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Objective:To investigate the feasibility of applying the ArcherQA three-dimensional (3D) dosimetric verification system in intensity-modulated radiotherapy (IMRT) plans for nasopharyngeal carcinoma (NPC).Methods:A retrospective analysis was conducted for 105 NPC patients′ IMRT plans developed using the Eclipse treatment planning system (TPS). Dose verification was conducted using the ArcherQA system and through portal dosimetry (PD). Moreover, this study compared γ passing rates (criteria: 3 mm/3%, TH = 10%) between ArcherQA and PD and the doses delivered to the target volume ( Dmean, D90%) and organs at risk (OARs) ( Dmean) between ArcherQA and TPS, and analyzed the 3D γ passing rates of each organ at risk calculated by ArcherQA. Results:The average 3D γ passing rate calculated by ArcherQA was (99.04±1.01)%, and the average 2D γ passing rate measured by PD was (99.49±0.78)%, with statistically significant differences ( t=-3.35, P< 0.05). The dosimetric differences to the target volume between ArcherQA and TPS were as follows: the average difference in Dmean to the gross tumor volume (GTV) was (0.57±0.48)%, and the average difference in D90% was (0.65±0.56)%. For the target volume, the average γ passing rate was (97.67±3.43)% for GTV, (97.80±4.35)% for GTVnd-L, (97.82±4.07)% for GTVnd-R, (97.88±2.44)% for CTV1, and (96.64±4.32)% for CTV2. The mean dose difference of each target volume was CTV1 (0.57±0.46)%, GTVnd-L (0.85±0.55)%, GTVnd-R (0.73±0.55)%, and CTV2 (0.88±0.52)%. For OARs, the mean γ passing rate was (99.93±0.22)% for the brainstem, (99.17±2.82)% for the optic chiasm, (100±0)% for the lens, (99.56±1.05)% for the spinal cord, (99.00±2.06)% for the thyroid, and (87.86±10.42)% for the trachea. Statistically significant differences in the average doses to OARs were observed ( t=-14.62 to 4.82, P<0.05), except for those to the left optic nerve, the right hippocampus, and the right parotid gland. Conclusions:Based on the high-performance GPU platform and the Monte Carlo dose algorithm, ArcherQA can provide accurate 3D dose distribution and 3D γ passing rates inside patients according to CT images and provide the dose volume histogram (DVH) of various regions of interest (ROIs). Therefore, the ArcherQA three-dimensional dose verification system can be applied to IMRT plans for NPC. Moreover, it is inducive to improve the treatment efficiency since it does not occupy the accelerator operation time.
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Objective:To analyze the dosimetric effects on off-center tumour treatment plan resulting from the MR-Linac-based isocenter position radiotherapy plan.Methods:The cases of 19 patients who were treated in Sun Yat-sen University Cancer Center in 2020 were collected in this study. Two different IMRT plans were designed for each patient with off-center tumor both for group A with planned isocenter position as IMRT and group B with planed target center position as geometric center. The conformity index and homogeneity index of target, the dose normal tissue and the number of MU were compared between two plans.Results:The two IMRT plans met clinical dosimetric requirements. No statistical differences were found both in homogeneity index and conformity index ( P>0.05). Also there was no differences found in doses to normal tissues. However, the MU number (1 149±903, t=2.804, P=0.012) in group A was higher than that in group B (970±652). Conclusions:It is feasible to perform MR-Linac-based off-center treatment plan.
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Alzheimer's disease（AD） is an irreversible neurodegenerative disease with clinical manifestations such as memory impairment， aphasia， impaired visuospatial skills， executive function impairment， and personality changes. AD has brought a heavy burden to the family and society due to its unrevealed pathogenesis and the lack of therapeutic approaches. Saponins， a group of oligoglycosides whose aglycones are triterpenes or spirosteroids， are divided into triterpene saponins and steroidal saponins， which have a variety of biological activities. At present， there is no systematic review on the anti-AD effect of saponins. According to the literature published in recent years， the authors summarized the studies of saponins in improving AD based on animal experiments. The results indicated that saponins enhanced learning ability and improved cognitive impairment by inhibiting amyloid β-protein （Aβ） cascade activity， suppressing microtubule-associated protein （tau） hyperphosphorylation， inhibiting neuronal oxidative stress， inhibiting inflammatory factors， regulating apoptosis， inhibiting cholinergic neuronal degeneration， promoting mitochondrial autophagy， regulating intestinal flora， and enhancing energy metabolism， which in turn improved the pathological state of AD animal models. The therapeutic effects of different saponins on AD are different. The present study discussed the effect of different aglycones and sugar chains on the anti-AD activity based on saponins and anti-AD effect to provide new ideas and a theoretical basis for the development and utilization of saponins.
