Title: Direct Quantification of Intervertebral Disc Water Content Using MRI
Background
Water content is a key parameter for simulating tissue swelling and nutrient diffusion. Accurately measuring water content throughout the intervertebral disc (NP = nucleus pulposus; AF = annulus fibrosus) is important for developing patient‐specific models. Water content is measured using destructive techniques, Quantitative MRI has been used to estimate water content and detect early degeneration, but it is dependent on scan parameters, concentration of free water molecules, and fiber architecture.
Purpose
To directly measure disc‐tissue water content using quantitative MRI and compare MRI‐based measurements with biochemical assays, and to quantify changes in disc geometry due to compression.
Study Type
Basic science, controlled.
Specimen
Twenty bone‐disc‐bone motion segments from skeletally mature bovines.
Field Strength/Sequence
7T/3D fast low angle shot (FLASH) pulse sequence and a T2rapid imaging with refocused echoes (RARE) sequence.
Assessment
Disc volumes, NP and AF volumetric water content, and T2relaxation times were measured through MRI; NP and AF tissue gravimetric water content, mass density, and glycosaminoglycan content were measured through a biochemical assay.
Statistical Tests
Correlations between MRI‐based measurement and biochemical composition were evaluated using Pearson's linear regression.
Results
Mechanical dehydration resulted in a decrease in disc volume by up to 20% and a decrease in disc height by up to 35%. Direct water content measurements for the NP was achieved by normalizing MRI‐based spin density by NP mass density (1.10 ± 0.03 g/cm3). However, the same approach underestimated water content in the AF by ~10%, which may be due to a higher concentration of collagen fibers and bound water molecules.
Data Conclusion
Spin density or spin density normalized by mass density to estimate NP and AF water content was more accurate than correlations between water content and relaxation times. Mechanical dehydration decreased disc volume and disc height, and increased maximum cross‐sectional area.
Hankiewicz, Janusz H.; Celinski, Zbigniew; Camley, Robert E.(
, Medical Physics)
AbstractPurpose
One standard method, proton resonance frequency shift, for measuring temperature using magnetic resonance imaging (MRI), in MRI‐guided surgeries, fails completely below the freezing point of water. Because of this, we have developed a new methodology for monitoring temperature with MRI below freezing. The purpose of this paper is to show that a strong temperature dependence of the nuclear relaxation timeT1in soft silicone polymers can lead to temperature‐dependent changes of MRI intensity acquired withT1weighting. We propose the use of silicone filaments inserted in tissue for measuring temperature during MRI‐guided cryoablations.
Methods
The temperature dependence ofT1in bio‐compatible soft silicone polymers was measured using nuclear magnetic resonance spectroscopy and MRI. Phantoms, made of bulk silicone materials and put in an MRI‐compatible thermal container with dry ice, allowed temperature measurements ranging from –60°C to + 20°C.T1‐weighted gradient echo images of the phantoms were acquired at spatially uniform temperatures and with a gradient in temperature to determine the efficacy of using these materials as temperature indicators in MRI. Ex vivo experiments on silicone rods, 4 mm in diameter, inserted in animal tissue were conducted to assess the practical feasibility of the method.
Results
Measurements of nuclear relaxation times of protons in soft silicone polymers show a monotonic, nearly linear, change with temperature (R2 > 0.98) and have a significant correlation with temperature (Pearson'sr > 0.99,p < 0.01). Similarly, the intensity of the MR images in these materials, taken with a gradient echo sequence, are also temperature dependent. There is again a monotonic change in MRI intensity that correlates well with the measured temperature (Pearson'sr < ‐0.98 andp < 0.01). The MRI experiments show that a temperature change of 3°C can be resolved in a distance of about 2.5 mm. Based on MRI images and external sensor calibrations for a sample with a gradient in temperature, temperature maps with 3°C isotherms are created for a bulk phantom. Experiments demonstrate that these changes in MRI intensity with temperature can also be seen in 4 mm silicone rods embedded in ex vivo animal tissue.
Conclusions
We have developed a new method for measuring temperature in MRI that potentially could be used during MRI‐guided cryoablation operations, reducing both procedure time and cost, and making these surgeries safer.
Bashyam, Ashvin; Frangieh, Chris J.; Li, Matthew; Cima, Michael J.(
, Magnetic Resonance in Medicine)
Purpose
Undiagnosed dehydration compromises health outcomes across many populations. Existing dehydration diagnostics require invasive bodily fluid sampling or are easily confounded by fluid and electrolyte intake, environment, and physical activity limiting widespread adoption. We present a portable MR sensor designed to measure intramuscular fluid shifts to identify volume depletion.
Methods
Fluid loss is induced via a mouse model of thermal dehydration (37°C; 15‐20% relative humidity). We demonstrate quantification of fluid loss induced by hyperosmotic dehydration with multicomponent T2 relaxometry using both a benchtop NMR system and MRI localized to skeletal muscle tissue. We then describe a miniaturized (~1000 cm3) portable (~4 kg) MR sensor (0.28 T) designed to identify dehydration‐induced fluid loss. T2 relaxometry measurements were performed using a Carr‐Purcell‐Meiboom‐Gill pulse sequence in ~4 min.
