17 results on '"R. Adam Horch"'
Search Results
2. WITHDRAWN: 3D-printed RF probeheads for low-cost, high-throughput NMR
- Author
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John C. Gore and R. Adam Horch
- Subjects
0301 basic medicine ,chemistry.chemical_classification ,Materials science ,business.industry ,Microfluidics ,Biomedical Engineering ,Biophysics ,Analytical chemistry ,3D printing ,Polymer ,Nuclear magnetic resonance spectroscopy ,law.invention ,03 medical and health sciences ,Capacitor ,030104 developmental biology ,chemistry ,law ,Electromagnetic coil ,Optoelectronics ,Radiology, Nuclear Medicine and imaging ,Metallizing ,business ,Electronic circuit - Abstract
3D printing has been exploited as a means to fabricate complete NMR probeheads containing arrays of miniature RF circuits for high-throughput solution-state NMR spectroscopy and potentially other purposes. 3D-printed NMR circuits of millimeter scale were constructed consisting of RF coils, variable tuning/matching capacitors, and liquid NMR sample cavities. Channels and cavities capable of being addressed using microfluidics are included in the probehead structure, providing a means for hydraulically-controlled RF tuning/matching and liquid NMR sample loading/unloading. Electrically conductive RF circuitry is defined within the 3D-printed polymer bodies by metallizing relevant channels and structures with silver. The unique properties of 3D printing enable facile construction of potentially thousands of coils at low cost, giving way to dense coil arrays for high-throughput NMR and novel coil geometries.
- Published
- 2017
3. Simple and robust saturation-based slice selection for ultrashort echo time MRI
- Author
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R. Adam Horch, Kevin D. Harkins, and Mark D. Does
- Subjects
Physics ,Amplitude ,Nuclear magnetic resonance ,Healthy volunteers ,Slice selection ,Radiology, Nuclear Medicine and imaging ,Ultrashort echo time ,Image enhancement ,Short t2 ,Saturation (magnetic) ,Decay curve - Abstract
Purpose To present a new method for localizing signal within a two-dimensional (2D) slice suitable for ultrashort echo time (UTE) imaging, called saturation-based UTE (sat-UTE). The new method digitally subtracts two acquisitions that are nonselectively excited with and without selective saturation of the slice of interest. Methods Sat-UTE was compared with half-pulse and double-half pulse excited UTE within phantoms, as well as 3D-UTE within ex vivo femur and in vivo tibia. Numerical simulations were also used to quantify the effects of slice profile broadening and signal component amplitudes for quantitative UTE. Results Sat-UTE is robust to suppress out-of-slice signal, and produces short T2 signal decay curves comparable to 3D-UTE, but has a lower signal to noise ratio efficiency compared with other slice-selective methods. Conclusion The proposed method is useful for fast, quantitative evaluation of short T2 signals, and is insensitive to gradient performance. Magn Reson Med 73:2204–2211, 2015. © 2014 Wiley Periodicals, Inc.
- Published
- 2014
4. Validation of quantitative bound- and pore-water imaging in cortical bone
- Author
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Mark D. Does, Daniel F. Gochberg, Mary Kate Manhard, R. Adam Horch, Jeffry S. Nyman, and Kevin D. Harkins
- Subjects
Scanner ,Pore water pressure ,Materials science ,Nuclear magnetic resonance ,medicine.anatomical_structure ,Power deposition ,Echo time ,medicine ,Bound water ,Radiology, Nuclear Medicine and imaging ,Cortical bone ,Translation (geometry) - Abstract
Purpose To implement and validate a previously proposed ultra-short echo time method for measuring collagen-bound- and pore-water concentrations in bone based on their T2 differences. Methods Clinically compatible ultra-short echo time image sequences for quantitative T2-based bound and pore-water imaging in bone were implemented and validated on a 3T human scanner and a 4.7T small bore system. Bound- and pore-water images were generating using T2-selective adiabatic pulses. In both cases, the magnetization preparation was integrated into a three-dimensional ultra-short echo time acquisition, with 16 radial spokes acquired per preparation. Images were acquired from human cadaveric femoral mid-shafts from which isolated bone samples were subsequently extracted for nonimaging analysis using T2 spectroscopic measurements. Results A strong correlation was found between imaging-derived concentrations of bound and pore water and those determined from the isolated bone samples. Conclusions These studies demonstrate the translation of the previously developed approaches for distinguishing bound and pore water from human cortical bone using practical human MRI constraints of gradient performance and radiofrequency power deposition. Magn Reson Med 71:2166–2171, 2014. © 2013 Wiley Periodicals, Inc.
