Research on multi-Atlas segmentation based on feature clustering / 中华放射肿瘤学杂志

Objective:To study the improvement of normal tissue region of interest (ROI) segmentation based on clustering-based multi-Atlas segmentation method, thereby achieving better delineation of organs at risk.Methods:CT images of 100 patients with cervical cancer who had completed treatment in Zhejiang Cancer Hospital during 2019-2020 were selected as the Atlas database. According to the volume characteristic parameters of the organs at risk (bladder, rectum and outer contour), the Atlas database was divided into several subsets by k-means clustering algorithm. The image to be segmented was matched to the corresponding Atlas library for multi-Atlas segmentation. The dice similarity coefficient (DSC) was used to evaluate the segmentation results.Results:Using 30 patients as the test set, the sub-Atlas generated by different clustering methods were compared for the improvement of image segmentation results. Compared with general multi-Atlas segmentation methods, clustering-based multi-Atlas segmentation method significantly improve the segmentation accuracy for the bladder (DSC=0.83±0.09 vs. 0.69±0.15, P<0.001) and the rectum (0.7±0.07 vs. 0.56±0.16, P<0.001), but no statistical significance was observed for left and right femoral head (0.92±0.04, 0.91±0.02) and bone marrow (0.91±0.06). The average segmentation time of clustering-based multi-Atlas segmentation method was shorter than that of the general multi-Atlas segmentation method (2.7 min vs. 6.3 min). Conclusion:The clustering-based multi-Atlas segmentation method can not only reduce the number of Atlas images registered with the image to be segmented, but also can be expected to improve the segmentation effect and obtain higher accuracy.

Analysis of the current team building of medical physics talent system in Hong Kong of China and its implications / 中华医院管理杂志

Medical physicists play an important role in the delivery of radiotherapy. Compared with China′s mainland, Hong Kong has established a more mature training mode and a more complete management system for medical physics talents. In this article, the authors introduced the current state of medical physics talent training, as well as the recruitment, certification and promotion of medical physicist in Hong Kong by querying the official websites of medical physics organizations, reviewing related literature and interviewing senior medical physicists in Hong Kong. The authors also analyzed the shortcomings in the construction of medical physics talent system in China′s mainland and made valuable suggestions.

Study of three-dimensional dose distribution prediction in cervical cancer brachytherapy based on U-Net fully convolutional network / 中华放射肿瘤学杂志

Objective:Topredict the three-dimensional dose distribution of regions of interest (ROI) with brachytherapy for cervical cancer based on U-Net fully convolutional network, and evaluate the accuracy of prediction model.Methods:First, 100 cases of cervical cancer intracavity combined with interstitial implantation were selected as the entire research data set, and divided into the training set ( n=72), validation set ( n=8), and test set ( n=20). Then the U-Net was used to construct two models based on whether the uterine tandem and the implantation needles were included as the distinguishing factors. Finally, dose distribution of 20 cases in the test set were predicted using the trained model, and comparative analysis was performed. The performance of the model was jointly evaluated by , and the mean absolute deviation (MAD). Results:Compared with the model without the uterine tandem and the implantation needles, the of the rectum was increased by (16.83±1.82) cGy ( P<0.05), and the or of the other ROI were not different significantly (all P>0.05). The MAD of the high-risk clinical target volume, rectum, sigmoid, small bowel, and bladder was increased by (11.96±3.78) cGy, (11.43±0.54) cGy, (24.08±1.65) cGy, (17.04±7.17) cGy and (9.52±4.35) cGy, respectively (all P<0.05). The MAD of the intermediate-risk clinical target volume was decreased by (120.85±29.78) cGy ( P<0.05). The mean value of MAD for all ROI was decreased by (7.8±53) cGy ( P<0.05), which was closer to the actual plan. Conclusions:U-Net fully convolutional network can be used to predict three-dimensional dose distribution of patients with cervical cancer undergoing brachytherapy. Combining the uterine tube with the implantation needles as the input parameters yields more accurate predictions than a single use of the ROI structure as the input.

Enlightenment and reference of training and certification mode of radiation therapist in the United States / 中华放射肿瘤学杂志

The training program of radiation therapists in the United States has been established early, and the mode of training, qualification and continuing education are relatively complete. Literature review was conducted at home and abroad and United States Department of Labor, American Registry of Radiologic Technologists, American Society of Radiologic Technologists as well as Joint Review Committee on Education in Radiologic Technology websites were reviewed. The training mode, qualification, work content, continuing education and employment situation of American radiotherapists were analyzed, aiming to provide some reference and enlightenment for the establishment of a new model for the training of professional radiologists suitable for the national conditions of China Mainland.

