AC Loss Measurement in NbSn Coil for a New Fast Switching-field MR Concept Magnet.

The ability to perform magnetic resonance (MR) imaging or spectroscopy at significantly different magnetic field strengths during scanning holds great potential for expanding the range of contrast parameter options and obtaining high "superthermal" spin polarization for increased signal-to-noise ratio (SNR) or measuring certain spins at what would otherwise be impractically high RF frequencies. Enabling measurements at multiple field strengths heretofore has required either rapidly altering the strength of a resistive magnet with pulsed currents or shuttling the specimen between two field regions. We propose a novel approach to switching-field MR that we expect to be practical for live animal and ultimately human imaging.

Quantitative H Magnetic Resonance Imaging on Normal and Pathologic Rat Bones by Solid-State H ZTE Sequence with Water and Fat Suppression.

Background: Osteoporosis (OP) and osteomalacia (OM) are metabolic bone diseases characterized by mineral and matrix density changes. Quantitative bone matrix density differentiates OM from OP. MRI is a noninvasive and nonionizing imaging technique that can measure bone matrix density quantitatively in ex vivo and in vivo.

Quantitative P magnetic resonance imaging on pathologic rat bones by ZTE at 7T.

Background: Osteoporosis is characterized by low bone mineral density (BMD), which predisposes individuals to frequent fragility fractures. Quantitative BMD measurements can potentially help distinguish bone pathologies and allow clinicians to provide disease-relieving therapies. Our group has developed non-invasive and non-ionizing magnetic resonance imaging (MRI) techniques to measure bone mineral density quantitatively.

X-nuclear MRS and MRI on a standard clinical proton-only MRI scanner.

In light of the growing interest deuterium metabolic imaging, hyperpolarized C, N, He, and Xe imaging, as well as P spectroscopy and imaging in large animals on clinical MR scanners, we demonstrate the use of a (radio)frequency converter system to allow X-nuclear MR spectroscopy (MRS) and MR imaging (MRI) on standard clinical MRI scanners without multinuclear capability. This is not only an economical alternative to the multinuclear system (MNS) provided by the scanner vendors, but also overcomes the frequency bandwidth problem of some vendor-provided MNSs that prohibit users from applications with X-nuclei of low magnetogyric ratio, such as deuterium (6.536 MHz/Tesla) and N (-4.

Detailed high quality surface-based mouse CAD model suitable for electromagnetic simulations.

Transcranial magnetic stimulation (TMS) studies with small animals can provide useful knowledge of activating regions and mechanisms. Along with this, functional magnetic resonance imaging (fMRI) in mice and rats is increasingly often used to draw important conclusions about brain connectivity and functionality. For cases of both low- and high-frequency TMS studies, a high-quality computational surface-based rodent model may be useful as a tool for performing supporting modeling and optimization tasks.

Correlation among alveolar bone assessments provided by CBCT, micro-CT, and 14 T MRI.

Objectives: The aim of this study was to evaluate bone mineral adipose tissue (BMAT) volume in 21 alveolar bone specimens, as determined by 14 T MRI, and correlate them to the radiodensity values obtained pre-operatively of regions of interest (ROIs) by cone beam computed tomography (CBCT), and to the bone-volume-to-tissue-volume ratio values obtained by micro-CT, the gold-standard for morphometric data collection.

Methods: Partially edentulous patients were submitted to a CBCT scan, and the radiographic bone densities in each ROI were automatically calculated using coDiagnostiX software. Based on the CBCT surgical planning, a CAD/CAM stereolithographic surgical guide was fabricated to retrieve a bone biopsy from the same ROIs scanned preoperatively, and then to orientate the subsequent implant placement.

Influence of receiver bandwidth on MRI artifacts caused by orthodontic brackets composed of different alloys.

Purpose: The aim of this study was to assess the role of bandwidth on the area of magnetic resonance imaging (MRI) artifacts caused by orthodontic appliances composed of different alloys, using different pulse sequences in 1.5 T and 3.0 T magnetic fields.

Composition and characteristics of trabecular bone in osteoporosis and osteoarthritis.

Background: Bone strength depends on multiple factors such as bone density, architecture and composition turnover. However, the role these factors play in osteoporotic fractures is not well understood.

Purpose: The aim of this study was to analyze trabecular bone architecture, and its crystal and organic composition in humans, by comparing samples taken from patients who had a hip fracture (HF) and individuals with hip osteoarthritis (HOA).

