A Microperfusion and In-Bore Oxygenator System Designed for Magnetic Resonance Microscopy Studies on Living Tissue Explants

Flint, Jeremy J.; Menon, Kannan; Hansen, Brian; Forder, John R.; Blackband, Stephen J.

doi:10.1038/srep18095

Cited by 7 publications

(14 citation statements)

References 53 publications

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“…Such measurements using cellular level MR microscopy may aid in resolving this modeling ambiguity by providing estimates of diffusivities in specific tissue compartments. So far only fixed tissue has been examined in this manner, but future experiments may be possible where the perfused acute brain slice model can be employed in a microscopy setup as in Reference 66.…”

Section: Discussionmentioning

confidence: 99%

White matter biomarkers from fast protocols using axially symmetric diffusion kurtosis imaging

et al. 2017

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White matter tract integrity (WMTI) can characterize brain microstructure in areas with highly aligned fiber bundles. Several WMTI biomarkers have now been validated against microscopy and provided promising results in studies of brain development and aging, as well as in a number of brain disorders. Currently, WMTI is mostly used in dedicated animal studies and clinical studies of slowly progressing diseases but has not yet emerged as a routine clinical tool. To this end, a less data intensive experimental method would be beneficial by enabling high resolution validation studies, and ease clinical applications by speeding up data acquisition compared to typical diffusion kurtosis imaging (DKI) protocols utilized as part of WMTI imaging. Here, we evaluate WMTI based on recently introduced axially symmetric DKI which has lower data demand than conventional DKI. We compare WMTI parameters derived from conventional DKI to those calculated analytically from axially symmetric DKI. We employ numerical simulations, as well as data from fixed rat spinal cord (1 sample) and in vivo human (3 subjects) and rat brain (4 animals). Our analysis shows that analytical WMTI based on axially symmetric DKI with sparse data sets (19 images) produces WMTI metrics that correlate strongly with estimates based on traditional DKI data sets (60 images or more). We demonstrate the preclinical potential of the proposed WMTI technique in in vivo rat brain (300 μm isotropic resolution with whole brain coverage in a one hour acquisition). WMTI parameter estimates are subject to a duality leading to two solution branches dependent on a sign choice which is currently debated. Results from both of these branches are presented and discussed throughout our analysis. The proposed fast WMTI approach may be useful for preclinical research and e.g. clinical evaluation of patients with traumatic white matter injuries or symptoms of neurovascular or neuroinflammatory disorders.

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Section: Discussionmentioning

confidence: 99%

White matter biomarkers from fast protocols using axially symmetric diffusion kurtosis imaging

et al. 2017

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“…Upon successful employment of the in-bore oxygenation device, gases present in the supplied carbogen will reach 100% saturation conditions within the aCSF perfusate. This can be demonstrated by varying the oxygen concentration of the supplied gas and measuring the change in dissolved oxygen content in the aCSF perfusate within the perfusion chamber using an oxygen meter ( Figure 1 ) 8 . According to Henry's law, the amount of dissolved gas that is in equilibrium with a liquid sample is directly proportional to the partial pressure of that gas provided that the temperature remains constant 12 .…”

Section: Representative Resultsmentioning

confidence: 99%

“… In the event no perfusate is seen exiting the return line into the waste reservoir, remove the probe body and confirm that perfusate flow has recommenced prior to attempting reinsertion. A schematic layout of the assembled perfusion system and imaging spectrometer has been described previously 8 . …”

Section: Protocolmentioning

confidence: 99%

“…To facilitate MR microscopy studies on living tissues, a protocol is presented which includes commercial microimaging hardware 7 interfaced to a purpose-built, MR compatible, in-bore oxygenator and perfusion device previously described 8 . Unique advantages of this design include cellular-level resolution capabilities in mammalian tissues and precision control over dissolved gas content and pH at the site of tissue perfusion.…”