Application of a multi-task learning-based light-weight convolution neural network for the automatic segmentation of organs at risk in thorax / 中华放射肿瘤学杂志

Objective:To evaluate the application of a multi-task learning-based light-weight convolution neural network (MTLW-CNN) for the automatic segmentation of organs at risk (OARs) in thorax.Methods:MTLW-CNN consisted of several layers for sharing features and 3 branches for segmenting 3 OARs. 497 cases with thoracic tumors were collected. Among them, the computed tomography (CT) images encompassing lung, heart and spinal cord were included in this study. The corresponding contours delineated by experienced radiation oncologists were ground truth. All cases were randomly categorized into the training and validation set ( n=300) and test set ( n=197). By applying MTLW-CNN on the test set, the Dice similarity coefficients (DSCs) of 3 OARs, training and testing time and space complexity (S) were calculated and compared with those of Unet and DeepLabv3+ . To evaluate the effect of multi-task learning on the generalization performance of the model, 3 single-task light-weight CNNs (STLW-CNNs) were built. Their structures were totally the same as the corresponding branches in MTLW-CNN. After using the same data and algorithm to train STLW-CNN, the DSCs were statistically compared with MTLW-CNN on the testing set. Results:For MTLW-CNN, the averages (μ) of lung, heart and spinal cord DSCs were 0.954, 0.921 and 0.904, respectively. The differences of μ between MTLW-CNN and other two models (Unet and DeepLabv3+ ) were less than 0.020. The training and testing time of MTLW-CNN were 1/3 to 1/30 of that of Unet and DeepLabv3+ . S of MTLW-CNN was 1/42 of that of Unet and 1/1 220 of that of DeepLabv3+ . The differences of μ and standard deviation (σ) of lung and heart between MTLW-CNN and STLW-CNN were approximately 0.005 and 0.002. The difference of μ of spinal cord was 0.001, but σof STLW-CNN was 0.014 higher than that of MTLW-CNN.Conclusions:MTLW-CNN spends less time and space on high-precision automatic segmentation of thoracic OARs. It can improve the application efficiency and generalization performance of the models.

Application of individual head-rest combined with thermoplastic fixation mask in position fixation for irradiation with helical tomotherapy for head and neck tumors / 中国基层医药

Objective:To compare the positioning errors of individual head-rest combined with thermoplastic fixation mask versus thermoplastic fixation mask alone in patients with head and neck tumors. Methods:Twenty-eight patients who received irradiation with helical tomotherapy in Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital) between October 2019 and April 2020 were included in this study. They were randomly assigned to receive position fixation with either individual head-rest combined with thermoplastic fixation mask (N1 group, n = 14) or thermoplastic fixation mask alone (N2 group, n = 14). Megavoltage computed tomography (MVCT) scanning registration was used to obtain the positioning errors in translation and rotation (ROLL) in the left-right (X), head-food (Y), and belly-back (Z) directions. There were a total of 841 CT scans, consisting of 425 scans in group N1 and 416 scans in group N2. Results:The positioning errors in X, Y, Z and ROLL directions in the N1 group were (1.37 ± 1.04) mm, (1.38 ± 1.12) mm, (1.47 ± 1.62) mm and (1.47 ± 1.62) ° respectively, and they were (1.57 ± 1.21) mm, (2.10 ± 1.51) mm, (1.61 ± 1.50) mm and (1.40 ± 1.30) ° respectively in the N2 group. There was significant difference in positioning errors in the Y direction between N1 and N2 groups ( P = 0.013). In the N1 group, the outward expansion boundaries in X, Y and Z directions was 4.15 mm, 4.23 mm and 4.81 mm respectively, and it was 4.77, 6.31 and 5.08 mm, respectively in the N2 group. In the X direction, there was significant difference in positioning errors taking 3 mm as the dividing point between N1 and N2 groups ( χ2 = 10.516, P < 0.001). In the Y direction, there was significant difference in positioning errors taking 1, 2 and 3 mm as the dividing points between N1 and N2 groups ( χ2 = 24.889, P < 0.001; χ2 = 42.202, P < 0.001; χ2 = 46.204, P < 0.001). In the Z direction, there was significant difference in positioning errors taking 2 mm as the dividing point between N1 and N2 groups ( χ2 = 7.335, P = 0.007). In the N1 group, the percentage of positioning errors < 3 mm in the X, Y and Z directions was 92%, 90% and 92%, respectively. Conclusion:Compared with thermoplastic fixation mask alone, individual head-rest combined with thermoplastic fixation mask can better effectively improve the positioning stability and reduce positioning errors in patients receiving irradiation with helical tomotherapy for head and neck tumors. The combined method is of certain innovation.