Results
T2 values from the portable MR sensor exhibited strong (R2= 0.996) agreement with benchtop NMR spectrometer. Thermal dehydration induced weight loss of 4 to 11% over 5 to 10 h. Fluid loss induced by thermal dehydration was accurately identified via whole‐animal NMR and skeletal muscle. The portable MR sensor accurately identified dehydration via multicomponent T2 relaxometry.
Conclusion
Performing multicomponent T2 relaxometry localized to the skeletal muscle with a miniaturized MR sensor provides a noninvasive, physiologically relevant measure of dehydration induced fluid loss in a mouse model. This approach offers sensor portability, reduced system complexity, fully automated operation, and low cost compared with MRI. This approach may serve as a versatile and portable point of care technique for dehydration monitoring.
Anderson, Valerie C.; Tagge, Ian J.; Li, Xin; Quinn, Joseph F.; Kaye, Jeffrey A.; Bourdette, Dennis N.; Spain, Rebecca I.; Riccelli, Louis P.; Sammi, Manoj K.; Springer, Jr, Charles S.; et al(
, Journal of Neuroimaging)
ABSTRACTBACKGROUND AND PURPOSE
Transvascular water exchange plays a key role in the functional integrity of the blood–brain barrier (BBB). In white matter (WM), a variety of imaging modalities have demonstrated age‐related changes in structure and metabolism, but the extent to which water exchange is altered remains unclear. Here, we investigated the cumulative effects of healthy aging on WM capillary water exchange.
METHODS
A total of 38 healthy adults (aged 36‐80 years) were studied using 7T dynamic contrast enhanced MRI. Blood volume fraction (vb) and capillary water efflux rate constant (kpo) were determined by fitting changes in the1H2O longitudinal relaxation rate constant (R1) during contrast agent bolus passage to a two‐compartment exchange model. WM volume was determined by morphometric analysis of structural images.
RESULTS
R1values and WM volume showed similar trajectories of age‐related decline. Among all subjects,vbandkpoaveraged 1.7 (±0.5) mL/100 g of tissue and 2.1 (±1.1) s−1, respectively. Whilevbshowed minimal changes over the 40‐year‐age span of participants,kpodeclined 0.06 s−1(ca. 3%) per year (r= −.66;P < .0005), from near 4 s−1at age 30 to ca. 2 s−1at age 70. The association remained significant after controlling for WM volume.
CONCLUSIONS
Previous studies have shown thatkpotracks Na+, K+‐ATPase activity‐dependent water exchange at the BBB and likely reflects neurogliovascular unit (NGVU) coupled metabolic activity. The age‐related decline inkpoobserved here is consistent with compromised NGVU metabolism in older individuals and the dysregulated cellular bioenergetics that accompany normal brain aging.
Borem, Ryan; Walters, Joshua; Madeline, Allison; Madeline, Lee; Gill, Sanjitpal; Easley, Jeremiah; Mercuri, Jeremy(
, Journal of Biomedical Materials Research Part A)
Abstract
Intervertebral disc (IVD) degeneration (IVDD) leads to structural and functional changes. Biomaterials for restoring IVD function and promoting regeneration are currently being investigated; however, such approaches require validation using animal models that recapitulate clinical, biochemical, and biomechanical hallmarks of the human pathology. Herein, we comprehensively characterized a sheep model of chondroitinase‐ABC (ChABC) induced IVDD. Briefly, ChABC (1 U) was injected into the L1/2, L2/3, and L3/4IVDs. Degeneration was assessed via longitudinal magnetic resonance (MR) and radiographic imaging. Additionally, kinematic, biochemical, and histological analyses were performed on explanted functional spinal units (FSUs). At 17‐weeks, ChABC treated IVDs demonstrated significant reductions in MR index (p= 0.030) and disc height (p= 0.009) compared with pre‐operative values. Additionally, ChABC treated IVDs exhibited significantly increased creep displacement (p= 0.004) and axial range of motion (p= 0.007) concomitant with significant decreases in tensile (p= 0.034) and torsional (p= 0.021) stiffnesses and long‐term viscoelastic properties (p= 0.016). ChABC treated IVDs also exhibited a significant decrease in NP glycosaminoglycan: hydroxyproline ratio (p= 0.002) and changes in microarchitecture, particularly in the NP and endplates, compared with uninjured IVDs. Taken together, this study demonstrated that intradiscal injection of ChABC induces significant degeneration in sheep lumbar IVDs and the potential for using this model in evaluating biomaterials for IVD repair, regeneration, or fusion.
