Quantitative solid-state NMR imaging of synthetic calcium phosphate implants

Ramanathan, Chandrasekhar; Ackerman, Jerome L.

doi:10.1002/(sici)1522-2594(199906)41:6<1214::aid-mrm18>3.0.co;2-h

Cited by 22 publications

(9 citation statements)

References 26 publications

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“…(see, e.g., Refs. [150][151][152][153][154][155][156][157][158][159]). A unique protonated phosphate group species could be identified by a differential CP technique in bone [152].…”

Section: Solid-state Nmr Spectroscopic Studies Of Hydroxyapatite-basementioning

confidence: 99%

“…The role of structural water molecules in bones has been studied by 1 H MAS NMR as well as 31 P{ 1 H} and 13 C{ 1 H} LG-CP MAS NMR spectroscopy [161,162]. Finally, magnetic resonance imaging (MRI) investigations of bones, implants, related materials are gaining increasing interest [163][164][165][166][167].…”

Section: Solid-state Nmr Spectroscopic Studies Of Hydroxyapatite-basementioning

confidence: 99%

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NMR studies of biomineralisation

Gröger

Lutz

Brunner

2009

Progress in Nuclear Magnetic Resonance Spectroscopy

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“…(see, e.g., Refs. [150][151][152][153][154][155][156][157][158][159]). A unique protonated phosphate group species could be identified by a differential CP technique in bone [152].…”

Section: Solid-state Nmr Spectroscopic Studies Of Hydroxyapatite-basementioning

confidence: 99%

Section: Solid-state Nmr Spectroscopic Studies Of Hydroxyapatite-basementioning

confidence: 99%

NMR studies of biomineralisation

Gröger

Lutz

Brunner

2009

Progress in Nuclear Magnetic Resonance Spectroscopy

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“…Solidstate imaging techniques such as single-point imaging [17] and its variants [18,19], while capable of capturing the short T 2 signals from bone [19], are rather inefficient as far as the scan times are concerned. Recently, solid-state imaging techniques based on radial acquisition schemes have been used to study bone mineral [20][21][22]. Toward the objectives of the present work, we implemented a three-dimensional radial projection imaging sequence [23], also described in previous work from this laboratory [15] to quantify bone mineral phosphorus and bone water.…”

Section: Introductionmentioning

confidence: 99%

Multi-modality study of the compositional and mechanical implications of hypomineralization in a rabbit model of osteomalacia

Anumula

Magland

Wehrli

et al. 2008

Bone

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Osteomalacia is characterized by hypomineralization of the bone associated with increased water content. In this work we evaluate the hypotheses that 1) 3D solid-state magnetic resonance imaging (MRI) of (31)P (SSI-PH) and (1)H (SSI-WATER) of cortical bone can quantify the key characteristics of osteomalacia induced by low-phosphate diet; and 2) return to normophosphatemic diet (NO) results in recovery of these indices to normal levels. Twenty female five-week old rabbits were divided into four groups. Five animals were fed a normal diet for 8 weeks (NOI); five a hypophosphatemic diet (0.09%) for the same period to induce osteomalacia (HYI). To examine the effect of recovery from hypophosphatemia an additional five animals received a hypophosphatemic diet for 8 weeks, after which they were returned to a normal diet for 6 weeks (HYII). Finally, five animals received a normal diet for the entire 14 weeks (NOII). The NOI and HYI animals were sacrificed after 8 weeks, the NOII and HYII groups after 14 weeks. Cortical bone was extracted from the left and right tibiae of all the animals. Water content was measured by SSI-WATER and by a previously reported spectroscopic proton-deuteron nuclear magnetic resonance (NMR) exchange technique (NMR-WATER), phosphorus content by SSI-PH. All MRI and NMR experiments were performed on a 9.4 T spectroscopy/micro-imaging system. Degree of mineralization of bone (DMB) was measured by micro-CT and elastic modulus and ultimate strength by 3-point bending. The following parameters were lower in the hypophosphatemic group: phosphorus content measured by SSI-PH (9.5+/-0.4 versus 11.1+/-0.3 wt.%, p<0.0001), ash content (63.9+/-1.7 versus 65.4+/-1.1 wt.%, p=0.05), ultimate strength, (96.3+/-16.0 versus 130.7+/-6.4 N/mm(2), p=0.001), and DMB (1115+/-28 versus 1176+/-24 mg/cm(3), p=0.003); SSI-WATER: 16.1+/-1.5 versus 14.4+/-1.1 wt.%, p=0.04; NMR-WATER: 19.0+/-0.6 versus 17.4+/-1.2 wt.%, p=0.01. Return to a normophosphatemic diet reduced or eliminated these differences (SSI-PH: 9.5+/-0.9 versus 10.6+/-0.8 wt.%, p=0.04; DMB: 1124+/-31 versus 1137+/-10 mg/cm(3), p=0.2; US: 95.6+/-18.6 versus 103.9+/-7.5 N/mm(2), p=0.2; SSI-WATER: 12.4+/-0.6 versus 12.2+/-0.3 wt.%, p=0.3) indicating recovery of the mineral density close to normal levels. Phosphorus content measured by SSI-PH was significantly correlated with DMB measured by micro-CT (r(2)=0.47, p=0.001) as well as with ultimate strength (r(2)=0.54, p=0.0004). The results show that the methods presented have potential for in situ assessment of mineralization and water, both critical to the bone's mechanical behavior.

