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Objective:To propose a markless patient setup workflow based on the optical surface monitoring system (AlignRT) and open-face mask immobilization for whole-course head tumor radiotherapy, assess the setup time and repositioning frequency of the proposed workflow, and conduct a comparative analysis of the differences, correlation, and consistency of the setup errors of the AlignRT and cone beam CT (CBCT) systems.Methods:A retrospective analysis was conducted for the data on the errors of 132 fractionated setup based on open-face mask immobilization of 33 head tumor patients. AlignRT-guided markless patient setup workflow was applied throughout the radiotherapy. Meanwhile, the body structures automatically generated by the treatment planning system were used as body references. The 6-degree-of-freedom (6DoF) setup errors (lateral, vertical, longitudinal, rotation, pitch, roll, and yaw directions), setup time, and repositioning frequency of the AlignRT and CBCT systems were recorded and analyzed. The Wilcoxon and Spearman analyses were used to statistically assess the differences and correlation of the setup errors of the two systems. Moreover, the Bland-Altman analysis was employed to evaluate the consistency of the two systems.Results:The 6DoF setup errors of CBCT were within the clinical tolerance (linear motions: -0.30 to 0.30 cm; rotational motions: -2.0° to 2.0°). The setup time and repositioning frequency of CBCT were (98 ± 31) s and 1.51% (2/132), respectively. There was no significant difference in setup errors between the two systems except those in x-axis ( Z = -3.11, P= 0.002), y-axis ( Z = -7.40, P<0.001), and Pitch ( Z= -4.48, P<0.001). There was a significant positive correlation between the setup errors along lateral ( rs = 0.47, P<0.001) and vertical ( rs = 0.29, P = 0.001) directions, rotation (Rtn; rs = 0.47, P<0.001), pitch (Pitch; rs = 0.28, P = 0.001) and roll (Roll; rs = 0.45, P<0.001) of the two systems. The 95% limits of agreement (95% LoA) of 6DoF setup errors were -0.12 to 0.09 cm, -0.07 to 0.17 cm, -0.19 to 0.20 cm, -1.0° to 0.9 °, -1.0° to 1.5°, and -0.9° to 1.0°, respectively. The 95% confidence interval (95% CI) of 95% LoA was -0.14 to 0.11 cm, -0.09 to 0.19 cm, -0.23 to 0.23 cm, -1.2° to 1.1°, -1.2° to 1.7°, and-1.0° to 1.1°, respectively, all of which were within the permissible error ranges. The 6DoF setup error difference of 3.41% (27/792< 5%) was beyond the 95% LoA. The maximum absolute differences of 6DoF setup errors within the 95% LoA were 0.12, 0.16, 0.19 cm, 0.9°, 1.5°, and 1.0°, respectively. Conclusions:The proposed markless setup workflow based on AlignRT combined with open-face mask immobilization for whole-course head tumor radiotherapy exhibits reasonable agreement and consistency with the patient setup using CBCT, with acceptable clinical efficiency. It can be applied to the first radiotherapy and the real-time monitoring of therapy to improve the safety and thus is of value in clinical applications.
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Objective:To investigate the performance of W2 plastic scintillator in megavolt photon and electron beams.Methods:The photon and electron beam energy provided by linear accelerator was used to collect data of the W2 scintillator. The parameters include the electrometer reading stability, W2 dose and dose rate linearity, and angular response. And the dose uncertainty of the W2 correction factors was also investigated.Results:The standard deviation of the electrometer reading stability was between 0.03 and 0.47. The linear regression factors of W2 dose were all 1.0; the maximum deviation of the dose rates was 0.61%. The Cerenkov light radiation correction factor(CLR) for 6 and 10 MV were 0.741 and 0.746, respectively, and the CLR for 6, 9, 12 and 15 MeV were 0.750, 0.753, 0.757 and 0.757, respectively. The maximum deviation of dose uncertainty for 15 MeV was 3.15%.Conclusions:The signal obtained by the blue and green channel was no angular dependence, the same as the high-energy electron beam, which verified that the Cerenkov radiation correction factor has good linearity. W2 plastic scintillator can be applied to non-coplanar radiotherapy dosimetry.
