Imago7 Foundation

Pisa, Italy

Imago7 Foundation

Pisa, Italy
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Giuliano A.,University of Pisa | Giuliano A.,National Institute of Nuclear Physics, Italy | Donatelli G.,University of Pisa | Cosottini M.,University of Pisa | And 4 more authors.
Hippocampus | Year: 2017

The hippocampus is one of the most interesting and studied brain regions because of its involvement in memory functions and its vulnerability in pathological conditions, such as neurodegenerative processes. In the recent years, the increasing availability of Magnetic Resonance Imaging (MRI) scanners that operate at ultra-high field (UHF), that is, with static magnetic field strength ≥7T, has opened new research perspectives. Compared to conventional high-field scanners, these systems can provide new contrasts, increased signal-to-noise ratio and higher spatial resolution, thus they may improve the visualization of very small structures of the brain, such as the hippocampal subfields. Studying the morphometry of the hippocampus is crucial in neuroimaging research because changes in volume and thickness of hippocampal subregions may be relevant in the early assessment of pathological cognitive decline and Alzheimer's Disease (AD). The present review provides an overview of the manual, semi-automated and fully automated methods that allow the assessment of hippocampal subfield morphometry at UHF MRI, focusing on the different hippocampal segmentation produced. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

De Ciantis A.,University of Florence | Barkovich A.J.,University of California at San Francisco | Cosottini M.,University of Pisa | Barba C.,University of Florence | And 7 more authors.
American Journal of Neuroradiology | Year: 2015

Background and Purpose: Polymicrogyria is a malformation of cortical development that is often identified in children with epilepsy or delayed development. We investigated in vivo the potential of 7T imaging in characterizing polymicrogyria to determine whether additional features could be identified. Materials and Methods: Ten adult patients with polymicrogyria previously diagnosed by using 3T MR imaging underwent additional imaging at 7T. We assessed polymicrogyria according to topographic pattern, extent, symmetry, and morphology. Additional imaging sequences at 7T included 3D T2∗ susceptibility-weighted angiography and 2D tissue border enhancement FSE inversion recovery. Minimum intensity projections were used to assess the potential of the susceptibility-weighted angiography sequence for depiction of cerebral veins. Results: At 7T, we observed perisylvian polymicrogyria that was bilateral in 6 patients, unilateral in 3, and diffuse in 1. Four of the 6 bilateral abnormalities had been considered unilateral at 3T. While 3T imaging revealed 2 morphologic categories (coarse, delicate), 7T susceptibility-weighted angiography images disclosed a uniform ribbonlike pattern. Susceptibility-weighted angiography revealed numerous dilated superficial veins in all polymicrogyric areas. Tissue border enhancement imaging depicted a hypointense line corresponding to the gray-white interface, providing a high definition of the borders and, thereby, improving detection of the polymicrogyric cortex. Conclusions: 7T imaging reveals more anatomic details of polymicrogyria compared with 3T conventional sequences, with potential implications for diagnosis, genetic studies, and surgical treatment of associated epilepsy. Abnormalities of cortical veins may suggest a role for vascular dysgenesis in pathogenesis. © 2015 AJNR Am J. Neuroradiol.

PubMed | Imago7 Foundation and National Institute of Nuclear Physics, Italy
Type: | Journal: Journal of magnetic resonance (San Diego, Calif. : 1997) | Year: 2015

A procedure for evaluating radio-frequency electromagnetic fields in anatomical human models for any matching and coupling conditions is introduced. The procedure resorts to the extraction of basis functions: such basis functions, which represent the fields produced by each individual port without any residual coupling, are derived through an algebraic procedure which uses the S parameter matrix and the fields calculated in one (only) full-wave simulation. The basis functions are then used as building-blocks for calculating the fields for any other S parameter matrix. The proposed approach can be used both for volume coil driven in quadrature and for parallel transmission configuration.

Giovannetti G.,National Research Council Italy | Giovannetti G.,CNR Institute of Neuroscience | Tiberi G.,IRCCS Stella Maris Foundation | Tiberi G.,Imago7 Foundation
Applied Magnetic Resonance | Year: 2016

The design and development of dedicated radiofrequency (RF) coils is a fundamental task to maximize the signal-to-noise ratio (SNR) in nuclear magnetic resonance (NMR) applications. Coil resistance reduces the SNR and should be minimized by employing conductors of appropriate shape and cross section. At RF, the conductor resistance is increased due to the skin effect, which distributes the current primarily on the surface of the conductor instead of uniformly over the cross section. In particular, in rectangular shape conductors the current density is concentrated in the high-curvature area and increases the conductor resistance, while rounded conductors present lower resistance and demonstrate improvements in performance especially in low-frequency tuned coils. This paper summarizes the different methods for estimating conductor losses in RF coils for NMR applications, whose performance strongly affect quality data. Because the impact to coil loss from conductors with different cross-sectional area is not something generally recognized and nor addressed in many other coil design works, we believe the review could be interesting for researchers working in the field of NMR coil design and development. © 2016, Springer-Verlag Wien.