A study of prediction model of lung dose in early stage non-small cell lung cancer with stereotactic body radiotherapy / 中华放射肿瘤学杂志

Objective@#To study a lung dose prediction method for the early stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy based on machine learning algorithm, and to evaluate the feasibility of application in planning quality assurance.@*Methods@#A machine learning algorithm was utilized to achieve DVH prediction. First, an expert plan dataset with 125 cases was built, and the geometric features of ROI, beam angle and dose-volume histogram(DVH) parameters in the dataset were extracted. Following a correlation model was established between the features and DVHs. Second, the geometric and beam features from 10 cases outside the training pool were extracted, and the model was adopted to predict the achievable DVHs values of the lung. The predicted DVHs values were compared with the actual planned results.@*Results@#The mean squared errors of external validation for the 10 cases in mean lung dose (MLD)MLD and V20 of the lung were 91.95 cGy and 3.12%, respectively. Two cases whose lung doses were higher than the predicted values were re-planned, and the results showed that the the lung doses were reduced.@*Conclusion@#It is feasible to utilize the anatomy and beam angle features to predict the lung DVH parameters for plan evaluation and quality assurance in early stage NSCLC patients treated with stereotactic body radiotherapy

Study of three-dimensional dose distribution prediction model in radiotherapy planning based on full convolution network / 中华放射肿瘤学杂志

Objective:To explore a three-dimensional dose distribution prediction method for the left breast cancer radiotherapy planning based on full convolution network (FCN), and to evaluate the accuracy of the prediction model.Methods:FCN was utilized to achieve three-dimensional dose distribution prediction. First, a volumetric modulated arc therapy (VMAT) plan dataset with 60 cases of left breast cancer was built. Ten cases were randomly chosen from the dataset as the test set, and the remaining 50 cases were used as the training set. Then, a U-Net model was built with the organ structure matrix as inputs and dose distribution matrix as outputs. Finally, the model was adopted to predict the dose distribution of the cases in the test set, and the predicted 3D doses were compared with actual planned results.Results:The mean absolute differences of PTV, ipsilateral lung, heart, whole lung and spinal cord for 10 cases were (119.95±9.04) cGy, (214.02±9.04) cGy, (116.23±30.96) cGy, (127.67±69.19) cGy, and (37.28±18.66) cGy, respectively. The Dice similarity coefficient (DSC) of the prediction dose and the planned dose in the 80% and 100% prescription dose range were 0.92±0.01 and 0.92±0.01. The γ rate of 3 mm/3% in the area of 80% and 10% prescription dose range were 0.85±0.03 and 0.84±0.02. Conclusion:FCN can be used to predict the three-dimensional dose distribution of left breast cancer patients undergoing VMAT.

Experience and efficacy of SBRT for lung cancer: an analysis of 142 patients / 中华放射肿瘤学杂志

Objective:To evaluate the clinical efficacy and safety of stereotactic body radiation therapy (SBRT) for stage Ⅰ-Ⅱ non-small cell lung cancer.Methods:Retrospective analysis of patients with early stage lung cancer who received SBRT in Zhejiang Cancer Hospital from 2012 to 2018 was conducted. The Kaplan-Meier method was used for survival analysis. The main endpoints of the study were locoregional control (LRC) and cancer specific survival (CSS).Results:A total of 142 eligible cases were included, with a median BED10100Gy (100-132Gy). The median age was 75.6 years (47.2-89.0 years), among which 75 patients were aged (greater than or equal to 75 years old). The median follow-up time was 31.0 months, for patients< 75 years old and patients ≥ 75 years old. The 5-year LRC were 84.5% and 95.8% respectively, 5-year CSS were 72.4% and 78.6% respectively, for patients< 75 years old and elderly patients. The systemic response was mild during treatment, no grade 4-5 adverse events occurred in all patients. The main acute side effect was radiation pneumonitis (RP) below grade 3. Grade 2 RP appeared in 14 patients (9.9%) after SBRT where grade 3 RP occurred in 2(1.4%). There was no treatment-related mortality in the SBRT group.Conclusions:SBRT is a safe and effective treatment for early primary lung cancer with satisfactory rates of LRC and CSS in 5 years and mild complication, which is similar to previous reports.

