MRI may be a noninvasive and alternative tool for skeletal age assessment in children, although few studies have reported on this topic. In this article, skeletal age was assessed over a wide range of ages using an open, compact MRI optimized for the imaging of a child's hand and wrist, and its validity was evaluated. MR images and their three‐dimensional segmentation visualized detailed skeletal features of each bone in the hand and wrist. Skeletal age was then independently scored from the MR images by two raters, according to the Tanner–Whitehouse Japan system. The skeletal age assessed by MR rating demonstrated a strong positive correlation with chronological age. The intrarater and inter‐rater reproducibilities were significantly high. These results demonstrate the validity and reliability of skeletal age assessment using MRI. Magn Reson Med, 2013.

Magnetic resonance fingerprinting (MRF) is a promising framework that allows the quantification of multiple magnetic resonance parameters with a single scan. MRF using fast imaging with steady-state precession (MRF-FISP) has robustness to off-resonance artifacts and has many applications in inhomogeneous fields. However, the spoiler gradient used in MRF-FISP is sensitive to diffusion motion, and may lead to quantification errors when the spoiler moment increases. In this study, we examined the effect of the diffusion weighting in MRF-FISP caused by spoiler gradients. The T2 relaxation times were greatly underestimated when large spoiler moments were used. The T2 underestimation was prominent for tissues with large values of T2 and diffusion coefficients. The T2 bias was almost independent of the apparent diffusion coefficient (ADC) and T2 values when the ADC map was measured and incorporated into the matching process. These results reveal that the T2 underestimation resulted from the diffusion weighting caused by the spoiler gradients.

Li diffusion was observed by ⁷Li nuclear magnetic resonance (NMR) spectroscopy in three single-crystal samples of LLZO–Ta (Li_6.5La₃Zr_1.5Ta_0.5O₁₂) grown by the floating zone melting method as well as a crushed sample in this study. Previously, the pulsed-gradient spin-echo ⁷Li NMR method was applied to Li⁺ diffusion measurements in inorganic solid electrolyte powder samples. Anomalous Li⁺ diffusion behaviors were observed such as dependence of the observing time (Δ) and pulsed-field-gradient strength (g), and the diffusive-diffraction patterns in short Δ in the echo-attenuation plots. In the powder samples, it is uncertain that the Li ions diffuse in the bulk within grain, across grains, or both. To date, the origins of the anomalous Li⁺ diffusion have not yet been clearly understood. From models of atomic-level lithium pathways, the micrometer-space diffusion channels are assumed to be narrow with curvatures. In contrast to the powder samples, a single crystal is supposed to be uniform without grain boundaries and the Li ions in single-crystal samples can diffuse in the bulk with negligible effects from the surface. The single-crystal samples are expected to give us proper answers. We found that the ⁷Li echo-attenuation plots of the single-crystal samples showed anomalous phenomena in dependence on Δ and g with much reduced manners. We found that the phenomena are inherent characteristics of Li⁺ diffusion in inorganic solid electrolytes. From the aspects of Li⁺ carrier numbers, the fast divergent Li⁺ diffusion constants, observed at short Δ with small g, contribute importantly to the electrochemical high ionic conduction measured by impedance spectroscopy.

Ion-conducting garnets are important candidates for use in all-solid Li batteries and numerous materials have been synthesized with high ionic conductivities. For understanding ion conduction mechanisms, knowledge on Li⁺ diffusion behaviour is essential. The proposed nano-scale lithium pathways are composed of tortuous and narrow Li⁺ channels. The pulsed gradient spin-echo (PGSE) NMR method provides time-dependent ⁷Li diffusion on the micrometre space. For powder samples, collision-diffraction echo-attenuation plots were observed in a short observation time, which had not been fully explained. The diffraction patterns were reduced or disappeared for single-crystal garnet samples of Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZO-Ta) and Li_6.5La₃Zr_1.5Nb_0.5O₁₂ (LLZO-Nb). The inner morphology and grain boundaries affect importantly the collision-diffraction behaviours which is inherent to powder samples. The ⁷Li diffusion observed by PGSE-NMR depends on the observation time (Δ) and the pulsed field gradient (PFG) strength (g) in both powder and single-crystal samples, and the anomalous effects were reduced in the single-crystal samples. The scattered Li diffusion constants converged to a unique value (D_Li) with a long Δ and a large g, which is eventually the smallest value. The D_Li activation energy was close to that of the ionic conductivity (σ). The D_Li values are plotted versus the σ values measured for four powder and two single-crystal garnet samples. Assuming the Nernst–Einstein (NE) relation which was derived for isolated ions in solution, the carrier numbers (N_NE) were estimated from the experimental values of D_Li and σ. The N_NE values of metal-containing garnets were large (<10²³ cm⁻³) and insensitive to temperature. They were larger than Li atomic numbers in cm³ calculated from the density, molecular formula and Avogadro number for LLZOs except for cubic LLZO (Li₇La₃Zr₂O₁₂, N_NE ∼ 10²⁰ cm⁻³).