The aim of this study was to explore the characteristic of 3DCT scanning phases and estimate the comparative amount of respiration motion information included in 3DCT and 4DCT by comparing the volumetric and positional difference between the volumes from 3DCT and 4DCT for the radiotherapy of non-small-cell lung cancer (NSCLC). A total of 28 patients with NSCLC sequentially underwent 3DCT and 4DCT simulation scans of the thorax during free breathing. The 4DCT images with respiratory signal data were reconstructed and sorted into 10 phases throughout a respiratory cycle. GTV-3D from 3DCT, GTV-0%, GTV-20%, GTV-50% and GTV-70% from end-inspiration, mid-expiration, end-expiration and mid-inspiration of 4DCT, and the internal GTV (IGTV-10) from the fused phase of 4DCT were delineated based on the 50% phase image, respectively. The differences in the position, size, matching index (MI) and degree of inclusion (DI) for different volumes were evaluated. The variation in the centroid shifts of GTV-0% and GTV-3D, GTV-20% and GTV-3D, GTV-50% and GTV-3D, and GTV-90% and GTV-3D in the 3D direction was not significant (P = 0.990). The size ratios of GTV-0%, GTV-20%, GTV-50%, GTV-70% and IGTV-10 to GTV-3D were 0.94 ± 0.18, 0.95 ± 0.18, 0.98 ± 0.15, 1.00 ± 0.18 and 1.60 ± 0.55, respectively. DIs of GTV-3D in IGTV-10, and IGTV-10 in GTV-3D were 0.88 ± 0.14 and 0.59 ± 0.16 (P < 0.001). The 3DCT scanning phases are irregular. The CTV-to-ITV expansion should be isotropic when defining the ITV on the 3DCT. The internal GTV derived from 4DCT cannot completely include the GTV from 3DCT. An additional margin may be required when defining the ITV-based 4DCT.
To explore the clip and the geometrical center displacements based on the four-dimensional computed tomography (4DCT) for external-beam partial breast irradiation (EB-PBI), fourteen breast cancer patients treated with breast-conserving surgery were recruited for EB-PBI and undertook 4DCT simulation during free breathing. The displacements of the selected clips and the geometrical center at left-right (LR), anterior-posterior (AP) and superior-inferior (SI) directions were measured. The comparison and the correlation of the displacement between the selected clips and the geometric center were analyzed. The displacements in AP and SI were greater than that in LR for the same selected clip (P < 0.05). Almost all the displacements of the geometrical center were greater than that of the selected clips in the same direction, (P < 0.05), except the displacements of lower clip in SI direction. The displacement of the geometric center showed a statistical correlation with the upper clip and lower clip in SI direction (both P < 0.05). Therefore, the internal margin in AP and SI directions should be greater than LR direction for the purpose of adequate target coverage and sparing more normal tissue. This study also indicates that the displacement of a single clip was not qualified to substitute for the displacement of the target based on all clips of the surgical cavity.
As new advanced vehicles, electromagnetic suspension (EMS)-type maglev trains have received wide attention because of their advantages such as high speed, no mechanical friction, low noise, low cost and energy consumption, strong climbing ability, and green environmental protection. The open-loop instability is one of the key points and difficulties for the levitation control systems of maglev trains. The closed-loop feedback control method must be applied to realize stable levitation. However, there are currently many levitation control methods just in theory. Considering their advantages and disadvantages, it is a major demand for maglev trains to select efficient, stable, applicable, and cost-saving methods to improve their dynamic performance and safety, which motivated this review. First, the current status of research on maglev trains is introduced in this paper, including types, system components, and research modes in various countries, followed by an analysis of the levitation control methods for EMS-type maglev trains. Then, the technical characteristics of the levitation control systems are described according to the basic principles of levitation systems, model building, mathematical derivation, and control objectives. Next, three kinds of typical levitation control methods are reviewed, namely, linear state feedback methods, nonlinear control methods, and intelligent control methods, according to their improvements and applications. Lastly, we summarize and evaluate the advantages and disadvantages of the three methods, and future developments of levitation control are suggested.
Photoinduced metal–organic framework (MOF) enabled heterogeneous thiol catalysis has been achieved for the first time. MOF Zr‐TPDCS‐1, consisting of Zr6‐clusters and TPDCS linkers (TPDCS=3,3′′,5,5′′‐tetramercapto[1,1′:4′,1′′‐terphenyl]‐4,4′′‐dicarboxylate), effectively catalyzed the borylation, silylation, phosphorylation, and thiolation of organic molecules. Upon irradiation, the fast electron transfer from TPDCS to Zr6‐cluster is believed to facilitate the formation of the thiyl radical, a hydrogen atom transfer catalyst, which competently abstracts the hydrogen from borane, silane, phosphine, or thiol for generating the corresponding element radical to engender the chemical transformations. The elaborate control experiments evidenced the generation of thiyl radicals in MOF and illustrated a radical reaction pathway. The gram‐scale reaction worked well, and the product was conveniently separated via centrifugation and vacuum with a turnover number (TON) of ≈3880, highlighting the practical application potential of heterogeneous thiyl‐radical catalysis.
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