Mesoscale diffusion magnetic resonance imaging of the ex vivo human hippocampus

Abstract A surface radio frequency coil was developed for small animal image acquisition in a pre-clinical magnetic resonance imaging system at 7 T. A flexible coil composed of two circular loops was developed to closely cover the object to be imaged. Electromagnetic numerical simulations were performed to evaluate its performance before the coil construction. An analytical expression of the mutual inductance for the two circular loops as a function of the separation between them was derived and used to validate the simulations. The RF coil is composed of two circular loops with a 5 cm external diameter and was tuned to 300 MHz and 50 Ohms matched. The angle between the loops was varied and the Q factor was obtained from the S11 simulations for each angle. B1 homogeneity was also evaluated using the electromagnetic simulations. The coil prototype was designed and built considering the numerical simulation results. To show the feasibility of the coil and its performance, saline-solution phantom images were acquired. A correlation of the simulations and imaging experimental results was conducted showing a concordance of 0.88 for the B1 field. The best coil performance was obtained at the 90° aperture angle. A more realistic phantom was also built using a formaldehyde-fixed rat phantom for ex vivo imaging experiments. All images showed a good image quality revealing clearly defined anatomical details of an ex vivo rat.

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Diffusion Magnetic Resonance Imaging-Based Biomarkers for Neurodegenerative Diseases

International Journal of Molecular Sciences ◽

10.3390/ijms22105216 ◽

2021 ◽

Vol 22 (10) ◽

pp. 5216

Author(s):

Koji Kamagata ◽

Christina Andica ◽

Ayumi Kato ◽

Yuya Saito ◽

Wataru Uchida ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Diffusion Tensor Imaging ◽

Magnetic Resonance ◽

Neurodegenerative Diseases ◽

Diffusion Magnetic Resonance Imaging ◽

New Technologies ◽

Diffusion Tensor ◽

Free Water ◽

Diffusion Kurtosis Imaging ◽

Resonance Imaging

There has been an increasing prevalence of neurodegenerative diseases with the rapid increase in aging societies worldwide. Biomarkers that can be used to detect pathological changes before the development of severe neuronal loss and consequently facilitate early intervention with disease-modifying therapeutic modalities are therefore urgently needed. Diffusion magnetic resonance imaging (MRI) is a promising tool that can be used to infer microstructural characteristics of the brain, such as microstructural integrity and complexity, as well as axonal density, order, and myelination, through the utilization of water molecules that are diffused within the tissue, with displacement at the micron scale. Diffusion tensor imaging is the most commonly used diffusion MRI technique to assess the pathophysiology of neurodegenerative diseases. However, diffusion tensor imaging has several limitations, and new technologies, including neurite orientation dispersion and density imaging, diffusion kurtosis imaging, and free-water imaging, have been recently developed as approaches to overcome these constraints. This review provides an overview of these technologies and their potential as biomarkers for the early diagnosis and disease progression of major neurodegenerative diseases.

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Multidetector-row computed tomography and magnetic resonance imaging of atherosclerotic lesions in human ex vivo coronary arteries

Atherosclerosis ◽

10.1016/j.atherosclerosis.2004.01.041 ◽

2004 ◽

Vol 174 (2) ◽

pp. 243-252 ◽

Cited By ~ 79

Author(s):

Konstantin Nikolaou ◽

Christoph R Becker ◽

Michael Muders ◽

Gregor Babaryka ◽

Juergen Scheidler ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Computed Tomography ◽

Magnetic Resonance ◽

Coronary Arteries ◽

Ex Vivo ◽

Multidetector Row Computed Tomography ◽

Resonance Imaging ◽

Multidetector Row ◽

Atherosclerotic Lesions

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High-Resolution Magnetic Resonance Imaging of the Human Median Nerve

Neurorehabilitation and Neural Repair ◽

10.1177/0888439004267074 ◽

2004 ◽

Vol 18 (2) ◽

pp. 80-87 ◽

Cited By ~ 11

Author(s):

Archie Heddings ◽

Mehmet Bilgen ◽

Randolph Nudo ◽

Bruce Toby ◽

Terence McIff ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

High Resolution ◽

Peripheral Nerve ◽

Median Nerve ◽

Ex Vivo ◽

Imaging Techniques ◽

Proton Density ◽

Resonance Imaging ◽

Imaging Protocols

Objectives. It is widely accepted that peripheral nerve repairs performed within 6 weeks of injury have much better outcomes than those performed at later dates. However, there is no diagnostic technique that can determine if a traumatic peripheral nerve injury requires surgical intervention in the early postinjury phase. The objective of this article was to determine whether novel, noninvasive magnetic resonance imaging techniques could demonstrate the microstructure of human peripheral nerves that is necessary for determining prognosis and determining if surgery is indicated following traumatic injury. Methods. Ex vivo magnetic resonance imaging protocols were developed on a 9.4-T research scanner using spin-echo proton density and gradient-echo imaging sequences and a specially designed, inductively coupled radio frequency coil. These imaging protocols were applied to in situ imaging of the human median nerve in 4 fresh-frozen cadaver arms. Results. Noninvasive high-resolution images of the human median nerve were obtained. Structures in the nerve that were observed included fascicles, interfascicular epineurium, perineurium, and intrafascicular septations. Conclusion. Application of these imaging techniques to clinical scanners could provide physicians with a tool that is capable of grading the severity of nerve injuries and providing indications for surgery in the early postinjury phase.

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Ex vivo magnetic resonance imaging of rat spinal cord at 9.4 T

Magnetic Resonance Imaging ◽

10.1016/j.mri.2005.02.003 ◽

2005 ◽

Vol 23 (4) ◽

pp. 601-605 ◽

Cited By ~ 13

Author(s):

Mehmet Bilgen ◽

Baraa Al-Hafez ◽

Thomas M. Malone ◽

Irina V. Smirnova

Keyword(s):

Magnetic Resonance Imaging ◽

Spinal Cord ◽

Magnetic Resonance ◽

Ex Vivo ◽

Resonance Imaging ◽

Rat Spinal Cord

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