Robust adaptive output stabilization using dynamic normalizing signal

For a class of nonlinear systems with dynamic uncertainties, robust adaptive stabilization problem is considered in this paper. Firstly, by introducing an observer, an augmented system is obtained. Based on the system, we construct an exp-ISpS Lyapunov function for the unmodeled dynamics, prove that the unmodeled dynamics is exp-ISpS, and then obtain a dynamic normalizing signal to counteract the dynamic disturbances. By the backstepping technique, an adaptive controller is given, it is proved that all the signals in the adaptive control system are globally uniformly ultimately bounded, and the output can be regulated to the origin with any prescribed accuracy. A simulation example further demonstrates the efficiency of the control scheme.

Application of interventional therapy via hepatic artery in pancreatic neuroendocrine neoplasms liver metastases

Pancreatic neuroendocrine neoplasm(PNEN)is the second most common malignant tumor of the pancreas.It has the characteristic of high metastases rate,and the liver is the most common site for metastasis.Metastasis affects prognosis and survival seriously.A number of earlier studies have shown that the interventional therapy via hepatic artery could reduce hepatic tumor burden and hormone secretion safely and rapidly,significantly improve objective response rate(ORR),and enhance the efficacy and prolong the survival time when combined with system therapy.The interventional therapy via hepatic artery plays an important role in the treatment of PNEN liver metastases.Interventional therapy via hepatic artery could possibly increase ORR,prolong progression-free survival,and even overall survival for appropriate patients.

A new Chinese standard for testing of quality control in medical proton/heavy ion beam radiotherapy equipment

With the development of social economy and radiotherapy technique,proton/heavy ion radiotherapy has been applied widely to clinical practices.At present,there are at least 29 hospitals in China at various stages of planning,construction,commissioning or clinical operation of medical proton/heavy ion beam radiotherapy equipment.Compared with common radiotherapy accelerators used in conventional external beam radiotherapy,the proton/heavy ion therapy system has more stringent requirements for quality control so as to achieve an optimum therapeutic effect.In order to protect the health rights of patients undergoing radiotherapy,to facilitate the relevant administrative supervision departments to carry out standard-based approval and routine supervision and to promote the development of related medical undertakings,the standard for testing of quality control for medical proton/heavy ion beam radiotherapy equipment is drafted to fill the gap in this regard in China and even worldwide.The standard contains five indicators and corresponding testing methods for radiological protection and safety and 16 indicators for quality control of equipment performance.The standard is a mandatory standard and is based on the relevant Chinese legal requirements for the testing of radiotherapy equipment,so all the indicators listed in the standard shall be tested.During the drafting of the standard,the opinions from hospitals that are currently using proton/heavy ion medical accelerators for radiotherapy purpose and from the related equipment manufacturers were taken into account.The draft standard was revised with reference to these opinions and the feasibility of the related quality control requirements.The official version of the standard was released on March 7,2023,and implementation is scheduled to begin on March 1,2024.

Construction of a computational MDCT model for simulations of the detector signals

Objective:To develop a computational model of a multi-detector CT scanner(MDCT),which could be used to simulate the signal of each detector element in the MDCT by using the Monte Carlo method.Methods:The CT scanner was modelled,including the X-ray source,the bowtie filter,the collimator,the couch and the detector panel.Under a general scanning condition,the signal in each detector element was simulated based on the model by using the MCNPX code.Both the energy spectra at different tube voltages and energy deposition in the detector panel at different collimations were simulated to test the robustness of the MDCT model built in this study.Furthermore,the simulated signals in each detector element were compared with their recorded signals.The accuracies were evaluated by the relative root mean square error(RRMSE)and the structural similarity(SSIM)for each detector element and the whole detector panel,respectively.Results:The simulated energy spectra before and after passing through the phantom and simulated energy deposition in the detector panel were rational.In the scan range from the apex of lung to pubic symphysis,the RRMSE of the 18 axial projections ranged from 0.02 to 0.17,with an average of 0.08.And the SSIMs were calculated to be 0.979 and 0.976 for projections with the largest peak signal and the smallest peak signal,respectively.Conclusions:The computational model of the MDCT developed in this study is accurate and successful,it is helpful for further accurate simulations of the radiation dose and image quality of the MDCT.