Dosimetric evaluation of VMAT radiation therapy technique for breast cancer after conservative surgery based on three different types of multileaf collimators

Objective Radiotherapy combined with conservative surgery plays an important role in the treatment of early-stage breast cancer. Volumetric modulated arc therapy(VMAT) has been introduced into clinical practice. The purpose of this study was to investigate the dosimetric effects of different multileaf collimators(MLC) on VMAT radiotherapy plans for treating breast cancer.Methods Fifteen breast cancer patients who were treated using a conventional technique in our department were selected to participate in this retrospective analysis. VMAT plans based on three types of Elekta MLCs [Beam Modulator(BM) with 4-mm leaf width, Agility with 5-mm leaf width and MLCi2 with 10-mm leaf width] were independently generated for each patient. Plan comparisons were performed based on dose-volume histogram(DVH) analysis including dosimetric parameters such as the homogeneity index(HI), conformity index(CI), Dmax, Dmin, and Dmean for the planning treatment volume(PTV), in addition to dose-volume parameters for the organs at risk(OARs). The delivery efficiency of the three types of MLCs was compared in terms of the beam delivery time and the monitor units(MUs) per fraction for each plan. Results Both target uniformity and conformity were improved in plans for Agility and BM MLC compared with the plan using MLCi2. The mean HI decreased from 1.14 for MLCi2 to 1.13 for BM and 1.10 for Agility, while the mean CI increased from 0.68 for MLCi2 to 0.73 for BM and 0.75 for Agility. Furthermore, at both low and high dose levels, smaller volumes of ipsilateral lung, heart, contralateral lung, and breast were irradiated with Agility MLC than with the other two types of MLCs. The delivery time with Agility MLC was reduced by 10.8% and 32.1%, respectively, compared with that for MLCi2 and BM.Conclusion Our results indicate that the Agility MLC exhibits a dosimetric advantage and a significant improvement in delivery efficiency for the treatment of breast cancer using VMAT.

Comparison of the effects of two typesof multileaf collimators on tumor control probabilityin radiotherapy for breast cancer after conservativesurgery based on the EUD model

Objective To compute and compare the tumor control probability(TCP) of volumetric modulated arc therapy(VMAT) for breast cancer after conservative surgery based on two types of multileaf collimator(MLC) through a retrospective planning study.Methods For a group of 9 patients diagnosed with left breast cancer,VMAT plan based on Agility MLC and beam modulator(BM) MLC were designed.The prescription dose was 50 Gy covering at least 95% of the planning target volume,2 Gy per fraction.TCPs were calculated according to dose-volume histogram(DVH) analysis.Results The TCP of the BM VMAT plan was slightly higher than that of the Agility VMAT plan(94.61% vs 94.23%) but was inferior with respect to delivery efficiency;the delivery time was reduced for Agility VMAT plan by 35% compared to BM VMAT plan.Conclusion For breast cancer radiation therapy after conservative surgery,BM VMAT plans provide slightly higher TCP while the delivery of Agility VMAT plans is significantly faster than the BM VMAT plans.

A dosimetric evaluation of flattening filter-free volumetric modulated arc therapy for postoperative treatment of cervical cancer

Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI), as well as organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.

Automatic delineation of organs at risk in non-small cell lung cancer radiotherapy based on deep learning networks

Objective To introduce an end-to-end automatic segmentation method for organs at risk(OARs)in chest computed tomography(CT)images based on dense connection deep learning and to provide an accurate auto-segmentation model to reduce the workload on radiation oncologists.Methods CT images of 36 lung cancer cases were included in this study.Of these,27 cases were randomly selected as the training set,six cases as the validation set,and nine cases as the testing set.The left and right lungs,cord,and heart were auto-segmented,and the training time was set to approximately 5 h.The testing set was evaluated using geometric metrics including the Dice similarity coefficient(DSC),95%Hausdorff distance(HD95),and average surface distance(ASD).Thereafter,two sets of treatment plans were optimized based on manually contoured OARs and automatically contoured OARs,respectively.Dosimetric parameters including Dmax and Vx of the OARs were obtained and compared.Results The proposed model was superior to U-Net in terms of the DSC,HD95,and ASD,although there was no significant difference in the segmentation results yielded by both networks(P>0.05).Compared to manual segmentation,auto-segmentation significantly reduced the segmentation time by nearly 40.7%(P<0.05).Moreover,the differences in dose-volume parameters between the two sets of plans were not statistically significant(P>0.05).Conclusion The bilateral lung,cord,and heart could be accurately delineated using the DenseNet-based deep learning method.Thus,feature map reuse can be a novel approach to medical image auto-segmentation.

