[Questionnaire Survey of Hands-on Seminar Using a Web Conferencing System in the COVID-19 Pandemic].

The purpose of this study was to evaluate the effectiveness of a hands-on seminar using a Web conferencing system, based on the post-event questionnaires of the face-to-face and online seminars of the hands-on seminar. For participants to feel realistic training in the online seminars, four educational videos explaining the procedure of the practical skill were created. We compared results of questionnaires acquired from participants after the face-to-face and online seminars. The questions about expectation, comprehension, satisfaction level, and lecture time for the seminars were graded on a 5-point scale. The higher the scores, the higher the rating, except for lecture time. A score of 3 was appropriate for the lecture time, with a higher score indicating that the seminar felt longer and a lower score indicating that the seminar felt shorter. In the evaluation of classroom lectures, such as expectation, comprehension, and satisfaction level for the seminars, there were no significant differences between the face-to-face and online seminars, and both achieved high scores of 4 or more. There was a significant difference in the evaluation of lecture time for classroom lectures, with participants feeling that it was too short in the face-to-face but just right in the online. In all evaluations for hands-on training and discussion, there were no significant differences between the face-to-face and online seminars, and both achieved high scores of 4 or more and time was short. It was concluded that our proposed online seminar approach could achieve a high level of evaluation as face-to-face seminars.

[Impact of Respiratory Motion on Point Doses for Three Whole-breast Irradiation Techniques after Breast-conserving Surgery].

PURPOSE: For whole-breast irradiation after breast-conserving surgery, computed tomography simulation (CTS) and irradiation are generally performed during free breathing. In treatment planning, there are three techniques: field-in-field (FIF), physical wedge (PW), and enhanced dynamic wedge (EDW). The aim of this study was to investigate the impact of respiratory motion on doses for these three irradiation techniques. METHODS: All doses were measured using an ionization chamber in a cylindrical phantom on a respiratory motion platform. Doses for each technique were measured with and without phantom motion. The dose without phantom motion was defined as the reference. The reference was compared to the dose with the phantom motion. The positions of the isocenter with respect to the ranges of phantom motion were set as exhale and intermediate. The phantom motion amplitude was set to 5 mm or 10 mm. The respiratory phase to initiate irradiation was varied as inhale, intermediate-inhale, exhale and intermediate-exhale. RESULTS: When the motion amplitude was 10 mm, the dose differences for the FIF, PW, and EDW techniques were 4.2%, 0.5%, and 0.8%, respectively, at the maximum. However, the dose difference for the FIF technique was -0.5% when the isocenter position was set to the intermediate phase of phantom motion. CONCLUSION: We found that the dose difference per fraction was reduced when the respiratory phase during CTS image acquisition was set to the intermediate phase. Meanwhile, the dose differences per fraction for the PW and EDW techniques were less affected by the respiratory motion.

[Effect of Gantry Speed on Image Quality of Four-dimensional Cone-beam Computed Tomography Using a Dynamic Phantom of Lung].

PURPOSE: The purpose of this paper was to determine the optimal imaging conditions for four-dimensional cone-beam computed tomography (4D-CBCT) using an X-ray tube and a flat-panel detector mounted on a radiotherapy device. METHODS: The optimal imaging conditions were examined by changing the gantry speed (GS) parameter that affected the exposure time. Exposed dose during imaging and image quality of moving phantom were compared between examined conditions. RESULTS: The weighted computed tomography dose index (CTDIW) decreased linearly with increasing GS. However, when GS was 180°/min or faster, the image quality degraded, and errors of 1 mm or more were observed regarding the size of mock tumor in the moving phantom. The accuracy of automatic image matching was within 0.1 mm when GS of 120°/min or slower was chosen. CONCLUSION: From the results of this study, we concluded that GS of 120°/min is the optimum imaging condition. Under this imaging condition, the exposure time and CTDIW can be reduced by about 50% without compromising the accuracy of image registration, compared to the conventional GS of 70°/min. In addition, it has been clarified that there is an event that image reconstruction is not performed correctly due to the influence of phantom artifacts without depending on GS.

The structure of SrTiO3(001)-2 × 1 surface analyzed by high-resolution medium energy ion scattering coupled with ab initio calculations.

High-resolution medium energy ion scattering (MEIS) spectrometry coupled with photoelectron spectroscopy revealed unambiguously that the initial SrTiO3(001) surface chemically etched in a buffered NH4F-HF solution was perfectly terminated with a single-layer (SL) of TiO2(001) and annealing the surface at 600-800 [ordinal indicator, masculine]C in ultrahigh vacuum (UHV) led to a (2 × 1)-reconstructed surface terminated with a double-layer (DL) of TiO2(001). After annealing in UHV, rock-salt SrO(001) clusters with two atomic layer height grew epitaxially on the DL-TiO2(001)-2 × 1 surface with a coverage of 20%-30%. High-resolution MEIS in connection with ab initio calculations demonstrated the structure of the DL-TiO2(001)-2 × 1 surface close to that proposed by Erdman et al. [Nature (London) 419, 55 (2002)] rather than that predicted by Herger et al. [Phys. Rev. Lett. 98, 076102 (2007)]. Based on the MEIS analysis combined with the ab initio calculations, we propose the most probable (2 × 1) surface structure.