Young Myoung Ko

Efficacy and Safety of Prostatic Arterial Embolization: Systematic Review with Meta-Analysis and Meta-Regression

Purpose: This study attempted to overcome the limitations of previous systematic reviews to determine the overall treatment efficacy and safety of prostatic arterial embolization compared with standard therapy. Materials and Methods: Meta‐analyses were done of randomized, controlled and single group trials. Meta‐regression analysis of the moderator effect was performed with single group analysis. The outcomes measured were mean changes in I‐PSS (International Prostate Symptom Score), quality of life, maximal urinary flow rate, prostate volume, post‐void residual volume and prostate specific antigen. Adverse events were compared as proportional differences between the embolization group and groups receiving other therapies in comparative studies. Results: A total of 16 studies met our selection criteria and were included in the meta‐analysis. Three studies were comparative and included a total of 297 subjects, including 149 in the experimental groups and 148 in the control groups. The other 13 studies were noncomparative and included a total of 750 experimental subjects. Pooled overall standardized mean differences for embolization in I‐PSS, maximal urinary flow rate and prostate volume were significantly impaired in the experimental vs control groups. Overall weighted mean differences for all outcomes except prostate specific antigen were significantly improved from baseline by embolization treatment in noncomparative studies. Sensitivity analysis of study duration showed that all outcome measurements did not differ before vs after 6 months. Conclusions: Although there is growing evidence of the efficacy and safety of prostatic arterial embolization for benign prostatic hyperplasia, this systematic review using meta‐analysis and meta‐regression showed that prostatic arterial embolization should still be considered an experimental treatment modality.

Epidemic-based information dissemination in wireless mobile sensor networks

In this paper, we consider wireless mobile sensor networks under extreme environments where nodes: 1) have local knowledge; 2) have limited computational power; 3) make distributed decisions; and 4) move rapidly over time. Information dissemination in these networks (or gossip) can be modeled via epidemic models that analyze behavior of the system mimicking the way diseases spread (or even gossip for that matter). However, the limitation on computational power and energy of nodes forces us to consider explicit stopping criteria that are seldom done in the literature. Furthermore, harsh environments considered in this paper prevent nodes from transmitting sensed information at specified time slots and hence might cause a large variation in intertransmission time distribution. The objective of this paper is to characterize the dynamics of the information spread and obtain performance measures based on stochastic modeling. We start with modeling information flow using a Markov chain and obtain performance measures such as time to transfer information and fraction of nodes receiving information. Then, we provide a method to obtain those performance measures when the assumption on intertransmission time distribution is relaxed, e.g., time-varying transmission rates and nonexponential intertransmission time distributions, which makes our model more realistic. We make a curious finding in that, for our proposed model, the average fraction of nodes receiving information is a parameter-free constant. We also show that our model is scalable and effective.

Validation and Reliability of a Smartphone Application for the International Prostate Symptom Score Questionnaire: A Randomized Repeated Measures Crossover Study

Background Smartphone-based assessment may be a useful diagnostic and monitoring tool for patients. There have been many attempts to create a smartphone diagnostic tool for clinical use in various medical fields but few have demonstrated scientific validity. Objective The purpose of this study was to develop a smartphone application of the International Prostate Symptom Score (IPSS) and to demonstrate its validity and reliability. Methods From June 2012 to May 2013, a total of 1581 male participants (≥40 years old), with or without lower urinary tract symptoms (LUTS), visited our urology clinic via the health improvement center at Soonchunhyang University Hospital (Republic of Korea) and were enrolled in this study. A randomized repeated measures crossover design was employed using a smartphone application of the IPSS and the conventional paper form of the IPSS. Paired t test under a hypothesis of non-inferior trial was conducted. For the reliability test, the intraclass correlation coefficient (ICC) was measured. Results The total score of the IPSS (P=.289) and each item of the IPSS (P=.157-1.000) showed no differences between the paper version and the smartphone version of the IPSS. The mild, moderate, and severe LUTS groups showed no differences between the two versions of the IPSS. A significant correlation was noted in the total group (ICC=.935, P<.001). The mild, moderate, and severe LUTS groups also showed significant correlations (ICC=.616, .549, and .548 respectively, all P<.001).There was selection bias in this study, as only participants who had smartphones could participate. Conclusions The validity and reliability of the smartphone application version were comparable to the conventional paper version of the IPSS. The smartphone application of the IPSS could be an effective method for measuring lower urinary tract symptoms.