Cosottini M.,IMAGO7 Foundation | Frosini D.,University of Pisa | Pesaresi I.,Neuroradiology Unit | Costagli M.,IMAGO7 Foundation | And 4 more authors.
Radiology | Year: 2014

Purpose: To evaluate the anatomy of the substantia nigra (SN) in healthy subjects by performing 7-T magnetic resonance (MR) imaging of the SN, and to prospectively define the accuracy of 7-T MR imaging in distinguishing Parkinson disease (PD) patients from healthy subjects on an individual basis. Materials and Methods: The 7-T MR imaging protocol was approved by the Italian Ministry of Health and by the local competent ethics committee. SN anatomy was described ex vivo on a gross brain specimen by using highly resolved proton-density (spin-echo proton density) and gradient-recalled-echo (GRE) images, and in vivo in eight healthy subjects (mean age, 40.1 years) by using GRE three-dimensional multiecho susceptibility-weighted images. After training on appearance of SN in eight healthy subjects, the SN anatomy was evaluated twice by two blinded observers in 13 healthy subjects (mean age, 54.7 years) and in 17 PD patients (mean age, 56.9 years). Deviations from normal SN appearance were described and indicated as abnormal, and both diagnostic accuracy and intra-and interobserver agreement for diagnosis of PD with 7-T MR imaging were calculated. Results: Three-dimensional multiecho susceptibility-weighted 7-T MR imaging reveals a three-layered organization of the SN allowing readers to distinguish pars compacta ventralis and dorsalis from pars reticulata. The abnormal architecture of the SN allowed a discrimination between PD patients and healthy subjects with sensitivity and specificity of 100% and 96.2% (range, 92.3%-100%), respectively. Intraobserver agreement (k = 1) and interobserver agreement (k = 0.932) were excellent. Conclusion: MR imaging at 7-T allows a precise characterization of the SN and visualization of its inner organization. Threedimensional multiecho susceptibility-weighted images can be used to accurately differentiate healthy subjects from PD patients, which provides a novel diagnostic opportunity. © 2014 RSNA.

Frosini D.,University of Pisa | Ceravolo R.,University of Pisa | Tosetti M.,IRCCS | Bonuccelli U.,University of Pisa | And 2 more authors.
Journal of Neural Transmission | Year: 2016

Ten healthy subjects (HS) and 15 patients with atypical parkinsonisms underwent 7-T susceptibility-weighted-imaging MR to evaluate substantia nigra (SN). All HS were judged “normal”. Twelve out of 15 patients exhibited bilateral abnormal SN while three patients with corticobasal degeneration (CBD) showed bilateral normal aspect of SN. Anatomical changes of SN at 7 T occur in multiple system atrophy and progressive supranuclear palsy as previously reported in Parkinson’s disease. Preserved SN in CBD confirms the pathological heterogeneity of this disease. © 2016, Springer-Verlag Wien.

Cosottini M.,IMAGO7 Foundation | Cosottini M.,University of Pisa | Frosini D.,University of Pisa | Pesaresi I.,Neuroradiology Unit | And 7 more authors.
American Journal of Neuroradiology | Year: 2015

BACKGROUND AND PURPOSE: Standard neuroimaging fails in defining the anatomy of the substantia nigra and has a marginal role in the diagnosis of Parkinson disease. Recently 7T MR target imaging of the substantia nigra has been useful in diagnosing Parkinson disease. We performed a comparative study to evaluate whether susceptibility-weighted angiography can diagnose Parkinson disease with a 3T scanner. MATERIALS AND METHODS: Fourteen patients with Parkinson disease and 13 healthy subjects underwent MR imaging examination at 3T and 7T by using susceptibility-weighted angiography. Two expert blinded observers and 1 neuroradiology fellow evaluated the 3T and 7T images of the sample to identify substantia nigra abnormalities indicative of Parkinson disease. Diagnostic accuracy and intra- and interobserver agreement were calculated separately for 3T and 7T acquisitions. RESULTS: Susceptibility-weighted angiography 7T MR imaging can diagnose Parkinson disease with a mean sensitivity of 93%, specificity of 100%, and diagnostic accuracy of 96%. 3T MR imaging diagnosed Parkinson disease with a mean sensitivity of 79%, specificity of 94%, and diagnostic accuracy of 86%. Intraobserver and interobserver agreement was excellent at 7T. At 3T, intraobserver agreement was excellent for experts, and interobserver agreement ranged between good and excellent. The less expert reader obtained a diagnostic accuracy of 89% at 3T. CONCLUSIONS: Susceptibility-weighted angiography images obtained at 3T and 7T differentiate controls from patients with Parkinson disease with a higher diagnostic accuracy at 7T. The capability of 3T in diagnosing Parkinson disease might encourage its use in clinical practice. The use of the more accurate 7T should be supported by a dedicated cost-effectiveness study. © 2015, American Society of Neuroradiology. All rights reserved.