Section: Introductionmentioning

confidence: 99%

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Metabolic Support of Excised, Living Brain Tissues During Magnetic Resonance Microscopy Acquisition

Flint

Menon

Hansen

et al. 2017

JoVE

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This protocol describes the procedures necessary to support normal metabolic functions of acute brain slice preparations during the collection of magnetic resonance (MR) microscopy data. While it is possible to perform MR collections on living, excised mammalian tissue, such experiments have traditionally been constrained by resolution limits and are thus incapable of visualizing tissue microstructure. Conversely, MR protocols that did achieve microscopic image resolution required the use of fixed samples to accommodate the need for static, unchanging conditions over lengthy scan times. The current protocol describes the first available MR technique that enables imaging of living, mammalian tissue samples at microscopic resolutions. Such data is of great importance to the understanding of how pathology-based contrast changes occurring at the microscopic level influence the content of macroscopic MR scans such as those used in the clinic. Once such an understanding is realized, diagnostic methods with greater sensitivity and accuracy can be developed, which will translate directly to earlier disease treatment, more accurate therapy monitoring and improved patient outcomes.While the described methodology focuses on brain slice preparations, the protocol is adaptable to any excised tissue slice given that changes are made to the gas and perfusate preparations to accommodate the tissue's specific metabolic needs. Successful execution of the protocol should result in living, acute slice preparations that exhibit MR diffusion signal stability for periods up to 15.5 h. The primary advantages of the current system over other MR compatible perfusion apparatuses are its compatibility with the MR microscopy hardware required to attain higher resolution images and ability to provide constant, uninterrupted flow with carefully regulated perfusate conditions. Reduced sample throughput is a consideration with this design as only one tissue slice may be imaged at a time.

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“…Proper placement of the samples such that these anatomical landmarks were overlapping the coil face was accomplished by hand using blunt-ended glass probes (300–500 μm tip) and a dissecting scope (Zeiss, OPMI 1-FC). Nylon components consisting of a circular mesh cutout (50 μm pore size) and notched retention ring were used to prevent the samples from moving and ensure they remained in constant contact with the surface coil face during imaging [6] . Once the sample was secured, PBS solution was used to fill the tissue well prior to sealing with PCR film (12 mm 2 , AB-0558).…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Diffusion tensor microscopy data (15.6 μm in-plane) of white matter tracts in the human, pig, and rat spinal cord with corresponding tissue histology

2016

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The following article contains nine diffusion tensor imaging (DTI) datasets acquired with magnetic resonance microscopy (MRM, 15.6 μm in-plane). All data was collected in the region bordering the ventral horn and white matter of cross sections from the spinal cord enlargements along with each sample׳s corresponding tissue histology. These data are collected in fixed spinal cord sections of varying thicknesses taken from rat (2×21 direction DTI datasets), pig (1×21 direction DTI dataset), and human (5×21 direction DTI datasets + 1×6 direction DTI dataset) tissue sources. Following MRM acquisition, the sections were histologically processed using Nissl or Black-Gold II (Histo-Chem Inc., 1BGII) myelin stain and imaged again using light microscopy techniques. Methodological procedures are an amalgamation of protocol components described previously (doi:10.1016/j.neuroimage.2010.04.03110.1016/j.neuroimage.2010.04.031 [1], doi:10.1016/j.neuroimage.2011.04.05210.1016/j.neuroimage.2011.04.052 [2]).

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A Microperfusion and In-Bore Oxygenator System Designed for Magnetic Resonance Microscopy Studies on Living Tissue Explants

Cited by 7 publications

References 53 publications

White matter biomarkers from fast protocols using axially symmetric diffusion kurtosis imaging

White matter biomarkers from fast protocols using axially symmetric diffusion kurtosis imaging

Metabolic Support of Excised, Living Brain Tissues During Magnetic Resonance Microscopy Acquisition

Diffusion tensor microscopy data (15.6 μm in-plane) of white matter tracts in the human, pig, and rat spinal cord with corresponding tissue histology

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