Approximations for the Queue Length Distributions of Time-Varying Many-Server Queues

This paper presents a novel and computationally efficient methodology for approximating the queue length (the number of customers in the system) distributions of time-varying non-Markovian many-server queues (e.g., Gt/Gt/nt queues), where the number of servers (nt) is large. Our methodology consists of two steps. The first step uses phase-type distributions to approximate the general interarrival and service times, thus generating an approximating Pht/Pht/nt queue. The second step develops strong approximation theory to approximate the Pht/Pht/nt queue with fluid and diffusion limits whose mean and variance can be computed using ordinary differential equations. However, by naively representing the Pht/Pht/nt queue as a Markov process by expanding the state space, we encounter the lingering phenomenoneven when the queue is overloaded. Lingering typically occurs when the mean queue length is equal or near the number of servers, however, in this case it also happens when the queue is overloaded and this time...

Bladder Recovery by Stem Cell Based Cell Therapy in the Bladder Dysfunction Induced by Spinal Cord Injury: Systematic Review and Meta-Analysis

Background Bladder dysfunction induced by spinal cord injury (SCI) can become problematic and severely impair the quality of life. Preclinical studies of spinal cord injury have largely focused on the recovery of limb function while neglecting to investigate bladder recovery. Objective The present study was performed to investigate and review the effect of stem cell-based cell therapy on bladder recovery in SCI. Methods We conducted a meta-analysis of urodynamic findings of experimental trials that included studies of stem cell-based cell therapy in SCI. Relevant studies were searched using MEDLINE, EMBASE and Cochrane Library (January 1990 - December 2012). Final inclusion was determined by a urodynamic study involving detailed numerical values. Urodynamic parameters for analysis included voiding pressure, residual urine, bladder capacity and non-voiding contraction (NVC). Meta-analysis of the data, including findings from urodynamic studies, was performed using the Mantel-Haenszel method. Results A total of eight studies were included with a sample size of 224 subjects. The studies were divided into different subgroups by different models of SCI. After a stem cell-based cell therapy, voiding pressure (-6.35, p <0.00001, I2 = 77%), NVC (-3.58, p <0.00001, I2 = 82%), residual urine (-024, p = 0.004, I2 = 95%) showed overall significant improvement. Bladder capacity showed improvement after treatment only in the transection type (-0.23, p = 0.0002, I2 = 0%). Conclusion After stem cell-based cell therapy in SCI, partial bladder recovery including improvement of voiding pressure, NVC, and residual urine was demonstrated. Additional studies are needed to confirm the detailed mechanism and to obtain an ideal treatment strategy for bladder recovery.

Integrating virtualization, speed scaling, and powering on/off servers in data centers for energy efficiency

Data centers consume a phenomenal amount of energy, which can be significantly reduced by appropriately allocating resources using technologies such as virtualization, speed scaling, and powering off servers. This article proposes a unified methodology that combines these technologies under a single framework to efficiently operate data centers. In particular, a large-scale Mixed Integer Program (MIP) is formulated that prescribes optimal allocation of resources while incorporating inherent variability and uncertainty of workload experienced by the data center. However, only for small to medium-sized clients it is possible to solve the MIP using commercial optimization software packages in a reasonable time. Thus, for large-sized clients a heuristic method is developed that is effective and fast. An extensive set of numerical experiments is performed to illustrate the methodology, obtain insights on the allocation policies, evaluate the quality of the proposed heuristic, and test the validity of the assumptions made in the literature. The results show that gains of up to 40% can be obtained by using the integrated approach rather than the traditional approach where virtualization, dynamic voltage/frequency scaling, and powering off servers are done separately.

