of variation (CV) values. Intensity homogeneity of GRE images was also assessed with in-plane CV.Results:Inter-session SDs of B0 and B1+ maps were significantly smaller in BH (P < 0.01). Inter-session CVs of GRE images were significantly smaller in qTx than BH and FB (P < 0.01, both); however, the CVs of BH were significantly smaller (P < 0.01). In-plane CVs of FB and BH with RF shimming were not significantly different with qTx; however, CVs of FB and BH with RF design were significantly smaller than those of qTx (P < 0.05 and P < 0.01, respectively).Conclusion:BH could improve the reproducibility of B0 and B1+ maps in pTx calibration scans and GRE images. These results might facilitate the development of pTx in human brain at 7T.

Repeatability of Brain Volume Measurements Made with the Atlas-based Method from T1-weighted Images Acquired Using a 0.4 Tesla Low Field MR Scanner.

Purpose:An understanding of the repeatability of measured results is important for both the atlas-based and voxel-based morphometry (VBM) methods of magnetic resonance (MR) brain volumetry. However, many recent studies that have investigated the repeatability of brain volume measurements have been performed using static magnetic fields of 1–4 tesla, and no study has used a low-strength static magnetic field. The aim of this study was to investigate the repeatability of measured volumes using the atlas-based method and a low-strength static magnetic field (0.4 tesla).Materials and Methods:Ten healthy volunteers participated in this study. Using a 0.4 tesla magnetic resonance imaging (MRI) scanner and a quadrature head coil, three-dimensional T1-weighted images (3D-T1WIs) were obtained from each subject, twice on the same day. VBM8 software was used to construct segmented normalized images [gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) images]. The regions-of-interest (ROIs) of GM, WM, CSF, hippocampus (HC), orbital gyrus (OG), and cerebellum posterior lobe (CPL) were generated using WFU PickAtlas. The percentage change was defined as [100 × (measured volume with first segmented image−mean volume in each subject)/(mean volume in each subject)] The average percentage change was calculated as the percentage change in the 6 ROIs of the 10 subjects.Results:The mean of the average percentage changes for each ROI was as follows: GM, 0.556%; WM, 0.324%; CSF, 0.573%; HC, 0.645%; OG, 1.74%; and CPL, 0.471%. The average percentage change was higher for the orbital gyrus than for the other ROIs.Conclusion:We consider that repeatability of the atlas-based method is similar between 0.4 and 1.5 tesla MR scanners. To our knowledge, this is the first report to show that the level of repeatability with a 0.4 tesla MR scanner is adequate for the estimation of brain volume change by the atlas-based method.

MRI-Based Measurement of Brain Stem Cross-Sectional Area in Relapsing-Remitting Multiple Sclerosis.

To determine if patients with relapsing-remitting multiple sclerosis (RRMS) have a reduced brain stem cross-sectional area (CSA) compared to age- and sex-matched controls. The brain stem is a common site of involvement in MS. However, relatively few imaging studies have investigated brain stem atrophy. Brain magnetic resonance imaging (MRI) was performed on patients and controls using a 1.5T MRI scanner with a quadrature head coil. Three-dimensional magnetization-prepared rapid acquisition gradient-echo (MPRAGE) images with 128 contiguous slices, covering the whole brain and brain stem and a T2-weighted image with3 mm transverse contiguous images were acquired. We measured the brain stem CSA at three sites, the midbrain, the pons, and the medulla oblongata in 35 RRMS patients and 35 controls using a semiautomated algorithm. CSA readings were normalized using the total external cranial volume to reduce normal population variance and increase statistical power. A significant CSA reduction was found in the midbrain (P ≤ .001), pons (P ≤ .001), and the medulla oblongata (P = .047) postnormalization. A CSA reduction of 9.3% was found in the midbrain, 8.7% in the pons, and 6.5% in the medulla oblongata. A significantly reduced, normalized brain stem CSA was detected in all areas of the brain stem of the RRMS patients, when compared to age- and gender-matched controls. Lack of detectable upper cervical cord atrophy in the same patients suggests some independence of the MS pathology in these regions.

Radiofrequency-shielding Effect of a Titanium Mesh Implanted for Cranioplasty.

