Characterisation of the Haemodynamic Response Function (HRF) in the neonatal brain using functional MRI

Background: Preterm birth is associated with a marked increase in the risk of later neurodevelopmental impairment. With the incidence rising, novel tools are needed to provide an improved understanding of the underlying pathology and better prognostic information. Functional Magnetic Resonance Imaging (fMRI) with Blood Oxygen Level Dependent (BOLD) contrast has the potential to add greatly to the knowledge gained through traditional MRI techniques. However, it has been rarely used with neonatal subjects due to difficulties in application and inconsistent results. Central to this is uncertainity regarding the effects of early brain development on the Haemodynamic Response Function (HRF), knowledge of which is fundamental to fMRI methodology and analysis. Hypotheses: (1) Well localised and positive BOLD functional responses can be identified in the neonatal brain. (2) The morphology of the neonatal HRF differs significantly during early human development. (3) The application of an age-appropriate HRF will improve the identification of functional responses in neonatal fMRI studies. Methods: To test these hypotheses, a systematic fMRI study of neonatal subjects was carried out using a custom made somatosensory stimulus, and an adapted study design and analysis pipeline. The neonatal HRF was then characterised using an event related study design. The potential future application of the findings was then tested in a series of small experiments. Results: Well localised and positive BOLD functional responses were identified in neonatal subjects, with a maturational tendency towards an increasingly complex pattern of activation. A positive amplitude HRF was identified in neonatal subjects, with a maturational trend of a decreasing time-to-peak and increasing positive peak amplitude. Application of the empirical HRF significantly improved the precision of analysis in further fMRI studies. Conclusions: fMRI can be used to study functional activity in the neonatal brain, and may provide vital new information about both development and pathology

Optimizing Stimulation and Analysis Protocols for Neonatal fMRI

The development of brain function in young infants is poorly understood. The core challenge is that infants have a limited behavioral repertoire through which brain function can be expressed. Neuroimaging with fMRI has great potential as a way of characterizing typical development, and detecting abnormal development early. But, a number of methodological challenges must first be tackled to improve the robustness and sensitivity of neonatal fMRI. A critical one of these, addressed here, is that the hemodynamic response function (HRF) in pre-term and term neonates differs from that in adults, which has a number of implications for fMRI. We created a realistic model of noise in fMRI data, using resting-state fMRI data from infants and adults, and then conducted simulations to assess the effect of HRF of the power of different stimulation protocols and analysis assumptions (HRF modeling). We found that neonatal fMRI is most powerful if block-durations are kept at the lower range of those typically used in adults (full on/off cycle duration 25-30s). Furthermore, we show that it is important to use the age-appropriate HRF during analysis, as mismatches can lead to reduced power or even inverted signal. Where the appropriate HRF is not known (for example due to potential developmental delay), a flexible basis set performs well, and allows accurate post-hoc estimation of the HRF

Continuous measurement of apparent Poisson's ratio for yarn based on omni-directional diameters

We proposed a new method for measuring apparent Poisson's ratio for yarn and developed a new tensile tester equipped with a digital micrometer that can measure the omni-directional diameter of the yarn annularly while the yarn is elongated. Values of apparent Poisson's ratio were obtained from the longitudinal and transverse strains continuously. The mean diameter measured omni-directionally was used to calculate the transverse strain for each longitudinal strain. We tested five spun yarns, one monofilament yarn and two filament yarns and obtained values of apparent Poisson's ratio against longitudinal strain for all samples. Apparent Poisson's ratio was not constant for spun and filament yarns, while it was constant for monofilament yarn. When the longitudinal strain was low, apparent Poisson's ratios of ring spun yarns and filament yarns were large, owing to the fiber packing density. As the longitudinal strain increased, apparent Poisson's ratio gradually decreased. Furthermore, we approximated the relationship between apparent Poisson's ratio and the longitudinal strain using a power function. The apparent Poisson values can be used in the simulation of fabrics.ArticleTEXTILE RESEARCH JOURNAL. 87(6):739-746 (2017)journal articl

The role of umbilical artery doppler indices in predicting perinatal outcome in preeclampsia

