Studies over the last few decades have demonstrated that intracellular pH (pHi) of solid tumors is maintained within a pH range of 7.0-7.2, while the extracellular pH (pHe) is acidic. A low pHe may be an important factor inducing more aggressive cancer phenotypes. Research into causes and consequences of this acid pH of tumors are highly dependent on accurate, precise and reproducible measurements, and these have undergone great changes since in the last decade. This review focuses on most recent advances of in vivo tumor pH measurement by pH-sensitive Positron emission tomography (PET) radiotracers, magnetic resonance spectroscopy (MRS), magnetic resonance imaging (MRI) and optical imaging.

Urban air quality information, e.g., PM2.5 concentration, is of great importance to both the government and society. Recently, there is a growing interest in developing low-cost sensors, installed on moving vehicles, for fine-grained air quality measurement. However, low-cost mobile sensors typically suffer from low accuracy and thus need careful calibration to preserve a high measurement quality. In this paper, we propose a two-phase data calibration method consisting of a linear part and a nonlinear part. We use MLS (multiple least square) to train the linear part, and use RF (random forest) to train the nonlinear part. We propose an automatic feature selection algorithm based on AIC (Akaike information criterion) for the linear model, which helps avoid overfitting due to the inclusion of inappropriate features. We evaluate our method extensively. Results show that our method outperforms existing approaches, achieving an overall accuracy improvement of 16.4% in terms of PM2.5 levels compared with state-of-the-art approach.

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Focused ultrasound (FUS) can be used to locally and temporally enhance vascular permeability, improving the efficiency of drug delivery from the blood vessels into the surrounding tissue. However, it is difficult to evaluate in real time the effect induced by FUS and to noninvasively observe the permeability enhancement. In this study, speckle-variance optical coherence tomography (SVOCT) was implemented for the investigation of temporal effects on vessels induced by FUS treatment. With OCT scanning, the dynamic change in vessels during FUS exposure can be observed and studied. Moreover, the vascular effects induced by FUS treatment with and without the presence of microbubbles were investigated and quantitatively compared. Additionally, 2D and 3D specklevariance images were used for quantitative observation of blood leakage from vessels due to the permeability enhancement caused by FUS, which could be an indicator that can be used to determine the influence of FUS power exposure. In conclusion, SVOCT can be a useful tool for monitoring FUS treatment in real time, facilitating the dynamic observation of temporal effects and helping to determine the optimal FUS power. Yasufumi, and R. Morishita, "Local delivery of plasmid DNA into rat carotid artery using ultrasound," Circulation 105(10), 1233-1239 (2002

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