Chinese Journal of Radiation Oncology

中华放射肿瘤学杂志

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Chinese Journal of Radiation Oncology

	2019 Vol.28 Issue.2 Published 2019-02-15

	Head and Neck Tumors Abdominal Tumors Thoracic Tumors Physics·Biology·Technique Review Articles Symposium

Head and Neck Tumors

	81	The impact of delineating guideline training on the hippocampal delineation
		Chu Jinjin, Zhu Zhengfei, Tong Tong, Yang Xi, Ni Jianjiao, Fan Xingwen
		Objective To explore the differences in the hippocampal delineation among different radiologists and to evaluate the impact of the delineating guideline training upon improving the accuracy of target area. Methods In this prospective study, 20 patients scheduled to receive whole brain radiation therapy were selected. Before and after the delineating guideline training, three physicians from Department of Radiation Oncology delineated the hippocampal targets three times for each patient. One physician from Department of Imaging Diagnosis delivered the delineating guideline training and delineated the hippocampus of 20 patients as the standard target area. The delineating targets before and after the training were statistically compared among different physicians. Results The conformity indexes with the standard target of three physicians before and after the training were 0.66±0.04 and 0.77±0.02,0.62±0.04 and 0.76±0.02,0.49±0.05 and 0.74±0.04,respectively. The conformity indexes were all statistically increased after the training (all P<0.05).The inter-observer variability significantly differed among different physicians before and after training (all P<0.05).The coefficient of variance of hippocampal volume before and after training were 0.16±0.06 and 0.08±0.04 with statistical significance (all P<0.05).Compared with all targets before training, the consistency of each physician was significantly improved after training (all P<0.05). Conclusion Hippocampal delineation guideline training can improve the accuracy of delineation.
		2019 Vol. 28 (2): 81-84 [Abstract] ( 473 ) [HTML 1KB] [ PDF 0KB] ( 0 )

Thoracic Tumors

	85	Relationship between factors of gross tumor volume and locoregional failure of radical intensity-modulated radiation therapy for esophageal carcinoma
		Zeng Jing, Pang Qingsong, Zhang Wencheng, Guan Yong, Qian Dong, Wang Ping, Qu Pengpeng, Zhao Lujun, Wang Jun, Wang Daquan, Shi Xiangyu, Liu Xiaojie
		Objective Investigate the relationship between gross tumor volume (GTV)-related factors includingGTV-T volume,the maximum thickness of the esophageal lesion plane and GTV-T volume/length(GTV-T volume divided by the length of the lesion calculated by the number of GTV-T layers) and the locoregional failure of radical intensity-modulated radiation therapy (IMRT) for esophageal carcinoma. Methods A total of 133 patients with esophageal cancer undergoing radical IMRT were enrolled. The factors related to GTV-T including GTV-T volume, the maximum thickness of the esophageal lesions, GTV-T volume/length were calculated. The relationship between GTV-T related factors and local recurrence of tumors was retrospectively analyzed. Results