[en] The high-temperature mechanical behaviour of a pre-industrial hybrid alkaline cement (HYC) was studied. The HYC in question contained 30 % Portland clinker and 70 % of a blend of slag, fly ash and a solid activator (mix of alkaline salts with a predominance of Na2SO4). The material was tested during exposure to high temperatures to establish its compressive and bending strength and elastic modulus, as well as fracture toughness, analysed using an innovative methodology to notch the hydrated cement paste specimens. Post-thermal treatment tests were also run to assess residual mechanical strength after 2 h of exposure to temperatures ranging from 400 °C to 1000 °C. TG/DTA, MIP and SEM were deployed to ascertain heat-induced physical-chemical changes in the structure. The higher mechanical strength during and after treatment exhibited by the hardened hybrid alkaline cement than the CEM I 42.5R ordinary portland cement (OPC) paste used as a reference was associated with the lower water and portlandite content found in HYC. Pseudo-plastic behaviour was observed at high temperatures in the loaded HYC in the tests conducted during exposure.

[en] The effect of Ta buffer layer in IrMn top spinvalve using high vacuum DC magnetron sputtering was investigated. An optimized thickness (3 nm) of the Ta buffer layer was proposed. With the 3 nm thick Ta buffer layer, high magnetoresistance ratios of 9.24%, an exchange bias field of 255x(10³/4π) A/m and a coercivity of 2.43x(10³/4π) A/m were obtained. These spinvalve structures can be the promising candidate of the robust giant magnetoresistance sensors for automobile and industrial-control system applications

[en] Purpose: To develop a tool for treatment planning optimization for fast radiotherapy delivered with very high-energy electron beams (VHEE) and to compare VHEE plans to state-of-the-art plans for challenging pelvis and H'N cases. Methods: Treatment planning for radiotherapy delivered with VHEE scanning pencil beams was performed by integrating EGSnrc Monte Carlo (MC) dose calculations with spot scanning optimization run in a research version of RayStation. A Matlab GUI for MC beamlet generation was developed, in which treatment parameters such as the pencil beam size and spacing, energy and number of beams can be selected. Treatment planning study for H'N and pelvis cases was performed and the effect of treatment parameters on the delivered dose distributions was evaluated and compared to the clinical treatment plans. The pelvis case with a 691cm3 PTV was treated with 2-arc 15MV VMAT and the H'N case with four PTVs with total volume of 531cm3 was treated with 4-arc 6MV VMAT. Results: Most studied VHEE plans outperformed VMAT plans. The best pelvis 80MeV VHEE plan with 25 beams resulted in 12% body dose sparing and 8% sparing to the bowel and right femur compared to the VMAT plan. The 100MeV plan was superior to the 150MeV plan. Mixing 100 and 150MeV improved dose sparing to the bladder by 7% compared to either plan. Plans with 16 and 36 beams did not significantly affect the dose distributions compared to 25 beam plans. The best H'N 100MeV VHEE plan decreased mean doses to the brainstem, chiasm, and both globes by 10-42% compared to the VMAT plan. Conclusion: The pelvis and H'N cases suggested that sixteen 100MeV beams might be sufficient specifications of a novel VHEE treatment machine. However, optimum machine parameters will be determined with the presented VHEE treatment-planning tool for a large number of clinical cases. BW Loo and P Maxim received research support from RaySearch Laboratories. E Hynning and B Hardemark are employees of RaySearch Laboratories

[en] Purpose: We evaluated the effect of very high-energy electron (VHEE) beam parameters on the planning of a lung cancer case by means of Monte Carlo simulations. Methods: We simulated VHEE radiotherapy plans using the EGSnrc/BEAMnrc-DOSXYZnrc code. We selected a lung cancer case that was treated with 6MV photon VMAT to be planned with VHEE. We studied the effect of beam energy (80 MeV, 100 MeV, and 120 MeV), number of equidistant beams (16 or 32), and beamlets sizes (3 mm, 5 mm or 7 mm) on PTV coverage, sparing of organs at risk (OARs) and dose conformity. Inverse-planning optimization was performed in a research version of RayStation (RaySearch Laboratories AB) using identical objective functions and constraints for all VHEE plans. Results: Similar PTV coverage and dose conformity was achieved by all the VHEE plans. The 100 MeV and 120 MeV VHEE plans were equivalent amongst them and were superior to the 80 MeV plan in terms of OARs sparing. The effect of using 16 or 32 equidistant beams was a mean difference in average dose of 2.4% (0%–7.7%) between the two plans. The use of 3 mm beamlet size systematically reduced the dose to all the OARs. Based on these results we selected the 100MeV-16beams-3mm-beamlet-size plan to compare it against VMAT. The selected VHEE plan was more conformal than VMAT and improved OAR sparing (heart and trachea received 125% and 177% lower dose, respectively) especially in the low-dose region. Conclusion: We determined the VHEE beam parameters that maximized the OAR dose sparing and dose conformity of the actually delivered VMAT plan of a lung cancer case. The selected parameters could be used for the planning of other treatment sites with similar size, shape, and location. For larger targets, a larger beamlet size might be used without significantly increasing the dose. B Palma: None. M Bazalova: None. B Hardemark: Employee, RaySearch Americas. E Hynning: Employee, RaySearch Americas. B Qu: None. B Loo Jr.: Research support, RaySearch, Varian. P Maxim: Research support, RaySearch, Varian