A study of prediction model of lung dose in early stage non-small cell lung cancer with stereotactic body radiotherapy / 中华放射肿瘤学杂志

Objective To study a lung dose prediction method for the early stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy based on machine learning algorithm,and to evaluate the feasibility of application in planning quality assurance.Methods A machine learning algorithm was utilized to achieve DVH prediction.First,an expert plan dataset with 125 cases was built,and the geometric features of ROI,beam angle and dose-volume histogram(DVH) parameters in the dataset were extracted.Following a correlation model was established between the features and DVHs.Second,the geometric and beam features from 10 cases outside the training pool were extracted,and the model was adopted to predict the achievable DVHs values of the lung.The predicted DVHs values were compared with the actual planned results.Results The mean squared errors of external validation for the 10 cases in mean lung dose (MLD) MLD and V20 of the lung were 91.95 cGy and 3.12％,respectively.Two cases whose lung doses were higher than the predicted values were re-planned,and the results showed that the the lung doses were reduced.Conclusion It is feasible to utilize the anatomy and beam angle features to predict the lung DVH parameters for plan evaluation and quality assurance in early stage NSCLC patients treated with stereotactic body radiotherapy

Evaluation of different volumetric-modulated arc therapy for the large planning target volume in T3 lung cancer / 中国基层医药

Objective@#To investigate the feasibility and dosimetric characteristics of using dual-arc volumetric modulated arc therapy and multiple partial-arc VMAT for T3 lung cancer.@*Methods@#From June 2016 to May 2018, thirteen lung cancer patients with large planning target volume were replanned with dual full arcs VMAT(F-VMAT) and six partial-arc s VMAT(P-VMAT)on RayStation v4.5 RayArc function.PTV volume median was 550.9cm3(ranged 402.2-834.8cm3) and to a prescribed dose of 60 Gy in 30 fractions.Equivalent target coverage was required for all plans, and clinical goals were evaluated using various dose-volume metrics.These included PTV dose conformity, mean lung/heart dose, lung V5, V10, V20, V30, heart V30 and V40, and Dmax of spinal canal.The total monitor units (MUs) were also examined.@*Results@#All VMAT plans satisfied the treatment criteria.F-VMAT achieved better homogeneity index(HI) and MUs than P-VMRT(t=-3.904, P=0.002), and the conformal number(CN) of tumor volumes was likely clinically indistinguishable.However, F-VMAT significantly reduced lung V5, V10 and mean lung dose[V5: (51.31±5.36)% vs.(43.44±5.28)%, t=6.908, P=0.00; V10: (38.34±3.26)% vs.(34.05±3.74)%, t=4.632, P=0.001; Dmean: (1 449±117.19)cGy vs.(1 375.38±148.98)cGy, t=4.93, P=0.00], and heart dosimetric parameters were also observed in favor of P-VMRT[V30: (20.6±10.4)% vs.(16.4±8.9)%, t=3.822, P=0.02; V40: (14.6±7.5)% vs.(11.88±7.1)%, t=3.096, P=0.009; Dmean: (1 442.9±651.2)cGy vs.(1 263.5±605.6)cGy, t=3.986, P=0.02], and there were no statistically significant differences in lung V20, V30 and spinal cord Dmax between the two groups(all P>0.05).@*Conclusion@#VMAT is an effective treatment for stage T3 lung cancer patients.The primary advantage of P-VMAT was the reduction in low dose area and decreased risk of symptomatic radioactive lung injury.It may be a priority for pulmonary malignancy patients with the large planning target volume.

