Handheld Laser Speckle Imaging System for Neonatal Blood Flow Imaging

Background and Objectives:Although abnormal blood flow is linked to clinical risk of illness in neonates, clinicians typically do not integrate flow measurements into routine monitoring in the neonatal intensive care unit (NICU). We and other research groups have previously demonstrated the ability of Laser Speckle Imaging (LSI) to measure changes in blood flow in both a laboratory and clinical settings. We postulate that LSI, in a clinic-friendly form factor, can provide important hemodynamic information in the NICU. Here, I describe initial efforts to develop a handheld LSI system and deploy it to University of California, Irvine Medical Center NICU.Study Design/Methods:I designed and fabricated a handheld LSI system based on design principles to insure successful implementation into a clinical setting. Using in-vitro tissue phantom systems, I assessed the system performance of handheld LSI versus a traditional mounted configuration. I collected multi-user data (n=7) to assess the variation in flow measurements attributed to user performance. I collected data from two in-vivo occlusion models to demonstrate that the handheld device can detect both qualitative and quantitative changes in blood flow. Finally, I acquired data from an on-going NICU based clinical study (n=30, to date) in which we collected LSI images of abdomen and the heel over a period of several months.Results:I demonstrate that the handheld nature of the device has little effect on the flow measurement sensitivity via a study that was focused on the characterization of tissue simulating phantoms. Flow phantoms were characterized using both bench top and handheld LSI instruments. I show that measurements of flow from these phantoms is not user dependent based on testing using a pool of 7 minimally trained users. I demonstrate that the handheld LSI system measures trends in flow that are similar to those reported previously using bench top LSI systems during in-vivo occlusion models. I observed up to an 83.9% increase in flow index measured in neonates at the abdomen after feeding, while only up to a 16.1% increase was observed in the heel. Lastly, I observed a statistically significant difference between the maximum range of flow index values measured at the abdomen in necrotizing enterocolitis neonates and a healthy population (P=.015).Conclusion:The handheld LSI system can measure changes in blood flow and is minimally sensitive to errors due to handheld motion. Flow changes found in the abdomen warrant further studies to investigate the feasibility of using the LSI to detect compromised intestinal blood flow in neonates. These results suggest that LSI may be capable of providing additional screening for neonates with suspected gut pathology

Effect of temperature on the level of corrosion caused by heavy petroleum on AISI 304 and AISI 444 stainless steel

This work presents a study on the influence of national heavy petroleum in the corrosion of the AISI 444 and AISI 304 stainless steels in simulated refining operation conditions. The petroleum was first characterized through physicochemical analysis (density, fluidity point, viscosity, sulfur concentration). In an attempt to understand the corrosion effect of temperature and of the type of heating the referred types of steel thermal treatments were carried out at three levels of temperature (200, 300 and 400 °C). The procedure was done in conditions close to those in the distillation column. Heat was gradually increased from room temperature, and directly heated to working temperature. Each treatment took 4 hours to be completed. Scanning electronic microscopy (SEM) and the analysis of X rays dispersive energy (EDX) were used after the trials to characterize the samples. The results show that treatment temperature, as well as the type of heating, has distinct influences on each type of steel

Analysis of Steady-state Creep and Creep Fracture of Directionally Solidified Eutectic Gamma/gamma'-alpha Alloy

The steady-state creep behavior of directionally solidified eutectic alloy Ni-30Mo-6Al-1.6V-1.2Re (wt pet) was investigated at temperatures between 1223 and 1323 K using constant strain rate tension creep tests. The steady-state stress is found to depend strongly on creep rate and temperature. The apparent power law stress exponent for steady-state stress is n = 7.5 +/- 0.3, and the apparent activation energy for creep of the eutectic gamma/gamma'-alpha composite is determined to be Q = 517 +/- 11 kJ mol(-1). When the steady-state creep is analyzed in terms of the effective stress and normalized with respect to the temperature dependence of the elastic modulus, the corrected activation energy for creep Q(c) is calculated to be between 412 and 424 kJ mol(-1) and the stress exponent between 5.7 and 6.0. The kinetics of the steady-state creep deformation within the studied temperature range involves the contribution of both the fibers and the matrix which creep during steady-state. Analysis of the fracture surfaces of the composite shows ductile fracture mode. The composite fails by growth and coalescence of microvoids in the matrix and by fiber fragmentation