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Proton therapy, thanks to the dose characteristics of the Bragg peak, according to which most of the radiation energy is delivered at the end of the beam with a very high dose gradient at the distal edge, can deliver a highly conformal radiation dose to the treatment volume. Currently, however, the benefit of this high dose gradient is not fully utilized in clinical practice due mainly to the dose-distribution uncertainty in the beam direction (i.e., the uncertainty of the beam range in the patient). In this paper, we present an imaging system based on gamma electron vertex imaging (GEVI), which is suitable for high-energy (1–30 MeV) gammas, and test its performance for therapeutic proton beams. GEVI images prompt gamma vertices, which are closely correlated with the dose distribution at the distal edge, by converting prompt gammas to electrons via Compton scattering and then tracking the recoiled electrons. Our experimental results show that the GEVI system can image the 2D vertices of the prompt gammas and, thus, can be utilized for the measurement of proton-beam ranges in patients. We believe, indeed, that GEVI makes possible real-time monitoring of in-vivo proton-beam ranges, whose utility significantly improves treatment effectiveness and enhances patient safety. We also expect that the GEVI system will find applications in other fields (e.g., gamma-ray astronomy, nuclear engineering, and high-energy physics) requiring high-energy-gamma (1–30 MeV) imaging.

The electrical and structural properties of strained-Si-on-insulator (sSOI) wafers were investigated. The strain, calculated from two-dimensional reciprocal space mapping, was found to be 0.78%, which is comparable to that of fully relaxed Si1−xGex film with Ge concentration of 20.6at.%. Based on the Raman peak shift combined with measured value of strain, the strain shift coefficient is extracted to be −736cm−1. The pseudo-metal-oxide-semiconductor field-effect transistor measurements, employed to characterize the electrical properties of sSOI wafers, showed that both electron and hole mobilities are enhanced by strain. The enhancement factor of electron mobility is larger than that of hole mobility.