Comparison of 3D Magnetization-transfer- and Spectral-presaturation-with-inversion-recovery-based Neuromelanin Imaging.

PURPOSE: Neuromelanin is visualized by optimizing the conditions of longitudinal relaxation (T1)-weighted imaging (T1WI). Although it was originally developed in 2D imaging, 3D imaging has been also reported, and T1WI sequences with magnetization transfer (MT) pulses are now widely used in 3D gradient echo (GRE) sequences. In this study, we assert that the use of spectral presaturation with inversion recovery (SPIR) may also be useful as an alternative to MT pulses, and we optimize SPIR and compare it with MT. METHODS: Neuromelanin images with MT pulse and SPIR (flip angles [FAs] = 19º, 22º, and 25º) were acquired from 30 healthy volunteers. To achieve the same acquisition time of 5 min, the slab thickness of the MT images was less than 1/3 of those of the SPIR images; the acquisition areas for MT and SPIR were the brainstem and the whole brain, respectively. Visual and quantitative evaluation was performed and compared on the four sequences acquired for the substantia nigra pars compacta (SNc) and the locus coeruleus (LC). For visual assessment, we used the mean score from a 3-point scale by two evaluators. For quantitative evaluation, the contrast ratios of SNc and LC were calculated in comparison with the background tissue signal. RESULTS: In visual assessments, the mean scores of the SPIR FA19º and FA22º images were better than others in the SNc. Regarding LC, the SPIR FA22º image yielded the best mean score. In quantitative evaluations, the MT image was significantly lower than the other three images in SNc. Regarding LC, there were no significant differences among the four acquired images (MT and SPIR FA19º, FA22º, and FA25º). CONCLUSIONS: Detection of neuromelanin in SNc and LC was improved by the use of SPIR compared to MT pulse in 3D neuromelanin imaging.

Simple method for whole-brain volumetric T(1)-weighted turbo spin-echo imaging.

We propose a simple scheme of 3D turbo spin echo (TSE) with low-refocusing flip angles (RFAs) for obtaining sufficient T1-weighted contrast. The low RFA can easily lead spins into a pseudo-steady-state (PSS) condition, but a preparation scheme is required for smooth transition into static PSS. For obtaining T1 contrast, PSS preparation is the most important factor, and therefore we focused on the PSS preparation. To optimize the T1 contrast in the proposed sequence, we compared the following parameters: RFAs of 90° and 30°, and a PSS preparation scheme of "90° + α/2" and asymptotic preparation. Subsequently, to demonstrate the quality of the proposed sequence, we compared the image quality regarding conventional 3D TSE and 2D spin echo (SE). A combination of an RFA of 30° and the "90° + α/2" preparation scheme showed the highest T1 contrast. The optimized sequence provided higher contrast and sharper images compared to 3D TSE, and it showed contrast and a signal-to-noise ratio similar to those of 2D SE.

Reevaluation of T2-weighted fast field echo (T2FFE): application to rapid volumetric black-blood imaging.

T2-fast field echo (T2FFE) sequence is a rapid T2-weighted steady state free precession sequence, but has not become a widely utilized MR-imaging strategy because of its low signal-to-noise ratio and high sensitivity to motion. These effects have seriously limited the clinical use of T2FFE and therefore T2FFE has not been used for routine clinical studies. Nevertheless, in this study, we have investigated the possibility of clinical application by re-optimization of the T2FFE on the current MRI systems. Our purpose in this study was to explore the sensitivity of T2FFE to flow spins using a flow phantom and a contrast optimization/comparison with 2D turbo spin-echo (TSE) T2-weighted images, and to evaluate its feasibility in volunteers and patients. This study demonstrated that the T2FFE sequence achieves rapid 3D T2-weighted black-blood imaging while minimizing the impact of motion using a low flip angle under the shortest repetition time and the shortest echo time conditions. Furthermore, 3D T2FFE with use of an optimal flip angle (30°-40°) can provide contrast equivalent to that of 2D TSE T2-weighted images. This proposed T2FFE sequence might be promising for numerous clinical applications.

Application of a charge-coupled device photon-counting technique to three-dimensional element analysis of a plant seed (alfalfa) using a full-field x-ray fluorescence imaging microscope.

A full-field x-ray fluorescence imaging microscope using a Wolter mirror was constructed at Photon Factory BL3C2. White x rays from a bending magnet were used to excite x-ray fluorescence and to enhance the x-ray fluorescence intensity. A photon-counting method using a charge-coupled device was applied to obtain an x-ray fluorescence spectrum at the image plane. The spatial distributions of some specific atoms such as Fe and Zn were obtained from photon-counting calculations. An energy resolution of 220 eV at the Fe Kalpha line was obtained from the x-ray fluorescence spectrum by the photon-counting method. The newly developed three-dimensional element mappings of the specific atoms were accomplished by the photon-counting method and a reconstruction technique using computed tomography.

Novel base-labile protecting groups for 5'-hydroxy function in solid-phase oligonucleotide synthesis.

The 6-(levulinyloxymethyl)-3-methoxy-2-nitrobenzoyl (LMMoNBz) and 2-(levulinyloxymethyl)-5-methoxy-4-nitrobenzoyl (LMMpNBz) groups were developed as novel base-labile protection for the 5'-hydroxy function in solid-phase oligonucleotide synthesis. A comparative study of the LMMoNBz, LMMpNBz and 2-(levulinyloxymethyl)-5-nitrobenzoyl (LMNBz) protecting groups for oligonucleotide synthesis proved strong feasibility for the LMMoNBz group.

6-(Levulinyloxymethyl)-3-methoxy-2-nitrobenzoyl and 2-(levulinyloxymethyl)-5-methoxy-4-nitrobenzoyl groups as novel base-labile groups for 5'-hydroxy protection in solid-phase oligonucleotide synthesis.

The 6-(levulinyloxymethyl)-3-methoxy-2-nitrobenzoyl (LMMoNBz) and 2-(levulinyloxymethyl)-5-methoxy-4-nitrobenzoyl (LMMpNBz) groups were developed as novel base-labile groups for 5'-hydroxy protection in solid-phase oligonucleotide synthesis. A comparative study of the utility of LMMoNBz, LMMpNBz, and 2-(levulinyloxymethyl)-5-nitrobenzoyl (LMNBz) groups is described.

Novel base-labile protecting groups for 5'-hydroxyl protection in the synthesis of oligonucleotides.

The 6-(levulinyloxymethyl)-3-methoxy-2-nitrobenzoyl (LMM0NBz) and 2-(levulinyloxy-methyl)-5-methoxy-4-nitrobenzoyl (LMMpNBz) groups were developed as novel base-labile protection for the 5'-hydroxyl group in solid-phase oligonucleotide synthesis. A comparative study on the utility of LMMoNBz, LMMpNBz, and 2-(levulinyloxymethyl)-5-nitrobenzoyl (LMNBz) groups for the synthesis of oligodeoxyribonucleotides, and the synthesis of oligoribonucleotides using the LMMoNBz group in combination with the acid-labile 1-ethoxyethylk (EE) group to protect the 2'-hydroxyl group, are described.