Index of microcirculatory resistance: state-of-the-art and potential applications in computational simulation of coronary artery disease / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The dysfunction of coronary microcirculation is an important cause of coronary artery disease (CAD). The index of microcirculatory resistance (IMR) is a quantitative evaluation of coronary microcirculatory function, which provides a significant reference for the prediction, diagnosis, treatment, and prognosis of CAD. IMR also plays a key role in investigating the interaction between epicardial and microcirculatory dysfunctions, and is closely associated with coronary hemodynamic parameters such as flow rate, distal coronary pressure, and aortic pressure, which have been widely applied in computational studies of CAD. However, there is currently a lack of consensus across studies on the normal and pathological ranges of IMR. The relationships between IMR and coronary hemodynamic parameters have not been accurately quantified, which limits the application of IMR in computational CAD studies. In this paper, we discuss the research gaps between IMR and its potential applications in the computational simulation of CAD. Computational simulation based on the combination of IMR and other hemodynamic parameters is a promising technology to improve the diagnosis and guide clinical trials of CAD.

Comparison of the onset of uterine contractions determined from tocodynamometry and maternal perception.

The aim of this study was to investigate the time difference (TD) between the onset of uterine contraction (UC) determined from tocodynamometry (TOCO) and identified by maternal perception. The online available Icelandic database was used to calculate TD, which was defined as the difference between when it was felt by a pregnant woman and the starting point on the UC signal recorded by a TOCO. A total of 295 TDs from 78 recordings (from a total of 33 participants; among them, 13 participants included at least 3 recordings from different gestational weeks) were analyzed with the overall mean±SD of TD calculated. For each individual participant with at least 3 recordings, regression analysis was then performed to investigate the relationship between the mean TD from each recording with gestational week, with their overall slope calculated. The results showed that 85.4% of TDs was within [-40, 40] s, with an overall mean TD of 3.04 s (p>0.05), indicating that there was no significant difference between the UC onset determined from TOCO and maternal perception. It was also noticed that 61.5% recordings (48 out of 78 recordings) had all positive or negative TD for all the UCs analyzed within a recording. Furthermore, the regression analysis showed that the regression line slope was negative for 10 out of the 13 participants with at least 3 recordings from different gestational weeks, resulting in that the overall slope (-2.85±5.58) was significantly negative (p<;0.05), and indicating that UC onset TD decreased with gestational weeks. In summary, this study quantitatively investigated the TD between the onset of UCs determined from TOCO and maternal perception, providing scientific evidence for future studies to understand the underlying mechanism of the time sequence of UC activity determined from different techniques.

Comparison of electrohysterogram characteristics during uterine contraction and non-contraction during labor.

Uterine contraction is one of the most important indication in the labor progression. Electrohysterogram (EHG) is a promising method for monitoring uterine contraction and discriminating efficient and inefficient contractions. This study aims to analyze the difference of EHG signals between two groups. EHG signals are recorded with abdominal electrodes from 20 pregnant women, including 10 in term labor group and 10 in non-labor group. Typical linear and nonlinear characteristics of EHG signals, including root mean square (RMS), peak frequency (PF), median frequency (MDF), mean frequency (MNF), parameters from wavelet decomposition (W4, W5) and time reversibility (Tr) are extracted. These characteristics are compared between contraction and non-contraction in term labor group and non-labor group. The result shows that RMS, W4 and W5 of contraction are significantly larger than non-contraction both within term labor group and between two groups (all p<;0.001). However, MDF and MNF are significantly smaller (all p<;0.05). Furthermore, all characteristics of non-contraction show no significant difference between two groups, except MNF. The variability of RMS, W4, W5 and Tr of contraction are significantly larger than non-contraction both within term labor group and between two groups (all p<;0.05, with p<;0.001 for W5 and Tr). However, the variability of MDF, PF and MNF are significantly smaller (all p<;0.05). Moreover, the variability of all characteristics of non-contraction shows no significant difference between two groups, except MNF. We have shown that characteristics of EHG signals and their variability during contraction are quite different from non-contraction. Therefore, it is feasible to separate uterine contractions and monitor uterine activity with EHG signals.

Assessing the effect of noise-reduction to the intelligibility of low-pass filtered speech.

Given the fact that most hearing-impaired listeners have low-frequency residual hearing, the present work assessed the effect of applying commonly-used singlechannel noise-reduction (NR) algorithms to improve the intelligibility of low-pass filtered speech, which simulates the effect of understanding speech with low-frequency residual hearing of hearing-impaired patients. In addition, this study was performed with Mandarin speech, which is characterized by its significant contribution of information present in (low-frequency dominated) vowels to speech intelligibility. Mandarin sentences were corrupted by steady-state speech-shaped noise and processed by four types (i.e., subspace, statistical-modeling, spectral-subtractive, and Wiener-filtering) of single-channel NR algorithms. The processed sentences were played to normal-hearing listeners for recognition. Experimental results showed that existing single-channel NR algorithms were unable to improve the intelligibility of low-pass filtered Mandarin sentences. Wiener-filtering had the least negative influence to the intelligibility of low-pass filtered speech among the four types of single-channel NR algorithms examined.