[Technical Status and Development Trend of Medical Electron Linear Accelerators].

More than 70% of tumor patients require radiotherapy. Medical electron linear accelerators are important high-end radiotherapy equipment for tumor radiotherapy. With the application of artificial intelligence technology in medical electron linear accelerator, radiotherapy has evolved from ordinary radiotherapy to today's intelligent radiotherapy. This study introduces the development history, working principles and system composition of medical electron linear accelerators. It outlines the key technologies for improving the performance of medical linear electron accelerators, including beam control, multi-leaf collimator, guiding technology and dose evaluation. It also looks forward to the development trend of major radiotherapy technologies, such as biological guided radiotherapy, FLASH radiotherapy and intelligent radiotherapy, which provides references for the development of medical electron linear accelerators.

[Structural Design and Penumbra Analysis of Dynamic Multi-leaf Collimator Leaf End].

Dynamic multi-leaf collimator, which has the function of radiation beam shaping, is a key executive component of tumor precise radiotherapy, and plays a core role in improving the accuracy, efficiency and quality of radiotherapy. A new type of collimator leaf end structure with circular arc and plane combination was studied, and collimator penumbra performance analysis model combining analytical expression and graphic analysis was developed. The influence of leaf end structure on penumbra was analyzed quantitatively, and a set of three-dimensional structure design of dynamic multi-leaf collimator was completed. The feasibility of the structural design and analysis model was verified through experimental measurements.

Efficacy and safety of extracorporeal shock wave on low back pain: A systematic review and meta-analysis.

BACKGROUND: Extracorporeal shock wave therapy (ESWT) is a relatively new type of treatment for many musculoskeletal disorders. However, ESWT for low back pain remains controversial as the pain relieve benefit is questionable. We performed this systematic review and meta-analysis to explore the effectiveness and safety of ESWT interventions on pain and disability in patients with low back pain (LBP). METHODS: In this meta-analysis, we searched electronic databases in the Pubmed, Embase, Cochrane's library, China National Knowledge Infrastructure, and Wanfang Database to determine the equivalence of ESWT and placebo for the treatment of LBP up to April 4, 2022. A number of other outcomes were measured, including functional status, quality of life, and psychological outcomes measured by the Oswestry Disability Index. Weighted mean differences were calculated for continuous outcomes, while risk ratios were calculated for binary outcomes. Stata 12.0 software was used for statistical analysis. RESULTS: Thirteen randomized controlled trials included for further analysis. Compared with control, the ESWT group showed lower pain intensity at month 1 (P < .05), as well as lower disability score at month 1 (P < .05) and at month 3 (P < .05). There was no statistically significant difference between ESWT and control groups in terms of the pain intensity at month 3 (P > .05). No serious adverse events related to treatment were reported. Sensitivity analysis demonstrates that the conclusions from this analysis were robust. CONCLUSIONS: ESWT is effective in alleviating pain and improving the functional outcomes for patients with LBP. However, there remains a lack of high-level evidence to verify their effectiveness and safety and support their clinical application.

Positive and negative photoion spectroscopy study of monochlorothiophenes.

Photolysis dynamics of monochlorothiophenes (2- and 3-chlorothiophenes) is investigated using positive and negative photoion mass spectrometry combined with the synchrotron vacuum ultraviolet radiation. A dozen of the daughter cations are observed in the time-of-flight mass spectra, and their appearance energies are determined by the photoion efficiency spectroscopy measurements. At the energetic threshold, the concerted process rather than a stepwise reaction for C(4)H(3)SCl(+) → C(2)HSCl(+) + C(2)H(2) and the ring-open isomers of the dehydrogenated thiophene cations (C(4)H(3)S(+) and C(4)H(2)S(+)) formed in C(4)H(3)SCl(+) → C(4)H(3)S(+) + Cl and C(4)H(2)S(+) + HCl are proposed on the basis of the B3LYP/6-311+G(3df,3pd) calculations. The chlorine anion (Cl(-)) is observed as the product of the photoion-pair dissociations in the energy range of 10.70-22.00 eV. A set of valence-to-Rydberg state transitions 12a' → np (n = 6, 7, 8, 9, 10, etc.) and several series of vibrational excitations are tentatively assigned in the Cl(-) spectrum of 2-chlorothiophene in the lower energy range of 10.90-12.00 eV.

Vacuum ultraviolet negative photoion spectroscopy of chloroform.

Negative ions Cl(-), Cl(2)(-), CCl(-), CHCl(-), and CCl(2)(-) are observed in vacuum-ultraviolet ion-pair photodissociations of chloroform (CCl(3)H) using the Hefei synchrotron radiation facility, and their ion production efficiency curves are recorded in the photon energy range of 10.00-21.50 eV. Two similar spectra of the isotope anions (35)Cl(-) and (37)Cl(-) indicate the following: Besides the strong bands corresponding to the electron transitions from valence to Rydberg orbitals converging to the ionic states, some additional peaks can be assigned with the energetically accessible multibody fragmentations; a distinct peak at photon energy 14.55 eV may be due to a cascade process (namely, the Cl(2) neutral fragment at the highly excited state D'2(3)Π(g) may be produced in the photodissociation of CCl(3)H, and then the Cl(-) anions are produced in the pulsed-field induced ion-pair dissociations of Cl(2) (D'2(3)Π(g))); two vibrational excitation progressions, nν(2)(+) and nν(2)(+) + ν(3)(+), and nν(4)(+) and nν(4)(+) + ν(2)(+), are observed around C̃ (2)E and D̃ (2)E ionic states, respectively. The enthalpies of the multibody fragmentations to Cl(2)(-), CCl(-), CHCl(-), and CCl(2)(-) are calculated with the thermochemistry data available in the literature, and these multibody ion-pair dissociation pathways are tentatively assigned in the respective anion production spectra.