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Objective:To characterize the imaging distortion of the 1.5T magnetic resonance imaging-guided linear accelerator (MR-Linac) and to analyze the influence of MR-Linac and peripheral devices on the geometric distortion.Methods:Specialized MRI imaging distortion phantom and analysis software were applied. The baseline of imaging distortion within diameter spherical volume (DSV) around the center of the magnet was established. The influence of the beam generation system, mechanical system and peripheral devices on the imaging distortion was analyzed. The long-term stability of imaging distortion was tested on the MR-Linac.Results:Imaging distortion of the MR-Linac was increased with the increasing distance to the center of the magnet. Within DSV 400 mm, few test points surpassed 1 mm imaging distortion in 3D directions. However, imaging distortion surpassed 2 mm in part of region within DSV 400-500 mm, with the largest distortion over 7 mm. Imaging distortion of the MR-Linac remained unchanged within 7 months after installation. And the influence of the MR-Linac and peripheral devices on the imaging distortion was only observed in the overall largest distortion within DSV 400-500 mm.Conclusions:Cautions should be taken during the application of high-field MR-Linac in patients whose tumor location is over 20 cm from the ISO center. Imaging distortion of the MR-Linac remains stable within 7 months after installation. The influence of the MR-Linac and peripheral devices on the imaging distortion is trivial, which can be neglected in clinical practice.
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Objective:To investigate the impacts of electron streaming effect (ESE) on out-of-field dose distribution in 1.5 T MRI-guided radiotherapy.Methods:Firstly, the Monaco v5.40.1 (Elekta AB, Stockholm, Sweden) treatment planning system (TPS) was implemented to investigate the ESE in a square field (5 cm × 5 cm) at the entry and exit sides of a special homogeneous water phantom. Afterward, a retrospective investigation was conducted into one laryngeal cancer case and one breast cancer case who had been treated on a conventional linear particle accelerator (linac). Then doses were recalculated in the Monaco system using a Unity machine model. Meanwhile, the out-of-field skin dose enhancement induced by ESE was investigated.Results:ESE-induced dose variations were observed at both the entry and exit sides of the phantom surface in the presence of a magnetic field, with the ESE on the exit side notably stronger than that on the entry side. For the laryngeal cancer case, the ESE was not notable and had insignificant impacts on the out-of-field skin dose. In contrast, ESE-induced in-air high-dose region outside the body stretched to the chin area for the breast cancer case. This led to the skin dose escalation of the chin at D1 cm 3 454.6 cGy. After the application of 1 cm bolus, the corresponding skin dose of the chin D1 cm 3 reduced to as low as 113.6 cGy, which is almost equivalent to that in the absence of a magnetic field ( D1 cm 3=92.5 cGy). Conclusions:The ESE in a magnetic field can alter out-of-field dose and lead to local dose enhancement along the electron path. Although the ESE had insignificant impacts on the out-of-field dose of the laryngeal cancer case, it reached the chin area of the breast cancer case. ESE can be effectively shielded by adding protective bolus.
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Objective:To investigate the feasibilityof the adaptive radiotherapy using high-field MR-Linac systems for head neck cancers and perform the evaluation of target coverage and dose criteria.Methods:This study investigated 128 treatment plans of six patients who were treated on 1.5T MR-Linacsystems in Sun Yat-sen University Cancer Center in 2019, compared the differences in target coverage and dose criteria between the dose accumulation in the adaptive radiotherapy using MR-Linac systems and the reference plans, and evaluated the target coverage and dose criteria of each fraction of adaptive plan based on daily MRI anatomy.Results:There was no significant change in the target coverage and dose criteria for each treatment fraction(<1%). However, the change of lens dose was significant (maximum 98%). In addition, the result showed that there was no significant difference in target coverage and dose criteria between the dose accumulation in adaptive radiotherapy using MR-Linac systems and reference plans.In contrast, the average dose to lens was increased by 31.7%.Conclusions:It is feasible to perform adaptive radiotherapy using 1.5T MR-Linacsystems for head neck cancers according tothe evaluation of target coverage and dose criteria. Additionally, since the actual dose tolens was quite different from the reference plan, the lens exposure should be considered in clinical practice.