Transient analysis of queues for peer-based multimedia content delivery

Consider a firm that sells online multimedia content. In order to manage costs and quality of service, this firm maintains a peer network that allows new users to download files from their peers who have previously downloaded the required files. The scenario can be modeled as a queueing system where the number of servers varies over time. Analytical models are developed that are based on fluid and diffusion approximations and allow analysis of transient system performance. The same approximations are used to analyze the steady-state behavior of this network. It is shown that the existing fluid and diffusion approximations are inaccurate for transient analysis. To address this shortcoming, a novel Gaussian-based adjustment is proposed and it significantly improves the accuracy of the approximations. Furthermore, the models used in this research can be extended seamlessly to the case of time-varying system parameters (e.g., arrival rates and service rates). Several numerical examples are provided that show how the proposed adjusted models work for the analysis of transient phenomena.

Efficacy and Safety of Initial Combination Treatment of an Alpha Blocker with an Anticholinergic Medication in Benign Prostatic Hyperplasia Patients with Lower Urinary Tract Symptoms: Updated Meta-Analysis.

Background There is still controversy as to whether initial combination treatment is superior to serial addition of anticholinergics after maintenance or induction of alpha blockers in benign prostatic hyperplasia (BPH)/lower urinary tract symptoms (LUTS) Objective The objective of this study was to determine the benefits and safety of initial combination treatment of an alpha blocker with anticholinergic medication in BPH/LUTS through a systematic review and meta-analysis. Methods We conducted a meta-analysis of improvement in LUTS using International Prostate Symptom Score (IPSS), maximal urinary flow rate (Qmax), post-voided residual volume (PVR), and quality of life (QoL). Results In total, 16 studies were included in our analysis, with a total sample size of 3,548 subjects (2,195 experimental subjects and 1,353 controls). The mean change in total IPSS improvement from baseline in the combination group versus the alpha blocker monotherapy group was -0.03 (95% CI: -0.14–0.08). The pooled overall SMD change of storage IPSS improvement from baseline was -0.28 (95% CI: -0.40 - -0.17). The pooled overall SMD changes of QoL, Qmax, and PVR were -0.29 (95% CI: -0.50 - -0.07), 0.00 (95% CI: -0.08–0.08), and 0.56 (95% CI: 0.23–0.89), respectively. There was no significant difference in the number of acute urinary retention (AUR) events or PVR. Conclusions Initial combination treatment of an alpha blocker with anticholinergic medication is efficacious for in BPH/ LUTS with improved measures such as storage symptoms and QoL without causing significant deterioration of voiding function.

Diffusion limits for the (MAPt/Pht/)N queueing network

In this paper, we prove strong approximations for the (MAPt/Pht/)N queueing network. These strong approximations allow us to derive fluid and diffusion limits for the queue length processes of the network. This extends recent work that provides fluid and diffusion limits in the single station setting.

Strong approximations for time-varying infinite-server queues with non-renewal arrival and service processes

ABSTRACT In real stochastic systems, the arrival and service processes may not be renewal processes. For example, in many telecommunication systems such as internet traffic where data traffic is bursty, the sequence of inter-arrival times and service times are often correlated and dependent. One way to model this non-renewal behavior is to use Markovian Arrival Processes (MAPs) and Markovian Service Processes (MSPs). MAPs and MSPs allow for inter-arrival and service times to be dependent, while providing the analytical tractability of simple Markov processes. To this end, we prove fluid and diffusion limits for MAPt/MSPt/∞ queues by constructing a new Poisson process representation for the queueing dynamics and leveraging strong approximations for Poisson processes. As a result, the fluid and diffusion limit theorems illuminate how the dependence structure of the arrival or service processes can affect the sample path behavior of the queueing process. Finally, our Poisson representation for MAPs and MSPs is useful for simulation purposes and may be of independent interest.