After cranioplasty with a titanium mesh, radiofrequency (RF)-shielding images appear during magnetic resonance (MR) imaging. To clarify their influence, we evaluated the effect of mesh position, phase-encoding direction, and type of coil employed. On a 1.5-tesla MR imager, we placed a titanium mesh board (100 × 100 × 0.8 mm) on the surface of a cubic phantom to mimic a human brain and used a quadrature coil and an 8-channel neurovascular coil to measure nonuniformity, signal decay ratio, and the B1 map. Nonuniformity was 6.7 times higher at the quadrature head coil and 1.6 times higher at the neurovascular coil when the mesh was on the phantom's right side or anterior to it than when it was on its superior end or absent. The profile of the signal decay ratio increased by 1.9% mm(-1) from 0 to 40 mm from the mesh side to the base value at the quadrature head coil when the mesh was on the phantom's right side and 0.9% mm(-1) from 0 to 80 mm at the neurovascular coil when the mesh was on the phantom's right side or anterior to it. The quadrature head coil showed greater incline of the profile when the mesh was on the right in coronal and axial views and no notable change in the profile in coronal and sagittal views when the mesh was on the superior end. In the B1 map, the flip angle was lower when the mesh was nearer. The response to the RF-shielding effect from a titanium mesh depends on the location of the mesh and the RF coil used but not on the phase-encoding direction.

Accuracy of 2-hydroxyglutarate quantification by short-echo proton-MRS at 3 T: A phantom study

PurposeWe set out to investigate the potential confounding effect of variable concentration of N-acetyl-l-aspartate (NAA) and Glutamate (Glu) on measurement of the brain oncometabolite 2-hydroxyglutarate (2HG) using a standard MRS protocol. This issue may arise due to spectral overlap at clinical magnetic field strengths and thus complicate the usage of 2HG as a putative biomarker of gliomas bearing mutations of the isocitrate dehydrogenase (IDH) 1 and 2 genes. MethodsSpectra from 25 phantoms (50 mL falcon test tubes) containing a range of known concentrations of 2HG, NAA and Glu were acquired using a clinical 3 T scanner with a quadrature head coil, single-voxel point-resolved spectroscopy sequence with TE = 30 ms. Metabolite concentrations were estimated by linear combination analysis and a simulated basis set. ResultsNAA and Glu concentrations can have a significant confounding effect on 2HG measurements, whereby the negative changes in concentration of these metabolites typically observed in (peri)lesional areas can lead to under-estimation of 2HG concentration with respect to spectra acquired in presence of physiological levels of NAA and Glu. ConclusionThe confounding effect of NAA and Glu concentration changes needs to be considered: in patients, it may mask the presence of 2HG at low concentrations, however it is not expected to lead to false positives. 2HG data acquired using standard short echo-time MRS protocols should be considered with caution.

Magnetic resonance spectroscopy imaging of medulla oblongata and substantia nigra in idiopathic Parkinson's disease

Objective: To use 1.5T 1H-MRS as a research tool in vivo and demonstrate the feasibility of obtaining long-echo 1H MR spectra in small volumes like substantia nigra (SN) and medulla oblongata (MO) in healthy volunteers and patients with Parkinson's disease (PD) and observe the clinical correlations. Subjects and Methods: Twenty patients of the idiopathic Parkinson’s disease (IPD) were recruited from the Out Patient Department of Neurology. Additionally, 14 age-matched healthy subjects were taken as controls group. After baseline evaluation, the patients satisfying inclusion and exclusion criteria underwent 1H-MRS study. All MR examinations were performed on a 1.5 T system (Philips Gyroscan Intera, Netherlands) using a standard quadrature head coil. Results: We succeeded to achieve 74.19% and 77.42% of spectra from MO and SN of both PD and control groups. MO showed slightly weak negative result to total UPDRS and UPDRS- II, but no significant correlation was found between metabolites and clinical indexes in MO. The result also showed no significant correlations between H&amp;Y scale and metabolites in MO and SN of PD patients. But there was a significant correlation between H&amp;Y, NAA/Cr and Cho/Cr in SN. Conclusions: MRS ratios from MO and SN does not play any significant role to differentiate PD from the normal subjects, but metabolites ratios from SN of PD patient can help to understand the progression and severity of the disease. Therefore, it is not practical to employ MRS as a diagnostic tool for PD. DOI: http://dx.doi.org/10.3126/ajms.v4i3.8066 Asian Journal of Medical Sciences 4(2013) 76-85

Crossed cerebellar hyperperfusion without restricted diffusion in status epilepticus

