Contrast circulation in adult fontan patients using MR Time Resolved Angiography: Application for CT pulmonary angiography

BackgroundWhen patients with Fontan circulation require a computed tomographic pulmonary angiogram (CTPA), there are significant challenges in achieving adequate contrast opacification due to the altered anatomical connections. This study used Time Resolved Angiography with Interleaved Stochastic Trajectories (TWIST) Magnetic Resonance Angiography (MRA) to examine contrast circulation in a cohort of patients with Fontan circulation who were having routine MRI follow up to inform the contrast timing of any subsequent CT.MethodsThis is a single centre, cross-sectional, observational, retrospective study. The time to peak (TTP) signal intensity from the MRA was recorded using regions of interest on the aorta, pulmonary arteries, cavae and Fontan conduit. Patients were grouped by ejection fraction, global longitudinal strain, indexed stroke volume and cardiac index to examine if these cardiac performance parameters affected the mean TTP. Statistical analysis was performed to find the mean TTP for each of the vessels, which was consequently compared between the different cardiac performance parameters.Results35 patients were included in the study. Mean TTP contrast enhancement was 31s in the thoracic aorta, 46s in the right pulmonary artery, 41s in the left pulmonary artery and 55s in the Fontan conduit. Cardiac performance shows no statistically significant relationship to the peak contrast enhancement whether measured by ejection fraction, global longitudinal strain, stroke volume index or cardiac index.ConclusionThe mean optimal timing for a single-phase examination of the Fontan circulation, following an upper limb injection, was 55 s following start of contrast injection irrespective of cardiac performance. In TWIST MRA, the IV bolus is 4–5 s duration. A longer bolus is required for CTA, around 20s, suggesting an additional delay will be required. We propose that an optimal single phase CTPA to be protocolled at 70 s following the start of contrast injection, assuming adequate iodinated contrast dose.     

Dating violence: A cross-lag path model with pregnant and parenting adolescents

IntroductionDating violence is a common problem among adolescents, particularly among Latinx pregnant and parenting adolescents, and can be detrimental to adolescent parents and their children. However, little is known about whether different forms of dating violence behaviors are stable over time or what influences changes in these behaviors. Therefore, the purpose of this study was to use an exploratory autoregressive cross-lag path model to analyze whether conflict resolution, verbally abusive, and physically abusive behaviors were stable over time and whether these behaviors predicted one another in the future.MethodA total of 285 pregnant or parenting adolescents attending eight high schools in the Southwestern U.S. completed a pre-test at the beginning of a semester, a follow-up survey at the end of the semester, and a post-test at the end of the following semester to longitudinally assess the strategies they used when resolving a conflict with their partners (i.e., conflict resolution strategies, verbally abusive behaviors, and/or physically abusive behaviors).Results and conclusionsAn autoregressive cross-lag model was performed to determine whether conflict resolution, verbally abusive, and physically abusive behaviors at one time point predicted the same variables in the future. Results from the autoregressive cross-lag model indicated that adolescents’ reports of their conflict resolution strategies and verbally abusive behaviors were stable across time, but their use of physically abusive behaviors were not. Additionally, conflict resolution strategies predicted lower levels of verbally abusive and physically abusive behaviors.     

Combining Fourier and lagged k-nearest neighbor imputation for biomedical time series data

Most clinical and biomedical data contain missing values. A patient’s record may be split across multiple institutions, devices may fail, and sensors may not be worn at all times. While these missing values are often ignored, this can lead to bias and error when the data are mined. Further, the data are not simply missing at random. Instead the measurement of a variable such as blood glucose may depend on its prior values as well as that of other variables. These dependencies exist across time as well, but current methods have yet to incorporate these temporal relationships as well as multiple types of missingness. To address this, we propose an imputation method (FLk-NN) that incorporates time lagged correlations both within and across variables by combining two imputation methods, based on an extension to k-NN and the Fourier transform. This enables imputation of missing values even when all data at a time point is missing and when there are different types of missingness both within and across variables. In comparison to other approaches on three biological datasets (simulated and actual Type 1 diabetes datasets, and multi-modality neurological ICU monitoring) the proposed method has the highest imputation accuracy. This was true for up to half the data being missing and when consecutive missing values are a significant fraction of the overall time series length.     

Cortical parameters predict bone strength at the tibial diaphysis,but are underestimated by HR-pQCT and μCT compared to histomorphometry