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Objective:To understand the components, performance, acceptance test and quality assurance (QA) protocols of the new Varian Halcyon accelerator through the procedures of installation product acceptance (IPA).Methods:Per Varian IPA protocol, TG-142 for LINAC and TG-148 for tomotherapy QA protocols, the software license, safety interlock, mechanical accuracy, dosimetric performance and imager system were checked thoroughly. Some parameters were benchmarked to the conventional TrueBeam system.Results:The system has been fully licensed. Safety interlock was normal. Mechanical accuracy: The maximum deviation of beam stability per gantry rotation was 1.13%. The size of isocenter was>0.59mm. The offsets of MV imager, collimation rotation and absolute gantry rotation were 0.09mm, -0.21° and 0.11°, respectively. The maximum offsets of couch, virtual-to-isocenter were 0.15mm (vertical) and -0.04mm (vertical), respectively. Beam performance: The depth deviation of maximum dose was 0.1cm. The offset of percentage depth dose at 10cm was 0.5%. The maximum deviations of off-axis-intensity, symmetry, and repeatability were 0.9%, 0.94% and -0.44%, respectively. MV imager: The dark field mean pixel value, noise, corrected pixels, defective lines, sensitivity and linearity disparity of dose were 614, 4.4, 3626, 0, 19177, and 0.47%, respectively. All values were within the range of tolerance. Visual check of contrast resolution and small object detection was all satisfactory.Conclusions:Without Halcyon-specific TG report or guidelines, manufacture-provided IPA manual can be helpful with the installation of acceptance and QA protocols. IPA has been successfully performed for Halcyon at Peking University Cancer Hospital. The automated workflow improves the clinical efficiency by simplifying the operations.
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Objective:To develope an automatic volumetric modulated arc therapy (VMAT) planning for rectal cancer based on a dose-prediction model for organs at risk(OARs) and an iterative optimization algorithm for objective parameter optimization.Methods:Totally 165 VMAT plans of rectal cancer patients treated in Peking University Cancer Hospital & Institute from June 2018 to January 2021 were selected to establish automatic VMAT planning. Among them, 145 cases were used for training the deep-learning model and 20 for evaluating the feasibility of the model by comparing the automatic planning with manual plans. The deep learning model was used to predict the essential dose-volume histogram (DVH) index as initial objective parameters(IOPs) and the iterative optimization algorithm can automatically modify the objective parameters according to the result of protocol-based automatic iterative optimization(PBAIO). With the predicted IOPs, the automatic planning model based on the iterative optimization algorithm was achieved using a program mable interface.Results:The IOPs of OARs of 20 cases were effectively predicted using the deep learning model, with no significantly statistical difference in the conformity index(CI) for planning target volume(PTV)and planning gross tumor volume(PGTV)between automatic and manual plans( P>0.05). The homogeneity index (HI) of PGTV in automatic and manual plans was 0.06 and 0.05, respectively( t=-6.92, P< 0.05). Compared with manual plans, the automatic plans significantly decreased the V30 for urinary bladder by 2.7% and decreased the V20 for femoral head sand auxiliary structure(avoidance)by 8.37% and 15.95%, respectively ( t=5.65, 11.24, P< 0.05). Meanwhile, the average doses to bladder, femoral heads, and avoidance decreased by 1.91, 4.01, and 3.88 Gy, respectively( t=9.29, 2.80, 10.23, P< 0.05) using the automatic plans. The time of automatic VMAT planning was (71.49±25.48)min in 20 cases. Conclusions:The proposed automatic planning based on dose prediction and an iterative optimization algorithm is feasible and has great potential for sparing OARs and improving the utilization rate of clinical resources.
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Objective:To analyze and compare the radiation dose and image quality of kilo-voltage cone beam CT systems on different Varian accelerator platforms, providing data to support clinical decisions on selecting optimal protocols for image-guided radiotherapy based on cost-effective ratio (image quality / radiation dose).Methods:The radiation dose and image quality of various CBCT systems and scanning protocols on Varian Edge, Truebeam and ix (new and old) LINACs were obtained using a CT dose index (CTDI) phantom combined with a CT ionization chamber and a Catphan604 phantom, respectively. Figure of merit (FOM) was used to evaluate the cost-effective ratio of the image guidance schemes.Results:Considerable inter-system varieties of FOMs were observed, varying from 0.65 (Image Gently-full trajectory) to 48.46 (Image Gently-half trajectory). The inter-protocol varieties were also large, where the mean±SD was 22.14±13.47.Conclusions:Considering the explicit inter-system and inter-protocol varieties, it is clinically favorable to evaluate the image guidance schemes based on machine-specific measurement. For instance, parameters and equipment with low CTDI w can be beneficial for dose-sensitive patients. High CNR regimen favors patients with high image quality requirements. For ordinary patients, cost-effective ratio in terms of FOM can be very helpful to guide the decision-making of clinical image-guided radiotherapy.
