Aiming at the disadvantages of traditional direct aperture optimization (DAO) method, such as slow convergence rate, prone to stagnation and weak global searching ability, a gradient-based direct aperture optimization (GDAO) is proposed. In this work, two different optimization methods are used to optimize the shapes and the weights of the apertures. Firstly, in order to improve the validity of the aperture shapes optimization of each search, the traditional simulated annealing (SA) algorithm is improved, the gradient is introduced to the algorithm. The shapes of the apertures are optimized by the gradient based SA method. At the same time, the constraints between the leaves of multileaf collimator (MLC) have been fully considered, the optimized aperture shapes are meeting the requirements of clinical radiation therapy. After that, the weights of the apertures are optimized by the limited-memory BFGS for bound-constrained (L-BFGS-B) algorithm, which is simple in calculation, fast in convergence rate, and suitable for solving large scale constrained optimization. Compared with the traditional SA algorithm, the time cost of this program decreased by 15.90%; the minimum dose for the planning target volume was improved by 0.29%, the highest dose for the planning target volume was reduced by 0.45%; the highest dose for the bladder and rectum, which are the organs at risk, decreased by 0.25% and 0.09%, respectively. The results of experiment show that the new algorithm can produce highly efficient treatment planning a short time and can be used in clinical practice.
The deoxyribonucleic acid (DNA) molecule damage simulations with an atom level geometric model use the traversal algorithm that has the disadvantages of quite time-consuming, slow convergence and high-performance computer requirement. Therefore, this work presents a density-based spatial clustering of applications with noise (DBSCAN) clustering algorithm based on the spatial distributions of energy depositions and hydroxyl radicals (·OH). The algorithm with probability and statistics can quickly get the DNA strand break yields and help to study the variation pattern of the clustered DNA damage. Firstly, we simulated the transportation of protons and secondary particles through the nucleus, as well as the ionization and excitation of water molecules by using Geant4-DNA that is the Monte Carlo simulation toolkit for radiobiology, and got the distributions of energy depositions and hydroxyl radicals. Then we used the damage probability functions to get the spatial distribution dataset of DNA damage points in a simplified geometric model. The DBSCAN clustering algorithm based on damage points density was used to determine the single-strand break (SSB) yield and double-strand break (DSB) yield. Finally, we analyzed the DNA strand break yield variation trend with particle linear energy transfer (LET) and summarized the variation pattern of damage clusters. The simulation results show that the new algorithm has a faster simulation speed than the traversal algorithm and a good precision result. The simulation results have consistency when compared to other experiments and simulations. This work achieves more precise information on clustered DNA damage induced by proton radiation at the molecular level with high speed, so that it provides an essential and powerful research method for the study of radiation biological damage mechanism.
Objective To systematically review the diagnostic value of Presepsin for sepsis. Methods Literatures were searched from PubMed, The Cochrane Library (Issue 6, 2017), EMbase, CNKI, CBM, VIP, and WanFang database, and the time was from inception to June 2017, to collect diagnostic studies about Presepsin for sepsis. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of included studies by QUADAS-2 tool. Then meta-analysis was performed by using RevMan 5.3 and Meta-Disc 1.4 software. Pooled sensitivity (Sen), specificity (Spe), positive likelihood ratio (LR+), negative likelihood ratio (LR-), diagnostic odds ratio (DOR), and area under the curve (AUC) of summary receiver operating characteristic curve (SROC) were calculated to assess the diagnostic value of individual diagnostic tests. Results A total of 23 studies with 2 925 sepsis patients and 1 852 controls were finally included. The results of meta-analysis showed that the pooled Sen, Spe, LR+, LR-, DOR, and AUC was 0.80 ［95% CI was (0.78, 0.81), P<0.000 1］, 0.83 ［95%CI was (0.81, 0. 84), P<0.000 1］, 4.78 ［95%CI was (3.62, 6.31), P<0.000 1］, 0.22 ［95%CI was (0.18, 0.27), P<0.000 1］, 23.64 ［95%CI was (16.00, 34.92), P<0.000 1］, and 0.91 ［95%CI was (0.89, 0.94), P<0.001］, respectively. Subgroup analysis showed that the pooled Sen, Spe, LR+, LR-, DOR, and AUC in Caucasian was 0.83 ［95% CI was (0.80, 0.86), P=0.000 1］, 0.79 ［95% CI was (0.76, 0.82), P<0.000 1］, 4.38 ［95%CI was (2.40, 8.02), P<0.000 1］, 0.23 ［95%CI was (0.16, 0.31), P=0.007 8］, 21.09 ［95% CI was (8.82, 50.41), P<0.000 1］, and 0.91 ［95%CI was (0.87, 0.92), P<0.001］ respectively, and in Asian was 0.79 ［95% CI was (0.77, 0.80), P<0.000 1］, 0.85 ［95%CI was (0.83, 0.87), P<0.000 1］,4.74 ［95%CI was (3.82, 5.89), P=0.011 1］, 0.22 ［95% CI was (0.17, 0.28), P<0.000 1］, 24.95 ［95%CI was (16.07, 38.74), P<0.000 1］, and 0.92 ［95%CI was (0.90, 0.95), P=0.001］ respectively, there was no significant difference between Caucasian and Asian in diagnostic accuracy of Presepsin (Z=0.41, P>0.05). Conclusion Current evidence indicates that Presepsin has great early diagnostic value for sepsis.
Objective To evaluate the significance of the ultrasound elastography (UE) strain ratio (SR) in the diagnosis of breast nodule by meta-analysis. Methods A computer-based online search was conducted in PubMed, The Cochrane Library (Issue 6, 2017), EMbase, CNKI, VIP, CBM, WanFang data databases, and so on (establishment time to June 2017), to collect the relevant diagnostic trials of the SR for breast nodules. Two reviewers independently screened literatures, extracted data, and evaluated the methodological quality of included studies. The meta-analysis was performed by using Stata 12.0 and Meta-Disc 1.4 software, and the combined indexes included sensitivity (Sen), specificity (Spe), positive likelihood ratio (LR+), negative likelihood ratio (LR–), and diagnostic odds ratio (DOR). Results A total of 26 studies were finally included. The results of meta-analysis showed that, the pooled Sen, Spe, LR+, LR–, and DOR was 0.88 (95% CI was 0.87 to 0.90), 0.85 (95% CI was 0.84 to 0.86), 6.66 (95% CI was 5.26 to 8.43), 0.14 (95% CI was 0.11 to 0.17), and 53.37 (95% CI was 34.96 to 81.49), respectively, P<0.000 1. Conclusion SR has high diagnostic accuracy in the differential diagnosis of benign and malignant breast nodules, it is worthy of widely utilized in the clinic.