- Published
- 2013
5. Partial removal of pore and loosely bound water by low-energy drying decreases cortical bone toughness in young and old donors
- Author
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Mary Katherine Manhard, Mark D. Does, Jeffry S. Nyman, Ahbid Zein-Sabatto, Sasidhar Uppuganti, Lacey E. Gorochow, and R. Adam Horch
- Subjects
Adult ,Male ,Aging ,Relaxometry ,Toughness ,Materials science ,Medial cortex ,Biomedical Engineering ,Article ,Bone remodeling ,Biomaterials ,Fractures, Bone ,Young Adult ,Tensile Strength ,Ultimate tensile strength ,Cadaver ,medicine ,Humans ,Bound water ,Femur ,Desiccation ,Aged ,Mechanical Phenomena ,Aged, 80 and over ,Bone mineral ,Temperature ,Water ,X-Ray Microtomography ,Middle Aged ,Biomechanical Phenomena ,medicine.anatomical_structure ,Mechanics of Materials ,Female ,Cortical bone ,Porosity ,Biomedical engineering - Abstract
With an ability to quantify matrix-bound and pore water in bone, 1H nuclear magnetic resonance (NMR) relaxometry can potentially be implemented in clinical imaging to assess the fracture resistance of bone in a way that is independent of current X-ray techniques, which assess bone mineral density as a correlate of bone strength. Working towards that goal, we quantified the effect of partial dehydration in air on the mechanical and NMR properties of human cortical bone in order to understand whether NMR is sensitive to water-bone interactions at low energy and whether such interactions contribute to the age-related difference in the toughness of bone. Cadaveric femurs were collected from male and female donors falling into two age groups: 21 to 60 years of age (young) and 74 to 99 years of age (old). After extracting two samples from the medial cortex of the mid-shaft, tensile tests were conducted on Wet specimens and paired, Partially Dry (PtlD) specimens (prepared by low-energy drying in air to remove ~3% of original mass before testing). Prior analysis by micro-computed tomography found that there were no differences in intra-cortical porosity between the Wet and PtlD specimens nor did an age-related difference in porosity exist. PtlD specimens from young and old donors had significantly less toughness than Wet specimens, primarily due to a dehydration-related decrease in post-yield strain. The low-energy drying protocol did not affect the modulus and yield strength of bone. Subsequent dehydration of the PtlD specimens in a vacuum oven at 62 °C and then 103 °C, with quantification of water loss at each temperature, revealed an age-related shift from more loosely bound water to more tightly bound water. NMR detected a change in both bound and pore water pools with low-energy air-drying, and both pools were effectively removed when bone was oven-dried at 62 °C, irrespective of donor age. Although not strictly significant due to variability in the drying and testing conditions, the absolute difference in toughness between Wet and PtlD tended to be greater for the younger donors that had higher bone toughness and more bound water for the wet condition than did the older donors. With sensitivity to low-energy bone-water interactions, NMR, which underpins magnetic resonance imaging, has potential to assess fracture resistance of bone as it relates to bone toughness.