Background: Preeclampsia currently accounts for the majority of causes of perinatal morbidity and mortality. Umbilical artery Doppler (UAD) is a non-invasive effective method of antenatal fetal surveillance for early detection and prevention of potentially adverse perinatal outcome in preeclampsia. The objective of this study is to predict adverse perinatal outcome using UAD in Preeclampsia. Methods: This was a prospective cohort study in which 170 consecutively consenting women with preeclampsia were recruited. An UAD was done using Voluson P8 ultrasound. The pulsatility index, resistance index, systolic/diastole ratio. Reduced end diastolic flow, absent end diastolic flow and reversed end diastolic flow were measured. The participants were divided into two groups based on UAD indices findings. Both groups were followed up to determine their perinatal outcomes.The data was analyzed using SPSS version 20.0 for windows (IBM SPSS Inc, Chicago, IL, USA). Categorical variables were analyzed using Chi-Square ( 2) test and Fisher's exact test p<0.05 was considered statistically significant. Specificity, sensitivity, PPV and NPV were determined. Results: The sensitivity, specificity, PPV, and NPV of umbilical artery Doppler in predicting adverse perinatal outcomes was 68.5%, 59.7%, 74.7%, and 52.1% respectively. Conclusions: Although the use of UAD indices in this study showed modest predictive values for adverse perinatal outcome in preeclampsia, it’s use should be combine with other methods of antenatal fetal surveillance to prevent adverse perinatal outcome.

Hie-Sanno mandara : The iconography of Kami and sacred landscape in medieval Japan.

This study on Hie-Sanno mandara from medieval Japan examines the pictorial representations of the kami and the landscape of the Hie Shrine, and considers the religious, historical, and cultural constituents that formed the iconography of Shinto-Buddhist mandara. The cult of Hie-Sanno flourished during the medieval periods in close association with the Enryaku-ji on Mt.Hiei, the historic sanctuary of Tendai Buddhism. The kami of the Hie Shrine, Sanno Gongen, were perceived as the protectors of the temple, and the images of Sanno Gongen developed under a strong Buddhist influence. The wide dissemination of the honji-suijaku theory, particularly during the Kamakura period (1185-1333), encouraged the development of a new genre of religious paintings that are distinguished from the authentic Buddhist mandalas by the term Shinto-Buddhist mandara. They exemplify the nature of the medieval Japanese religiosity in which various elements from the indigenous belief, the Buddhist philosophy, and the Daoist tradition were entwined in a complex web of associations. In this study, examples of Hie-Sanno mandara are categorized according to their subject matters into three basic types, honji-butsu mandara, suijaku mandara, and miya mandara. The visual images are naturally the central concern, but in order to elucidate the iconography of mandara, I have adopted an interdisciplinary approach and referred to studies in religion, history, and literature as well as art history and archaeology. The first chapter provides the historical background to the development of the Hie-Sanno cult, and the second and third chapters examine the iconography of the kami, while the fourth and fifth chapters discuss the iconography of landscape and attempt to define the concept of sacred space in historical context. Each chapter focuses on particular images that reflect the philosophical and functional requirements of the period, and where necessary, comparisons and references were made to relevant contemporary images

A Simple fMRI Compatible Robotic Stimulator to Study the Neural Mechanisms of Touch and Pain.

This paper presents a simple device for the investigation of the human somatosensory system with functional magnetic imaging (fMRI). PC-controlled pneumatic actuation is employed to produce innocuous or noxious mechanical stimulation of the skin. Stimulation patterns are synchronized with fMRI and other relevant physiological measurements like electroencephalographic activity and vital physiological parameters. The system allows adjustable regulation of stimulation parameters and provides consistent patterns of stimulation. A validation experiment demonstrates that the system safely and reliably identifies clusters of functional activity in brain regions involved in the processing of pain. This new device is inexpensive, portable, easy-to-assemble and customizable to suit different experimental requirements. It provides robust and consistent somatosensory stimulation, which is of crucial importance to investigating the mechanisms of pain and its strong connection with the sense of touch