Crossed cerebellar diaschisis (CCD) has originally been reported as metabolic depression on positron emission tomography in the cerebellar hemisphere contralateral to supratentorial infarction [1]. CCD has currently been documented in status epilepticus using magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) [2]. However, combined diffusion and perfusion profiles have remained controversial in CCD with status epilepticus. A 46-year-old woman was admitted to our hospital for the treatment of status epilepticus. Nine days before admission, she had presented with convulsion in the left limbs and been admitted to another hospital. Her convulsion was initially controlled with intravenous diazepam, but subsequent treatment with several anti-epileptic drugs was unsuccessful and she was diagnosed with drug-induced rash. Upon admission to our hospital, a brain MRI revealed a small cyst in the right mesial temporal lobe, which was speculated as the seizure focus. T2-weighted MRI (T2WI) showed mild hyperintensity and edematous changes in the right frontal, posterior temporal, parietal, and occipital cortices, and the left cerebellar hemisphere (Fig. 1a). Diffusion-weighted MRI (DWI) revealed mild hyperintensity and apparent diffusion coefficient (ADC) showed a slight increase in the T2WI hyperintensity regions of the right cerebral cortex; ADC values were mildly higher in the right temporal cortex (8.37 9 10 ± 7.04 9 10 mm/s) than in the contralateral area (7.90 9 10 ± 1.77 9 10 mm/s). On the other hand, ADC values were similar in the bilateral cerebellar hemispheres (right, 6.07 9 10 ± 4.06 9 10 mm/s; left, 6.08 9 10 ± 5.43 9 10 mm/s; Fig. 1b). I-Iodoamphetamine (IMP) SPECT, which reflects brain perfusion, revealed hyperperfusion in these regions (Fig. 1c). Carbamazepine, which had been spared because of the druginduced skin lesions, was prescribed in combination with steroids, and her seizures were finally controlled. T2WI intensity was normal 2 weeks after admission (Fig. 1d). I-IMP SPECT performed on the same day showed mild hyperperfusion in the right cerebral cortex and symmetric perfusion in the cerebellar hemispheres (Fig. 1e). MRI studies were performed on a 3-T instrument (Signa EXCITE HD 3.0T, GE Medical Systems, Milwaukee, WI, USA) with a standard quadrature head coil. The parameters of DWI were as follows: time of repetition = 10,000 ms, time of echo = 86.6 ms, field of view = 24 cm, matrix size = 128 9 128 with echo planar sequence, b value = 1,500 s/mm, and slice thickness/gap = 5/1 mm. This study has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Neuroimaging studies of the present case demonstrated crossed hyperintensity on T2WI concurrent with hyperperfusion on SPECT. Of note, ADC was mildly increased, not decreased, in the present case. Previous reports of CCD in status epilepticus have documented DWI hyperintensity of the ipsilateral cortical ribbon and the contralateral cerebellar hemisphere [2, 3]. Restricted diffusion (reduced ADC) has been speculated, without clear evidence, in the DWI hyperintensity lesions of CCD in status epilepticus [2, 3], which contradicts our observations. K. Fujita (&) Y. Izumi R. Kaji Department of Clinical Neuroscience, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto-cho, Tokushima 770-8503, Japan e-mail: kof@clin.med.tokushima-u.ac.jp

Ytterbium-based PARACEST Agent: Feasibility of CEST Imaging on a Clinical MR Scanner

We investigated the feasibility of performing chemical exchange saturation transfer (CEST) imaging using ytterbium-based paramagnetic CEST (PARACEST) agents on a clinical magnetic resonance (MR) scanner. We prepared solutions of 3 different ytterbium-based PARACEST agents at concentrations of 5, 10, 20, and 50 mM at a pH of 7.4 and at a concentration of 50 mM at pHs of 3.0, 5.0, 7.4, and 9.5. We acquired images with a turbo spin echo technique using a quadrature head coil and a clinical 3.0-tesla MR system in accordance with the safety limits of the specific absorption rate (SAR). We acquired CEST images with presaturation offset frequencies from -5,000 Hz (-39.1 ppm) to 5,000 Hz (39.1 ppm) with an interval of 500 Hz (3.9 ppm) for each condition. We repeated each scan 3 times and then calculated the mean and standard deviations of the magnitude of the CEST effect at different concentrations and pH values for each agent. We used one-way analysis of variance and Tukey's honestly significant difference post hoc test to compare mean values of the magnitude of the CEST effect obtained at different concentrations and pH values. P < 0.05 was considered significant. PARACEST agents showed a strong CEST effect at their specific presaturation offset frequencies. For each agent, the CEST effect showed significant concentration dependency (P < 0.05), increasing with agent concentration, and significant pH dependency (P < 0.05), with strong effect near physiological pH. CEST imaging using ytterbium-based PARACEST agents might be feasible on a clinical MR scanner with further modifications, such as adjustments of the presaturation radiofrequency pulse and imaging protocols.