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Objective:To develop a new method to set up patients using optical surface monitoring system and to compare it with the conventional method in head radiotherapy.Methods:A total of 358 set-ups (130 with the conventional method and 228 with the new method ), which were from 99 head tumor patients in Beijing Cancer Hospital treated between May 2018 to April 2019, obtained by using Image Guided Radiotherapy were retrospectively analyzed. The distributions of set-up errors, the number of abnormal positions, and the set-up time were compared to evaluate the potential advantages of the new method .Results:The mean (± standard deviation) absolute values of setup errors of the new method were (0.07±0.07) , (0.08±0.06) and (0.06±0.06) cm for the vertical, lateral, and longitudinal, (0.53±0.41)°, (0.59±0.44)° and (0.59±0.46)° for the rotation, pitch and roll, respectively. In the new method , the setup accuracy was improved( t=3.24-6.10, P<0.001)and the number of abnormal positions was greatly reduced(χ 2=60.66, P<0.001). Compared with the conventional method, the patient setup time was slightly reduced by the new method , but the difference was not statistically significant ( P>0.05). Conclusions:The new high-precision method to set up patients using optical surface monitoring system improves the accuracy of patients′ position, decreases the corrections applied by 6DoF couch, reduces the probability of abnormal positions, and suggests the potential benefit in head radiotherapy.
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Objective@#To evaluate the cost-effectiveness of seasonal influenza vaccination, compared to no vaccination, for the elderly aged ≥60 years old in China.@*Methods@#A static life-time Markov model is conducted to simulate the Chinese elderly population aged ≥60 years old. Taking the health care system perspective, one-year analytic cycle length is used for each influenza season. The model was assumed to be repeated until the individual reaches 100 years old. Three interventions were evaluated, including no vaccination, annual trivalent influenza vaccination, and annual quadrivalent influenza vaccination. Using the threshold of 3 times GDP per capita per Quality-adjusted life year (QALY) (193 932/QALY), the incremental cost-effectiveness ratio (ICER) was calculated to compare the cost-effectiveness of every two interventions.Model inputs like data for costs and utilities were from studies on Chinese population if they were available. QALY was used to measure health utility. One-way sensitivity analysis and probabilistic sensitivity analysis were adopted to quantify the level of confidence of the model output.@*Results@#The total influenza associated costs of no vaccination would be 603 CNY per person, while the total costs of annual trivalent vaccination would be 1 027 CNY. Using trivalent vaccine would result in 0.007 QALY gained per person compared to no vaccination, with an increased cost of 424 CNY per person. The ICER of trivalent vaccination over no vaccination for all the elderly population in China would be 64 026 CNY per QALY gained, which was less than the threshold of 3 times GDP per capita. The total costs of annual quadrivalent vaccination would be 1 988 CNY. Using quadrivalent vaccine would result in 0.008 additional QALY gained per person compared to no vaccination, with an increased cost of 1 385 CNY per person. The ICER of quadrivalent vaccination over no vaccination would be 174 081 CNY per QALY gained, which was less than the threshold of 3 times GDP per capita.@*Conclusion@#Vaccinating elderly population would improve health utilities at higher health care costs for the elderly. Using the threshold of 3 times GDP per capita per QALY (193 932/QALY), both trivalent and quadrivalent vaccination would be cost-effective compared to no vaccination in elderly Chinese population.
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Objective To compare two pretreatment plan QA methods for HalcyonTM accelerator using Portal Dosimetry (PD),and PTW OCTAVIUS 1500 detector array + Octagonal phantom (Oct 1500)respectively.Methods Parallel measurement-based pretreatment QA using two methods was performed for 22 IMRT/VMAT plans (74 fields) that have been used to treat 20 patients recruited in the Halcyon clinical trial.Several γ 2D comparisons were also applied to provide guidelines for Halcyon planning QA.Results Using Oct1500 method,the γ 2D passing rates for 74 fields in 22 Plans were 95.26±3.59,95.01±3.62 (Local Dose),99.05± 1.35,98.57± 1.96 (Max Dose) respectively.Two-related samples non-parametric tests suggested that the differences between the evaluation criteria were of statistical significance (Z =-7.220,-4.108,P＜0.05).For PD method,the γ 2D passing rates were 84.11％ ± 1.35％ (1 mm/1％),99.07％± 1.35％ (2 mm/2％),and 99.86％ ± 1.35％ (3 mm/3％).Two-related samples non-parametric tests suggested that the differences between evaluation criteria of PD method were statistically significant (Z =-7.475,-7.475,-6.906,P＜0.05).For 74 fields and max dose,3 mm/3％ evaluation criteria,two-related samples non-parametric tests suggested that the differences between PD and Oct1500 method were statistically significant (Z=-5.072,P＜0.05).Conclusions Both methods can be used for Halcyon pretreatment plan QA.PD is superior to Oct1500 with respect to efficiency and spatial resolution-induced verification accuracy.The criteria of 2 mm/2％ for PD,and Max Dose/3 mm/3％ for Oct1500 was suggested.
