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Vishnu Ramesh T, Narongrit FW, Susnjar A, Rispoli JV. Stretchable receive coil for 7T small animal MRI. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 353:107510. [PMID: 37343393 DOI: 10.1016/j.jmr.2023.107510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 05/15/2023] [Accepted: 06/10/2023] [Indexed: 06/23/2023]
Abstract
Receive coils used in small animal MRI are rigid, inflexible surface loops that do not conform to the anatomy being imaged. The recent trend toward design of stretchable coils that are tailored to fit any anatomical curvature has been focused on human imaging. This work demonstrates the application of stretchable coils for small animal imaging at 7T. A stretchable coil measuring 3.5 × 3.5 cm was developed for acquisition of rat brain and spine images. The SNR maps of the stretchable coil were compared with those of a traditional flexible PCB coil and a commercial surface coil. Stretch and conformance testing of the coil was performed. Ex vivo images of rat brain and spine from the stretchable a coil was acquired using T1 FLASH and T2 Turbo RARE sequences. The axial phantom SNR maps showed that the stretchable coil provided 48.5% and 42.8% higher SNR than the commercial coil for T1-w and T2-w images within the defined ROI. A 33% increase in average penetration depth was observed within the ROI using the stretchable coil when compared to the commercial coil. The ex-vivo rat brain and spine images showed distinguishable anatomical details. Stretching the coil reduced the resonant frequency with reduction in SNR, while the conformance to varying sample volumes increased the resonant frequency with decreased SNR. This study also features an open-source plug-and-play system with preamplifiers that can be used to interface surface coils with the 7T Bruker scanner.
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Affiliation(s)
- Thejas Vishnu Ramesh
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Folk W Narongrit
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA; Elmore Family School of Electrical and Computer Engineering, West Lafayette, IN 47907, USA
| | - Antonia Susnjar
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
| | - Joseph V Rispoli
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA; Elmore Family School of Electrical and Computer Engineering, West Lafayette, IN 47907, USA; Department of Radiology and Medical Imaging, University of Virginia, Charlottesville, VA 22903, USA.
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Optimization of Keyhole Imaging Parameters for Glutamate Chemical Exchange Saturation Transfer MRI at 7.0 T. Mol Imaging Biol 2019; 22:924-930. [PMID: 31858369 DOI: 10.1007/s11307-019-01461-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
PURPOSE To evaluate the effects of a reference image and keyhole factor (Kf) selections for high-frequency substitution on keyhole imaging technique for applications in glutamate chemical exchange saturation transfer (GluCEST) imaging. PROCEDURES The CEST data were obtained using a 7.0 T MRI scanner. We used varied Kf ranges that constituted from 16.67 to 75 % of the full k-space. The reference image was respectively selected for - 3 and + 3 ppm images that associated with the GluCEST calculation and the unsaturated image. The zero-padding algorithm was applied for the missing k-space lines in the low-frequency data collected to compare the results obtained from using the keyhole imaging technique. All the techniques were evaluated using a healthy rat group and extended to the status epilepticus rat group to explore their applicability and usability. RESULTS The calculated GluCEST signals and visually inspected results from the reconstructed GluCEST maps indicated that the combination of unsaturated image as a reference image, and over 50 % of Kf showed consistent signals and image quality compared with the fully sampled CEST data. CONCLUSIONS Combining the keyhole imaging technique with GluCEST imaging enables stable image reconstruction and quantitative evaluation, and this approach is potentially applicable in various CEST imaging applications.
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Kim JH, Song SK. Diffusion tensor imaging of the mouse brainstem and cervical spinal cord. Nat Protoc 2013; 8:409-17. [PMID: 23424749 DOI: 10.1038/nprot.2013.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Concurrent and/or progressive degeneration of upper and lower motor neurons (LMNs) causes neurological symptoms and dysfunctions in motor neuron diseases (MNDs) such as amyotrophic lateral sclerosis (ALS). Although brain lesions are readily detected, magnetic resonance imaging of the brainstem and cervical spinal cord lesions resulting from damage to LMNs has proven to be difficult. With the development of mouse models of MNDs, a noninvasive neuroimaging modality capable of detecting lesions resulting from axonal and neuronal injury in mouse brainstem and cervical spinal cord could improve our understanding of the underlying mechanism of MNDs and aid in the development of effective treatments. Here we present a protocol that allows the concomitant acquisition of high-quality in vivo full-diffusion tensor magnetic resonance images from the mouse brainstem and cervical spinal cord using the actively decoupled, anatomically shaped pair of coils--the surface-receive coil and the minimized volume-transmit coil. To improve the data quality, we used a custom-made nose cone to monitor respiratory motion for synchronizing data acquisition and assuring physiological stability of mice under examination. The protocol allows the acquisition of in vivo diffusion tensor imaging of the mouse brainstem and cervical spinal cord at 117 μm × 117 μm in-plane resolution with a 500-μm slice thickness in 1 h on a 4.7-T horizontal small animal imaging scanner equipped with an actively shielded gradient coil capable of pulsed gradient strengths up to 18 G cm(−1) with a gradient rise time of ≤295 μs.