Demineralized bone matrix (DBM) has been widely used clinically for dental, craniofacial and skeletal bone repair, as an osteoinductive and osteoconductive material. 3D printing (3DP) enables the creation of bone tissue engineering scaffolds with complex geometries and porosity. Photoreactive methacryloylated gelatin nanoparticles (GNP-MAs) 3DP inks have been developed, which display gel-like behavior for high print fidelity and are capable of post-printing photocrosslinking for control of scaffold swelling and degradation. Here, novel DBM nanoparticles (DBM-NPs, ∼400 nm) were fabricated and characterized prior to incorporation in 3DP inks. The objectives of this study were to determine how these DBM-NPs would influence the printability of composite colloidal 3DP inks, assess the impact of ultraviolet (UV) crosslinking on 3DP scaffold swelling and degradation and evaluate the osteogenic potential of DBM-NP-containing composite colloidal scaffolds. The addition of methacryloylated DBM-NPs (DBM-NP-MAs) to composite colloidal inks (100:0, 95:5 and 75:25 GNP-MA:DBM-NP-MA) did not significantly impact the rheological properties associated with printability, such as viscosity and shear recovery or photocrosslinking. UV crosslinking with a UV dosage of 3 J/cm2 directly impacted the rate of 3DP scaffold swelling for all GNP-MA:DBM-NP-MA ratios with an ∼40% greater increase in scaffold area and pore area in uncrosslinked versus photocrosslinked scaffolds over 21 days in phosphate-buffered saline (PBS). Likewise, degradation (hydrolytic and enzymatic) over 21 days for all DBM-NP-MA content groups was significantly decreased, ∼45% less in PBS and collagenase-containing PBS, in UV-crosslinked versus uncrosslinked groups. The incorporation of DBM-NP-MAs into scaffolds decreased mass loss compared to GNP-MA-only scaffolds during collagenase degradation. An in vitro osteogenic study with bone marrow-derived mesenchymal stem cells demonstrated osteoconductive properties of 3DP scaffolds for the DBM-NP-MA contents examined. The creation of photoreactive DBM-NP-MAs and their application in 3DP provide a platform for the development of ECM-derived colloidal materials and tailored control of biochemical cue presentation with broad tissue engineering applications.
Yang, Bo, Wendland, Michael F., and O'Connell, Grace D. Direct Quantification of Intervertebral Disc Water Content Using MRI. Journal of Magnetic Resonance Imaging 52.4 Web. doi:10.1002/jmri.27171.
Yang, Bo, Wendland, Michael F., & O'Connell, Grace D. Direct Quantification of Intervertebral Disc Water Content Using MRI. Journal of Magnetic Resonance Imaging, 52 (4). https://doi.org/10.1002/jmri.27171
Yang, Bo, Wendland, Michael F., and O'Connell, Grace D.
"Direct Quantification of Intervertebral Disc Water Content Using MRI". Journal of Magnetic Resonance Imaging 52 (4). Country unknown/Code not available: Wiley Blackwell (John Wiley & Sons). https://doi.org/10.1002/jmri.27171.https://par.nsf.gov/biblio/10456768.
@article{osti_10456768,
place = {Country unknown/Code not available},
title = {Direct Quantification of Intervertebral Disc Water Content Using MRI},
url = {https://par.nsf.gov/biblio/10456768},
DOI = {10.1002/jmri.27171},
abstractNote = {BackgroundWater content is a key parameter for simulating tissue swelling and nutrient diffusion. Accurately measuring water content throughout the intervertebral disc (NP = nucleus pulposus; AF = annulus fibrosus) is important for developing patient‐specific models. Water content is measured using destructive techniques, Quantitative MRI has been used to estimate water content and detect early degeneration, but it is dependent on scan parameters, concentration of free water molecules, and fiber architecture. PurposeTo directly measure disc‐tissue water content using quantitative MRI and compare MRI‐based measurements with biochemical assays, and to quantify changes in disc geometry due to compression. Study TypeBasic science, controlled. SpecimenTwenty bone‐disc‐bone motion segments from skeletally mature bovines. Field Strength/Sequence7T/3D fast low angle shot (FLASH) pulse sequence and a T2rapid imaging with refocused echoes (RARE) sequence. AssessmentDisc volumes, NP and AF volumetric water content, and T2relaxation times were measured through MRI; NP and AF tissue gravimetric water content, mass density, and glycosaminoglycan content were measured through a biochemical assay. Statistical TestsCorrelations between MRI‐based measurement and biochemical composition were evaluated using Pearson's linear regression. ResultsMechanical dehydration resulted in a decrease in disc volume by up to 20% and a decrease in disc height by up to 35%. Direct water content measurements for the NP was achieved by normalizing MRI‐based spin density by NP mass density (1.10 ± 0.03 g/cm3). However, the same approach underestimated water content in the AF by ~10%, which may be due to a higher concentration of collagen fibers and bound water molecules. Data ConclusionSpin density or spin density normalized by mass density to estimate NP and AF water content was more accurate than correlations between water content and relaxation times. Mechanical dehydration decreased disc volume and disc height, and increased maximum cross‐sectional area. Level of Evidence Technical Efficacy Stage J. Magn. Reson. Imaging 2020;52:1152–1162.},
journal = {Journal of Magnetic Resonance Imaging},
volume = {52},
number = {4},
publisher = {Wiley Blackwell (John Wiley & Sons)},
author = {Yang, Bo and Wendland, Michael F. and O'Connell, Grace D.},
}
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