Application of biological optimization of hypofractionated radiotherapy post conservative surgery for breast cancer

Objective The aim of the study was to discuss the application of biological optimization and its difference from physical optimization in hypofractionated radiotherapy for breast cancer after conservative surgery.Methods This retrospective study enrolled 15 randomly chosen patients with left-sided breast cancer who received radiotherapy.The volumetric arc therapy(VMAT)technique was used to redesign treatment plans with physical functions(PF)group,biological-physical functions combined(BF+PF and PF+BF)groups,and biological functions(BF)group.The dosimetric differences based on the above four optimization methods were assessed by calculating and analyzing the corresponding dose-volume parameters.Results The target parameters of the four groups differed significantly(P<0.05)except for the conformity index(CI).The tumor control probability(TCP)values in the BF and BF+PF groups were higher than those in the PF and PF+BF groups.Moreover,the dose-volume parameters of the ipsilateral lung in the BF group were less than those of three other groups,while the monitor unit(MU)in the BF group was approximately 16%lower than those of the PF and PF+BF groups.Conclusion Biological functions were useful to increase the equivalent uniform dose(EUD)and TCP values of the target,decrease the dose-volume parameters of the organs-at-risk(OARs),and improve treatment efficiency.

两种四维CT重建算法对肺癌放疗靶区勾画影响的体模研究(英文)

Objective: The purpose of this study was to evaluate the performance of the phase-binning algorithm and amplitude-binning algorithm for four-dimensional computed tomography(4DCT) reconstruction in lung cancer radiation therapy. Methods: Quasar phantom data were used for evaluation. A phantom of known geometry was mounted on a four-dimensional(4D) motion platform programmed with twelve respiratory waves(twelve lung patients trajectories) and scanned with a Philips Brilliance Big bore 16-slice CT simulator. The 4DCT images were reconstructed using both phase- and amplitude-binning algorithms. Internal target volumes(ITVs) of the phase- and amplitude-binned image sets were compared by evaluation of shape and volume distortions. Results: The phantom experiments illustrated that, as expected, maximum inhalation occurred at the 0% amplitude and maximum exhalation occurred at the 50% amplitude of the amplitude-binned 4DCT image sets. The amplitude-binned algorithm rendered smaller ITV than the phase-binning algorithm. Conclusion: The amplitude-binning algorithm for 4DCT reconstruction may have a potential advantage in reducing the margin and protecting normal lung tissue from unnecessary irradiation.

乳腺癌保乳术后常规、三维适形及两种调强放疗技术剂量学评估(英文)

Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.

Estimation of the effect of target and normal tissue sparing based on equivalent uniform dose-based optimization in hypofractionated radiotherapy for lung cancer

Objective This study aims to investigate the dosimetric differences among four planning methods of physical and biological optimization in hypofractionated radiation therapy for non-small cell lung cancer(NSCLC).Methods Ten NSCLC patients receiving radiation therapy were chosen for this retrospective study.Volumetric modulated arc treatment plans for each patient were remade with dose-volume(DV)functions,biological-physical functions,and biological functions,using the same constraint parameters during optimization.The dosimetric differences between the four types of plans were calculated and analyzed.Results For the target,equivalent uniform dose(EUD)of the EUD and EUD+DV groups was approximately 2.8%–3.6%and 3.2%–3.7%higher than those of the DV and DV+EUD groups,respectively.The average tumor control probability(TCP)of the EUD and EUD+DV groups was also significantly higher than those of the other two groups(P<0.05).The difference in heterogeneity index(HI)among the four groups was also statistically significant(P<0.05),while the difference of conformity index(CI)was not significant(P>0.05).For the organs at risk,the differences of EUD,V5,V10,V20,V30 of normal lung tissues were not statistically significant(P>0.05);however,the mean lung dose of the EUD and EUD+DV groups was slightly lower than those of the other two groups.Conclusion The biological optimization method has obvious advantages of improving EUD and TCP of the target,while decreasing the exposed dose of normal lung.This result is meaningful in choosing plan optimization methods in routine work.