There was positively linear association between the locoregional failure rate of GTV-T and the volume of GTV-T. The volume of GTV-T tumor was 36 cm³, the maximum wall thickness was 2.5 cm, and the GTV-T volume/length was calculated as 5.3 cm². These critical values could be utilized to predict the risk of locoregional failure of IMRT for esophageal carcinoma. Conclusions The GTV-T factors can be adopted to predict the local control and the risk of locoregional failure of radical IMRT for esophageal carcinoma to certain extent.
		2019 Vol. 28 (2): 85-89 [Abstract] ( 498 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	90	Comparative analysis between induction chemotherapy combined with concurrent chemoradiotherapy and chemoradiotherapy alone for thoracic esophageal squamous cell carcinoma
		Wang Xiushen, Xi Mian, Bu Shanshan, Xu Gang, Ge Hong
		Objective To compare the clinical efficacy and safety between induction chemotherapy (IC) followed by concurrent chemotherapy (CRT) and CRT alone in patients with inoperable thoracic esophageal squamous cell carcinoma (ESCC). Methods Between 2002 and 2015, clinical data of 267 thoracic ESCC patients undergoing definitive CRT based on docetaxel combined with cisplatin were retrospectively analyzed. Through a matched case-control study, 85 patients receiving IC combined with CRT were matched to those undergoing CRT alone at a ratio of 1vs.1, according to age, gender, performance status, tumor location, tumor length, and TNM staging as the matching factors. Clinical efficacy and safety between two groups were statistically compared. Kaplan-Meier survival analysis was used to analyze the survival. The log-rank test was adopted to examine within-group differences. The Cox regression model was used for multivariate analysis. Results The median follow-up time for 170 patients was 18 months (range, 3-72 months). The overall objective response rates in the IC and CRT groups were 74.1% and 58.8%(P=0.035). The 3-year overall survival (OS) and progress-free survival (PFS) rates in the IC group were 44.2% and 34.8%, significantly higher than 29.7% and 15.4% in the CRT group (P=0.028, P=0.015). Subgroup analysis revealed that patients responsive to IC obtained significantly better OS (P=0.002), PFS (P=0.001), and local recurrence-free survival (LRFS)(P=0.002) compared with the IC non-responder, whereas the distant metastasis-free survival (DMFS) did not significantly differ (P=0.166). The incidence rate of grade 3–4 leukopenia in the IC group was significantly higher than that in the CRT group (38.8% vs. 24.7%, P=0.048). Multivariate analysis revealed that age and the addition of IC were independent prognostic factors for OS (P=0.003,0.016). Conclusions Compared with concurrent CRT, IC in combination with CRT can yield better short-term efficacy and longer survival for ESCC patients. The risk of hematological toxicity in the IC group is relatively higher but tolerable. Prospective randomized trials are required to confirm the clinical efficacy and safety of IC for thoracic ESCC patients.
		2019 Vol. 28 (2): 90-95 [Abstract] ( 485 ) [HTML 1KB] [ PDF 0KB] ( 0 )