Evaluation of different volumetric-modulated arc therapy for the large planning target volume in T3 lung cancer / 中国基层医药

Objective To investigate the feasibility and dosimetric characteristics of using dual - arc volumetric modulated arc therapy and multiple partial-arc VMAT for T3 lung cancer.Methods From June 2016 to May 2018,thirteen lung cancer patients with large planning target volume were replanned with dual full arcs VMAT (F-VMAT) and six partial-arc s VMAT( P-VMAT) on RayStation v4.5 RayArc function.PTV volume median was 550.9cm3(ranged 402.2-834.8cm3 ) and to a prescribed dose of 60 Gy in 30 fractions.Equivalent target coverage was required for all plans,and clinical goals were evaluated using various dose-volume metrics.These included PTV dose conformity,mean lung/heart dose,lung V5 ,V10 ,V20 ,V30 ,heart V30 and V40 ,and Dmax of spinal canal.The total monitor units ( MUs) were also examined. Results All VMAT plans satisfied the treatment criteria. F - VMAT achieved better homogeneity index ( HI) and MUs than P -VMRT( t = -3.904,P =0.002),and the conformal number(CN) of tumor volumes was likely clinically indistinguishable.However,F-VMAT significantly reduced lung V5 ,V10 and mean lung dose[V5:(51.31 ± 5.36)% vs.(43.44 ± 5.28)%,t=6.908,P=0.00;V10:(38.34 ± 3.26)% vs.(34.05 ± 3.74)%,t=4.632,P=0.001;Dmean:(1 449 ± 117.19)cGy vs.(1 375.38 ± 148.98)cGy, t=4.93, P =0.00 ], and heart dosimetric parameters were also observed in favor of P - VMRT [ V30 : (20.6 ± 10.4)% vs.(16.4 ± 8.9)%,t =3.822,P =0.02;V40:(14.6 ± 7.5)% vs.(11.88 ± 7.1)%,t =3.096,P =0.009;Dmean:(1 442.9 ± 651.2)cGy vs.(1 263.5 ± 605.6)cGy,t=3.986,P=0.02],and there were no statisti-cally significant differences in lung V20,V30 and spinal cord Dmax between the two groups(all P>0.05).Conclusion VMAT is an effective treatment for stage T3 lung cancer patients. The primary advantage of P - VMAT was the reduction in low dose area and decreased risk of symptomatic radioactive lung injury.It may be a priority for pulmonary malignancy patients with the large planning target volume.

Comparison of clinical prognosis between stereotactic body radiotherapy and surgical treatment for early-stage non-small cell lung cancer after propensity score matching / 中华放射肿瘤学杂志

Objective To evaluate the clinical efficacy between stereotactic body radiotherapy (SBRT) and surgical treatment for stage Ⅰ-Ⅱ non-small cell lung cancer (NSCLC).Methods Clinical data of 120 patients with early-stage NSCLC who underwent SBRT or surgical treatment in Zhejiang Cancer Hospital from 2012 to 2015 were retrospectively analyzed.Propensity score matching was carried out between two groups.Sixty eligible patients were enrolled in each group.In the SBRT group,the 80％ isodose line covered 95％ of the planning target volume,and the 100％ isodose line covered 100％ of the internal gross tumor volume.The fractional dose was 5-15 Gy and the median biologically equivalent dose was 100 Gy (range:57.6-150.0 Gy).In the operation group,32 patients underwent video-assisted thoracoscopic lobectomy and 9 patients underwent wedge resection or segmentectomy.Results All patients successfully completed corresponding treatment and were followed up.The median follow-up was 32.3 months (range:8.6-68.4 months).In the operation group,3 patients died from infection within postoperative 90 d,whereas no case died in the SBRT group (P=0.079).In the SBRT group,3 patients died of other factors besides tumor (cerebral infarction,heart disease,etc.) during follow-up.Local-regional recurrence occurred in 12 patients including 5 cases in the operation group and 7 in the SBRT group (P=0.543).In the operation group,11 patients experienced distant metastases with a median disease-free survival (DFS) of 33.5 months.In the SBRT group,6 patients had distant metastases and the median DFS was 38.4 months (P=0.835,P=0.178).In the SBRT group,the 1-and 3-year overall survival rates were 93％ and 83％,and 95％ and 83％ in the operation group (P=0.993).Conclusions The 1-and 3-year overall survival rates and local control rate do not significantly differ between SBRT and operation for patients with early-stage NSCLC.

