Assessment of watershed characteristics with limited water quantity and quality data.

The evaluations of water quantity and quality and then modeling of its phenomenon are required for water quality protection in Brady Creek watershed. This study is to predict the monthly flow, reservoir storage volume, and salinity; estimate the benefit of brush and aging flood-retardation dam control; and evaluate the impact of evaporation and discharge from Waste Water Treatment Plans (WWTP). The Soil and Water Assessment Tool (SWAT) model is verified with the monthly flow developed for pre-dam construction condition and shows the difference of - 9% and 10% than measured average flow for calibration and validation periods, respectively. The SWAT monthly flows are adjusted by 1963-2010 yearly conversion factors and are used as the input in the Water Rights Analysis Package (WRAP) model. The WRAP model verified with measured reservoir storage volume and total dissolved solid shows the average differences of simulated reservoir storage volume and salinity by - 13% lower and 11% higher for calibration period and 0% and 3% higher for validation period than measured average value, respectively. The impacts from brush and dams controls increase the runoff but also increase the water quality parameters. The impact of evaporation and WWTP discharge provide the information of relative impact for watershed phenomenon.

Single-cell radioluminescence microscopy with two-fold higher sensitivity using dual scintillator configuration.

Radioluminescence microscopy (RLM) is an imaging technique that allows quantitative analysis of clinical radiolabeled drugs and probes in single cells. However, the modality suffers from slow data acquisition (15-30 minutes), thus critically affecting experiments with short-lived radioactive drugs. To overcome this issue, we suggest an approach that significantly accelerates data collection. Instead of using a single scintillator to image the decay of radioactive molecules, we sandwiched the radiolabeled cells between two scintillators. As proof of concept, we imaged cells labeled with [18F]FDG, a radioactive glucose popularly used in oncology to image tumors. Results show that the double scintillator configuration increases the microscope sensitivity by two-fold, thus reducing the image acquisition time by half to achieve the same result as the single scintillator approach. The experimental results were also compared with Geant4 Monte Carlo simulation to confirm the two-fold increase in sensitivity with only minor degradation in spatial resolution. Overall, these findings suggest that the double scintillator configuration can be used to perform time-sensitive studies such as cell pharmacokinetics or cell uptake of short-lived radiotracers.

Screening capacity and cost-effectiveness of the human papillomavirus test versus cervicography as an adjunctive test to Pap cytology to detect high-grade cervical dysplasia.

OBJECTIVE: This study compared the screening capacities and cost-effectiveness of the human papillomavirus (HPV) test versus cervicography as an adjunctive test to Papanicolaou (Pap) cytology to detect high-grade cervical neoplasia in Korea, a country with a high prevalence of cervical cancer. STUDY DESIGN: Of 33,531 Korean women who underwent cervicography as a screening test for cervical cancer between January 2015 and December 2016, we retrospectively analyzed the records of 4117 women who simultaneously or subsequently underwent Pap cytology, an HPV test, cervicography, and colposcopically directed biopsy. At a threshold of cervical intraepithelial neoplasia grade 2 or worse (CIN2+), based on colposcopic biopsy, we compared the diagnostic capacities and cost-effectiveness of these screening tools. RESULTS: The CIN2+ prevalence was 10.8% (446 of 4117 women) and the positive rate of high-risk HPV was 61.0% (2511 of 4117 women). Cervicography as an adjunctive to Pap cytology was a more sensitive test (97.5% vs 93.7%) with a higher odds ratio (15.65 vs 5.86) than the HPV test for detection of CIN2+ (P-value = 0.003). Moreover, the cost of cervicography co-testing was 23% less than that of HPV co-testing, decreasing the cost per patient with CIN2+ lesions from $1474 to $1135. CONCLUSION: Cervicography and Pap co-testing had superior screening capacity and cost-effectiveness for detection of preinvasive cervical lesions than HPV and Pap co-testing and may be an effective and cost-saving screening strategy in clinical practice in country with a high prevalence of cervical cancer.

Toward a Droplet-Based Single-Cell Radiometric Assay.

Radiotracers are widely used to track molecular processes, both in vitro and in vivo, with high sensitivity and specificity. However, most radionuclide detection methods have spatial resolution inadequate for single-cell analysis. A few existing methods can extract single-cell information from radioactive decays, but the stochastic nature of the process precludes high-throughput measurement (and sorting) of single cells. In this work, we introduce a new concept for translating radioactive decays occurring stochastically within radiolabeled single-cells into an integrated, long-lasting fluorescence signal. Single cells are encapsulated in radiofluorogenic droplets containing molecular probes sensitive to byproducts of ionizing radiation (primarily reactive oxygen species, or ROS). Different probes were examined in bulk solutions, and dihydrorhodamine 123 (DHRh 123) was selected as the lead candidate due to its sensitivity and reproducibility. Fluorescence intensity of DHRh 123 in bulk increased at a rate of 54% per Gy of X-ray radiation and 15% per MBq/ml of 2-deoxy-2-[18F]-fluoro-d-glucose ([18F]FDG). Fluorescence imaging of microfluidic droplets showed the same linear response, but droplets were less sensitive overall than the bulk ROS sensor (detection limit of 3 Gy per droplet). Finally, droplets encapsulating radiolabeled cancer cells allowed, for the first time, the detection of [18F]FDG radiotracer uptake in single cells through fluorescence activation. With further improvements, we expect this technology to enable quantitative measurement and selective sorting of single cells based on the uptake of radiolabeled small molecules.