Dosimetric analysis of tomotherapy-based intensity-modulated radiotherapy with and without bone marrow sparing for the treatment of cervical cancer

Objective The aim of the study was to compare tomotherapy-based bone marrow-sparing intensity-modulated radiotherapy(BMS-IMRT) with intensity-modulated radiotherapy(IMRT) without entering the pelvic bone marrow as a planning constraint in the treatment of cervical cancer after hysterectomy. Methods BMS-IMRT and IMRT plans were designed for a cohort of nine patients. The prescribed dose was 45 Gy in 1.8 Gy daily fractions, and 95% of the planned target volume received this dose. The doses were computed using a commercially available treatment planning system with the convolution/superposition algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI) as well as organ at risk dose and volume parameters. Results BMS-IMRT had advantages over IMRT in terms of CI, but was equivalent to the latter in HI. V5, V10, V20, V30, and V40 of pelvic bone marrow in BMS-IMRT decreased by 0.06%, 17.33%, 22.19%, 13.85%, and 16.46%, respectively, compared with IMRT. Except for V30 of the small bowel and V30 and V40 of the bladder, no statistically significant differences were found between BMS-IMRT and IMRT in the small bowel, bladder, and rectum. Conclusion For cervical cancer patients receiving tomotherapy-based radiotherapy after hysterectomy, BMS-IMRT reduced pelvic bone marrow volume receiving low-dose radiation, and it may be conducive to preventing acute hematologic toxicity.

Establishment of a Construct-specific Real-time PCR Method for Quantitative Detection of Genetically Modified Maize Line MIR604

In this study, a construct-specific real-time PCR method for quantitative detection of genetically modified maize line MIR604 was established with prim- ers and probes designed based on vector sequence of MIR604 under optimized reaction system and thermal cycling condition. By using the established method, six non-genetically modified crops, genetically modified maize line MIR604 and other non-target genetically modified crops were detected. According to the results, flu- orescence signal could be detected in genomie DNA of MIR604, but other non-genetically modified crops and non-target genetically modified crops exhibited no fluo- rescence signal of MIR604 molecular fragment. Certified reference materials containing 1% MIR604 were detected with the established method and the results indi- cated that the average relative content in the test samples was 1.05%. The sensitivity analysis results indicated that MIR604 nucleic acid fragment with at least five copies could be detected with the established method. In conclusion, the construct-specific real-time PCR method for quantitative detection of genetically modified maize line MIR604 is of high specificity, accuracy and sensitivity, which provides technical support for safety supervision of genetically modified organisms in China.

Evaluation of Uncertainty in Measuring the Content of CaM V35S Promoter in Genetically Modified Soybean,GTS40-3-2,by Real-time Quantitative PCR

[ Objective ] This study aimed to investigate the major contributors to the measurement uncertainty in quantitative analysis of genetically modified ingreclients and improve the quality of quantitative detection of genetically modified components. [ Method] The content of CaMV35S promoter （parameter） in GTS40- 3-2 soybean powder samples was measured to estimate the measurement uncertainty preliminarily. [ Result] Type A uncertainty （uA） ＇ type B uncertainty （uB） and combined standard uncertainty （Uc） were 0.0 004, 0.002 and 0.002, respectively. At a confidence level ofp = 95% and freedom degree of Voff = 3 251, coverage factor k = 1.96, expanded uncertainty U = 0.004. The final measurement result was C = 0.028 ± 0. 004, which was dose to the conventional true value （0.03）. Thus, the measurement uncertainty was relatively small, indicating a high quality of measurement. In this study, uncertainty evaluation indicated that the deviation of micro liquid transfer made the greatest contribution to the measurement uncertainty. [ Cludusion ] The deviation of micro liquid transfer should be reduced to im- prove the quality of measurement.

Dosimetric comparison of different multileaf collimators in volumetric modulated arc therapy for malignant pleural mesothelioma

Objective The aiom of the study was to compare the impacts of two types of multileaf collimators(MLC) [standard MLC with a width of 10 mm(s MLC) and micro-MLC with a width of 5 mm(m MLC)] on volumetric modulated arc therapy(VMAT) planning for malignant pleural mesothelioma. Methods VMAT for ten patients with inoperable malignant pleural mesotheliomas was retrospectively planned with the s MLC and m MLC. Histogram-based dose-volume parameters of the planning target volume(PTV) [conformity index(CI) and homogeneous index(HI)] and organs-at-risk were compared for VMAT plans with s MLC(s MLC-VMAT) and m MLC(m MLC-VMAT). Results The m MLC-VMAT plans were more efficient(average delivery time: 2.67±1.49 min) than the s MLC-VMAT plans(average delivery time: 4.21 ± 2.03 min; P < 0.05). Moreover, compared to the s MLC plans, the m MLC plans demonstrated advantages in the dose coverage of the PTV(CI 0.75 ± 0.08 vs 0.73 ± 0.09; HI 1.09 ± 0.02 vs 1.10 ± 0.02), although the difference was not statistically significant(P > 0.05). In addition, significant dose sparing in the fraction of the ipsilateral lung volume receiving > 20 Gy(V20; 54.72 ± 27.08 vs 58.52 ± 29.30) and > 30 Gy(V30; 42.74 ± 27.86 vs 46.86 ± 31.49) radiation, respectively, was observed for the m MLC plans(P < 0.05). Conclusion Comparing s MLC-VMAT and m MLC-VMAT not only demonstrated the higher efficiency and better optimal target coverage of m MLC-VMAT, but also considerably improved the dose sparing of the ipsilateral lung in the VMAT plans for malignant pleural mesothelioma.