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Objective:To assess proton biological dose with using two kinds of relative biological effect models and to compare them with traditional clinical proton biological dose ( Dose1.1). Methods:Based on Particle simulation tools(TOPAS), physical dose, LET d and LET t were calculated in water phantom and two anthropomorphic phantoms (brain and prostate tumors) respectively. Then DoseLET d and DoseLET t were calculated according to different relative biological effect models, an RBE was 1.1 in traditional clinical proton biological dose calculation. Three kinds of biological doses were compared in the water phantom. To quantify the differences between three method in anthropomorphic phantoms, three points ( D1, D2, D3) were selected according to the physical dose to compare the biological dose. Results:DoseLET d and DoseLET t in water phantom showed the same trend with water depth and both of them were higher than Dose1.1 at the end of proton beam range. The maximal difference between DoseLET d and DoseLET t in the anthropomorphic phantoms was 10.08 cGy, where the relative difference was less than 5%. When DoseLET d and DoseLET t were compared with Dose1.1, the maximal differences in brain tumor target were 71.97 cGy and 61.91 cGy respectively, where the relative differences were less than 25%. The maximal differences in prostate tumor target were 25.95 and 19.96 cGy respectively, where the relative differences were less than 12%. However, the differences outside the target were very small, where the maximal differences in brain and prostate tumors were 5.99 cGy and 9.92 cGy respectively, and the relative differences were less than 5%. Conclusions:Biological doses calculated by two method are of little difference in both water and anthropomorphic phantoms, however, large differences were observed when they were compared with the traditional clinical proton biological dose especially in the high dose area.
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Objective Because of high precision and mild side effects,intensity-modulated proton therapy (IMPT) has become a hot spot in the radiotherapy field.Nevertheless,the precision of IMPT is extremely sensitive to the range uncertainties.In this paper,a novel robust optimization method was proposed to reduce the effect of range uncertainty upon IMPT.Methods Firstly,the robust optimization model was established which contained three types of range including the increased range,the normal range and the shortened range.The objective function was expressed in quadratic function.The organ dose contribution matrix of each range was calculated by proton pencil beam algorithm.The range deviation was discretized and the probability of each range was obtained based on the Gauss distribution function.Finally,the conjugate gradient method was adopted to find the optimal solution to make the actual dose coverage of the target area and the organs at risk distributed within the expected dose as possible.Results The 3 sets of simulation tests provided by the AAPM TG-119 Report were utilized to evaluate the effectiveness of this method:nasopharyngeal carcinoma,prostate and "C"-type cases.Compared with conventional IMPT optimization approach,this novel method was less sensitive to the range uncertainty.When the range deviation occurred,the dose coverage of the target area and organs at risk of the nasopharyngeal carcinoma and prostate cases almost reached the expected dose,and the high dose coverage of the target area and organs at risk protection were improved in the"C"-type cases.Conclusions To compensate for the range uncertainty,this novel method can enhance the dose coverage of the target area and reduce the dose coverage of the organs at risk.
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Objective To explore the feasibility of application of the Monte Carlo method to simulate the whole body dose distribution in patients with total body X (γ) ray irradiation by comparing the actual measurement results.Methods A Monte Carlo model of a 6 MV Elekta Synergy Clinical linear accelerator was established by MCNPX.According to the relationship between the CT value and the density of the material,the CT of the ATOM physical phantom was converted into a voxel phantom for MCNPX calculation.The dose distribution of the whole body was simulated in the total body X (γ) ray irradiation.The simulated results were compared with the measurement values of the thermoluminescence dosimetry at different positions in the ATOM physical phantom to analyze the differences.Results The difference between the depth dose curve and the off-axis dose curve and the actual measurement values calculated by the 6 MV accelerator treatment head model in the water tank was less than 2％,with the maximum dose depth of approximately 1.5 cm and field size of 10 cm× 10 cm,which were consistent with the actual measurement values.The maximum difference between the simulated results at different locations in the body and the thermoluminescence dosimeter was approximately 4％,and the simulated results of MCNPX were almost in good agreement with the results of thermoluminescence.Conclusions The whole body dose distribution in patient with total body X (γ) ray irradiation can be accurately simulated by MCNPX.Monte Carlo simulation makes it possible to optimize the uniformity of the total body dose during the total body irradiation process.
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Objective To observe the correlation between vitamin D and liver cirrhosis classification in hepatic diabetes.Methods Thirty-eight patients with hepatic diabetes,48 patients with type 2 diabetes and 30 cases of healthy controls were collected.The level of serum 25-(OH)D3 was determined,and the Child-Pugh score was calculated.The correlation between pathogenesis and pathogenetic condition of hepatic diabetes was analyzed.Results The levels of serum 25-(OH)D3 in hepatic diabetes patients,type 2 diabetes patients and healthy controls were (38.23 ± 12.47),(63.33 ± 13.58) and (86.14 ± 16.25) μ mol/L,and there was statistical difference (P ＜ 0.05).There was negative correlation in hepatic diabetes between serum 25-(OH)D3 level and liver cirrhosis Child-Pugh score (r =-0.363,P ＜ 0.05).Conclusion Low level of vitamin D may be one of the pathogenesis of hepatic diabetes.