Ex vivo mouse brain microscopy at 15T with loop-gap RF coil.

The design of a loop-gap-resonator RF coil optimized for ex vivo mouse brain microscopy at ultra high fields is described and its properties characterized using simulations, phantoms and experimental scans of mouse brains fixed in 10% formalin containing 4 mM Magnevist™. The RF (B) and magnetic field (B) homogeneities are experimentally quantified and compared to electromagnetic simulations of the coil. The coil's performance is also compared to a similarly sized surface coil and found to yield double the sensitivity.

Assessment of alveolar bone marrow fat content using 15 T MRI.

Objectives: Bone marrow fat is inversely correlated with bone mineral density. The aim of this study is to present a method to quantify alveolar bone marrow fat content using a 15 T magnetic resonance imaging (MRI) scanner.

Study Design: A 15 T MRI scanner with a 13-mm inner diameter loop-gap radiofrequency coil was used to scan seven 3-mm diameter alveolar bone biopsy specimens.

MR Coagulation: A Novel Minimally Invasive Approach to Aneurysm Repair.

Purpose: To demonstrate a proof of concept of magnetic resonance (MR) coagulation, in which MR imaging scanner-induced radiofrequency (RF) heating at the end of an intracatheter long wire heats and coagulates a protein solution to effect a vascular repair by embolization.

Materials And Methods: MR coagulation was simulated by finite-element modeling of electromagnetic fields and specific absorption rate (SAR) in a phantom. A glass phantom consisting of a spherical cavity joined to the side of a tube was incorporated into a flow system to simulate an aneurysm and flowing blood with velocities of 0-1.

Saturation-inversion-recovery: A method for T measurement.

Spin-lattice relaxation (T) has always been measured by inversion-recovery (IR), saturation-recovery (SR), or related methods. These existing methods share a common behavior in that the function describing T sensitivity is the exponential, e.g.

Injectable Aorta Tissue Paste for Vocal Fold Medialization: Residence Time, Biocompatibility, and Comparison to Predicates in a Guinea Pig Subdermal Model.

Objectives: Aortic homografts integrate well with laryngeal tissue when used in reconstructive surgery. It was hypothesized that a paste of aortic homograft, rich in slow-to-degrade elastin, would compare favorably in residence time and biocompatibility to predicate materials used for vocal fold injection-medialization.

Methods: An injectable aorta paste (AP) was made by pulverizing aortic homografts at -196°C (cryomilling).

Two-Dimensional Magnesium Phosphate Nanosheets Form Highly Thixotropic Gels That Up-Regulate Bone Formation.

Hydrogels composed of two-dimensional (2D) nanomaterials have become an important alternative to replace traditional inorganic scaffolds for tissue engineering. Here, we describe a novel nanocrystalline material with 2D morphology that was synthesized by tuning the crystallization of the sodium-magnesium-phosphate system. We discovered that the sodium ion can regulate the precipitation of magnesium phosphate by interacting with the crystal's surface causing a preferential crystal growth that results in 2D morphology.

MR-based motion correction for PET imaging using wired active MR microcoils in simultaneous PET-MR: phantom study.

Purpose: Artifacts caused by head motion present a major challenge in brain positron emission tomography (PET) imaging. The authors investigated the feasibility of using wired active MR microcoils to track head motion and incorporate the measured rigid motion fields into iterative PET reconstruction.

Methods: Several wired active MR microcoils and a dedicated MR coil-tracking sequence were developed.

Motion compensation for brain PET imaging using wireless MR active markers in simultaneous PET-MR: phantom and non-human primate studies.

Brain PET scanning plays an important role in the diagnosis, prognostication and monitoring of many brain diseases. Motion artifacts from head motion are one of the major hurdles in brain PET. In this work, we propose to use wireless MR active markers to track head motion in real time during a simultaneous PET-MR brain scan and incorporate the motion measured by the markers in the listmode PET reconstruction.

Influence of bone marrow composition on measurements of trabecular microstructure using decay due to diffusion in the internal field MRI: simulations and clinical studies.

Purpose: Decay due to diffusion in the internal field (DDIF) MRI allows for measurements of microstructures of porous materials at low spatial resolution and thus has potential for trabecular bone quality measurements. In trabecular bone, solid bone changes (osteoporosis) as well as changes in bone marrow composition occur. The influence of such changes on DDIF MRI was studied by simulations and in vivo measurements.