- Published
- 2013
6. Clinically compatible MRI strategies for discriminating bound and pore water in cortical bone
- Author
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Daniel F. Gochberg, R. Adam Horch, Mark D. Does, and Jeffry S. Nyman
- Subjects
Adult ,Male ,Pathology ,medicine.medical_specialty ,Population ,Sensitivity and Specificity ,Article ,Young Adult ,Pore water pressure ,Body Water ,Image Interpretation, Computer-Assisted ,Cadaver ,medicine ,Humans ,Bound water ,Radiology, Nuclear Medicine and imaging ,Femur ,Clinical imaging ,education ,Aged ,Aged, 80 and over ,education.field_of_study ,medicine.diagnostic_test ,Chemistry ,Discriminant Analysis ,Reproducibility of Results ,Water ,Magnetic resonance imaging ,Bone fracture ,Middle Aged ,medicine.disease ,Magnetic Resonance Imaging ,medicine.anatomical_structure ,Female ,Cortical bone ,Porosity ,Algorithms ,Biomedical engineering - Abstract
Advances in modern magnetic resonance imaging (MRI) pulse sequences have enabled clinically practical cortical bone imaging. Human cortical bone is known to contain a distribution of T1 and T2 components attributed to bound and pore water, although clinical imaging approaches have yet to discriminate bound from pore water based on their relaxation properties. Herein, two clinically compatible MRI strategies are proposed for selectively imaging either bound or pore water by utilizing differences in their T1s and T2s. The strategies are validated in a population of ex vivo human cortical bones, and estimates obtained for bound and pore water are compared to bone mechanical properties. Results show that the two MRI strategies provide good estimates of bound and pore water that correlate to bone mechanical properties. As such, the strategies for bound and pore water discrimination shown herein should provide diagnostically useful tools for assessing bone fracture risk, once applied to clinical MRI. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
- Published
- 2012
7. Origins of the ultrashort-T21H NMR signals in myelinated nerve: A direct measure of myelin content?
- Author
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R. Adam Horch, John C. Gore, and Mark D. Does
- Subjects
medicine.diagnostic_test ,Chemistry ,Magnetic resonance imaging ,Direct measure ,Myelin ,medicine.anatomical_structure ,Nuclear magnetic resonance ,medicine ,Proton NMR ,Radiology, Nuclear Medicine and imaging ,Clinical imaging ,Sciatic nerve ,Magnetization transfer ,Myelinated nerve - Abstract
Recently developed MRI techniques have enabled clinical imaging of short-lived 1H NMR signals with T2 < 1 ms. Using these techniques, novel signal enhancement has been observed in myelinated tissues, although the source of this enhancement has not been identified. Herein, we report studies of the nature and origins of ultrashort T2 (uT2) signals (50 μs < T2 < 1 ms) from amphibian and mammalian myelinated nerves. NMR measurements and comparisons with myelin phantoms and expected myelin components indicate that these uT2 signals arise predominantly from methylene 1H on/in the myelin membranes, which suggests that direct measurement of uT2 signals can be used as a new means for quantitative myelin mapping. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc.
- Published
- 2011
8. RF coil considerations for short-T 2 MRI
- Author
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Mark D. Does, Ken Wilkens, R. Adam Horch, and Daniel F. Gochberg
- Subjects
Resonator ,Nuclear magnetic resonance ,Materials science ,Electromagnetic coil ,Acoustics ,Electromagnetic shielding ,Radiology, Nuclear Medicine and imaging ,Pulse sequence ,Signal ,Sensitivity (electronics) ,Radiofrequency coil ,Radio wave - Abstract
With continuing hardware and pulse sequence advancements, modern MRI is gaining sensitivity to signals from short-T(2) (1)H species under practical experimental conditions. However, conventional MRI coils are typically not designed for this type of application, as they often contain proton-rich construction materials that may contribute confounding (1)H background signal during short-T(2) measurements. An example of this is shown herein. Separately, a loop-gap style coil was used to compare different coil construction materials and configurations with respect to observed (1)H background signal sizes in a small animal imaging system. Background signal sources were spatially identified and quantified in a number of different coil configurations. It was found that the type and placement of structural coil materials around the loop-gap resonator, as well as the coil's shielding configuration, are critical determinants of the coil's background signal size. Although this study employed a loop-gap resonator design, these findings are directly relevant to standard volume coils commonly used for MRI.