Uncertainty in Detecting Specific Fragment of Genetically Modified Maize Event NK603 by Real-time Fluorescence Quantitative PCR

In this study, the event-specific real-time fluorescence quantitative PCR method established by Siehuan Academy of Agricultural Sciences was employed to detect the content of flanking fragment （specific fragment） in samples containing 2% genetically modified maize event NK603. The uncertainty of detection results was evaluated based on various uncertainty sources, such as PCR amplification system, data analysis and micropipette. The results showed that A-type uncertainty （ uA ）, B-type uncertainty （ uB ）, combined standard uncertainty （ uC ） and expanded uncertainty （ U95 ） were 0. 000 8,0.1301,0. 001 and 0. 002, respectively; the final detection result was 1.9% ±0.002. Thus, the main uncertainty in detecting flanking fragment of genetically modified maize event NK603 with realtime fluorescence quantitative PCR method was derived from the random effect in the experimental process.

Luminescent Properties of Europium Complexes with Different Long Chains in Langmuir-Blodgett (LB) Films

A series of europium(III) complexes with different chain length, tris [2-m-pyridylmethanamido-5-phenyl- (1,3,4)-oxadiazole] mono [2-(4-n-alkylphenyl)-iminazole (4,5-f)-1,10-phenanthroline] Eu(III) [Eu(PMA)3Nn (n = 6, 10, 14,18)] were synthesized. All of these amphiphilic europium(III) complexes could form stable Langmuir film at air/water interface and could be transferred onto hydrophilic quartz and mica substrates by measurement of UV spectra in which the absorbance of the LB films at about 288 nm scales showed the linearity with the number of layers deposited. In order to investigate relation between fluorescence properties and the arrangement of molecular in LB films, surface topography of monolayer films were observed by atomic force microscopy (AFM). Results showed that the emission spectra have Eu(III) characteristic peaks and strong emission strength. It is interesting that the molecular with looser arrangement in LB films has better monochromacity, which illustrated that energy might transferred more easily from ligand to Eu(III) in loosen structure films.

Development of an Event-specific Quantitative PCR for Genetically Modified Maize (Zea mays) Event NK603

[ Objective ] The aim of this study was to develop a quantitative PCR detection method for genetically modified maize event NK603, so as to provide ba- sis for quantitative analysis of event NK603. [ Methods ] A quantitative PCR detection method for genetically modified maize event NK603 was developed using primers and Taqman probe designed according to the flanking sequence of event NK603, which was then adopted to detect the samples containing 2% NK603 stand- ard （with uncertain quantity of 10% ）. [ Results ] The slope of standard curve ranged between -3.6 and -3.1, and the correlation coefficient was higher than 0. 99. The amplification efficiency of this method reached 100.2%, fallen between 90% and 110%. The detected quantity of the experimental sample was 1.9%, closer to the true quantity （2%）. [ Conclusion] This quantitative PCR detection method for genetically modified maize event NK603 is very precise and can be a- dopted in routine testing analysis.

Electromagnetic Functional Surface and Its Field-controllable Effect

State Key Laboratory of New Ceramics and Fine Processing,School of Materials Science and Engineering,Tsinghua University,Beijing 100084,China Precise and effective control of light has always been pursued.For thousands of years,people

Microglia modulation with 1070-nm light attenuates Aβ burden and cognitive impairment in Alzheimer’s disease mouse model

