c. geng

Disseminated Peritoneal Leiomyomatosis (DPL) is a rare benign illness characterized by numerous smooth muscle nodules over the peritoneal surface of the abdomen and pelvis. It mostly occurs in women of reproductive age, seldom in the postmenopausal women and men. We herein report two DPL cases and both of them took 18F-FDG PET/CT (Fluorine 18 Fluorodeoxyglucose Positron Emission Tomography) examination. On PET/CT images, all DPL nodules presented low to moderate metabolism, and the range of SUVmax (standard uptake value) was 1.9 to 4.4. An unusual diagnosis of DPL was difficult to make.

This study aims to investigate voxel-level dose calculation methods and improve its calculation efficiency in nuclear medicine that can consider animal-specific heterogeneous tissue compositions and radiopharmaceutical biodistributions simultaneously.

The voxelized mouse phantom was constructed from real mouse CT images and simulated using the Monte Carlo GEANT4 code. According to the dynamic PET images of real mouse, the real distribution of radiopharmaceutical activity was set in the Monte Carlo simulation. The sampling method to improve the calculation efficiency was proposed. Two voxel-level dose calculation methods were implemented in this study. The average absorbed dose in vital target organs and the tumor was calculated by the proposed voxel-level dose calculation methods and the traditional MIRD method respectively. The results of the average absorbed dose calculated by the two methods were compared. Based on the voxel-level dose calculation method, the three-dimensional dose distribution in organs and the tumor was obtained and evaluated.

The relative difference of average absorbed dose between the two voxel-level dose calculation methods was mostly less than 10%. The sampling method proposed to improve calculation efficiency for the voxel-level dose calculation can decrease the calculation time by ~34% with less deviation.

The results confirmed that the voxel-level dose calculation methods proposed in this study allow for more accurate and efficient assessment of the internal radiation dose.

The lattice Boltzmann models, especially the pseudopotential models, have been developed to investigate multicomponent multiphase fluids in presence of phase change process. However, the interparticle force between different components causes compressibility error in the non-phase-change component. This restricts the model capability in quantitative analysis of the physical foaming process, such as expansion rate and decay time. In the present study, a multicomponent multiphase pseudopotential phase change model (the MMPPCM) is improved by introducing an effective mass form of high-pressure-difference multicomponent model in the non-phase-change component. The improved model is compared with the MMPPCM based on simulations of the phase change process of static and moving fluids, as well as the physical foaming process. Density variation of non-phase-change component and its effect on flow field characteristics are analyzed during the phase change process. Simulation results of physical foaming process lead to about 10% ~ 20% reduction of the compressibility error for the improved model as compared with the results of MMPPCM. The improved model also enhances the computational stability of phase change simulation of the static droplets.

Dose modulation is a key factor in practical proton therapy. This study investigates the dose modulation methodology of irregular radiation field (IRF)-based proton therapy using forward radiation treatment planning and conformal dose layer stacking (CDLS) methods.

The geometric configuration of a virtual multi-leaf system was constructed to generate IRFs during Monte Carlo simulations. Two patient geometries—lymphatic metastasis and brain tumors—were configured to investigate the dosimetric feasibility and applications of IRF-based proton therapy in ideal patient anatomies. The investigated tumors were divided into slices perpendicular to proton beam axis. Segments were designed to be conformal to the profiles of these tumor slices. Conformal dose layers were produced by modulating the proton intensities and energies of the predesigned segments. Then, these dose layers were stacked throughout the tumors to obtain sufficient and conformal tumor doses.

From the proposed IRF-based proton therapy, tumors with 4-7 cm extents along the depth direction could be treated with fewer than 10 segments. The lymphatic metastasis and brain tumors were sufficiently covered by 95% dose lines, while appropriate distal and proximal dose conformities were achieved. The maximum tumor doses did not exceed 110%.

Theoretically, the proposed IRF-based proton therapy using forward planning and CDLS methods is feasible from the viewpoint of dosimetry. This study can serve as a foundation for future investigations of potential proton therapy methods based on fast conformal dose layer stacking using radiation fields with irregular shapes.