In vivo potassium MRI of the human heart.

PURPOSE: Potassium ions (K+ ) play a critical role in cardiac electrophysiology, and changes in their concentration reflect pathophysiological processes related to cardiovascular diseases. Here, we investigated the feasibility of in vivo 39 K MRI of the human heart. To achieve this, we developed, evaluated, and applied a 39 K/1 H RF coil, which is tailored for 39 K MRI of human heart at 7.0T. METHODS: The performance of the 39 K/1 H RF coil was evaluated by electromagnetic field and specific absorption ratio simulations using 2 (male/female) human voxel models. The RF coil was evaluated at the bench and applied in an in vivo proof-of-principle study involving 7 healthy volunteers. The experiments were performed using a 7.0T whole-body MR system in conjunction with a 3D density-adapted projection reconstruction imaging technique. RESULTS: For in vivo 39 K MRI of the human heart, a nominal spatial resolution of 14.5 × 14.5 × 14.5 mm3 within a total scan time of 30 min was achieved. The average SNR within the heart was 9.6 ± 2.4. CONCLUSION: This work validates the design of a 39 K/1 H RF coil for cardiac MR at 7.0T and demonstrates for the first time in vivo the feasibility of 39 K MRI of the human heart.

The role of maternal attention-directing strategies in 9-month-old infants attaining joint engagement.

Coordinated joint engagement (CJE) is a behavioral measure used in the infant-caregiver interaction paradigm to measure joint attention. To know how mothers scaffold infant attention to prompt joint engagement states, this study attempted to determine (a) which specific maternal attention-directing strategies facilitate CJE in mother-infant interactions and (b) how attention-directing strategies precede a range of infant engagement states. Free play in 33 low-SES dyads was analyzed sequentially, a method that reveals temporal relations between the behaviors involved in an interaction. Maintaining was the only strategy that preceded CJE, and Introducing and Redirecting preceded infant Engagement with Object, Onlooking, and Supported Joint Engagement. The results point to the scaffolding role of Maintaining and the mediating role of Introducing and Redirecting maternal strategies. To understand how low-SES infants attain CJE is important given the relation between joint attention and cognitive development. Implications of the results for interventions aimed at reducing socioeconomic inequities in early cognitive development are discussed.

Evaluating school and parent reports of the national student achievement testing system (SIMCE) in Chile: access, comprehension, and use.

This evaluation examined school and parent reports of the national student achievement testing system (SIMCE) in Chile regarding three dimensions: access, comprehension, and use. We conducted phone surveys with a representative sample of directors (N=375), teachers (N=1145) and parents (N=625), and we collected more in-depth data through interviews and focus groups in 16 of these schools. The results indicate that access to the reports is not an obstacle to use for school actors, but it is for parents. While summative ratings of the reports in terms of their clarity and utility were generally very positive, the actual recall and interpretation of even basic information (assessed through case scenarios) was incorrect for a majority of teachers and parents, and reported uses of the information were both intended and unintended in nature. We also found some statistically significant differences regarding comprehension and use among subgroups of our sample. Our findings are especially relevant given the expectations attached to the use of the reports for school improvement on the one hand, and parents' behavior as critical consumers of education on the other hand.