Cortical bone and its microstructure are crucial for bone strength, especially at the long bone diaphysis. However, it is still not well-defined how imaging procedures can be used as predictive tools for mechanical bone properties. This study evaluated the capability of several high-resolution imaging techniques to capture cortical bone morphology and assessed the correlation with the bone's mechanical properties. The microstructural properties (cortical thickness [Ct.Th], porosity [Ct.Po], area [Ct.Ar]) of 11 female tibial diaphysis (40–90 years) were evaluated by dual-energy X-ray absorptiometry (DXA), high-resolution peripheral-quantitative-computed-tomography (HR-pQCT), micro-CT (μCT) and histomorphometry. Stiffness and maximal torque to failure were determined by mechanical testing. T-Scores determined by DXA ranged from 0.6 to −5.6 and a lower T-Score was associated with a decrease in Ct.Th (p ≤ 0.001) while the Ct.Po (p ≤ 0.007) increased, and this relationship was independent of the imaging method. With decreasing T-Score, histology showed an increase in Ct.Po from the endosteal to the periosteal side (p = 0.001) and an exponential increase in the ratio of osteons at rest to those after remodelling. However, compared to histomorphometry, HR-pQCT and μCT underestimated Ct.Po and Ct.Th. A lower T-Score was also associated with significantly reduced stiffness (p = 0.031) and maximal torque (p = 0.006). Improving the accuracy of Ct.Po and Ct.Th did not improve prediction of the mechanical properties, which was most closely related to geometry (Ct.Ar). The ex-vivo evaluation of mechanical properties correlated with all imaging modalities, with Ct.Th and Ct.Po highly correlated with the T-Score of the tibial diaphysis. Cortical microstructural changes were underestimated with the lower resolution of HR-pQCT and μCT compared to the histological ‘gold standard’. The increased accuracy did not result in an improved prediction for local bone strength in this study, which however might be related to the limited number of specimens and thus needs to be evaluated in a larger collective.     

Two types of ictal phase-amplitude couplings in epilepsy patients revealed by spectral harmonicity of intracerebral EEG recordings

ObjectiveSpectral harmonicity of the ictal activity was analyzed regarding two clinically relevant aspects, (1) as a confounding factor producing ‘spurious’ phase-amplitude couplings (PAC) which may lead to wrong conclusions about the underlying ictal mechanisms, and (2) its role in how good PAC is in correspondence to the seizure onset zone (SOZ) classification performed by the epileptologists.MethodsPAC patterns observed in intracerebral electroencephalography (iEEG) recordings were retrospectively studied during seizures of seven patients with pharmacoresistant focal epilepsy. The time locked index (TLI) measure was introduced to quantify the degree of harmonicity between frequency bands associated to the emergence of PAC during epileptic seizures.Results(1) Harmonic and non harmonic PAC patterns coexist during the seizure dynamics in iEEG recordings with macroelectrodes. (2) Harmonic PAC patterns are an emergent property of the periodic non sinusoidal waveform constituting the epileptiform activity. (3) The TLI metric allows to distinguish the non harmonic PAC pattern, which has been previously associated with the ictal core through the paroxysmal depolarizing shifts mechanism of seizure propagation.ConclusionsOur results suggest that the spectral harmonicity of the ictal activity plays a relevant role in the visual analysis of the iEEG recordings performed by the epileptologists to define the SOZ, and that it should be considered for the proper interpretation of ictal mechanisms.SignificanceThe proposed harmonicity analysis can be used to improve the delineation of the SOZ by reliably identifying non harmonic PAC patterns emerging from fully recruited cortical and subcortical areas.     

Modelling the electric field and the current density generated by cerebellar transcranial DC stimulation in humans

ObjectiveTranscranial Direct Current Stimulation (tDCS) over the cerebellum (or cerebellar tDCS) modulates working memory, changes cerebello-brain interaction, and affects locomotion in humans. Also, the use of tDCS has been proposed for the treatment of disorders characterized by cerebellar dysfunction. Nonetheless, the electric field (E) and current density (J) spatial distributions generated by cerebellar tDCS are unknown. This work aimed to estimate E and J distributions during cerebellar tDCS.MethodsComputational electromagnetics techniques were applied in three human realistic models of different ages and gender.ResultsThe stronger E and J occurred mainly in the cerebellar cortex, with some spread (up to 4%) toward the occipital cortex. Also, changes by ±1 cm in the position of the active electrode resulted in a small effect (up to 4%) in the E and J spatial distribution in the cerebellum. Finally, the E and J spreads to the brainstem and the heart were negligible, thus further supporting the safety of this technique.ConclusionsDespite inter-individual differences, our modeling study confirms that the cerebellum is the structure mainly involved by cerebellar tDCS.SignificanceModeling approach reveals that during cerebellar tDCS the current spread to other structures outside the cerebellum is unlike to produce functional effects.     

镇江市大气颗粒物（PM10和PM2.5）对居民每日死亡率影响的时间序列分析

目的 评价镇江市大气颗粒物（PM10和PM2.5）短期暴露对居民每日死亡率的影响。方法 采用基于广义相加模型的时间序列分析方法评估大气颗粒物对镇江市居民死亡率的影响。结果 PM10和PM2.5对人群死亡影响存在滞后效应和累积滞后效应,对女性和≥65岁人群的影响更为显著。PM10和PM2.5分别在累积滞后1 d和2 d时效应最大,PM10和PM2.5每升高10 μg/m3,居民死亡率分别增加0.52%（95%CI:0.10%～0.94%）和0.79%（95%CI:0.14%～1.43%）。结论 镇江市大气颗粒物与居民的超额死亡风险显著相关。