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Objective To compare the impact of immobilization base plates composed of 7 types of materials on the MR-simulation imaging quality used for radiotherapy,aiming to provide reference data for clinical applications.Methods Using identical T1 and T2 sequences of Siemens MR-simulator,the MR images of ACR Large Phantom were acquired on the Orfit carbon fiber laminate,polycarbonate (PC),high precision base plate (HP),Jinan Huayuxin BR,WR,KP and SP materials,respectively.The imaging quality without any plate was used as the baseline data.The following metrics were compared:1.High-contrast spatial resolution:the sharpness of 3 pairs of hole arrays was observed,which represented resolutions of 1.1 mm,1.0 mm and 0.9 mm on the LR and AP directions;2.Image intensity uniformity in terms of percent integral uniformity (PIU):PIU =100× [1-((high-low)/(high +low)];3.Low-contrast resolution:distinguishable spokes representing resolutions of 5.1％,3.6％,2.5％ and 1.4％ were recorded.According to ACR recommendations,high-contrast resolution of 1.0 mm,PIU of T1WI and T2＞82％and low-contrast spoke difference＜3 were considered as clinically acceptable.Results High-contrast T1WI and T2WI resolutions of no plate,PC plate,HP plate and KP material were all 0.9 mm,and those of the remaining materials were =worse than 0.9 mm.The T1WI and T2WI PIU of no plate was＞87％,and the PIU of carbon fiber plate was reduced by＞ 25％.The PIU decrease of remaining materials was within ±4％.Except the carbon fiber plate,the low-contrast spokes of the remaining materials were within ±3 compared with the reference.Conclusions In clinical settings,carbon fiber plate exerts the most significant effect upon the MR-simulation imaging quality,which is unsuitable for MR simulation.Imaging quality of PC and HP plates are consistent with that of no plate.BR and KP materials exert slight effect upon MR signal.The remaining materials are of potential values for the manufacture of immobilization devices and accessories.
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Objective To standardize the uncertainty assessment work of nationwide radiological technical service institutions in respect to individual dose monitoring, to enhance the relevant capability and to ensure the quality of assessment. Methods The 2017 nationwide individual dose monitoring assessment for external exposure was carried out, and the problems found in uncertainty assessment in the submitted reports were analyzed and summarized. Results A total of 259 personal dose monitoring technical service institutions submitted their completed assessment reports and verification/calibration certificates. The accuracy rate of Class A uncertainty evaluation was 20.8％ and that of class B 55.2％ for calibration, 50.6％ for energy response, 25.5％ for angle ring and 51.4％ non-linearity response, respectively. The accuracy rate of effective digits of the estimated values and their uncertainty was 30.4％. Conclusions The ability of these individual dose monitoring institutions to assess uncertainties remains to be improved. It is recommended to enhance systematic training of the institutions with respect to uncertainty evaluation and to standardize the assessment reports, so as to improve the accuracy of the monitoring result and the quality of accuracy reporting.
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Objective To use thermoluminescense dosimeters (TLDs) to evaluate the radiation doses to various critical organs in the computerized imaging reference systems (CIRS) 5 years old pediatric anthropomorphic phantom result ing from Varian kilovohage cone beam CT (kV-CBCT) system based on the standard scanning protocols.Effective dose were also calculated based on dose measurement.Methods A batch of TLDs with consistency no larger than 2％ were selected and annealed.First,the doses in an anthropomorphic pelvic phantom were measured using a CT chamber and TLDs,respectively,based on the standard pelvic protocols.The ratio of the both measurements is the TLD conversion coefficient.Other TLDs from the same batch were placed between two tissue-equivalent inserts and placed into the pre-drilled organ cavities of the pediatric phantom.By using standard protocols,the organs dose were measured,based on which the corresponding effective doses were calculated.Results The TLD conversion coefficient was 3.91 mGy/per reading.By using the standard head,low-dose thorax,pelvis protocol,the whole body effective dose was 0.63,6.85 and 19.3 mSv,respectively.Conclusions It is feasible for using the CT chamber-calibrated TLDs to measure the radiation doses from kV-CBCT to pediatric anthropomorphic phantom.The effective dose in pelvic protocol was higher than in thorax and head protocol,indicating that the pelvic protocol has a penitential to lead to larger radiation damage and higher risk of secondary cancer.
