Feasibility of fat-saturated T2-weighted magnetic resonance imaging with slice encoding for metal artifact correction (SEMAC) at 3T

Background and Purpose

Fluid-sensitive MR imaging in postoperative evaluation is important, however, metallic artifacts is inevitable. The purpose is to investigate the feasibility of fat-saturated slice encoding for metal artifact correction (SEMAC)-corrected T2-weighted magnetic resonance (MR) at 3T in patients with spinal prostheses.

Methods

Following institutional review board approval, 27 SEMAC-encoded spinal MRs between September 2012 and October 2013 in patients with spinal metallic prostheses were analyzed. The MR images were scanned on a 3T MR system including SEMAC-corrected and uncorrected fast spin echo (FSE) T2-weighted MR images with fat-saturation. Two musculoskeletal radiologists compared the image sets and qualitatively analyzed the images using a five-point scale in terms of artifact reduction around the prosthesis, visualization of the prosthesis and pedicle, and intervertebral neural foramina. Quantitative assessments were performed by calculating the ratio of signal intensity from the fixated vertebra and that from upper level vertebra. For statistical analyses, paired t-test was used.

Results

Fat-saturated SEMAC-corrected T2-weighted MR images enabled significantly improved metallic artifact reduction (P < 0.05). Quantitative evaluation of the signal intensity ratio of screw-fixated vertebra and upper level vertebra showed a significantly lower ratio on fat-saturated SEMAC images (P < 0.05), however, the high signal intensity of signal pile-up could be not completely corrected.

Conclusion

SEMAC correction in fat-suppressed T2-weighted MR images can overcome the signal loss of metallic artifacts and provide improved delineation of the pedicle screw and peri-prosthetic region. Signal pile-up, however, could not be corrected completely, therefore readers should be cautious in the evaluation of marrow around the prosthesis.     

Inhomogeneous low frequency spin dynamics in La(1.65)Eu(0.2)Sr(0.15)CuO(4)

We report Cu and La nuclear magnetic resonance measurements in the title compound that reveal an inhomogeneous glassy behavior of the spin dynamics. A low temperature peak in the La spin lattice relaxation rate and the "wipeout" of Cu intensity both arise from these slow electronic spin fluctuations that reveal a distribution of activation energies. Inhomogeneous slowing of spin fluctuations appears to be a general feature of doped lanthanum cuprate.     

Probing the exposure of tyrosine and tryptophan residues in partially folded proteins and folding intermediates by CIDNP pulse-labeling

A nuclear magnetic resonance (NMR) technique has been devised to probe the structures of disordered, partially folded states of proteins at the level of individual amino acid residues. Chemically induced dynamic nuclear polarization (CIDNP) is first generated in exposed aromatic side-chains of the denatured state and then transferred to the high-resolution NMR spectrum of the native state by stimulating rapid refolding of the protein. Crucial improvements in sensitivity were achieved by carrying out the polarization-producing photochemistry in a deoxygenated sample of the disordered state of the protein in a magnetic field of 4.0 T and recording the (1)H NMR spectrum of the refolded native state at 9.4 T (400 MHz). Application of this method to the low pH molten-globule state of alpha-lactalbumin reveals remarkably nativelike environments for the aromatic residues in the primary hydrophobic core of the protein. This result provides compelling evidence that the detailed fold of a protein can be established prior to the formation of the cooperative close-packed native structure.     

Synthesis and properties of new ultraviolet–blue‐emissive fluorene‐based aromatic polyoxadiazoles with confinement moieties

Three families of fluorene–oxadiazole‐based polymers with confinement moieties have successfully been prepared by the two‐step method for polyoxadiazole synthesis. These polymers show good solubility in common organic solvents, high thermal stability, and strong violet and blue photoluminescence in solution and as films, respectively. Their low‐lying highest occupied molecular orbital/lowest unoccupied molecular orbital energy levels originate from the electron deficiency of an oxadiazole moiety, and this suggests that they may be useful for blue‐emitting and electron‐transport/hole‐blocking layers in electroluminescent devices. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 674–683, 2003