Photobiomodulation,by utilizing low-power light in the visible and near-infrared spectra to trigger biological responses in cells and tissues,has been considered as a possible therapeutic strategy for Alzheimer’s disease(AD),while its specific mechanisms have remained elusive.Here,we demonstrate that cognitive and memory impairment in an AD mouse model can be ameliorated by 1070-nm light via reducing cerebralβ-amyloid(Aβ)burden,the hallmark of AD.The glial cells,including microglia and astrocytes,play important roles in Aβclearance.Our results show that 1070-nm light pulsed at 10 Hz triggers microglia rather than astrocyte responses in AD mice.The 1070-nm lightinduced microglia responses with alteration in morphology and increased colocalization with Aβare sufficient to reduce Aβload in AD mice.Moreover,1070-nm light pulsed at 10 Hz can reduce perivascular microglia and promote angiogenesis to further enhance Aβclearance.Our study confirms the important roles of microglia and cerebral vessels in the use of 1070-nm light for the treatment of AD mice and provides a framework for developing a novel therapeutic approach for AD.

In vivo flow cytometry reveals a circadian rhythm of circulating tumor cells

Circulating tumor cells(CTCs)is an established biomarker of cancer metastasis.The circulation dynamics of CTCs are important for understanding the mechanisms underlying tumor cell dissemination.Although studies have revealed that the circadian rhythm may disrupt the growth of tumors,it is generally unclear whether the circadian rhythm controls the release of CTCs.In clinical examinations,the current in vitro methods for detecting CTCs in blood samples are based on a fundamental assumption that CTC counts in the peripheral blood do not change significantly over time,which is being challenged by recent studies.Since it is not practical to draw blood from patients repeatedly,a feasible strategy to investigate the circadian rhythm of CTCs is to monitor them by in vivo detection methods.Fluoresce nee in vivo flow cytometry(IVFC)is a powerful optical technique that is able to detect fluoresce nt circulating cells directly in living animals in a noninvasive manner over a long period of time.In this study,we applied fluorescence IVFC to monitor CTCs noninvasively in an orthotopic mouse model of human prostate cancer.We observed that CTCs exhibited stochastic bursts over cancer progression.The probability of the bursting activity was higher at early stages than at late stages.We longitudinally monitored CTCs over a 24-h period,and our results revealed striking daily oscillations in CTC counts that peaked at the onset of the night(active phase for rodents),suggesting that the release of CTCs might be regulated by the circadian rhythm.

Active control of EIT-like response in a symmetry-broken metasurface with orthogonal electric dipolar resonators

The active control of electromagnetic response in metamaterial and mutual coupling between resonant building blocks is of fundamental importance in realizing high-quality metamaterials. In this work, we propose and experimentally demonstrate the tunabilities of symmetry-broken metasurfaces made of orthogonal electric dipolar resonators. The metasurface with vertical and horizontal wires is integrated with a PIN diode for active control.It is found that the electromagnetically induced transparency(EIT)-like spectrum appears due to the destructive or constructive interferences between the two electric dipolar modes when the structural symmetry broken is introduced to the metasurface. Different from previous works on the EIT-like effect, there is only electric dipole response in our metasuface. The microscopic response of the metasurface is numerically calculated to illustrate the mode coupling between the orthogonal electric dipolar resonators. By applying temporal coupled-mode theory,the interaction between the electromagnetic wave and the symmetry-broken metasurface is described, and the characteristic parameters of the resonator system, which determine the electromagnetic response of the metasurface, are acquired.

黑磷敏化的金/氮化碳异质结全光谱废水产氢性能研究

光催化废水产氢技术是缓解日益严峻的能源和环境危机的有效方法.然而,由于载流子复合率较高、太阳光利用率较低,目前光催化活性仍然难以满足工业发展的需要.基于以上问题,本文设计了具有全谱太阳光响应的黑磷敏化的金/氮化碳(BP/Au/CN)异质结光催化剂,该三元异质结可以在实现降解双酚A的同时,将水分解为氢气,其光催化产氢活性可达到195.8μmol h^(−1)g^(−1).此外,在紫外-可见光照射下,BP/Au/CN的光催化产氢活性可以达到1400.8μmol h^(−1)g^(−1),是CN或BP/CN样品的近70倍,Au/CN异质结的2倍.光催化活性的提高表明异质结中三种元素具有良好的协同作用.本文将一系列实验表征与理论计算相结合,对BP/Au/CN的光催化机理进行了系统研究.结果表明,黑磷的全谱太阳光吸收能力、金的电子传输介质作用以及三种材料匹配的功函数是其光催化活性提高的关键因素.此外,通过金和黑磷的欧姆接触以及Au/CN杂化体系中肖特基异质结的构筑,实现了电子从黑磷到金,再到氮化碳的单向转移,从而提高了载流子的传输性能.