- Published
- 2010
9. Characterization of 1 H NMR signal in human cortical bone for magnetic resonance imaging
- Author
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Richard D. Dortch, R. Adam Horch, Mark D. Does, Daniel F. Gochberg, and Jeffry S. Nyman
- Subjects
Relaxometry ,medicine.diagnostic_test ,Chemistry ,Relaxation (NMR) ,Magnetic resonance imaging ,Nuclear magnetic resonance spectroscopy ,Characterization (materials science) ,medicine.anatomical_structure ,Nuclear magnetic resonance ,medicine ,Proton NMR ,Radiology, Nuclear Medicine and imaging ,Cortical bone ,Magnetization transfer - Abstract
Recent advancements in MRI have enabled clinical imaging of human cortical bone, providing a potentially powerful new means for assessing bone health with molecular-scale sensitivities unavailable to conventional X-ray-based diagnostics. In human cortical bone, MRI is sensitive to populations of protons (1H) partitioned among water and protein sources, which may be differentiated according to intrinsic NMR properties such as chemical shift and transverse and longitudinal relaxation rates. Herein, these NMR properties were assessed in human cortical bone donors from a broad age range, and four distinct 1H populations were consistently identified and attributed to five microanatomical sources. These findings show that modern human cortical bone MRI contrast will be dominated by collagen-bound water, which can also be exploited to study human cortical bone collagen via magnetization transfer. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.
- Published
- 2010
10. Aqueous urea as a model system for bi-exponential relaxation
- Author
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R. Adam Horch and Mark D. Does
- Subjects
Relaxometry ,Magnetic Resonance Spectroscopy ,Aqueous solution ,Materials science ,genetic structures ,Radiological and Ultrasound Technology ,Solid-state physics ,Doping ,Biophysics ,Water ,Thermodynamics ,Model system ,Magnetic Resonance Imaging ,Solutions ,chemistry.chemical_compound ,Nuclear magnetic resonance ,Models, Chemical ,chemistry ,Urea ,Relaxation (physics) ,Radiology, Nuclear Medicine and imaging ,sense organs ,Bi exponential - Abstract
To evaluate the utility of aqueous urea, doped inner- and outer-sphere relaxation agents, as an adjustable two-component model system.T2 was measured from 12 molal urea mixtures at pH 7.0 with varying amounts of the MnCl2 and FeO(1.44) (Feridex, Berlex Inc, Montville, NJ).Bi-exponential relaxation was observed, with rates that were bilinearly related to [MnCl2] and [FeO(1.44)]. FeO(1.44) had comparable relaxivities on both urea and water, while MnCl2 relaxivity was15x larger for water than for urea.Aqueous urea, doped with inner- and outer-sphere contrast agents, is a two-compartment model system, which can be exhibit a wide range of different T2s and signal fractions.
- Published
- 2007
11. In Vivo Quantitative MR Imaging of Bound and Pore Water in Cortical Bone
- Author
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Jeffry S. Nyman, Mark D. Does, Daniel F. Gochberg, Mary Kate Manhard, and R. Adam Horch
- Subjects
Adult ,Male ,Bone and Bones ,Pore water pressure ,Young Adult ,In vivo ,Mole ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Original Research ,medicine.diagnostic_test ,business.industry ,Hydrogen-1 ,Quantitative mr ,Water ,Magnetic resonance imaging ,Anatomy ,Magnetic Resonance Imaging ,Communications ,medicine.anatomical_structure ,Cortical bone ,Female ,Collagen ,business ,Biomedical engineering - Abstract
To translate and evaluate an in vivo magnetic resonance (MR) imaging protocol for quantitative mapping of collagen-bound and pore water concentrations in cortical bone that involves relaxation-selective ultrashort echo time (UTE) methods.All HIPAA-compliant studies were performed with institutional review board approval and written informed consent. UTE imaging sequences were implemented on a clinical 3.0-T MR imaging unit and were used for in vivo imaging of bound and pore water in cortical bone. Images of the lower leg and wrist were acquired in five volunteers each (lower leg: two men and three women aged 24, 24, 49, 30, and 26 years; wrist: two men and three women aged 31, 23, 25, 24, and 26 years) to generate bound and pore water concentration maps of the tibia and radius. Each volunteer was imaged three times, and the standard error of the measurements at the region-of-interest (ROI) level was computed as the standard deviation across studies, pooled across volunteers and ROIs.Quantitative bound and pore water maps in the tibia and radius, acquired in 8-14 minutes, had per-voxel signal-to-noise ratios of 18 (bound water) and 14 (pore water) and inter-study standard errors of approximately 2 mol (1)H per liter of bone at the ROI level.The results of this study demonstrate the feasibility of quantitatively mapping bound and pore water in vivo in human cortical bone with practical human MR imaging constraints.
