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PurposeThis study develop a novel linear energy transfer (LET) optimization method for intensity-modulated proton therapy (IMPT) with minimum monitor unit (MMU) constraint using the alternating direction method of multipliers (ADMM).Material and methodsThe novel LET optimization method (ADMM-LET) was proposed with (1) the dose objective and the LET objective as the optimization objective and (2) the non-convex MMU threshold as a constraint condition. ADMM was used to solve the optimization problem. In the ADMM-LET framework, the optimization process entails iteratively solving the dose sub-problem and the LET sub-problem, simultaneously ensuring compliance with the MMU constraint. Three representative cases, including brain, liver, and prostate cancer, were utilized to evaluate the performance of the proposed method. The dose and LET distributions from ADMM-LET were compared to those obtained using the published iterative convex relaxation (ICR-LET) method.ResultsThe results demonstrate the superiority of ADMM-LET over ICR-LET in terms of LET distribution while achieving a comparable dose distribution. More specifically, for the brain case, the maximum LET (unit: keV/µm) at the optic nerve decreased from 5.45 (ICR-LET) to 1.97 (ADMM-LET). For the liver case, the mean LET (unit: keV/µm) at the clinical target volume increased from 4.98 (ICR-LET) to 5.50 (ADMM-LET). For the prostate case, the mean LET (unit: keV/µm) at the rectum decreased from 2.65 (ICR-LET) to 2.14 (ADMM-LET).ConclusionThis study establishes ADMM-LET as a new approach for LET optimization with the MMU constraint in IMPT, offering potential improvements in treatment outcomes and biological effects.

This study developed a voxelized scomber japonicus phantom through CT scanning images for the purpose of radiation protection in the environment, which gives a realistic description of the scomber japonicus ’s anatomy. The absorbed fraction (AF) values of the voxelized scomber japonicus phantom were calculated for photons and electrons in the energies of 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 MeV using Monte Carlo toolkit Geant4. Furthermore, the S-factor values for four radionuclides ( ^134 Cs, ^137 Cs, ^131 I and ^90 Sr) in the organs/tissues were evaluated using the monoenergetic AF values based on the radioisotope decay data, and compared with that obtained directly through whole emission spectra simulation. The voxelized scomber japonicus phantom would be a good candidate for dosimetry in non-human biota for the environmental dosimetry, and the built database of AF values can be used for dose calculations of any radioactive contaminations.

Potato bears the burden of eliminating hunger and supporting food security. Quantitative assessment of potato drought disaster risk can help the sustainable development of the potato industry and improve the regional disaster management capacity. This is also a major and urgent demand for food security. This study constructed a comprehensive drought condition index (CDCI) for different months of the potato growing season based on the Soil-Plant-Atmosphere Continuum (SPAC) system, quantitatively assessed potato drought disaster risk based on the four-factor theory of natural disaster risk formation, and discussed the historical and future planting environmental conditions in Inner Mongolia, China. The results showed that the non-overlap between suitable areas of agro-climatic resources and main planting areas is the main reason for the occurrence of potato drought disasters, and the "Extremely high risk area" and "High risk area" areas were concentrated in the current main planting areas, which was one of the problems encountered in the sustainable development of potato industry in Inner Mongolia. The analysis of future drought hazard changes indicates the need to pay attention not only to the possible persistence of drought hazard in Near term, but also to the possible waterlogging hazard in Mid-Long term. The different situations of land use/cover change (LUCC) in Inner Mongolia and various agricultural resources and environmental zones (AgriREZones) have confirmed the necessity of separating regions for agricultural drought risk analysis and management. The present study can be used as a reference for adjusting the layout of the potato industry and provide a basis for agricultural disaster prevention and reduction. • A comprehensive drought condition index was constructed based on the "Soil-Plant-Atmosphere" continuum. • Agricultural resources and environment zoning is conducted to facilitate site-specific research. • In the coming period, in addition to drought there is also a need to pay attention to possible waterlogging. [ABSTRACT FROM AUTHOR]