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Affiliation(s)
- Joong Hee Kim
- Department of Radiology, Washington University, St. Louis, Missouri, USA
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Constantinides C, Angeli S. Elimination of mutual inductance in NMR phased arrays: the paddle design revisited. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 222:59-67. [PMID: 22820010 DOI: 10.1016/j.jmr.2012.06.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 06/09/2012] [Accepted: 06/11/2012] [Indexed: 06/01/2023]
Abstract
This study proposes a method to empirically minimize mutual inductance, using passive end-ring circular paddles, with neighboring coil loops placed in a non-overlapped configuration. The proposed concepts are validated through B(1)-field simulations for resonant coils at f(o)=300.5 MHz, having various sizes (3-10 cm), and for paddles with sizes ranging from 16 to 30 mm, and bench tests on constructed 4×4cm(2) two- (1×2) and four-coil loop (2×2) planar arrays. Simulation results yield total mean percentage B(1)-field differences of only 7.03% between the two non-overlapping coil array configurations (paddles vs. no-paddles). Pair-wise comparisons of elicited mean B(1)-field differences from the use of different circular and rectangular paddle sizes, yield values <5.3%. Theoretical calculation of the normalized mutual coupling coefficient in the non-overlapped coil configuration reduces to almost zero with optimally sized-paddles having a radius of approximately 28% the coil's largest dimension. In the absence of paddles, differences in the split of resonance peaks of 9.9 MHz were observed for the two coils in the 1×2 array, which vanished with paddle placement. Single coil responses (unloaded/loaded) without paddles, and responses from array coils with use of optimally-sized paddles yielded quality factor ratios that ranged between 1.1-1.86 and 1.0-1.5, respectively. Phantom and mouse loaded reflection coefficients S(11)/S(22) were -16.7/-16.2dB and -28.2/-16.1 dB, for the two array loops, respectively. Under unloaded conditions and in the absence of paddles, split resonances were observed for the 1×2 array, yielding transmission coefficients of -5.5 to -8.1 dB, reversing to single resonance responses upon paddle placements, with transmission coefficients of -14.4 to -15.6 dB.
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Affiliation(s)
- Christakis Constantinides
- Department of Mechanical and Manufacturing Engineering, School of Engineering, University of Cyprus, Cyprus.
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Enomoto A, Hirata H. Sequential CW-EPR image acquisition with 760-MHz surface coil array. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 209:244-249. [PMID: 21320789 DOI: 10.1016/j.jmr.2011.01.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 01/19/2011] [Accepted: 01/19/2011] [Indexed: 05/30/2023]
Abstract
This paper describes the development of a surface coil array that consists of two inductively coupled surface-coil resonators, for use in continuous-wave electron paramagnetic resonance (CW-EPR) imaging at 760 MHz. To make sequential EPR image acquisition possible, we decoupled the surface coils using PIN-diode switches, to enable the shifting of the resonators resonance frequency by more than 200 MHz. To assess the effectiveness of the surface coil array in CW-EPR imaging, two-dimensional images of a solution of nitroxyl radicals were measured with the developed coil array. Compared to equivalent single coil acquired images, we found the visualized area to be extended approximately 2-fold when using the surface coil array. The ability to visualize larger regions of interest through the use of a surface coil array, may offer great potential in future EPR imaging studies.