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Objective To quantify the correlations between Elekta XVI cone beam CT dose and various scanning protocols,providing mathematical models to assess the protocol-dependency of imaging dose during imnage guided radiotherapy.Methods Based on standard protocols and various combinations of kVp and mA on an XVI mounted on an Elekta Versa HD accelerator,the air KERMA was measured at various positions in a standard PTW CTDI body phantom using calibrated PTW 30009 kV chamber and UNIDOS webline electrometer.Weighted CT dose index (CTDIw) was computed thereafter.SigmaPlot 10.0 was used to fit the measurements against mA and/or kVp yielding empirical functions.Results Under standard protocols,the CTDIw of Varian OBI was only 11.23％ (chest) and 9.15％ (pelvis) of Elekta XVI.Using the default and other 4 investigated kVp values,the central and peripheral KERMA were both proportional to mA,and vet the slope value a varied dramatically from 0.479 to 6.679.Major affecting factors included kVp settings,measurement locations,and dosimetric mnetrics,etc.None linear regressions were used to fit kVp against KERMA at various locations and CTDIw (R2 ＞ 0.997).The differences between all coefficients were statistically significant (P ＜ 0.05).The impact of changing both mA and kVp on the dose to phantom center can be described as mGy =(5.917-0.197 ×kVp+0.002 × kVp2-5.063 × 10-6 × kVp3) × mA.Conclusions Imaging dose of Elekta XVI is strongly dependent on scanning paraneters.The proposed mathematical models can be used as efficient and robust indicators of such dependency.
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ObjectiveTo observe the effect of Qishen Tongluo Zengzhi decoction on cognitive impairment in patients with acute phase of ischemic stroke.Methods A prospective randomized controlled trial was conducted, and 130 patients with acute phase of ischemic stroke and cognitive impairment accompanied by Qi deficiency and blood stasis and stagnationof phlegm-dampness syndrome admitted into the Neurology and Rehabilitation Departments of Rizhao Hospital of Traditional Chinese Medicine(TCM) Affiliated to Shandong University of TCM were randomly divided into treatment group and control group, 65 cases in each group. In the two groups, conventional internal treatment was given to all patients, and in the treatment group, additionally the Qishen Tongluo Zengzhi decoction was administered orally(composition: astragalus membranaceus 30 g, radix pseudostellariae 30 g, notoginseng 10 g,spatholobus stem 25 g, hirudo 3 g, pberetima 10 g, radix paeoniae rubra 12 g, Chinese angelica 12 g, peach kernel 10 g, carthamus tinctorious 10 g, achyranthes 12 g, radix rhapontici 10 g, rhizoma alismatis 6 g, Acorus gramineus Soland 9 g, polygala root 9 g, rhizoma cyperi 10 g, herba siegesbeckiae 15 g),one dose a day. While in the control group, oxiracetam 4.0 g intravenous drip was given, once a day. The whole course was 21 days in both groups. Before and after treatment, the cognitive function of all the patients in two groups was assessed by Mini-Mental State Examination(MMSE)and Montreal Cognitive Assessment(MoCA) scores, and incubation period and amplitude of P300 wave were recorded.Results Finally 62 cases were in treatment group and 63 cases in control group. Before treatment, the comparisons of the MMSE score, MoCA score and P300 latent period and amplitude between the two groups had no statistically significant differences(allP>0.05). After treatment in the two groups, the MMSE score, MoCA score and P300 wave amplitude were elevated, P300 latency period was shortened compared with those before treatment, and the changes were more prominent in treatment group〔score of MMSE: 25.33±2.32 vs. 21.68±2.29, score of MoCA(score): 26.61±3.06 vs. 22.40±2.93, P300 wave incubation period(ms): 349.62±20.01 vs. 371.87±19.63, P300 wave amplitude(μV): 8.70±2.92 vs. 5.72±2.33,allP<0.01〕.ConclusionQishen Tongluo Zengzhi decoctioncan effectively intervene cognitive impairment in patients with acute phase of ischemic stroke, and improve their cognitive function.