- Published
- 2015
12. Nanoreinforcement of Poly(propylene fumarate)-Based Networks with Surface Modified Alumoxane Nanoparticles for Bone Tissue Engineering
- Author
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Amit S. Mistry, Andrew R. Barron, Naureen Shahid, Antonios G. Mikos, R. Adam Horch, and Mark D. Timmer
- Subjects
Acrylate polymer ,Materials science ,Polymers and Plastics ,Surface Properties ,Biocompatible Materials ,Bioengineering ,Polypropylenes ,Bone and Bones ,Biomaterials ,chemistry.chemical_compound ,Fumarates ,Flexural strength ,Polymer chemistry ,Materials Chemistry ,Nanotechnology ,Aluminum Compounds ,Prepolymer ,chemistry.chemical_classification ,Tissue Engineering ,Flexural modulus ,Biomaterial ,Polymer ,Biodegradable polymer ,Nanostructures ,Photopolymer ,chemistry ,Chemical engineering - Abstract
A novel composite material has been fabricated for bone tissue engineering scaffolds utilizing the biodegradable polymer poly(propylene fumarate)/poly(propylene fumarate)-diacrylate (PPF/PPF-DA) and surface-modified carboxylate alumoxane nanoparticles. Various surface-modified nanoparticles were added to the polymer including a surfactant alumoxane, an activated alumoxane, a mixed alumoxane containing both activated and surfactant groups, and a hybrid alumoxane containing both groups within the same substituent. These nanocomposites, as well as polymer resin and unmodified boehmite composites, underwent flexural and compressive mechanical testing and were examined using electron microscopy. Hybrid alumoxane nanoparticles dispersed in PPF/PPF-DA exhibited over a 3-fold increase in flexural modulus at 1 wt % loading compared to polymer resin alone. No significant loss of flexural or compressive strength was observed with increased loading of hybrid alumoxane nanoparticles. These dramatic improvements in flexural properties may be attributed to the fine dispersion of nanoparticles into the polymer and increased covalent interaction between polymer chains and surface modifications of nanoparticles.
- Published
- 2004
13. In Vitro Cytotoxicity of Injectable and Biodegradable Poly(propylene fumarate)-Based Networks: Unreacted Macromers, Cross-Linked Networks, and Degradation Products
- Author
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Mark D. Timmer, R. Adam Horch, Catherine G. Ambrose, Antonios G. Mikos, and Heungsoo Shin
- Subjects
Polymers and Plastics ,Biocompatibility ,Double bond ,Cell Survival ,Biocompatible Materials ,Bioengineering ,Polypropylenes ,Cell Line ,Biomaterials ,Fumarates ,Absorbable Implants ,Cell Adhesion ,Materials Chemistry ,Animals ,Organic chemistry ,Viability assay ,Cytotoxicity ,chemistry.chemical_classification ,Molecular Structure ,Biomaterial ,Adhesion ,Fibroblasts ,Combinatorial chemistry ,In vitro ,Rats ,Cross-Linking Reagents ,Acrylates ,chemistry ,Degradation (geology) - Abstract
This study evaluates the in vitro biocompatibility of an injectable and biodegradable polymeric network based on poly(propylene fumarate) (PPF) and the cross-linking agent PPF-diacrylate (PPF-DA). Using a methyl tetrazolium (MTT) assay, the effect of the concentrations of PPF and PPF-DA on the cytotoxicity of its unreacted macromers, cross-linked networks, and degradation products was examined. The influence of network structure properties on cell viability and attachment to the cross-linked material was also investigated. The unreacted macromers exhibited a time- and dose-dependent cytotoxic response that increased with more PPF-DA in the mixture. Conversely, the cross-linked networks formed with more PPF-DA did not demonstrate an adverse response because increases in conversion and cross-linking density prevented the extraction of toxic products. Fibroblast attachment was observed on the PPF/PPF-DA networks with the highest double bond conversions. The degradation products, obtained from the complete breakdown of the networks in basic conditions, displayed a dose-dependent cytotoxic response. These results show that there are concerns regarding the biocompatibility of injectable, biodegradable PPF/PPF-DA networks but also sheds light onto potential mechanisms to reduce the cytotoxic effects.