Technical Note: DTI measurements of fractional anisotropy and mean diffusivity at 1.5 T: Comparison of two radiofrequency head coils with different functional designs and sensitivities

Diffusion tensor imaging (DTI) is highly sensitive to noise and improvement of radiofrequency coil technology represents a straightforward way for augmenting signal-to-noise ratio (SNR) performance in magnetic resonance imaging (MRI) scanners. The aim of this study was to characterize the dependence of DTI measurements of fractional anisotropy (FA) and mean diffusivity (MD) on the choice of head coil, comparing two head coils with different functional designs and sensitivities. Fourteen healthy subjects underwent DTI acquisitions at 1.5 T. Every subject was scanned twice, using a standard quadrature birdcage head coil (coil-A) and an eight-channel array head coil (coil-B). FA and MD maps, estimated using both the linear least squares (LLS) and nonlinear least squares (NLLS) methods, were nonlinearly normalized into a standard space. Then, volumetric regions of interest encompassing typical white and gray matter structures [splenium of the corpus callosum (SCC), internal capsule (IC), cerebral peduncles (CP), middle cerebellar peduncles (MCP), globus pallidus (GP), thalamus (TH), caudate (CA), and putamen (PU)] were analyzed. Significant differences and trends of variation in DTI measurements were assessed by the Wilcoxon test for paired samples with and without Bonferroni correction for multiple comparisons, respectively. The overall SNR of coil-B was 30% higher than that of coil-A. When comparing DTI measurements (coil-B versus coil-A), mean FA values (SCC, IC, and TH), mean MD values (IC, CP, GP, and TH), FA standard deviation (CP, MCP, GP, and CA), and MD standard deviation (IC, CP, TH, and PU) resulted decreased (significant difference, p(cor) < 0.05, or trend of variation, P(uncor) < 0.05) in several gray and white matter regions of the human brain. With the exception of CP, the results in terms of revealed significant difference or trend of variation were independent of the method (LLS and NLLS) used for estimating the diffusion tensor. In various gray and white matter structures, the eight-channel array head coil yielded more precise and accurate measurements of DTI derived indices compared to the standard quadrature birdcage head coil.

The depth of the olfactory sulcus is an indicator of congenital anosmia

Background and Purpose: In congenital anosmia, the olfactory bulb and olfactory tract can be both aplastic or hypoplastic. In clinical routine they are sometimes difficult to assess. We thus want to investigate morphologic differences of the olfactory sulcus in patients with isolated anosmia (IA) since birth or early childhood in comparison to controls in a large group of subjects; to investigate whether the depth of the olfactory sulcus (OS) indicates IA. Materials and Methods: Within the context of a two-center study we investigated 36 IA patients in comparison to 40 controls. Imaging was performed with a standard quadrature head coil (1.5 T; T1 and T2-weighted spin echo sequences were used (coronal plane perpendicular to frontal skull base). We assessed olfactory bulb volume by planimetric contouring, and OS depth in the plane of the posterior tangent through the eyeballs (PPTE). Results: Looking at the OS depth in the PPTE, none of the healthy controls exhibited a depth of less than 8 mm. In IA patients, 10 had an OS deeper than 8 mm, while 26 had OS depth lower than 8 mm. Thus, if we consider an OS depth lower than 8 mm it clearly indicates IA, with a specificity of 1 while the sensitivity is 0.72. Conclusions: In IA, the OS depth in the PPTE is a useful clinical indicator. Indeed, if it is ≤ 8 mm, it clearly indicates IA, with a specificity of 1. If it is deeper, the measure does not clearly predict IA.

Changes in the Frontotemporal Cortex and Cognitive Correlates in First-Episode Psychosis

BackgroundLoss of cortical volume in frontotemporal regions has been reported in patients with schizophrenia and their relatives. Cortical area and thickness are determined by different genetic processes, and measuring these parameters separately may clarify disturbances in corticogenesis relevant to schizophrenia. Our study also explored clinical and cognitive correlates of these parameters.MethodsThirty-seven patients with first-episode psychosis (34 schizophrenia, 3 schizoaffective disorder) and 38 healthy control subjects matched for age and sex took part in the study. Imaging was performed on an magnetic resonance imaging 1.5-T scanner. Area and thickness of the frontotemporal cortex were measured using a surface-based morphometry method (Freesurfer). All subjects underwent neuropsychologic testing that included measures of premorbid and current IQ, working and verbal memory, and executive function.ResultsReductions in cortical area, more marked in the temporal cortex, were present in patients. Overall frontotemporal cortical thickness did not differ between groups, although regional thinning of the right superior temporal region was observed in patients. There was a significant association of both premorbid IQ and IQ at disease onset with area, but not thickness, of the frontotemporal cortex, and working memory span was associated with area of the frontal cortex. These associations remained significant when only patients with schizophrenia were considered.ConclusionsOur results suggest an early disruption of corticogenesis in schizophrenia, although the effect of subsequent environmental factors cannot be excluded. In addition, cortical abnormalities are subject to regional variations and differ from those present in neurodegenerative diseases.

