Fast method for 1D non-cartesian parallel imaging using GRAPPA.

MRI with non-Cartesian sampling schemes can offer inherent advantages. Radial acquisitions are known to be very robust, even in the case of vast undersampling. This is also true for 1D non-Cartesian MRI, in which the center of k-space is oversampled or at least sampled at the Nyquist rate. There are two main reasons for the more relaxed foldover artifact behavior: First, due to the oversampling of the center, high-energy foldover artifacts originating from the center of k-space are avoided. Second, due to the non-equidistant sampling of k-space, the corresponding field of view (FOV) is no longer well defined. As a result, foldover artifacts are blurred over a broad range and appear less severe. The more relaxed foldover artifact behavior and the densely sampled central k-space make trajectories of this type an ideal complement to autocalibrated parallel MRI (pMRI) techniques, such as generalized autocalibrating partially parallel acquisitions (GRAPPA). Although pMRI can benefit from non-Cartesian trajectories, this combination has not yet entered routine clinical use. One of the main reasons for this is the need for long reconstruction times due to the complex calculations necessary for non-Cartesian pMRI. In this work it is shown that one can significantly reduce the complexity of the calculations by exploiting a few specific properties of k-space-based pMRI.     

Fast Three Dimensional Magnetic Resonance Imaging

To reduce the scan time in three-dimensional (3D) imaging, the authors consider alternative trajectories for traversing k-space. They differ from traditional 3D trajectories, such as 3DFT, in that they employ time-varying gradients allowing longer readouts and in turn a reduced scan time. Some of these trajectories reduce by an order of magnitude the number of excitations compared with 3DFT and provide flexibility for trading off signal-to-noise ratio for scan time. Other concerns are the minimum echo time and flow/motion properties. As examples, the authors show two applications: A 3D data set of the head (field of view of 30 x 30 x 7.5 cm and resolution of 1.5 x 1.5 x 1.5 mm) acquired in 56 s using a stack of spirals in 3D k-space; and a 3D movie of the heart (20 x 20 x 20 cm field of view, 2 x 2 x 2 mm resolution, and 16 time frames per cardiac cycle) acquired in 11 min using a cones trajectory.     

Transitions Between Frailty States and Its Predictors in a Cohort of Community-Dwelling Spaniards

ObjectivesStudy the frequency and determinants of frailty transitions in a community-dwelling older population.DesignPopulation-based prospective longitudinal study [The Toledo Study of Healthy Ageing (TSHA)].Setting and Participants1748 community-dwelling individuals aged >65 years living in Toledo, a Spanish province.MethodsFrailty was measured with the Fried phenotype. Logistic models were used to assess the associations of sociodemographic, clinical, life-habits, functional, physical performance, and analytical variables with frailty transitions (losing robustness, transitioning from prefrailty to robustness, and from prefrailty to frailty) over a median of 5.2 years.ResultsMean age on enrolment was 75 years, and 55.8% were females. At baseline, 10.3% were frail and 43.1% prefrail. At follow-up, 35.8% of the frail individuals recovered to a prefrail and 15.1% to a robust state. In addition, 43.7% of the prefrail participants became robust, but 14.5% developed frailty. Of those robust at baseline, 32.9% became prefrail and 4.2% frail. In multivariate logistic models, chair-stands had a predictive role in all transitions studied: linearly in keeping robustness and with a floor effect (5 stands) in transitions from prefrailty to robustness and (inversely) from prefrailty to frailty. More depressive symptoms were associated with unfavorable transitions. Not declaring the amount of alcohol drunk and low grip strength were associated with loss of robustness. Hearing and cognitive impairment, low physical activity and smoking with transitioning from prefrailty to frailty. Autonomy for instrumental activities of daily living and uricemia were associated with transitions between robustness and prefrailty in both directions. Increasing body mass index in the range of moderate to severe obesity hampered regaining robustness.Conclusions and ImplicationsSpontaneous improvement of frailty measured with the Fried phenotype is frequent, mainly to prefrailty. Most of the variables associated with transitions are modifiable and suggest research topics and interventions to reduce frailty in clinical and social care settings.     

