[en] Highlights: • Drying kinetics of yacon (Smallanthus sonchifolius) were investigated. • Drying took place in the falling rate period. • The Midilli et al. model was the best models describing the drying behavior of yacon. • The effective diffusivity coefficients varied from 1.092 to 7.388 × 10⁻⁷ m²/s. • The avtivation energy for moisture diffusion was found to be 30.00 kJ/mol. - Abstract: Heat pump drying kinetics and quality characteristics of yacon at different drying temperatures (5, 15, 25, 35 and 45 °C) and air velocities (0.5, 1.0, 1.5 and 2.0 m/s) were investigated. Results indicated that drying took place in the falling rate period. The drying temperature and air velocity had a significant effect on drying behavior of yacon slices. Drying time decreased with increasing drying temperature and air velocity. Eight mathematical models were selected to describe and compare the drying kinetics of yacon. Comparisons were based on the coefficient of determination (R²), reduced chi-square (χ²) and root mean square error (RMSE). Among the models tested, the Midilli et al. model achieved the best fit. Moisture transfer from yacon slice was described by applying the Fick’s diffusion model. Effective diffusivity coefficients (D_eff) increased with increasing drying temperature and were found to range from 1.092 to 7.388 × 10⁻⁷ m²/s. The temperature dependence of the effective diffusivity was described by the Arrhenius-type relationship and the activation energy for the diffusion of the moisture associated with the yacon was found to be 30.00 kJ/mol. Drying temperature and air velocity had little effects (p > 0.05) on the total color difference, shrinkage rate and rehydration rate of dried yacon slcies

[en] Objective: To explore the influence of dose rate reference control level on the design of accelerator shielding. Methods: According to the standards of GBZ 126-2011, GBZ/T 201.1-2007 and GBZ/T 201.2-2011, two different shielding calculation methods, based on the dose rate reference control level and week dose control level, were used to calculate and compare the thickness of accelerator room shielding. Results: Under the same condition of maximum weekly workload, the obtained results were different when the calculated dose rate reference control value was larger than dose rate reference control level (2.5 μSv/h). The maximum difference of shielding thickness reached 64 cm. Meanwhile, considering dose rate reference control level, the different accelerator rates could lead to different radiation shielding thickness. Conclusions: The dose rate at reference point must be first calculated before calculating shielding thickness. The calculation should be made on the premise that dose rate reference control level is met. (authors)

[en] Objective: To find the optimal beam arrangement for clinical cervical cancer treatment with intensity modulated radiation therapy (IMRT) technique through comparison between different beam arrangements. Methods: Six IMRT plans were designed for 10 patients with cervical cancer. The prescribed dose was 46 Gy, while the fractionated dose was 2 Gy, and 5, 7 9 equispaced beams were applied. The initial beam angle degrees were 0 and 180. The terms of target coverage, target dose uniformity, and target conformability were calculated and compared. Results: The target conformabilities between 7 and 9-beam plans were identical, and dose uniformity between the two angles beams was the best in 7-beam plan. The target coverage was satisfactory in 5-beam plan, but the dose uniformity and target conformability in it were inferior to those in 7 and 9-beam. The dose on normal tissues in 9-beam plan was not less than that in 5-beam plans, but the treatment was prolonged due to the increased segments and monitor units (MU). Conclusions: Considering the physical and biological factors during the cervical cancer treatment with IMRT, 7-beam plan would be the best choice for the beam design. (authors)

[en] Objective: To compare the accuracy of enhanced dynamic wedge (EDW) models of adaptive convolution algorithm (ACA) in Pinnacle³ 9.0 and anisotropic analytical algorithm (AAA), and pencil beam convolution (PBC) algorithms in Eclipse 7.3 treatment planning systems (TPS). Methods: To evaluate the accuracy of the three algorithm models, we compared actual measurement values with TPS calculation values of EDW wedge factors under for different fields in which Varian-21EX 6 MV X-ray was applied, and also compared the actual dose distribution profile with that of TPS. Results: The deviations of EDW wedge factors of symmetry fields and asymmetric fields are within 2.8% and 19.4% for ACA in P innacle³ 9.0. Meanwhile, the deviations are 1.0% and 2.0% for AAA, 1.2% and 3.0% for PBC in Eclipse 7.3. The deviations between measurement and calculation of all fields' profile for ACA is within 3% and within 2.7% for AAA within 4.0% for PBC in wedge direction. For the dose distributions, we evaluated the pass rates of three algorithms using gamma analysis. The gamma pass rates among all the three algorithms in symmetry and asymmetric fields are above 87% and 85% respectively. After the removal of the penumbra zone, the pass rates among all the three algorithms are above 96% in symmetry fields, and above 95% in asymmetric fields, respectively. Conclusions: AAA and PBC algorithms in symmetric and asymmetric fields can meet the need of clinical applications. While, wedge factor of ACA should not be used in clinical due to its greater error in asymmetric fields. (authors)