Infratentorial lesion volume correlates with sensory functional system in multiple sclerosis patients: a 3.0-Tesla MRI study

This study sought to correlate lesion volume in infratentorial areas using 3.0-T proton-density (PD)-weighted images with disability scales and appropriate functional system scores in patients with multiple sclerosis (MS). We examined 20 consecutive patients (13 women and 7 men) with a median age of 47 years (range 26-70). Neurological examination included the Expanded Disability Status Scale and its functional systems, the Barthel Index (BI) and the Rivermead Mobility Index (RMI). MRI scans were performed on a system operating at 3.0 T using a quadrature birdcage head coil. Acquired images imported as Digital Imaging and Communication in Medicine (DICOM) files, and the region of interest (ROI) files were converted to Neuroimaging Informatics Technology Initiative (NIfTI) format and normalised to the Montreal Neurological Institute (MNI) standard template. An automated segmentation algorithm was used to distinguish between supratentorial and infratentorial areas. Normalisation to the magnetisation-prepared rapid acquisition with gradient echo (MPRAGE) T1-weighted sequence allowed lesion volume estimation in the different anatomical areas. A significant correlation was found between infratentorial lesion volume and the sensory functional system score (rho=0.76, p=0.002). No significant correlation was found between supratentorial lesion volume and Expanded Disability Status Scale (EDSS), RMI and BI scores. The described method, by means of anatomical assignment of MS lesions, allows detection of significant correlation coefficients between clinical and MRI lesion burden in MS patients at the infratentorial level.

High-resolution depiction of the cranial nerves in the posterior fossa (N III–N XII) with 2D fast spin echo and 3D gradient echo sequences at 3.0 T

Purpose The objective of this study was to evaluate the influence of high-resolution imaging obtainable with the higher field strength of 3.0 T on the visualization of the brain nerves in the posterior fossa by using T 2-weighted fast spin echo (FSE) and fast imaging employing steady-state gradient echo (GRE) sequences as the most suitable techniques to visualize each of the cranial nerves. Materials and methods In total, 20 nerves were investigated on MR images of 12 volunteers each and selected for comparison, respectively, with the FSE sequences with 5-mm and 2-mm section thicknesses and GRE sequences acquired with a 3.0-T scanner and a quadrature head coil. The resulting MR images were evaluated by three independent readers who rated image quality according to depiction of anatomic detail and contrast with use of a rating scale. Results In general, decrease of the slice thickness showed a significant increase in the detection of nerves as well as in the image quality characteristics. As expected, artifacts were prominent in high-field imaging of the posterior fossa with GRE sequences. Nevertheless, comparing FSE and GRE imaging, the course of brain nerves and brainstem vessels was visualized best with use of the three-dimensional (3D) pulse sequence, although with respect to structural identification and contrast according to the rating scale, observer scores were not significantly improved. Conclusion The comparison revealed the clear advantage of a thin section. The increased resolution enabled immediate identification of all brainstem nerves. Although image quality is impaired at GRE at high field strength, this sequence most distinctly and confidently depicted pertinent structures and enables 3D reconstruction in order to illustrate complex relations of the brainstem.

Counteracting radio frequency inhomogeneity in the human brain at 7 Tesla using strongly modulating pulses

We report flip angle and spoiled gradient echo measurements at 7 Tesla on human brains in three-dimensional imaging, using strongly modulating pulses to counteract the transmitted radiofrequency inhomogeneity problem. Compared with the standard square pulse results, three points of improvement are demonstrated, namely: (i) the removal of the bright center (typical at high fields when using a quadrature head coil), (ii) the substantial gain of signal in the regions of low B(1) intensity, and (iii) an increased 35% signal uniformity over the whole brain at the flip angle where maximum contrast between white and gray matter occurs. We also find by means of simulations that standard BIR-4 adiabatic pulses need several times more energy to reach a similar performance at the same field strength.

Hippocampal Volumes in First-Episode Psychosis

Hippocampal Volumes in First-Episode Psychosis