Measurement of nuclear reaction cross sections by using Cherenkov radiation toward high-precision proton therapy

Monitoring the in vivo dose distribution in proton therapy is desirable for the accurate irradiation of a tumor. Although positron emission tomography (PET) is widely used for confirmation, the obtained distribution of positron emitters produced by the protons does not trace the dose distribution due to the different physical processes. To estimate the accurate dose from the PET image, the cross sections of nuclear reactions that produce positron emitters are important yet far from being sufficient. In this study, we measured the cross sections of 16O(p,x)15O, 16O(p,x)13N, and 16O(p,x)11C with a wideenergy range (approximately 5–70 MeV) by observing the temporal evolution of the Cherenkovradiation emitted from positrons generated via β+ decay along the proton path. Furthermore, we implemented the new cross sectional data into a conventional Monte Carlo (MC) simulation, so that a direct comparison was possible with the PET measurement. We confirmed that our MC results showed good agreement with the experimental data, both in terms of the spatial distributions and temporalevolutions. Although this is the first attempt at using the Cherenkov radiation in the measurements of nuclear cross sections, the obtained results suggest the method is convenient and widely applicable for high precision proton therapy

A comparative study of the biomass properties of <i>Erianthus</i> and sugarcane: lignocellulose structure, alkaline delignification rate, and enzymatic saccharification efficiency

<p>A comprehensive understanding of the structure and properties of gramineous lignocelluloses is needed to facilitate their uses in biorefinery. In this study, lignocelluloses from fractionated internode tissues of two taxonomically close species, <i>Erianthus arundinaceus</i> and sugarcane (<i>Saccharum</i> spp.), were characterized. Our analyses determined that syringyl (S) lignins were predominant over guaiacyl (G) or <i>p</i>-hydroxyphenyl (H) lignins in sugarcane tissues; on the other hand, S lignin levels were similar to those of G lignin in <i>Erianthus</i> tissues. In addition, tricin units were detected in sugarcane tissues, but not in <i>Erianthus</i> tissues. Distributions of lignin inter-monomeric linkage types were also different in <i>Erianthus</i> and sugarcane tissues. Alkaline treatment removed lignins from sugarcane tissues more efficiently than <i>Erianthus</i> tissues, resulting in a higher enzymatic digestibility of sugarcane tissues compared with <i>Erianthus</i> tissues. Our data indicate that <i>Erianthus</i> biomass displayed resistance to alkaline delignification and enzymatic digestion.</p> <p>We found differences in lignocellulose properties (1) to (3) both between Erianthus and sugarcane and between their inner and outer internode tissues.</p