PubMed | University of Ferrara, Neuroradiology Unit, Imago7 Foundation, General Electric and 3 more.
Type: Journal Article | Journal: European radiology | Year: 2016

This study aimed to assess the performance of a Silent zero time of echo (ZTE) sequence for T1-weighted brain imaging using a 7T MRI system.The Silent sequence was evaluated qualitatively by two neuroradiologists, as well as quantitatively in terms of tissue contrast, homogeneity, signal-to-noise ratio (SNR) and acoustic noise. It was compared to conventional T1-weighted imaging (FSPGR). Adequacy for automated segmentation was evaluated in comparison with FSPGR acquired at 7T and 1.5T. Specific absorption rate (SAR) was also measured.Tissue contrast and homogeneity in Silent were remarkable in deep brain structures and in the occipital and temporal lobes. Mean tissue contrast was significantly (p<0.002) higher in Silent (0.25) than in FSPGR (0.11), which favoured automated tissue segmentation. On the other hand, Silent images had lower SNR with respect to conventional imaging: average SNR of FSPGR was 2.66 times that of Silent. Silent images were affected by artefacts related to projection reconstruction, which nevertheless did not compromise the depiction of brain tissues. Silent acquisition was 35dB(A) quieter than FSPGR and less than 2.5dB(A) louder than ambient noise. Six-minute average SAR was <2W/kg.The ZTE Silent sequence provides high-contrast T1-weighted imaging with low acoustic noise at 7T. Silent is an MRI technique allowing zero time of echo acquisition Its feasibility and performance were assessed on a 7T MRI system Image quality in several regions was higher than in conventional techniques Imaging acoustic noise was dramatically reduced compared with conventional imaging Silent is suitable for T1-weighted head imaging at 7T.

PubMed | General Electric, Imago7 Foundation, National Institute of Nuclear Physics, Italy, University of Pisa and IRCCS Stella Maris Foundation
Type: Journal Article | Journal: Bioelectromagnetics | Year: 2015

Local specific absorption rate (SAR) evaluation in ultra high field (UHF) magnetic resonance (MR) systems is a major concern. In fact, at UHF, radiofrequency (RF) field inhomogeneity generates hot-spots that could cause localized tissue heating. Unfortunately, local SAR measurements are not available in present MR systems; thus, electromagnetic simulations must be performed for RF fields and SAR analysis. In this study, we used three-dimensional full-wave numerical electromagnetic simulations to investigate the dependence of local SAR at 7.0T with respect to subject size in two different scenarios: surface coil loaded by adult and child calves and quadrature volume coil loaded by adult and child heads. In the surface coil scenario, maximum local SAR decreased with decreasing load size, provided that the RF magnetic fields for the different load sizes were scaled to achieve the same slice average value. On the contrary, in the volume coil scenario, maximum local SAR was up to 15% higher in children than in adults.

PubMed | Imago7 Foundation
Type: Journal Article | Journal: Neuroradiology | Year: 2014

This contribution presents a magnetic resonance imaging (MRI) acquisition technique named Tissue Border Enhancement (TBE), whose purpose is to produce images with enhanced visualization of borders between two tissues of interest without any post-processing.The technique is based on an inversion recovery sequence that employs an appropriate inversion time to produce images where the interface between two tissues of interest is hypo-intense; therefore, tissue borders are clearly represented by dark lines. This effect is achieved by setting imaging parameters such that two neighboring tissues of interest have magnetization with equal magnitude but opposite sign; therefore, the voxels containing a mixture of each tissue (that is, the tissue interface) possess minimal net signal. The technique was implemented on a 7.0 T MRI system.This approach can assist the definition of tissue borders, such as that between cortical gray matter and white matter; therefore, it could facilitate segmentation procedures, which are often challenging on ultra-high-field systems due to inhomogeneous radiofrequency distribution. TBE allows delineating the contours of structural abnormalities, and its capabilities were demonstrated with patients with focal cortical dysplasia, gray matter heterotopia, and polymicrogyria.This technique provides a new type of image contrast and has several possible applications in basic neuroscience, neurogenetic research, and clinical practice, as it could improve the detection power of MRI in the characterization of cortical malformations, enhance the contour of small anatomical structures of interest, and facilitate cortical segmentation.

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