- Published
- 2003
14. Effect of physiological temperature on the mechanical properties and network structure of biodegradable poly(propylene fumarate)-based networks
- Author
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Antonios G. Mikos, Mark D. Timmer, R. Adam Horch, and Catherine G. Ambrose
- Subjects
Materials science ,Compressive Strength ,Double bond ,Biomedical Engineering ,Biophysics ,Network structure ,Biocompatible Materials ,Bioengineering ,Polyenes ,Mechanics ,Polypropylenes ,Biomaterials ,Poly(propylene fumarate) ,Fumarates ,Polymer chemistry ,Reactivity (chemistry) ,Inert ,chemistry.chemical_classification ,Tissue Engineering ,Temperature ,Biodegradation, Environmental ,Cross-Linking Reagents ,Compressive strength ,Chemical engineering ,chemistry ,Degradation (geology) - Abstract
Poly(propylene fumarate) (PPF)-based networks have exhibited increases in mechanical properties during their initial stages of degradation. This study was designed to investigate whether physiological temperatures are the source of this reinforcing behavior by influencing the formation of additional crosslinks within the network. Utilizing a model PPF network formed with the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA), cylindrical specimens were stored in an inert environment and conditioned at -20 and 37 degrees C while their mechanical properties and network structure were monitored over a six week period. The PPF/PPF-DA specimens exposed to physiological temperatures showed an increase in compressive modulus from 1674 +/- 88 to 2059 +/- 75 MPa. The double bond conversion improved as well, from 64 +/- 1 to 70 +/- 1%, indicating that crosslinks were being formed in the network. The additional reactivity occurred exclusively with unreacted fumarate bonds. PPF/PPF-DA networks stored at -20 degrees C showed no changes in mechanical properties; however, they increased when subsequently conditioned at 37 degrees C. The results were used to explain that PPF-based networks undergo a biphasic degradation behavior due to the competing hydrolytic degradation and thermal induced crosslinking. In addition, heat treating the networks at higher temperatures can be utilized as a means to further reinforce PPF-based materials.
- Published
- 2003
15. Origins of the ultrashort-T2 1H NMR signals in myelinated nerve: a direct measure of myelin content?
- Author
-
R Adam, Horch, John C, Gore, and Mark D, Does
- Subjects
Rats, Sprague-Dawley ,nervous system ,Phantoms, Imaging ,Xenopus ,Animals ,Cattle ,Optic Nerve ,Nerve Tissue ,Magnetic Resonance Imaging ,Sciatic Nerve ,Myelin Sheath ,Article ,Rats - Abstract
Recently developed MRI techniques have enabled clinical imaging of short-lived (1)H NMR signals with T(2)1 ms. Using these techniques, novel signal enhancement has been observed in myelinated tissues, although the source of this enhancement has not been identified. Herein, we report studies of the nature and origins of ultrashort T(2) (uT(2)) signals (50 μsT(2)1 ms) from amphibian and mammalian myelinated nerves. NMR measurements and comparisons with myelin phantoms and expected myelin components indicate that these uT(2) signals arise predominantly from methylene (1)H on/in the myelin membranes, which suggests that direct measurement of uT(2) signals can be used as a new means for quantitative myelin mapping.
