ABSTRACT
Brain functional network changes over time along with the process of brain development, disease, and aging. However, most of the available measurements for evaluation of the difference (or similarity) between the individual brain functional networks are for charactering static networks, which do not work with the dynamic characteristics of the brain networks that typically involve a long-span and large-scale evolution over the time. The current study proposes an index for measuring the similarity of dynamic brain networks, named as dynamic network similarity (DNS). It measures the similarity by combining the "evolutional" and "structural" properties of the dynamic network. Four sets of simulated dynamic networks with different evolutional and structural properties (varying amplitude of changes, trend of changes, distribution of connectivity strength, range of connectivity strength) were generated to validate the performance of DNS. In addition, real world imaging datasets, acquired from 13 stroke patients who were treated by transcranial direct current stimulation (tDCS), were used to further validate the proposed method and compared with the traditional similarity measurements that were developed for static network similarity. The results showed that DNS was significantly correlated with the varying amplitude of changes, trend of changes, distribution of connectivity strength and range of connectivity strength of the dynamic networks. DNS was able to appropriately measure the significant similarity of the dynamics of network changes over the time for the patients before and after the tDCS treatments. However, the traditional methods failed, which showed significantly differences between the data before and after the tDCS treatments. The experiment results demonstrate that DNS may robustly measure the similarity of evolutional and structural properties of dynamic networks. The new method appears to be superior to the traditional methods in that the new one is capable of assessing the temporal similarity of dynamic functional imaging data.
Subject(s)
Humans , Aging/physiology , Brain/physiology , Brain Mapping , Magnetic Resonance Imaging/methods , Nerve Net/physiology , Transcranial Direct Current Stimulation/methodsABSTRACT
Objective To explore the predictive value of dynamic serum phosphorus levels in the evaluation of prognosis in patients with sepsis. Methods A retrospective study was conducted. The septic patients admitted to intensive care unit (ICU) of the Second People's Hospital of Changzhou from January 2016 to June 2017 were enrolled, who were ≥18 years old and whose length of ICU stay > 72 hours. These patients were divided into survival group and death group according to 28-day outcome. The general information, the acute physiology and chronic health evaluation Ⅱ(APACHE Ⅱ) score within 24 hours of ICU admission, the serum phosphorus at 1, 3, 5, 7 days after admission were collected. Receiver operating characteristic curve (ROC) was plotted according to the dynamic serum phosphorus levels and APACHE Ⅱ score for evaluating the predictive value of 28-day prognosis. Kaplan-Meier survival curve was used to analyze the 28-day cumulative survival rate between two groups of patients, who were divided according to the corresponding time of the serum phosphorus cut-off value. Results ① Eighty-five patients with sepsis were enrolled, among whom 25 cases were in the death group and the mortality was 29.4%. APACHE Ⅱ score in the death group was significantly higher than that in the survival group (22.28±3.98 vs. 16.05±5.44, P < 0.01), the rate of using vasoactive drugs was significantly higher than that in the survival group [64.0% (16/25) vs. 31.7% (19/60), P < 0.01], but there was no significant difference in the length of invasive mechanical ventilation and ICU stay between two groups.② The level of serum phosphorus was increased in survival group along with time of the treatment, and the death group showed a downward trend. The levels of serum phosphorus at 3, 5, 7 days after admission to ICU in death group were significantly lower than those in survival group (mmol/L: 0.90±0.24 vs. 1.05±0.19 at 3 days, 0.96±0.16 vs. 1.11±0.17 at 5 days, 0.83±0.19 vs. 1.21±0.14 at 7 days, all P < 0.01).③ROC curve analysis showed that APACHE Ⅱ score and serum phosphorus level on the 7th day could significantly predict 28-day mortality in patients with sepsis, and the areas under ROC curve (AUC) of them were 0.813 and 0.945 respectively (both P < 0.01). The AUC of serum phosphorus level on the 3rd day and 5th day were 0.692 and 0.745 respectively (both P < 0.01). Based on serum phosphorus cut-off value 1.01 mmol/L on the 7th day to evaluate the predictive value of 28-day mortality, the sensitivity was 91.7%, the specificity was 84.0%, the positive and negative likelihood ratios were 5.73 and 0.10 respectively. ④ Kaplan-Meier survival analysis showed that the 28-day survival rate was significantly higher and the length of survival was significantly longer if the serum phosphorus were higher than the cut-off value at different time points of ICU admission. The 28-day survival rate was significantly higher and the length of survival was significantly longer in the patients with serum phosphorus > 1.01 mmol/L than those serum phosphorus ≤ 1.01 mmol/L on the 7th day [28-day survival rate: 93.2% (55/59) vs. 22.7% (5/22), χ2= 49.697, P = 0.000; survival period (days): 27.1±3.6 vs. 19.8±7.8, t = 4.768, P =0.000]. Conclusion The continuous decline of serum phosphorus indicates poor prognosis, and the serum phosphorus level on the 7th day is one of the most important indicator to evaluate the prognosis of patients with sepsis.