Synthesis and Characterization of Nanoapatites Organofunctionalized with Aminotriphosphonate Agents.

Organofunctionalized apatite nanoparticles were prepared using a one step process involving dissolution/precipitation of natural phosphate rock and covalent grafting of nitrilotris(methylene)triphosphonate (NTP). The synthesized materials were characterized by Brunauer-Emmett-Teller (BET) surface measurement, thermogravimetry, inductively coupled plasma emission spectroscopy (ICP-ES), elemental analysis, multinuclear solid state cross-polarization/magic angle spinning (CP/MAS) and single-pulse NMR spectroscopy, transmission electron microscopy (TEM) and energy dispersive x-ray analysis (EDXA). After grafting BET measurements yielded particle specific surface areas ranging from 88 to 193 m(2) g(-1) depending on the grafted phosphonate.

MRI of trabecular bone using a decay due to diffusion in the internal field contrast imaging sequence.

Purpose: To characterize the DDIF (Decay due to Diffusion in the Internal Field) method using intact animal trabecular bone specimens of varying trabecular structure and porosity, under ex vivo conditions closely resembling in vivo physiological conditions. The DDIF method provides a diffusion contrast which is related to the surface-to-volume ratio of the porous structure of bones. DDIF has previously been used successfully to study marrow-free trabecular bone, but the DDIF contrast hitherto had not been tested in intact specimens containing marrow and surrounded by soft tissue.

Bone mineral imaged in vivo by 31P solid state MRI of human wrists.

Purpose: To implement solid state (31)P MRI ((31)P SMRI) in a clinical scanner to visualize bone mineral.

Materials And Methods: Wrists of seven healthy volunteers were scanned. A quadrature wrist (31)P transmit/receive coil provided strong B(1) and good signal-to-noise ratio (SNR).

Bone matrix imaged in vivo by water- and fat-suppressed proton projection MRI (WASPI) of animal and human subjects.

Purpose: To demonstrate water- and fat-suppressed proton projection MRI (WASPI) in a clinical scanner to visualize the solid bone matrix in animal and human subjects.

Materials And Methods: Pig bone specimens and polymer pellets were used to optimize the WASPI method in terms of soft-tissue suppression, image resolution, signal-to-noise ratio, and scan time on a 3T MRI scanner. The ankles of healthy 2-3-month-old live Yorkshire pigs were scanned with the optimized method.

Quantitative (31)P NMR spectroscopy and (1)H MRI measurements of bone mineral and matrix density differentiate metabolic bone diseases in rat models.

In this study, bone mineral density (BMD) of normal (CON), ovariectomized (OVX), and partially nephrectomized (NFR) rats was measured by (31)P NMR spectroscopy; bone matrix density was measured by (1)H water- and fat-suppressed projection imaging (WASPI); and the extent of bone mineralization (EBM) was obtained by the ratio of BMD/bone matrix density. The capability of these MR methods to distinguish the bone composition of the CON, OVX, and NFR groups was evaluated against chemical analysis (gravimetry). For cortical bone specimens, BMD of the CON and OVX groups was not significantly different; BMD of the NFR group was 22.

Quantitative bone matrix density measurement by water- and fat-suppressed proton projection MRI (WASPI) with polymer calibration phantoms.

The density of the organic matrix of bone substance is a critical parameter necessary to clinically evaluate and distinguish structural and metabolic pathological conditions such as osteomalacia in adults and rickets in growing children. Water- and fat-suppressed proton projection MRI (WASPI) was developed as a noninvasive means to obtain this information. In this study, a density calibration phantom was developed to convert WASPI intensity to true bone matrix density.

A comparison of the physical and chemical differences between cancellous and cortical bovine bone mineral at two ages.

To assess possible differences between the mineral phases of cortical and cancellous bone, the structure and composition of isolated bovine mineral crystals from young (1-3 months) and old (4-5 years) postnatal bovine animals were analyzed by a variety of complementary techniques: chemical analyses, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and (31)P solid-state magic angle spinning nuclear magnetic resonance spectroscopy (NMR). This combination of methods represents the most complete physicochemical characterization of cancellous and cortical bone mineral completed thus far. Spectra obtained from XRD, FTIR, and (31)P NMR all confirmed that the mineral was calcium phosphate in the form of carbonated apatite; however, a crystal maturation process was evident between the young and old and between cancellous and cortical mineral crystals.