Objective:This study analyzed different definitions of the conformity index (CI), homogeneity index (HI), and gradient index (GI) used in evaluation of prostate cancer stereotactic body radiation therapy. Methods:A total of 10 patients with localized prostate cancer staged T1-T2a were selected randomly, from which two stereotactic body radiation therapy plans were designed with CyberKnife and EDGE systems for each patient based on the same images and contours. CI, HI, and GI with different definitions were calculated based on a dose-volume histogram of treatment plans. Results:For four definitions of CI, the results showed that the values calculated by the Radiation Therapy Oncology Group, Lomax and Scheib, and Van't Riet were closer to 1 for EDGE plans, except for that by the Saint-Anne, Lariboisiere, and Tenon group. Meanwhile, CI values of Van't Riet et al were lower than other definitions, which showed high accuracy to describe the conformity between the target volume and prescribed isodose line. For five definitions of HI, CyberKnife plans showed lower values than EDGE plans. HI calculated based on the D 2 (D 5 ) and D 98 (D 95 ) were lower than that calculated by the D max to D min , whereas the standard deviation was higher than others. For the dose GI, the results of effective radius and modified GI showed that EDGE plans had a steeper dose fall-off, which is inverse to the conventional GI. Conclusions:These indexes can all be objective tools for the evaluation of plan quality. Our results showed better conformity of dose distribution and dose gradient for EDGE plans, but better uniformity for CyberKnife plans. The conformation number and S-index were recommended to accurately describe the conformity and uniformity of dose distribution. The ∆R iso and modified GI were also recommended to calculate the dose gradient. K E Y W O R D Sconformity, dose gradient, homogeneity, plan quality, stereotactic body radiotherapy

No abstract

Polymer matrix composites with lightweight, low dielectric constant (ε) and dielectric loss tangent (tan δ), high‐temperature resistance, and excellent mechanical properties are urgently needed in the fields of aviation, aerospace, transportation, and wireless communication services. In this work, 3D woven spacer Kevlar/polyimide composites (3DKPC) with excellent dielectric properties and robust mechanical properties were designed and obtained by combining 3D weaving technology and thermal imidization process. Results show that the volume density of the prepared composites is as low as 0.24 g·cm−3, but its compressive strength can be up to 6.24 MPa. The dielectric constant and loss tangent of 3DKPC at room temperature are extremely low, with the value of ~1.32 and 6.9 × 10−3, respectively. Moreover, the compressive strength retention rate is more than 96% and the dielectric constant can be consistently lower than 1.36 when the temperature increases from 25 to 300°C, demonstrating the outstanding mechanical and dielectric stability of 3DKPC. In addition, as an application example of resulting composites, a microstrip antenna with 3DKPC as the substrate material was designed, followed by the simulation of its electromagnetic properties via High Frequency Structural Simulator. The results display that the gain of the microstrip antenna is 6.2 dB, which is superior to those of many other reported microstrip antennas, indicating that the 3DKPC proposed here has great application potential in aerospace, wireless communication, and other fields.

Among the agricultural crops, wheat is one of the most important and broadly planted food crops. However, abundant wheat straw resources were used to incinerate, which was a great waste of fiber resources, and meanwhile caused great pollution to the ecological environment. In this work, a simple hot compress method that used intact wheat straw with different volume fractions (20% and 30%) as a filler to reinforce the polylactic acid resin was explored to prepare a biodegradable composite by thermal compression method. Initially, the compressed wheat straw exhibited excellent tensile strength (96.86 MPa), even higher than intact wheat straw (92.18 MPa). The surface modification treatment was carried out with 2% and 4% concentrations of sodium hydroxide (NaOH). Then the tensile and bending strength of the modified wheat straw/polylactic acid composites were 32.41 MPa and 78.52 MPa, which were 22.16% and 22.44% higher than those of the untreated composites. The scanning electron microscopy images of the surface of modified wheat straw and fractured composite cross section revealed significantly rougher surface morphology and stronger interfacial bonding with the matrix. This work demonstrated the feasibility and good mechanical property of the composites reinforced with intact wheat straw by simple hot compression method, which provided a possible strategy to utilize the straw materials for multiple applications.