Reproducing the Hemoglobin Saturation Profile, a Marker of the Blood Oxygenation Level Dependent (BOLD) fMRI Effect, at the Microscopic Level

The relationship between hemoglobin and triglycerides in moyamoya disease: A cross-sectional study

Hemoglobin (Hb) and lipid metabolism are critical in the pathophysiology of moyamoya disease (MMD), and Hb and triglycerides (TGs) both play roles in the development of cerebrovascular illness. However, there is little evidence of a link between Hb and TGs in patients with MMD. This study aimed to determine the association between Hb and TGs in patients who had recently been diagnosed with MMD. From March 2013 to December 2018, 337 patients clinically diagnosed with MMD were admitted to our hospital. Among these, 235 were selected for analysis in this retrospective, cross-sectional study. Each patient's clinical features were documented. For analysis, we used univariate analysis, smoothed-curve fitting, and multivariable, piecewise linear regression. Overall, the mean±standard deviation patient age was 48.14 ± 11.24 years, 44.68% were men, and the mean Hb concentration was 135.72 ± 18.99 g/L. After controlling for relevant confounders, smoothed-curve fitting revealed a nonlinear association between the Hb and TG concentrations (P = 0.0448). When the Hb concentration was below 141 g/L, multivariate piecewise linear regression analysis revealed a significant association between the Hb and TG concentrations [β: 0.01, 95% confidence interval (CI): 0.00, 0.01; P = 0.0182], although the association disappeared above this threshold (β:−0.00, 95% CI:−0.01, 0.01; P = 0.4429). In individuals newly diagnosed with MMD, there is a significant correlation between Hb and TGs, which may be connected to MMD pathogenesis.

Evaluation of Tumor Development Using Hemoglobin Saturation Profile on Rodent Dorsal Window Chamber

Tumor development can be indirectly evaluated using features of the tumor microenvironment (TME), such as hemoglobin saturation (HbSat), blood vessel dilation, and formation of new vessels. High values of HbSat and other features of the TME could indicate high metabolic activity and could precede the formation of angiogenic tumors; therefore, changes in HbSat profile can be used as a biomarker for tumor progression. One methodology to evaluate HbSat profile over time, and correlate it with tumor development in vivo in a preclinical model, is through a dorsal skin-fold window chamber. In this chapter, we provide a detailed description of this methodology to evaluate hemoglobin saturation profile and to predict tumor development. We will cover the surgical preparation of the mouse, the installation/maintenance of the dorsal window chamber, and the imaging processing and evaluation to the HbSat profile to predict new development of new tumor areas over time. We included, in this chapter, step by step examples of the imaging processing method to obtain pixel level HbSat values from raw pixels data, the computational method to determine the HbSat profile, and the steps for the classification of the areas into tumor and no-tumor.

Existence of Initial Dip for BCI: An Illusion or Reality

A tight coupling between the neuronal activity and the cerebral blood flow (CBF) is the motivation of many hemodynamic response (HR)-based neuroimaging modalities. The increase in neuronal activity causes the increase in CBF that is indirectly measured by HR modalities. Upon functional stimulation, the HR is mainly categorized in three durations: (i) initial dip, (ii) conventional HR (i.e., positive increase in HR caused by an increase in the CBF), and (iii) undershoot. The initial dip is a change in oxygenation prior to any subsequent increase in CBF and spatially more specific to the site of neuronal activity. Despite additional evidence from various HR modalities on the presence of initial dip in human and animal species (i.e., cat, rat, and monkey); the existence/occurrence of an initial dip in HR is still under debate. This article reviews the existence and elusive nature of the initial dip duration of HR in intrinsic signal optical imaging (ISOI), functional magnetic resonance imaging (fMRI), and functional near-infrared spectroscopy (fNIRS). The advent of initial dip and its elusiveness factors in ISOI and fMRI studies are briefly discussed. Furthermore, the detection of initial dip and its role in brain-computer interface using fNIRS is examined in detail. The best possible application for the initial dip utilization and its future implications using fNIRS are provided.