Performance evaluation of 18 F radioluminescence microscopy using computational simulation.

PURPOSE: Radioluminescence microscopy can visualize the distribution of beta-emitting radiotracers in live single cells with high resolution. Here, we perform a computational simulation of 18 F positron imaging using this modality to better understand how radioluminescence signals are formed and to assist in optimizing the experimental setup and image processing. METHODS: First, the transport of charged particles through the cell and scintillator and the resulting scintillation is modeled using the GEANT4 Monte-Carlo simulation. Then, the propagation of the scintillation light through the microscope is modeled by a convolution with a depth-dependent point-spread function, which models the microscope response. Finally, the physical measurement of the scintillation light using an electron-multiplying charge-coupled device (EMCCD) camera is modeled using a stochastic numerical photosensor model, which accounts for various sources of noise. The simulated output of the EMCCD camera is further processed using our ORBIT image reconstruction methodology to evaluate the endpoint images. RESULTS: The EMCCD camera model was validated against experimentally acquired images and the simulated noise, as measured by the standard deviation of a blank image, was found to be accurate within 2% of the actual detection. Furthermore, point source simulations found that a reconstructed spatial resolution of 18.5 µm can be achieved near the scintillator. As the source is moved away from the scintillator, spatial resolution degrades at a rate of 3.5 µm per µm distance. These results agree well with the experimentally measured spatial resolution of 30-40 µm (live cells). The simulation also shows that the system sensitivity is 26.5%, which is also consistent with our previous experiments. Finally, an image of a simulated sparse set of single cells is visually similar to the measured cell image. CONCLUSIONS: Our simulation methodology agrees with experimental measurements taken with radioluminescence microscopy. This in silico approach can be used to guide further instrumentation developments and to provide a framework for improving image reconstruction.

Evaluation of a BGO-Based PET System for Single-Cell Tracking Performance by Simulation and Phantom Studies.

A recent method based on positron emission was reported for tracking moving point sources using the Inveon PET system. However, the effect of scanner background noise was not further explored. Here, we evaluate tracking with the Genisys4, a bismuth germanate-based PET system, which has no significant intrinsic background and may be better suited to tracking lower and/or faster activity sources. Position-dependent sensitivity of the Genisys4 was simulated in Geant4 Application for Tomographic Emission (GATE) using a static (18)F point source. Trajectories of helically moving point sources with varying activity and rotation speed were reconstructed from list-mode data as described previously. Simulations showed that the Inveon's ability to track sources within 2 mm of localization error is limited to objects with a velocity-to-activity ratio < 0.13 mm/decay, compared to < 0.29 mm/decay for the Genisys4. Tracking with the Genisys4 was then validated using a physical phantom of helically moving [(18)F] fluorodeoxyglucose-in-oil droplets (< 0.24 mm diameter, 139-296 Bq), yielding < 1 mm localization error under the tested conditions, with good agreement between simulated sensitivity and measured activity (Pearson correlation R = .64, P << .05 in a representative example). We have investigated the tracking performance with the Genisys4, and results suggest the feasibility of tracking low activity, point source-like objects with this system.

Single-cell tracking with PET using a novel trajectory reconstruction algorithm.

Virtually all biomedical applications of positron emission tomography (PET) use images to represent the distribution of a radiotracer. However, PET is increasingly used in cell tracking applications, for which the "imaging" paradigm may not be optimal. Here, we investigate an alternative approach, which consists in reconstructing the time-varying position of individual radiolabeled cells directly from PET measurements. As a proof of concept, we formulate a new algorithm for reconstructing the trajectory of one single moving cell directly from list-mode PET data. We model the trajectory as a 3-D B-spline function of the temporal variable and use nonlinear optimization to minimize the mean-square distance between the trajectory and the recorded list-mode coincidence events. Using Monte Carlo simulations (GATE), we show that this new algorithm can track a single source moving within a small-animal PET system with 3 mm accuracy provided that the activity of the cell [Bq] is greater than four times its velocity [mm/s]. The algorithm outperforms conventional ML-EM as well as the "minimum distance" method used for positron emission particle tracking (PEPT). The new method was also successfully validated using experimentally acquired PET data. In conclusion, we demonstrated the feasibility of a new method for tracking a single moving cell directly from PET list-mode data, at the whole-body level, for physiologically relevant activities and velocities.