Experience and efficacy of SBRT for lung cancer:an analysis of 200 patients / 中华放射肿瘤学杂志

Objective To evaluate the safety and clinical efficacy of stereotactic body radiation therapy (SBRT) for lung cancer.Methods A retrospective analysis was performed on 200 patients with primary non-small cell lung cancer (NSCLC)(118 patients) or solitary pulmonary metastasis (82 patients) who underwent SBRT in Zhejiang Cancer Hospital from January 2012 to September 2015.The 80% isodose line covered 95% of the planning target volume,and the 100% isodose line covered 100% of the internal gross tumor volume.The fractional dose was 4.0-18.0 Gy daily or every other day,and the biologically equivalent dose ranged from 40.0 to 151.2 Gy (median 100 Gy).Results All patients completed treatment.The follow-up rate was 96.0%.The complete response and partial response rates were 14.8%(17/115) and 65.2%(75/115) for the primary tumor group,versus 25%(19/77) and 38%(29/77) for the metastasis group.The incidence rates of grade Ⅱ and Ⅲ acute radiation pneumonitis were 4.7% and 3.1%,respectively.The median follow-up was 14.9 months.The 1-and 2-year local control rates were 95.7% and 84.3% for the primary tumor group,versus 92% and 73% for the metastasis group.The 1-and 2-year overall survival rates were 94.5% and 92.0% for the primary tumor group,versus 85% and 62% for the metastasis group.Conclusions SBRT is a safe and effective treatment for early primary NSCLC and solitary pulmonary metastasis,resulting in high 1-and 2-year local control and overall survival rates and low rate of complications.

A quantitative analysis of tumor site specific setup based on 1 485 daily MVCT scans from helical tomotherapy / 中国基层医药

Objective To assess the variation in patient setup corrections for three different anatomic treat-ment sites using daily pretreatment megavoltage CT(MVCT)in helical tomotherapy,and to analyze alternative refer-ence margins for specific tumor site.Methods Sixty patients treated for three anatomical sites on helical tomotherapy were analyzed.Daily MVCT was carried out for registration and setup corrections before each treatment fraction.Setup errors and rotational setup corrections from 587 head and neck,500 thoracic,371 abdomen and gynecology MCVT imaging were input to statistical analysis.Incidences of three dimensional vector error lengths were calculated for each anatomic site.Overall distribution histograms of the three -dimensionally error was presented using GraphPad Prism 5.The distributions of systematic and random setup errors were quantitative analyzed and the additional margins required were also taken into account.Results 1 458 MVCT scans were implemented for sixty patients.Head and neck had lower frequencies of translational setup errors than others.Frequency of at least 3mm three -dimensional setup errors for head and neck,thoracic,abdomen and gynecology was 55.3%,70.8%,79.8%,respectively.This fre-quency decreased to 17.5%,40.6%,47.2% if 3D vector distance ≥5mm was scored.Overall systematic errors ranged from -1.4mm to 2.7mm,abdomen and gynecology had the largest setup errors in the vertical direction which was statistically significant(χ2 =19.3,P <0.05).The suggested margins should be increased by 4 -7 mm in three -dimensional direction for head and neck,9 -14mm for thoracic,10 -17mm for abdomen and gynecology.Conclusion Differences in setup corrections are perceived between head and neck,thoracic,abdomen and gynecology.The accura-cy of patient positioning can be improved if pre -treatment daily MVCT scans are put into use.Results from setup cor-rection can provide evidence for tumor treatment margin and improve the accuracy of regular radiotherapy.

Using compensate angles to correct rotation set-up errors in radiotherapy / 中国医学装备

Objective:The purpose of this paper is to introduce a method of using compensate angles to eliminate rotation set-up errors without six-degree of freedom couch. Methods: To detect six-degree of freedom set-up errors, cone-beam computed tomography (CBCT) scans were acquired. These set-up errors were defined as a matrix to transform from accelerator coordinate system to patient coordinate system. Two independent vectors were defined to describe angles of gantry, collimator and couch in accelerator machine. Transformation of vectors were determined by transformation matrix and re-calculated back to the machine angles. Results:It was found that compensate angles can fully corrected the rotation angles in set-up with limited time consuming. It is feasible to implement compensate angles in routinely radiation procedure. Conclusion:With this method, it is possible to implement the complete corrections of set-up errors in radiotherapy without six-degree of freedom couch and it is convenient in operation as well.