Abdominal Tumors

	96	Treatment trends and prognosis of breast ductal carcinoma in situ:a single center analysis
		Liu Weixin, Wang Shulian, Song Yongwen, Tang Yu, Jing Hao, Wang Jianyang, Zhang Jianghu, Jin Jing, Wang Weihu, Liu Yueping, Fang Hui, Ren Hua, Qi Shunan, Lu Ningning, Tang Yuan, Li Ning, Li Yexiong
		Objective To analyze the changes in treatment patterns,clinical characteristics,treatment outcomes and prognostic factors of ductal carcinoma in situ (DCIS). Methods Clinical data of 617 female patients admitted to our institution between 2000 and 2013 were retrospectively analyzed. Kaplan-Meier survival analysis was adopted to calculate the local control (LC),disease-free survival (DFS) and overall survival (OS) rates. Log-rank test was utilized to identify the prognostic factors. Results Along the number of DCIS patients was gradually increased year by year,the proportion of breast conservative surgery was also elevated. However,mastectomy remained the primary surgical method. A total of 374 patients underwent mastectomy,160 cases received breast conservative surgery plus radiotherapy and 83 underwent breast conservative surgery alone. Postoperatively,366 patients (83.6%) with positive hormone receptor received hormone therapy and 45 patients (7.3%) underwent chemotherapy. The median follow-up time was 47 months. The 5-year LC,DFS and OS rates were 98.4%,97.5% and 98.9%,respectively. Univariate analysis demonstrated that Her-2-positive patients obtained worse OS (P=0.019). Although mastectomy group had more adverse factors compared with breast conservative surgery with or without radiotherapy groups,similar survival results were obtained among three groups. Mastectomy yielded better LC and DFS compared with breast conservative surgery alone. Conclusions DCIS patients obtain favorable clinical prognosis between the breast conservative surgery and mastectomy groups. The LC rate in the mastectomy group is better than that in the breast conservative surgery group.
		2019 Vol. 28 (2): 96-101 [Abstract] ( 738 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	102	Predicting the risk of non-sentinel lymph node metastasis in breast cancer patients with 1-2 positive sentinel lymph nodes
		Huang Zhou, Tang Yu, Wang Shulian, Song Yongwen, Jin Jing, Fang Hui, Zhang Jianghu, Jing Hao, Wang Jianyang, Liu Yueping, Chen Bo, Qi Shunan, Li Ning, Tang Yuan, Lu Ningning, Li Yexiong
		Objective To evaluate the risk factors of non-sentinel lymph node (NSLN) metastasis in breast cancer patients with 1-2 positive sentinel lymph nodes and to establish a new Nomogram prediction model. Methods Clinicopathological data of breast cancer patients who were diagnosed with 1–2 positive lymph nodes and underwent axillary lymph node dissection (ALND) without neoadjuvant chemotherapy from January 2008 to December 2014 were retrospectively analyzed. Measurement data between two groups were analyzed by chi-square test. Multivariate analysis was performed by logistic regression model. The prediction accuracy of the Nomogram model was evaluated using the area under the receiver operating characteristic curve (AUC) and calibration curves. Results A total of 270 patients were recruited in this study. Among them, 87(32.2%) patients had NSLN metastases. The median age was 46 years old (21-80 years), the median number of SLNs was 4(1-10) and the median number of axillary lymph nodes was 20(10-41). Univariate analysis demonstrated that the pathological grade, the size of SLN metastasis, the number of negative and positive SLNs were the risk factors of NSLN metastasis (P=0.001-0.045). Multivariate analysis showed that pathological grade, the number of negative and positive SLNs were independent risk factors of NSLN metastasis (P=0.000-0.041). The AUC value of Nomogram prediction model for NSLN metastasis was 0.70.The false negative rate of Nomogram was 10.5% when the cut-off point of predictive probability was ≤ 15%. Conclusions The Nomogram is a useful prediction model for evaluating NSLN metastasis. ALND or axillary radiotherapy can be avoided for patients with a low probability of NSLN metastasis.
		2019 Vol. 28 (2): 102-107 [Abstract] ( 687 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	108	Clinical efficacy of radiotherapy for stage ⅠE Primary ocular adnexal mucosa associated lymphoid tissue lymphoma
		Zhao Shuixi, Su Dan, Xu Yang, Cao Jingxu, Yang Xinji, Xiao Lihua
		Objective To evaluate the dose response and prognosis of patients with stage ⅠE primary ocular adnexal mucosa associated lymphoid tissue lymphoma (POAml) treated with radiotherapy. Methods Clinical date of 93 patients (117 eyes) with stage ⅠE POAml treated from November 2003 to July 2015 were retrospectively analyzed.The dose response was evaluated by observing the ocular changes in exophthalmos. The survival rate was calculated by using the Kaplan-Meier survival analysis. The log-rank test and univariate analysis were used for prognostic analysis. Results For patients treated with a dose of ≥27 Gy,the response rate of exophthalmos was 69.0%(29/42).The median response dose was 7.2 Gy (5.4-19.8 Gy).For all patients,the local control rate was 100%.The 5-and 10-year overall survival (OS) rates were 92% and 82%.The 5-and 10-year cause-specific survival (CSS) rates were equally 98%.The 5-and 10-year progression-free survival (PFS) rate were 90% and 88%.The univariate prognostic analysis demonstrated that the International Prognostic Index (IPI) score and age were the prognostic factors of PFS rate (both P=0.04). Conclusions POAml is sensitive to radiation therapy. Radiotherapy alone can yield excellent local control and long-term survival in POAml patients. A prescription dosage of 18 Gy dose can obtain favorable clinical efficacy.
		2019 Vol. 28 (2): 108-112 [Abstract] ( 487 ) [HTML 1KB] [ PDF 0KB] ( 0 )