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Affiliation(s)
- Ayano Enomoto
- Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo 060-0814, Japan
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Pillai DR, Heidemann RM, Kumar P, Shanbhag N, Lanz T, Dittmar MS, Sandner B, Beier CP, Weidner N, Greenlee MW, Schuierer G, Bogdahn U, Schlachetzki F. Comprehensive small animal imaging strategies on a clinical 3 T dedicated head MR-scanner; adapted methods and sequence protocols in CNS pathologies. PLoS One 2011; 6:e16091. [PMID: 21326876 PMCID: PMC3034718 DOI: 10.1371/journal.pone.0016091] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 12/09/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Small animal models of human diseases are an indispensable aspect of pre-clinical research. Being dynamic, most pathologies demand extensive longitudinal monitoring to understand disease mechanisms, drug efficacy and side effects. These considerations often demand the concomitant development of monitoring systems with sufficient temporal and spatial resolution. METHODOLOGY AND RESULTS This study attempts to configure and optimize a clinical 3 Tesla magnetic resonance scanner to facilitate imaging of small animal central nervous system pathologies. The hardware of the scanner was complemented by a custom-built, 4-channel phased array coil system. Extensive modification of standard sequence protocols was carried out based on tissue relaxometric calculations. Proton density differences between the gray and white matter of the rodent spinal cord along with transverse relaxation due to magnetic susceptibility differences at the cortex and striatum of both rats and mice demonstrated statistically significant differences. The employed parallel imaging reconstruction algorithms had distinct properties dependent on the sequence type and in the presence of the contrast agent. The attempt to morphologically phenotype a normal healthy rat brain in multiple planes delineated a number of anatomical regions, and all the clinically relevant sequels following acute cerebral ischemia could be adequately characterized. Changes in blood-brain-barrier permeability following ischemia-reperfusion were also apparent at a later time. Typical characteristics of intra-cerebral haemorrhage at acute and chronic stages were also visualized up to one month. Two models of rodent spinal cord injury were adequately characterized and closely mimicked the results of histological studies. In the employed rodent animal handling system a mouse model of glioblastoma was also studied with unequivocal results. CONCLUSIONS The implemented customizations including extensive sequence protocol modifications resulted in images of high diagnostic quality. These results prove that lack of dedicated animal scanners shouldn't discourage conventional small animal imaging studies.
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Affiliation(s)
- Deepu R. Pillai
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
- Department of Genetics and Neurobiology, Biozentrum, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Robin M. Heidemann
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Siemens Healthcare Sector, Erlangen, Germany
| | - Praveen Kumar
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
- Department of Neurology, University Medical Centre, RWTH Aachen, Aachen, Germany
| | - Nagesh Shanbhag
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
| | - Titus Lanz
- RAPID Biomedical GmbH, Würzburg-Rimpar, Germany
| | - Michael S. Dittmar
- Department of Anaesthesiology, Regensburg University Medical Centre, Regensburg, Germany
| | - Beatrice Sandner
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
| | - Christoph P. Beier
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
- Department of Neurology, University Medical Centre, RWTH Aachen, Aachen, Germany
| | - Norbert Weidner
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
- Institute for Paraplegia, University of Heidelberg, Heidelberg, Germany
| | - Mark W. Greenlee
- Institute for Experimental Psychology, University of Regensburg, Regensburg, Germany
| | - Gerhard Schuierer
- Center for Neuroradiology, Regensburg University Medical Centre and Bezirksklinikum Regensburg, Regensburg, Germany
| | - Ulrich Bogdahn
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
| | - Felix Schlachetzki
- Department of Neurology, Regensburg University Medical Centre, Regensburg, Germany
- * E-mail:
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In vivo diffusion tensor imaging of thoracic and cervical rat spinal cord at 7 T. Magn Reson Imaging 2009; 27:1236-41. [PMID: 19520537 DOI: 10.1016/j.mri.2009.05.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2008] [Revised: 02/17/2009] [Accepted: 05/06/2009] [Indexed: 11/20/2022]
Abstract
In vivo diffusion tensor imaging (DTI) of rat cervical and thoracic spinal cord was performed using a three-element phased array coil at 7 T. The magnetic field was shimmed over the spinal cord in real time using an in-house developed automatic algorithm. Echo planar imaging (EPI)-based diffusion-weighted images (DWIs) were acquired with 21 gradient encoding directions. The DWIs were tensor encoded, and diffusion tensor metrics, fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity (lambda(0)) and transverse diffusivity (lambda( perpendicular)) were determined for both white matter (WM) and gray matter (GM). The results on six normal rats indicated no significant differences in the diffusion tensor metrics between thoracic and cervical regions. However, the DTI-derived metrics in cervical spinal cord from our study are somewhat different from the published results in rats. The possible reasons for these differences are suggested.
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