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“…At 800 s the observed DNP signal enhancement is 40. As the RF field is comparable to the strength of the local proton dipolar field in the sample (γB loc /2π ≈ 85 kHz, estimated from the proton linewidth), it induces mixing between the nuclear Zeeman and nuclear dipolar reservoirs [13,14,15,16,17,18,19]. The signal increase obtained following this mixing indicates that, following microwave irradiation, the bulk dipolar reservoir had a lower effective spin temperature than the Zeeman reservoir.…”

Section: Arxiv:07054671v1 [Cond-matother] 31 May 2007mentioning

confidence: 99%

Rapid diffusion of dipolar order enhances dynamic nuclear polarization

2008

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In a dynamic nuclear polarization experiment on a 40 mM solution of 4-amino-TEMPO in a 40:60 water/glycerol mixture, we have observed that the bulk dipolar reservoir is cooled to a spin temperature of 15.5 µK, following microwave irradiation for 800 s. This is significantly cooler than the 35 mK spin temperature of the Zeeman reservoir. Equilibration of the two reservoirs results in a 50 % increase in the NMR signal intensity, corresponding to a Zeeman spin temperature of 23 mK. In order to achieve this polarization directly, it was necessary to irradiate the sample with microwaves for 1500 s. Cooling of the dipolar reservoir occurs during polarization transport through the magnetic field gradient around the paramagnetic impurity, and is rapidly communicated to the bulk by dipolar spin diffusion. As dipolar spin diffusion is significantly faster than Zeeman spin diffusion, the bulk dipolar reservoir cools faster than the Zeeman reservoir. This process can be exploited to rapidly polarize the nuclear spins, by repeatedly cooling the dipolar system and transferring the polarization to the Zeeman reservoir. PACS numbers:Dynamic nuclear polarization (DNP) has been extensively used to study ordering in dielectric crystals, for the creation of polarized spin targets, and for NMR signal enhancement [1]. Microwave irradiation of a coupled electron-nuclear spin system can facilitate a transfer of polarization from the electron to the nuclear spin. In the case of dielectric materials considered here, the electron spins are localized and the non-equilibrium polarization of the bulk nuclei is generated via a two-stage process: a polarization exchange local to the defect; and spin transport to distribute the polarization throughout the sample. Here the DNP process is essentially the inverse of the standard T 1 relaxation mechanism in dielectric solids [2].In dielectric materials DNP typically occurs via either the solid effect or thermal mixing [1,3,4]. The solid effect occurs in systems in which the electron-nuclear coupling is not purely isotropic. The anisotropic coupling mixes the nuclear Zeeman levels, and the forbidden transitions become partially allowed. High power microwaves are used to saturate one of the forbidden transitions, and rapid electron spin relaxation creates the non-equilibrium nuclear polarization. Thermal mixing occurs in systems in which the linewidth of the electron spins is larger than the nuclear Zeeman frequency. If the linewidth is homogeneous, off-resonance microwave irradiation of the electron spin line produces a cooling of the electron spin dipolar reservoir. A flip-flop interaction between two electron spins in the same line (separated by the nuclear Zeeman * Author to whom correspondence should be addressed. Electronic address: sekhar@mit.edu FIG. 1: Schematic illustration of the spin diffusion barrier around the electron spin. Nuclear spin diffusion within the barrier is suppressed due to the large difference in Zeeman energies between the spins. frequency), flips the nuclear spin. If the...

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Quantitative solid-state NMR imaging of synthetic calcium phosphate implants

Cited by 22 publications

References 26 publications

NMR studies of biomineralisation

NMR studies of biomineralisation

Multi-modality study of the compositional and mechanical implications of hypomineralization in a rabbit model of osteomalacia

Rapid diffusion of dipolar order enhances dynamic nuclear polarization

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