Troubleshooting Arterial-Phase MR Images of Gadoxetate Disodium-Enhanced Liver.

Gadoxetate disodium is a widely used magnetic resonance (MR) contrast agent for liver MR imaging, and it provides both dynamic and hepatobiliary phase images. However, acquiring optimal arterial phase images at liver MR using gadoxetate disodium is more challenging than using conventional extracellular MR contrast agent because of the small volume administered, the gadolinium content of the agent, and the common occurrence of transient severe motion. In this article, we identify the challenges in obtaining high-quality arterial-phase images of gadoxetate disodium-enhanced liver MR imaging and present strategies for optimizing arterial-phase imaging based on the thorough review of recent research in this field

Applying Mixed-Effects Location Scale Modeling to Examine Within-Person Variability in Physical Activity Self-Efficacy

Abstract: Background: Physical activity self-efficacy is conceptualized as a construct that is changeable and responsive to contextual factors. The current study applied mixed-effects location scale modeling to examine within-person variability in physical activity self-efficacy among middle-aged and older adults (N = 14 adults, mean age = 59.4 years) who were attempting behavior change. Methods: An electronic diary was used to record self-reported self-efficacy and physical activity via Ecological Momentary Assessment (EMA) twice a day (2:00 pm and 9:00 pm). Data from weeks 1-6 were analyzed using a Mixed-Effects Location Scale Model in SAS PROC NLMIXED. Results: Participants differed from each other in the degree to which physical activity self-efficacy varied from day to day (p = .03). Within-person variation in self-efficacy was negatively related to levels of brisk walking each week (p = .002), and decreased over time (p = .03). Conclusions: Preliminary results suggest that fluctuations in self-efficacy may be as important for predicting short-term behavior as the overall or mean level of self-efficacy

Mother-child Dyadic Influences of Affect on Everyday Movement Behaviors: Evidence from an Ecological Momentary Assessment Study

Background Research has shown that affect is associated with everyday movement behaviors in children and adults. However, limited work to date has investigated dyadic influences of momentary affect on moderate-to-vigorous physical activity (MVPA) and sedentary time among children and their mothers using ecological momentary assessment (EMA). Methods Mothers and their children (eight to 12-years-old at baseline) from the Los Angeles metropolitan area participated in a longitudinal study with six semi-annual measurement waves across three years. During each measurement wave, mothers and children reported momentary negative and positive affect via a custom smartphone-based EMA application across seven days (randomly sampled up to eight times per day). Each dyad member’s momentary affective states were used to predict their own and the other dyad member’s accelerometer-measured MVPA and sedentary time in the prompt-matched 45-min time window. Multilevel modeling within the actor-partner interdependence model (APIM) framework was applied to accommodate the nested dyadic nature of the data. Results At the within-subject level, when children had higher-than-usual positive affect, they engaged in greater MVPA and less sedentary time in the prompt-matched 45-min window (actor effects; ps \u3c .001). When mothers experienced higher-than-usual positive affect, they engaged in more sedentary time in the same 45-min window (actor effect; p \u3c .001). Children’s higher-than-usual positive affect also predicted more MVPA time of their mothers (partner effect; p \u3c .05). At the between-subjects level, for mothers who reported higher average negative affect than other mothers, their children overall had less MVPA and more sedentary time (partner effects ps \u3c .05). Conclusions This study extends the literature by demonstrating that mothers’ and children’s everyday physical activity and sedentary time are not only associated with their own affective states, but also may be influenced by the affective states of each other. Our findings suggest that affective states have the potential to influence movement behaviors in mother-child dyads’ everyday lives. Affective underpinnings of physical activity and sedentary behaviors should be further studied in order to develop family-based intervention strategies to influence these behaviors

Using pre-prandial blood glucose to assess eating in the absence of hunger in free-living individuals

Our ability to understand and intervene on eating in the absence of hunger (EAH) as it occurs in peoples' natural environments is hindered by biased methods that lack ecological validity. One promising indicator of EAH that does not rely on self-report and is easily assessed in free-living individuals is glucose. Here, we hypothesize that elevated pre-prandial blood glucose concentrations (PPBG), which reflect a source of readily-available, short-term energy, are a biological indicator of EAH. This was a 7-day observational study of N = 41, 18-24 year old men and women with BMI < 25 kg/m2 (60%) or BMI ≥ 25 kg/m2 (40%). We collected data using ecological momentary assessment from people in their natural environments. We defined EAH by self-report (perceived EAH) and by PPBG thresholds using two methods (standardized, PPBG < 85 mg/dl; personalized, PPBG < individual fasting levels). Multilevel modeling was used to analyze the data. N = 963 eating events were reported. There were significantly (p < .05) fewer perceived EAH events (25%) as compared to standardized (62%) and personalized PPBG-defined EAH events (51%). Consistent with published literature, perceived EAH was more likely to occur at a higher PPBG (p < .01), particularly among participants with a BMI ≥ 25 kg/m2 (pint < .01). Additionally, discordance between perceived EAH and PPBG-defined EAH, indicating a perception of hunger at an eating event when PPBS was elevated, was less likely among participants with a BMI < 25 kg/m2 vs. those with a BMI ≥ 25 kg/m2 (pint < .01) as well as at snacks vs. meals (pint < .01). These findings provide preliminary support for using PPBG as a biological indicator of EAH in free-living individuals.24 month embargo; available online 9 July 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]