Numerical Simulations of Flow and Mass Transport in Micro-Fluidic Components for Modular Bio-Analytic Chip Applications

Microfluidics has received a great deal of attention in the past decade. The ability of modular microfluidic chips to miniaturize integrate chemical and biological systems (µTAS) can be greatly productive in terms of cost and efficiency. During the design of these modular devices, misalignment of materials, geometrical or both is one of the most common problems. These misalignments can have adverse effect in both pressure driven and electrokinetically driven flows. In the present work, Numerical Simulations have been performed to study the effect of material and geometrical mismatch on the flow behavior and species progression in microfluidic interconnects. In the case of electrokinetic flows, simulations were performed for 13%, 50%, 58% and 75% reduction in the available flow area at the mismatch plane. Correlations were developed to predict the flow rate reduction due to the geometrical mismatch in electrokinetic flows. A 13% flow area reduction was found to be insignificant and did not cause an appreciable sample loss. As the amount of geometrical mismatch increases (i.e. area reduction is more than 40%), it can have a significant effect on the sample resolution and on the flow behavior. In the case of pressure driven flows, Numerical Simulations have been performed for three types of interconnection methods: End-to-End, Channel Overlap, and Tube-in- Reservoir interconnection. The effects of geometrical misalignments in these three interconnection methods have been investigated and the results were interpreted in terms of the pressure drop and equivalent length. The amount of misalignment was varied by changing the available flow area ratios. All the configurations were simulated for practically relevant Reynolds numbers ranging from 0.075 to 75. Correlations were developed to predict the pressure drop for any given misalignment area ratio. It was found that for the misalignment area ratio of 2:1 or more, the increase in pressure drop can be drastic. Numerical simulations of Injection and separation were also performed to study the effect of curvatures on the elongation of generated plugs. These end curvatures are commonly encountered during high precision micromilling process as a method to fabricate polymer microfluidic devices. The effect of pinching and pullback voltages on the generation of the sample plugs was investigated and optimum conditions to minimize plug dispersion were found

Towards real-time topical detection and characterization of FDG dose infiltration prior to PET imaging

To dynamically detect and characterize 18F-fluorodeoxyglucose (FDG) dose infiltrations and evaluate their effects on positron emission tomography (PET) standardized uptake values (SUV) at the injection site and in control tissue

Towards real-time topical detection and characterization of FDG dose infiltration prior to PET imaging

PURPOSE: To dynamically detect and characterize (18)F-fluorodeoxyglucose (FDG) dose infiltrations and evaluate their effects on positron emission tomography (PET) standardized uptake values (SUV) at the injection site and in control tissue. METHODS: Investigational gamma scintillation sensors were topically applied to patients with locally advanced breast cancer scheduled to undergo limited whole-body FDG-PET as part of an ongoing clinical study. Relative to the affected breast, sensors were placed on the contralateral injection arm and ipsilateral control arm during the resting uptake phase prior to each patient’s PET scan. Time activity curves (TACs) from the sensors were integrated at varying intervals (0–10, 0–20, 0–30, 0–40, and 30–40 min) post-FDG and the resulting areas-under-the-curve (AUCs) were compared to SUVs obtained from PET. RESULTS: In cases of infiltration, observed in three sensor recordings (30%), the injection arm TAC shape varied depending on the extent and severity of infiltration. In two of these cases TAC characteristics suggested the infiltration was partially resolving prior to image acquisition, although it was still apparent on subsequent PET. Areas under the TAC 0–10 and 0–20 min post-FDG were significantly different in infiltrated versus non-infiltrated cases (Mann-Whitney, p < 0.05). When normalized to control, all TAC integration intervals from the injection arm were significantly correlated with SUV(peak) and SUV(max) measured over the infiltration site (Spearman ρ ≥ 0.77, p < 0.05). Receiver operating characteristic (ROC) analyses, testing the ability of the first 10 minutes of post-FDG sensor data to predict infiltration visibility on the ensuing PET, yielded an area under the ROC curve of 0.92. CONCLUSION: Topical sensors applied near the injection site provide dynamic information from the time of FDG administration through the uptake period and may be useful in detecting infiltrations regardless of PET image field of view. This dynamic information may also complement the static PET image to better characterize the true extent of infiltrations