High-precision micromilling was assessed as a tool for the rapid fabrication of mold masters for replicating microchip devices in thermoplastics. As an example, microchip electrophoresis devices were hot embossed in poly(methylmethacrylate) (PMMA) from brass masters fabricated via micromilling. Specifically, sidewall roughness and milling topology limitations were investigated. Numerical simulations were performed to determine the effects of additional volumes present on injection plugs (i.e., shape, size, concentration profiles) due to curvature of the corners produced by micromilling. Elongation of the plug was not dramatic (< 20%) for injection crosses with radii of curvatures to channel width ratios less than 0.5. Use of stronger pinching potentials, as compared to sharp-corner injectors, were necessary in order to obtain short sample plugs. The sidewalls of the polymer microstructures were characterized by a maximum average roughness of 115 nm and mean peak height of 290 nm. Sidewall roughness had insignificant effects on the bulk EOF as it was statistically the same for PMMA microchannels with different aspect ratios compared to LiGA-prepared devices with a value of ca. 3.7 · 10 À4 cm 2 /(V s). PMMA microchip electrophoresis devices were used for the separation of pUC19 Sau3AI double-stranded DNA. The plate numbers achieved in the micromilled-based chips exceeded 1 million/m and were comparable to the plate numbers obtained for the LiGA-prepared devices of similar geometry.

Purpose 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. 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 SUVpeak and SUVmax 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.

Purpose: Previous studies have demonstrated how imaging of the breast with patients lying prone using a supportive positioning device markedly facilitates longitudinal and/or multimodal image registration. In this contribution, the authors' primary objective was to determine if there are differences in the standardized uptake value (SUV) derived from [ 18 F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) in breast tumors imaged in the standard supine position and in the prone position using a specialized positioning device. Methods: A custom positioning device was constructed to allow for breast scanning in the prone position. Rigid and nonrigid phantom studies evaluated differences in prone and supine PET. Clinical studies comprised 18F-FDG-PET of 34 patients with locally advanced breast cancer imaged in the prone position (with the custom support) followed by imaging in the supine position (without the support). Mean and maximum values (SUV peak and SUV max , respectively) were obtained from tumor regions-of-interest for both positions. Prone and supine SUV were linearly corrected to account for the differences in 18F-FDG uptake time. Correlation, Bland-Altman, and nonparametric analyses were performed on uptake time-corrected and uncorrected data. Results: SUV from the rigid PET breast phantom imaged in the prone position with the support device was 1.9% lower than without the support device. In the nonrigid PET breast phantom, prone SUV with the support device was 5.0% lower than supine SUV without the support device. In patients, the median (range) difference in uptake time between prone and supine scans was 16.4 min (13.4-30.9 min), which was significantly-but not completely-reduced by the linear correction method. SUV peak and SUV max from prone versus supine scans were highly correlated, with concordance correlation coefficients of 0.91 and 0.90, respectively. Prone SUV peak and SUV max were significantly lower than supine in both original and uptake time-adjusted data across a range of index times (P << 0.0001, Wilcoxon signed rank test). Before correcting for uptake time differences, Bland-Altman analyses revealed proportional bias between prone and supine measurements (SUV peak and SUV max ) that increased with higher levels of FDG uptake. After uptake time correction, this bias was significantly reduced (P < 0.01). Significant prone-supine differences, with regard to the spatial distribution of lesions relative to isocenter, were observed between the two scan positions, but this was poorly correlated with the residual (uptake time-corrected) prone-supine SUV peak difference (P = 0.78).Conclusions: Quantitative 18F-FDG-PET/CT of the breast in the prone position is not deleteriously affected by the support device but yields SUV that is consistently lower than those obtained in the standard supine position. SUV differences between scans arising from FDG uptake time differences can be substantially reduced, but not removed entirely, with the current correction method. SUV from the two sca...

Low-cost modular polymer microfluidic platforms integrating several different functional units may potentially reduce the cost of molecular and environmental analyses, and enable broader applications. Proper function of such systems depends on well-characterized assembly of the instruments. Passive alignment is one approach to obtaining such assemblies. Model modular devices containing passive alignment features, hemispherical pins in v-grooves, and integrated alignment standards for characterizing the accuracy of the assemblies were replicated in polycarbonate using doubled-sided injection molding. The dimensions and locations of the assembly features and alignment standards were measured. The assemblies had mismatches from 16 ± 4 to 20 ± 6 µm along the x-axis and from 103 ± 7 to 118 ± 11 µm along the y-axis. The vertical variation from the nominal value of 287 µm ranged from −10 ± 4 to 34 ± 7 µm. An assembly tolerance model was used to estimate the accuracy of the assemblies based on the manufacturing variations of the alignment structures. Variation of the alignment structure features were propagated through the assembly using Monte Carlo methods. The estimated distributions matched the measured experimental results well, with differences of 2%-13% due to unmodeled aspects of the variations Accurate assembly of advanced polymer microsystems is feasible and predictable in the design phase.[2014-0125] he is working on microfluidic devices/systems for stroke detection and polymer-based micromodels for flow visualization in artifical porous media. His current research interests include micro/nano fabrication techniques and their applications to bioMEMS, enhanced oil recovery, and micro/nano scale sensors and actuators.

Introduction Dietary conditions may affect liver [18F]FDG kinetics due to arterial and portal vein (PV) input. The purpose of this study was to evaluate kinetic models of [18F]FDG metabolism under a wide range of dietary interventions taking into account variations in arterial (HA) and portal vein (PV) input. Methods The study consisted of three groups of rats maintained under different diet interventions: 12 h fasted, 24 h fasted and those fed with high fructose diet. [15O]H2O PET imaging was used to characterize liver flow contribution from HA and PV to the liver's dual input function (DIF). [18F]FDG PET imaging was used to characterize liver metabolism. Differences in [18F]FDG kinetics in HA, PV and liver under different diet interventions were investigated. An arterial to PV Transfer Function (TF) was optimized in all three dietary states to noninvasively estimate PV activity. Finally, two compartment 3-parameter (2C3P), two compartment 4-parameter (2C4P), two compartment 5-parameter (2C5P), and three compartment 5-parameter (3C5P) models were evaluated and compared to describe the kinetics of [18F]FDG in the liver across diet interventions. Sensitivity of the compartmental models to ratios of HA to PV flow fractions was further investigated. Results Differences were found in HA and PV [18F]FDG kinetics across 12 h fasted, 24 h fasted and high fructose fed diet interventions. A two exponential TF model was able to estimate portal activity in all the three diet interventions. Statistical analysis suggests that a 2C3P model configuration was adequate to describe the kinetics of [18F]FDG in the liver under wide ranging dietary interventions. The net influx of [18F]FDG was lowest in the 12 h fasted group, followed by 24 h fasted group, and high fructose diet. Conclusions A TF was optimized to non-invasively estimate PV time activity curve in different dietary states. Several kinetic models were assessed and a 2C3P model was sufficient to describe [18F]FDG liver kinetics despite differences in HA and PV kinetics across wide ranging dietary interventions. The observations have broader implications for the quantification of liver metabolism in metabolic disorders and cancer, among others.