Analysis on set-up errors of position fixation with simple perforated foam pad in colorectal cancer radio-therapy / 中国基层医药

Objective To explore the set-up errors of position fixation with simple perforated foam pad in colorectal cancer radiotherapy and their causes as well as the improvement measures.Methods Sixty cases of color-ectal cancer patients undergoing radiotherapy were collected.Prone position was adopted with the position fixed by perforated foam pad and membrane.CBCT imaging was taken weekly before treatment,setup errors were corrected if necessary.Errors throughout the course of treatment for each patient were recorded and compared between patients, followed by analyzing the reasons of errors.Results Before calibration,the maximum errors on the direction of left and right (X-axis),front and back (Z),upside and downside (Y)in these 60 patients were 0.5cm,0.9cm and 0.7cm respectively with the average errors of (0.22 ±0.03)cm,(0.38 ±0.03)cm and (0.27 ±0.04)cm respec-tively.Conclusion The method of applying perforated foam pad and thermoplastic mask in colorectal cancer radio-therapy is currently the most commonly used in the clinical position fixation techniques,by which the small intestine, bladder and other pelvic tissues can be well protected.Due to poor comfort prone position,it is necessary to further improve perforated foam pad through improving the quality of the foam pad,thus improving patients comfort and posi-tioning repeatability and reducing position fixation errors.

A application study of dose constraint template in intensity modulated radiation therapy planning for early stage nasopharyngeal carcinoma / 中华放射医学与防护杂志

Objective To investigate a feasibility of using dose constraint template (DCT) to increase conformity index (CI) of planning target volume (PTV) and improve intensity modulated radiation therapy (IMRT) planning efficiency for early stage nasopharyngeal carcinoma. Methods Ten patients with pathological diagnosed and treated by IMRT were selected for this study. Target volumes were delineated with Corvus 6.3 of treatment planning system, two dose limiting regions(DLR) around PIN were added by extending from PIN,each DLR was 1 cm thick. We created three plans:Plan0,Planl and Plan2. PianO was without DLR and DCT, Planl without DLR but with DCT, Plan2 with both condition;but to compare dose distribution in PLTV and normal tissue using three plans. Results Three plans could fill equal request of dose distribution in PLTV and normal tissue, and their difference was not statistical significant. CI of Plan2 was increased and planning time was decreased significantly compared with Piano and Planl. Conclusloa Usage of DCT together with DLR can increase CI of PTV and improve IMRT planning efficiency for early stage nasopharyngeal carcinoma, planning time is shortened significantly.

Inhibition of Bcl-2 Antisense Oligonucleotide Combined with Radiation against Lung Carcinoma Cells / 浙江中医药大学学报

[Objective] To study the inhibitory effect of bcl-2 antisense oligonucleotide(ASODN)combined with radiation on lung carcinoma cells NCI-H446.[Method]The cultured NCI-H446 lung carcinoma cells were divided into 5 groups:control,pure radiation,nonsense+radiation,lipofectin+radiation,ASODN+radiation.Every group except for control were assayed by MTT on the inhibition rates,24h,48h,72h after 10Gy irradiation respectively.[Results]The inhibitions of lung carcinoma cells NCI-H446 were observed in ASODN+radiation,lipofectin+radiation,nonsense+radiation and pure radiation groups.The differences between the ASODN+radiation group and the other three groups were significant(P

Bcl-2 Antisense Oligodeoxynucleotides Increase Apoptosis of Lung Cancer Cells Induced by Radiation / 医学研究杂志

Objective To study the effects of Bcl-2 antisense oligodeoxynucleotides(ASODN)on the apoptosis of lung cancer cells induced by radiation in vitro.Methods NCI-H446 lung cancer cell strains were divided into 5 groups:control simple radiation,lipofectin plus radiation,nonsense sqnence radiation and ASODN plus radiation.The cells cultured in five groups were collected at 6h,12h,24h,48h and 72h,with Wright-Giemsa stain,morphology analysis for which was done;the mRNA expression for p53、bcl-2 and PTEN gene was examined by RT-PCR half quantivity and DNA-ploid of the cells in five groups was detected by flow cyfometric method.Results Cell proliferation is obviously restrained and conformation is changed too with the shape crimpled and adherence function decreased obviously after irradiated for 10 Gy dose by the linac;p53 and PTEN expression clearly increased for the combination of Bcl-2 ASODN and bcl-2 mRNA expression clearly decreased.The apoptosis rate after 72 hours among control,pure radiation,lipofectin+radiation,nonsense+radiation and ASODN +radiation grouop is 0.14?0.09,13.17?2.47,11.84?1.76,13.72?1.4,21.26?2.97 respectively,the difference between ASODN combined with radiation grouop and other 4 groups are significant(P