[en] Purpose: To evaluate the effect of metal implants on treatment plans for radiation therapy with very high-energy electron (VHEE) beams. Methods: The DOSXYZnrc/BEAMnrc Monte Carlo (MC) codes were used to simulate 50–150MeV VHEE beam dose deposition and its effects on steel and titanium (Ti) heterogeneities in a water phantom. Heterogeneities of thicknesses ranging from 0.5cm to 2cm were placed at 10cm depth. MC was also used to calculate electron and photon spectra generated by the VHEE beams' interaction with metal heterogeneities. The original VMAT patient dose calculation was planned in Eclipse. Patient dose calculations with MC-generated beamlets were planned using a Matlab GUI and research version of RayStation. VHEE MC treatment planning was performed on water-only geometry and water with segmented prostheses (steel and Ti) geometries with 100MeV and 150MeV beams. Results: 100MeV PDD 5cm behind steel/Ti heterogeneity was 51% less than in the water-only phantom. For some cases, dose enhancement lateral to the borders of the phantom increased the dose by up to 22% in steel and 18% in Ti heterogeneities. The dose immediately behind steel heterogeneity decreased by an average of 6%, although for 150MeV, the steel heterogeneity created a 23% increase in dose directly behind it. The average dose immediately behind Ti heterogeneities increased 10%. The prostate VHEE plans resulted in mean dose decrease to the bowel (20%), bladder (7%), and the urethra (5%) compared to the 15MV VMAT plan. The average dose to the body with prosthetic implants was 5% higher than to the body without implants. Conclusion: Based on MC simulations, metallic implants introduce dose perturbations to VHEE beams from lateral scatter and backscatter. However, when performing clinical planning on a prostate case, the use of multiple beams and inverse planning still produces VHEE plans that are dosimetrically superior to photon VMAT plans. BW Loo and P Maxim received research support from RaySearch laboratories; B Hardemark and E Hynning are employees of RaySearch

[en] Purpose: To evaluate the performance of 100–120 MeV very-high energy electron (VHEE) scanning pencil beams to radiotherapy by means of Monte Carlo (MC) simulations. Methods: We selected five clinical cases with target sizes of 1.2 cm"3 to 990.4 cm"3. We calculated VHEE treatment plans using the MC EGSnrc code implemented in a MATLAB-based graphical user interface developed by our group. We generated phase space data for beam energies: 100 and 120 MeV and pencil beam spot sizes of 1, 3, and 5 mm at FWHM. The number of equidistant beams considered in this work was 16 or 32. Dose was calculated and then imported into a research version of RayStation where treatment plan optimization was performed. We compared the VHEE plans with the clinically delivered volumetric modulated arc therapy (VMAT) plan to evaluate VHEE plans performance. Results: VHEE plans provided the same PTV coverage and dose homogeneity than VMAT plans for all the cases. In average, the mean dose to organs at risk (OARs) was 24% lower for the VHEE plans. The structures that benefited the most from using VHEE were: large bowel for the esophagus case, chest wall for the liver case, brainstem for the acoustic case, carina for the lung case, and genitalia for the anal case, with 23.7–34.6% lower dose. VHEE dose distributions were more conformal than VMAT solution as confirmed by conformity indices CI100 and CI50. Integral dose to the body was in average 19.6% (9.2%–36.5%) lower for the VHEE plans. Conclusion: We have shown that VHEE plans resulted in similar or superior dose distributions compared to clinical VMAT plans for five different cases and a wide range of target volumes, including a case with a small target (1.2 cm"3), which represents a challenge for VMAT planning and might require the use of more complex non-coplanar VMAT plans. B Palma: None. M Bazalova: None. B Hardemark: Employee, RaySearch Laboratories AB. E Hynning: Employee, RaySearch Laboratories AB. B Qu: None. B Loo Jr.: Research support, RaySearch, Varian. P Maxim: Research support, RaySearch, Varian