Age-dependent changes in the neural substrates of empathy in autism spectrum disorder

In typical development, empathic abilities continue to refine during adolescence and early adulthood. Children and adolescents with autism spectrum disorders (ASD) show deficits in empathy, whereas adults with ASD may have developed compensatory strategies. We aimed at comparing developmental trajectories in the neural mechanisms underlying empathy in individuals with ASD and typically developing control (TDC) subjects. Using an explicit empathizing paradigm and functional magnetic resonance imaging, 27 participants with ASD and 27 TDC aged 12–31 years were investigated. Participants were asked to empathize with emotional faces and to either infer the face’s emotional state (other-task) or to judge their own emotional response (self-task). Differential age-dependent changes were evident during the self-task in the right dorsolateral prefrontal cortex, right medial prefrontal cortex, right inferior parietal cortex, right anterior insula and occipital cortex. Age-dependent decreases in neural activation in TDC were paralleled by either increasing or unchanged age-dependent activation in ASD. These data suggest ASD-associated deviations in the developmental trajectories of self-related processing during empathizing. In TDC, age-dependent modulations of brain areas may reflect the ‘fine-tuning’ of cortical networks by reduction of task-unspecific brain activity. Increased age-related activation in individuals with ASD may indicate the development of compensatory mechanisms.     

Longitudinal physical activity trajectories from childhood to adulthood and their determinants: The Young Finns Study

Determining lifelong physical activity (PA) trajectories and their determinants is essential to promote a physically active lifestyle throughout the life‐course. We aimed to identify PA trajectories from childhood to midlife and their determinants in a longitudinal population‐based cohort. This study is a part of the Cardiovascular Risk in Young Finns Study. From 1980, a population‐based cohort (N = 3596; 1764 boys/1832 girls, age 3‐18 years) has been followed up for 31 years. PA indices were formed based on self‐reported data (between age 9‐49 years) on frequency, duration, and intensity of leisure (during childhood) or high‐intensity (at later age) PA and on sports club participation/competitions. PA trajectories were analyzed using group‐based trajectory modeling. Childhood (age 12 years), young adulthood (age 24 years), and early midlife (age 37 years) determinants were analyzed. Five PA trajectories were identified: persistently active (6.6%), decreasingly active (13.9%), increasingly active (13.5%), persistently low active (51.4%, reference group), persistently inactive (14.6%). In childhood, rural residential area (OR 0.45, 95% CI 0.21‐0.96) and high academic performance (OR 2.18; 95% CI 1.58‐3.00) associated with persistently active group. In early midlife, smoking (OR 1.66; 95% CI 1.07‐2.58) associated with persistently inactive group, regular alcohol drinking (OR 2.91; 95% CI 1.12‐7.55) with persistently active group and having children (OR 2.07; 95% CI 1.27‐3.38) with decreasingly active group. High adulthood education associated with both decreasingly (OR 1.87; 95% CI 1.05‐3.35) and increasingly (OR 2.09; 95% CI 1.19‐3.68) active groups. We identified five PA trajectories from childhood into midlife. Most prominent determinants were academic achievement, education, having children and health habits (i.e. smoking/alcohol use).     

Urban health advantage or urban health penalty? Urban-rural disparities in age trajectories of physiological health among Chinese middle-aged and older women and men

During the past decades, China has experienced rapid urbanization and aging. This study investigated sex-stratified urban-rural disparities in age trajectories of physiological health in China. We obtained data from 21686 individuals aged 45 years or above from 2011 baseline survey of the China Health and Retirement Longitudinal Study (CHARLS) and the 2015 follow-up. It examined 11 biomarkers of physiological health classified into four summary indices: cardiovascular index, metabolic index, inflammation index, and allostatic load. This study found that the “urban health penalty” approach dominates the “urban health advantage” approach in middle and early old age, but the dominance of the “urban health penalty” approach is offset or even reversed by the “urban health advantage” approach in older age.     

Neurodevelopmental outcomes of extremely preterm infants: theoretical and epidemiological perspectives to guide shared-care decision-making

Although births below 28 completed weeks' of gestation contribute to less than 1% of all preterm births globally, the impact of extreme prematurity (EPT) on neurodevelopmental outcomes across the life-course is disproportionately large. Higher rates and increased severity of neurodevelopmental impairments (NDIs) are reported among extremely preterm infants (EPIs). Cognitive skills, motor skills (manifesting as cerebral palsy) and vision are most commonly affected, with effects pervasive throughout school, adolescence and early adulthood. In addition, poorer academic outcomes and higher rates of psychiatric morbidity are seen among EPTs. Consistent improvements in EPI survival in recent years has not been matched with improvements in neurodevelopmental outcomes, especially for those born at less than 25 gestational weeks. However, over the last 20 years, several national and cross-national cohort studies have helped advance our understanding of extreme prematurity's developmental and life-course consequences. Here we provide an overview of the key findings from 13 multi-centre cohorts measuring neurodevelopmental outcomes and discuss the theoretical and epidemiological perspectives of NDIs in the context of extreme prematurity to guide communication with families and shared care decision-making.