Comparison of drug-eluting stent and bare-mental stent in the complex small vessel intervention.
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Adult↗
Biomedical subjects
Qing Hou
Publications and source records attributed to Qing Hou.
[Compare drug-eluting stent to bare-metal stent in prognosis on treating diffuse coronary lesions].
OBJECTIVE: Compare drug-eluting stent (DES) to bare-metal stent (BMS) in prognosis on treating diffuse coronary lesions and analysis risk factor of treating complex and diffuse lesions in PCI. METHODS: 205 consecutive patients with complex and diffuse coronary lesions enrolled our hospital, who were treated with more than 25 mm long DES or BMS. We exclude unsuccessful operation and location. All patients received medical treatment by guideline, and aspirin 300 mg and clopidogrel 75 mg once daily were continued at 6 months after the procedure. The patients were followed up after 6 months. RESULTS: The study population were consisted of 205 patients that there were 181 man, and 24 women, who got 382 stents for 227 target lesions in coronary. There were 93.8% C and 6.2% B2 ACC/AHA type lesion. There were 86.8% patients with binary or above vessel treated. The average reference vessel diameter was 2.88 +/- 0.43 mm. The average stent length of per lesion was 40.09 +/- 12.94 mm. There were 54.2% lesions treated with overlapping stent. There were not different between DES and BMS in patients baseline characteristics, but RVD of group DES less than of group BMS (2.80 +/- 0.37 mm, 3.10 +/- 0.48 mm, P = 0.005) in lesion baseline characteristics. After 6 months, restenosis rate in group DES was less than in group BMS (15.4%, 48.4%, P < 0.001). There were obvious superiority TVR of DES than of BMS (11.6%, 38.5%, P < 0.001). The rate of local restenosis in group of DES was higher than that in group of BMS (33.3%, 18.2%, P = 0.029). We analyzed the risk factors for diffuse lesion by a logistic regression model, the significant univariate clinical and angiographic predictors of restenosis were treating with overlapping stent (OR = 2.82, P = 0.017) and drug-eluting stent (OR = 5.71, P < 0.001). CONCLUSIONS: We find that implantation of DES in patients with diffuse lesions in coronary is relatively more safe and associated with more good clinical outcomes, than of BMS.
Aged↗
[The field shape optimization in conformal radiation therapy by MLC rotation].
Conformal radiation therapy using multi-leaf collimator (MLC) is considered as a conventional technology in the hospital nowadays. However the stepped leaf edge caused by the finite width of the leaves could influence the conformality that could be achievable. In this paper, the effect produced by rotating the collimator angle on the conformality was investigated. A method, in which multiple MLC fields of various rotation angles are applied, has been proposed to have the targets be more uniformly irradiated and thus to eliminate the cold spots on the targets and hot spots in normal tissues. By simulation, it has been shown that the multiple MLC field method can eliminate the stepped leaf edges and improve the conformality significantly, moreover, the PTV can receive a more uniform delivery with cold spot eliminated.
Humans↗
[Enhanced digitally reconstructed radiographs generated by ray tracing].
Digitally reconstructed radiographs (DRR) which greatly contribute to the quality control of radiotherapy are critical element in the process of virtual simulation in radiotherapy. In this paper, an algorithm based on ray tracing has been used to generate the DRR. By applying an exponential transformation to the electronic density determined by CT value, the generated DRR can be enhanced by adjusting the attenuation and the transformation parameter.
Computer Simulation↗
A graph-searching method for MLC leaf sequencing under constraints.
A new leaf-sequencing algorithm for step-and-shoot IMRT that is based on a graph-searching technique is described. An iterative process guided by a quantitative measure for the complexity of the initial or residual intensity pattern is used to identify the field segments shaped by a multileaf collimator (MLC). Given a user selected number of intensity levels, the algorithm searches deliverable segment candidates considering all intensity levels and two collimator positions separated by 90 degrees. The candidates for each intensity level are obtained as the least number of segments to cover the areas with equal or higher intensity. The shape of a deliverable segment is adjusted by leaving out certain beam elements for later delivery if this results in a simpler residual intensity pattern and the segment is still deliverable. For a MLC design that does not allow leaf interdigitation, it is initially assumed that a single segment cannot cover two disjoined areas. Among all candidates the segment with the greatest reduction of the complexity of the residual intensity distribution is chosen for the current step of iteration. The iterative process generates a set of deliverable segments of simply connected areas. These segments are combined later under specific MLC constraints. Different orders of segment combination are considered for minimizing the beam-on time. The final segments are sequenced to minimize the leaf travel. This algorithm has been tested using randomly generated intensity distributions and clinical cases for the Varian, Siemens, and Elekta MLC systems. The results show that as the number of intensity levels is increased, the numbers of segments and MUs increase only modestly. Using two collimator angles results in decreases in the required number of segments and the number of monitor units that can be as much as 20%.