- Published
- 2010
16. RF coil considerations for short-T2 MRI
- Author
-
R Adam, Horch, Ken, Wilkens, Daniel F, Gochberg, and Mark D, Does
- Subjects
Imaging, Three-Dimensional ,Polycarboxylate Cement ,Radio Waves ,Cadaver ,Humans ,Equipment Design ,Femur ,Magnetic Resonance Imaging ,Polytetrafluoroethylene ,Copper ,Article - Abstract
With continuing hardware and pulse sequence advancements, modern MRI is gaining sensitivity to signals from short-T(2) (1)H species under practical experimental conditions. However, conventional MRI coils are typically not designed for this type of application, as they often contain proton-rich construction materials that may contribute confounding (1)H background signal during short-T(2) measurements. An example of this is shown herein. Separately, a loop-gap style coil was used to compare different coil construction materials and configurations with respect to observed (1)H background signal sizes in a small animal imaging system. Background signal sources were spatially identified and quantified in a number of different coil configurations. It was found that the type and placement of structural coil materials around the loop-gap resonator, as well as the coil's shielding configuration, are critical determinants of the coil's background signal size. Although this study employed a loop-gap resonator design, these findings are directly relevant to standard volume coils commonly used for MRI.
- Published
- 2010
17. Partial removal of pore and loosely bound water by low-energy drying decreases cortical bone toughness in young and old donors.
- Author
-
Nyman JS, Gorochow LE, Adam Horch R, Uppuganti S, Zein-Sabatto A, Manhard MK, and Does MD
- Subjects
- Adult, Aged, Aged, 80 and over, Biomechanical Phenomena, Cadaver, Female, Femur diagnostic imaging, Fractures, Bone metabolism, Fractures, Bone physiopathology, Humans, Male, Middle Aged, Porosity, Temperature, Tensile Strength, X-Ray Microtomography, Young Adult, Aging, Desiccation, Femur physiology, Mechanical Phenomena, Water chemistry
- Abstract
With an ability to quantify matrix-bound and pore water in bone, (1)H nuclear magnetic resonance (NMR) relaxometry can potentially be implemented in clinical imaging to assess the fracture resistance of bone in a way that is independent of current X-ray techniques, which assess bone mineral density as a correlate of bone strength. Working towards that goal, we quantified the effect of partial dehydration in air on the mechanical and NMR properties of human cortical bone in order to understand whether NMR is sensitive to water-bone interactions at low energy and whether such interactions contribute to the age-related difference in the toughness of bone. Cadaveric femurs were collected from male and female donors falling into two age groups: 21-60 years of age (young) and 74-99 years of age (old). After extracting two samples from the medial cortex of the mid-shaft, tensile tests were conducted on Wet specimens and paired, Partially Dry (PtlD) specimens (prepared by low-energy drying in air to remove ∼3% of original mass before testing). Prior analysis by micro-computed tomography found that there were no differences in intra-cortical porosity between the Wet and PtlD specimens nor did an age-related difference in porosity exist. PtlD specimens from young and old donors had significantly less toughness than Wet specimens, primarily due to a dehydration-related decrease in post-yield strain. The low-energy drying protocol did not affect the modulus and yield strength of bone. Subsequent dehydration of the PtlD specimens in a vacuum oven at 62°C and then 103°C, with quantification of water loss at each temperature, revealed an age-related shift from more loosely bound water to more tightly bound water. NMR detected a change in both bound and pore water pools with low-energy air-drying, and both pools were effectively removed when bone was oven-dried at 62°C, irrespective of donor age. Although not strictly significant due to variability in the drying and testing conditions, the absolute difference in toughness between Wet and PtlD tended to be greater for the younger donors that had higher bone toughness and more bound water for the wet condition than did the older donors. With sensitivity to low-energy bone-water interactions, NMR, which underpins magnetic resonance imaging, has potential to assess fracture resistance of bone as it relates to bone toughness., (Published by Elsevier Ltd.)
- Published
- 2013
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