[en] Objective: To compare the dosimetric differences between two plans of RapidArc and 5F-IMRT for breast cancer radiotherapy after breast-conserving surgery. Methods: Eight female patients with left-sided breast cancer after breast-conserving surgery were selected. A dose of 50 Gy in 25 fractions was prescribed for plans of RapidArc and 5F-IMRT. Target conformity index (CI), homogeneity index (HI), target coverage, exposure dose volume delivered to organ at risk were compared between two plans. At the same time, treatment delivery time and monitor units (MU) were also compared. Results: The target conformity index (CI) in RapidArc plan (0.88±0.03) was higher than that in 5F-IMRT plan (0.79±0.02, t = 8.28, P < 0.05). The homogeneity index (HI) in RapidArc plan 9.01±0.73 was significantly lower than that in 5F-IMRT plan 10.44±1.08 (t = -2.73, P < 0.05). For the dose volume delivered to the ipsilateral lung in two plans, the values of V₁₀, V₂₀, V₃₀, and D_mean in RapidArc plan were lower than those in 5F-IMRT plan(t = -7.53, -7.20, -8.39, -7.80, P < 0.05). However, the value of V₅ in RapidArc plan was higher than that in 5F-IMRT plan (t = 5.67, P < 0.05). For the heart, the values of V₅, V₁₀ and D_mean in RapidArc plan were higher than those in IMRT plan (t = 10.46, 28.76, 5.40, P < 0.05), while the value of V₃₀ in RapidArc plan was lower than that in 5F-IMRT plan (t = -6.12, P < 0.05). The values of V₅ in contralateral lung and breast were higher in RapidArc plan than those in 5F-IMRT plan (lung:t = 21.50, P < 0.05; breast:t = 5.44, P < 0.05). The MU in RapidArc plan was decreased by 25%, and the average treatment delivery time was saved by 60%, compared with that of 5F-IMRT plan. Conclusions: During breast cancer radiotherapy after breast-conserving surgery, compared with 5F-IMRT plan, the RapidArc plan could improve the target HI, and reduce both the irradiated dose in high-dose volume and MU, and shorten the treatment time, but increased the exposed volume in low-dose volume of normal tissues. (authors)

[en] Objective: To evaluate the influences of various field-defining method of Varian accelerator on radiation dosimetry parameters, and provide theoretical basis for the beam modeling of the treatment planning system (TPS). Methods: The percentage depth dose (PDD), the off-axis ratio (OAR) and the total scattering factors (Scp) of radiation fields were measured in three different conditions, including collimators (JAW), multileaf collimator(MLC) and JAW + MLC. The measured data was analyzed and compared with each other. Results: The PDD of central axis was marginally influenced by three field-defining method. In both directions, the MLC-defined field sizes were larger by a maximum of 2.9 mm (left-right) or 1.7 mm (gun-target) than the JAW-defined ones. In the left-right direction, the width of field penumbra shaped by MLC was larger than the field of the same size as defined by JAW. The result of gun-target direction was to the contrary. In both directions, the field penumbra and size displayed no significant differences as defined by JAW + MLC or JAW. Conclusions: The field size, penumbra width, and the total scattering factors were influenced by field-defining method, which indicates that special attention should be paid to the dosimetric parameters of MLC during TPS beam modeling for IMRT planning. (authors)

[en] Objective: To evaluate dosimetry advantage and clinical application of hybrid intensity-modulated radiotherapy with 3DCRT/VMAT in radiotherapy with tumor bed boost after breast-conservative surgery. Methods: Ten patients with breast cancer after breast-conservative surgery were enrolled. Under the same optimization conditions, the VMAT-based hybrid planning (3DCRT + VMAT) and the IMRT-based hybrid planning (3DCRT + Imr) are designed respectively. The conformity index (CI), homogeneity index (Hi), volume of exposure dose on organs at risk in patients from two plans were compared. Results: According to the hybrid plan of 3Dcrt + VMAT, D₉₅ of Planning Target Volume (PTV) is 50.29 ± 0.25, which is superior to that from 3DCRT + IMRT, 50.69 ± 0.20 (P < 0.05). There was neither statistical difference of D₉₅ and PTV between two plans, nor difference of CI and HI of pretreatment gross tumor volume (PGTV). In the comparison with exposure dose volume delivered to the heart in two plans, the values of V₃₀ and D_mean in the plan of 3DCRT + VMAT were lower than the ones in 3DCRT + IMRT (P < 0.05). D_mean of the contra-lateral breast in the 3DCRT + VMAT group is 1.31 ± 0.44, that is inferior to the group of 3DCRT + IMRT, which is 1.88 ± 0.28 (P < 0.05). While V₅, V₁0, V₂0, D_mean of ipsilateral lung dose and D_mean of cardiac and contra-lateral lung dose had no statistical difference (P > 0.05). The monitor units (MU) of 3DCRT/VMAT Plan were 31% (P < 0.05) less than that of 3DCRT + IMRT Plan, while the average treatment time of the former plan was 38% (P < 0.05) less than the latter. Conclusion: Compared with the IMRT-based hybrid plan, the VMAT-based hybrid plan better protects the heart and the healthy breast while ensuring the conformity and uniformity of the target area, and significantly shortens the schedule execution time. Therefore, it has a high potential for clinical application. (authors)

[en] We successfully overcome the problem of cross-talk in multiplexed metasurface design and realize the multiplexed metasurface with five printing images in both theoretical and experimental aspects, by employing the coherent pixel design considering coherent superposition of all the sub-elements. Compared with most previous studies where the integrated printing images were usually no more than three, our study shows obvious improvement. More importantly, in our approach all the sub-elements, which were crystalline silicon nanobricks with the size of 320 × 80 × 230 nm³, were arranged in a square space of 1.45 × 1.45 μm² following the closest packing way, enabling our multiplexed metasurface to have a potential of effective physical information capacity of printing image reaching the optical diffraction limit. Our study not only enlarges the information capacity of metasurfaces by expanding the integrated number of printing image in one metasurface, but also can promote metasurface applications in various fields such as information storage and encoding. (paper)