Algorithms↗
A method to improve spatial resolution and smoothness of intensity profiles in IMRT treatment planning.
In IMRT optimization, the size of beamlets used for optimizing the beam intensity distributions is a planner-selected parameter. The appropriate setting for the beamlet size is critical to the outcome of IMRT planning. With too small beamlets the dose calculation can be inaccurate, and the resulting intensity profiles can be unnecessarily complex and difficult to generate. Relatively simple intensity profiles can be obtained using large beamlets. However, this may compromise the conformity of the dose distribution. In this paper we present a method, in which multiple beamlet matrices displaced from each other by a shift in MLC leaf travel direction are used instead of the single beamlet matrix per beam in a conventional method, to achieve finer spatial resolution for the intensity distribution than the given beamlet size. Two test cases were used to assess the method by the resultant DVHs and dose distributions and characteristic indices of the intensity profiles. The results show that this method can produce optimized dose distributions that are similar to those produced by the conventional inverse planning method with the benefit of smoother intensity profiles that are easier to deliver with a computer controlled MLC.
Biophysical Phenomena↗
An optimization algorithm for intensity modulated radiotherapy--the simulated dynamics with dose-volume constraints.
We have developed a new method for optimization in intensity modulated radiation therapy (IMRT) that makes use of simulated dynamics in a classical system of interacting particles. An analogy is drawn between intensity profile optimization in IMRT and relaxation to the equilibrium configuration in a dynamic system. The intensities of beamlets are equivalent to the positions of the virtual particles. The potential energy of the system is defined by the objective function, which determines the equations of motion for the virtual particles. In this paper, we present the implementation of dose constraints and dose-volume constraints. Our strategy is to optimize the dose to the planned target volume (PTV) while keeping all constraints to the organs at risk (OARs) satisfied rigorously. A simple quadratic objective function is used that only includes terms for PTV voxels. By this approach, no additional parameters other than that for prescribing desired dose and constraints, such as importance factors, are needed. The hard constraints that require non-negative beamlet intensities and that the dose at any voxel in an OAR cannot exceed a maximum tolerance, are implemented as semi-transmittable potential barriers of infinite height. Dose-volume constraints are handled by placing hard constraints on partial volumes. Handling of the clinically applied constraints was tested using phantoms and clinical cases. Our results show that the dose-volume histogram (DVH) type of plan prescription can be fulfilled with satisfactory PTV coverage. In addition to the convenience of implementation, our method can achieve a high computational efficiency with the understanding of the dynamic behavior of the system.
Algorithms↗
Beam orientation optimization for IMRT by a hybrid method of the genetic algorithm and the simulated dynamics.
We have developed a new method for beam orientation optimization in intensity-modulated radiation therapy (IMRT). The problem of beam orientation optimization in IMRT is solved by a decoupled two-step iterative process: (1) optimization of the intensity profiles for given beam configurations; (2) selection of optimal beam configurations based on the ranking by an objective function score for the results of the intensity profile optimization. The simulated dynamics algorithm is used for the intensity profile optimization. This algorithm enforces both the hard constraints and dose-volume constraints. A genetic algorithm is used to select beam orientation configurations. The method has been tested for both a simulated and clinical case, and the results show that beam orientation optimization significantly improved IMRT plans within a time period that is clinically acceptable. The results also show the dependence of the optimal orientation configurations on the prescribed constraints. In addition, beam orientation optimization by the method described here can provide multiple plans with similar dose distributions. This degeneracy characteristic can be exploited to our advantage in introducing additional planning objectives, e.g., the smoothness of intensity profiles, for the selection of the optimal plan among the degenerate configurations for treatment delivery.
Algorithms↗