[en] Purpose: To quantitatively evaluate the strategic innovation and accuracy variation of deformation registration algorithm for parotid glands using the similarity Dice coefficient during the course of radiation therapy (RT) for nasopharyngeal cancer (NPC). Methods: Daily MVCT data for 10 patients with pathologically proven nasopharyngeal cancers were analyzed. The data were acquired using tomotherapy (TomoTherapy, Accuray) at the PLA General Hospital. The prescription dose to the primary target was 70Gy in 33 fractions. Two kinds of contours for parotid glands on daily MVCTs were obtained by populating these contours from planning CTs to the daily CTs via rigid-body registration with or without the rotation shifts using the in-house tools and the Adaptive plan software (Adaptive Plan, TomoTherapy), and were edited manually if necessary. The diffeomorphic Demons algorithm developed in the in-house tool was used to propagate the parotid structures from the daily CTs to planning CTs. The differences of the mapped parotid contours in two methods were evaluated using Dice similarity index (DSI). Two-tailed t-test analysis was carried out to compare the DSI changes during the course of RT. Results: For 10 patient plans, the accuracy of deformation image registration (DIR) with the rotation shift was obviously better than those without the rotation shift. The Dice scores of the ipsi- and contra-lateral parotids for with and without the rotation shifts were found to be correlated with each other [0.904±0.031 vs 0.919±0.030 (p<0.001); 0.900±0.031 vs 0.910±0.032 (p<0.001)]. The Dice scores for the parotids have shown the reduction with the changes of parotid volumes during RT. The DSI values between the first and last fraction were 0.932±0.020 vs 0.899±0.030 in 10 patient plans. Conclusion: DIR was successfully improved using the strategic innovation for ART. And the decrease of DIR accuracy has also been found during the delivery of fractionated radiotherapy. This work was supported in part by the grant from Chinese Natural Science Foundation (Grant No. 11105225).

[en] Ferromagnetic Fe₃O₄-doped MgB₂ bulks were first fabricated in this work by the hot pressing method. It was found that Fe₃O₄ does not react with Mg or B during the fabrication process. Peak J_c values of the 5 wt% Fe₃O₄-doped MgB₂ are higher than 10⁶ A cm^-2 in the temperature range 5-30 K. Especially at 30 K, the peak J_c is 1.02 x 10⁶ A cm^-2 for the 5 wt% Fe₃O₄-doped MgB₂, the highest values at 30 K found in the literature, and about seven times that of the 5 wt% SiC-doped MgB₂ sample. The drop in J_c with increasing field for the Fe₃O₄-doped MgB₂ is significantly slower than that of the SiC-doped MgB₂ at 30 K. These results indicate that the Fe₃O₄-doped MgB₂ is a potential superconductor to be used at temperatures greater than 25 K which is a critical temperature for large-scale practical applications.

[en] The effects of growth time on the structure and morphology of cubic GaN nucleation layers on GaAs(001) substrates by metalorganic chemical vapor deposition (MOCVD) have been investigated using a synchrotron X-ray diffraction (XRD). The XRD results show that the GaN 111 reflections at 54.74 degree in x are a measurable component, however the 002 reflections parallel to GaAs(001) surface are not detected. The XRD Φ scans and pole figures give a convincing proof that the GaN nucleation layers show exactly the cubic symmetrical structure. The coherence lengths along the close-packed <111> direction estimated from the 111 peak are nanometer order of magnitude. The optimal photoluminescence (PL) spectrum was obtained from the cubic GaN layer deposited on the nucleation layer for 60 sec

[en] Purpose: This study will use Monte Carlo to simulate the Cyberknife system, and intend to develop the third-party tool to evaluate the dose verification of specific patient plans in TPS. Methods: By simulating the treatment head using the BEAMnrc and DOSXYZnrc software, the comparison between the calculated and measured data will be done to determine the beam parameters. The dose distribution calculated in the Raytracing, Monte Carlo algorithms of TPS (Multiplan Ver4.0.2) and in-house Monte Carlo simulation method for 30 patient plans, which included 10 head, lung and liver cases in each, were analyzed. The γ analysis with the combined 3mm/3% criteria would be introduced to quantitatively evaluate the difference of the accuracy between three algorithms. Results: More than 90% of the global error points were less than 2% for the comparison of the PDD and OAR curves after determining the mean energy and FWHM.The relative ideal Monte Carlo beam model had been established. Based on the quantitative evaluation of dose accuracy for three algorithms, the results of γ analysis shows that the passing rates (84.88±9.67% for head,98.83±1.05% for liver,98.26±1.87% for lung) of PTV in 30 plans between Monte Carlo simulation and TPS Monte Carlo algorithms were good. And the passing rates (95.93±3.12%,99.84±0.33% in each) of PTV in head and liver plans between Monte Carlo simulation and TPS Ray-tracing algorithms were also good. But the difference of DVHs in lung plans between Monte Carlo simulation and Ray-tracing algorithms was obvious, and the passing rate (51.263±38.964%) of γ criteria was not good. It is feasible that Monte Carlo simulation was used for verifying the dose distribution of patient plans. Conclusion: Monte Carlo simulation algorithm developed in the CyberKnife system of this study can be used as a reference tool for the third-party tool, which plays an important role in dose verification of patient plans. This work was supported in part by the grant from Chinese Natural Science Foundation (Grant No. 11275105). Thanks for the support from Accuray Corp.