Physics·Biology·Technique

	113	Commissioning and testing of treatment planning system model of an Edge accelerator with a high-definition multi-leaf collimator
		Ma Yangguang, Wang Tao, Hu Jinyan, Zhang Zheng, Wang Fangna, Wang Xuemin, Guo Yuexin
		Objective To investigate the commissioning and testing of the Eclipse model of an Edge accelerator with high-definition multi-leaf collimator (HD-MLC).Methods The percentage depth dose (PDD), profile, output factor measured by Razor and CC13 were statistically compared with the standard data. Penumbra, transmission factor (TF), leakage, concave-convex groove, accuracy of movement and dosimetry leaf gap (DLG) were measured with EBT3, electronic portal image device (EPID) and PTW SRS1000&SRS1500. The optimal DLG/TF was acquired when the γ pass rate of test cases was the highest. The point dose of regular fields, intensity-modulated radiation therapy (IMRT) and volume-modulated radiation therapy (VMAT) was verified with FC65-G. The planar dose of these case was verified with Octavius 4D and EBT3.Results The measured PDD data were consistent with the standard data. The measured penumbra of 3 cm and 4 cm square fields was smaller, whereas that of 6 cm square field was larger than the standard values. The left and right edge, field size, center of the field were distributed within the range of -1.0-0.4 mm、0.2-1.7 mm,-0.3-1.9 mm and -0.1-0.8 mm, respectively. The mean penumbra of the left and right MLC in different positions were (2.5±0.042) mm and (2.7±0.005) mm. The leakage of MLC was 0.009-0.016. The measured DLG/TF was 0.1861 cm/0.0116 and the optimal DLG/TF was 0.015 cm/0.014. The differences of point dose of all the test cases except the one which was in the low-dose area were within ±3%. Local and global γ pass rates of all IMRT were 79.81%-100% and 96.3%-100% (3%/3 mm), 71.3%-98.9% and 94.3%-99.8% for VMAT cases.Conclusions This method can accurately test and commission the Eclipse treatment planning model of Edge Linac equipped with HD-MLC.
		2019 Vol. 28 (2): 113-118 [Abstract] ( 565 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	119	Robust optimization of intensity-modulated proton therapy for range uncertainty
		Pei Xi, Xu Yao, Zhang Lian, Pi Yifei, Liu Hongdong, Xu Xie
		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.
		2019 Vol. 28 (2): 119-124 [Abstract] ( 607 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	125	Commissioning of dynamic jaw delivery in tomotherapy
		Hu Zhihui, Zhang Ke, Huang Peng, Dai Jianrong
		Objective To evaluate the dosimetric penumbra and delivery accuracy of dynamic jaw delivery in tomotherapy. Methods The jaw positioning hardware and the beam model were updated. Mechanical alignments were verified after the upgrade of the jaw positioning hardware. PDDs and beam profiles were measured by a two-dimensional water tank and compared with the new beam model. Dose penumbras in the longitudinal direction were compared between the dynamic and fixed jaw plans for different field width. Delivery accuracy was evaluated by point dose measurements with A1SL chamber and gamma analysis on the dose distribution measured by ArcCheck detector array. Results Mechanical alignments were in tolerance and beam characteristics were tuned to match the dynamic jaw beam model. Differences in the field width between the measured results and reference data were< 0.3% for both symmetric and asymmetric profiles in the longitudinal direction. The dose penumbra in dynamic jaw delivery was reduced from 17.92 mm to 7.51 mm for 2.5 cm jaw, and from 33.73 mm to 6.97 mm for 5.0 cm jaw, close to the penumbra of the traditional 1.0 cm jaw. IMRT verification of clinical cases was performed by A1SL ion chamber and ArcCheck detector array. The mean point dose difference was 0.33%±0.73% between the calculated and meassured data. Gamma analysis of dose distributions revealed that approximately 99.8% of the points satisfied the gamma criteria of 3% dose difference and 3 mm distance-to-agreement and the mean passing rates remained 97.9% even with tightest criteria of 2%/2 mm, and 100.0% with the criteria of 4%/4 mm, respectively. Conclusions Dosimetric penumbra in the longitudinal direction is significantly improved by the dynamic jaw delivery. Both the mechanical alignment and treatment delivery are qualified, suggesting that this new treatment is accurate and reliable.
		2019 Vol. 28 (2): 125-130 [Abstract] ( 390 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	131	Effect of down-regulation NEK-2 level on radio-sensitibity of A549 cells
		Chen Chenglong, Peng Yiru, Zhang Nan, Xue Lian, Yu Dong
		Objective To investigate the influence of down-regulation NEK-2 level on the radiosensitivity of A549 cells. Methods NEK-2 siRNA was transfected to A549 cells with liposome and NEK-2 expression level was inspected by Western blot. The radiosensitivity was detected by clone formation experiment. Cell cycle and cell apoptosis were analyzed by flow cytometry. Immunofluorescence experiment was used to detect the DNA double strand break and repair. Results NEK-2 siRNA successfully suppressed NEK-2 expression in A549 cells and resuced the cell proliferation ability after irradiation compared to the blank control group and the negative control group. It can improve the radiosensitivity of A549 cells (The radiosensitivity of A549 cells enhanced significantly.).The D0 values declined form 1.80 Gy to 1.40 Gy,and the sensitizing enhancement ratio was 1.32.After irradiation,compared to negative control group,the apoptosis rate was significantly improved (7.85% to 17.17%),cells in G2/M phase were obviously increased (9.23% to 30.16%),the DNA double strand break rate was increased (100% to 165%) and the DNA damage repair rate was reduced (100% to 48%) in NEK-2 siRNA group. The comparisons among the groups wer statistically significant (P<0.05). Conclusions NEK-2 siRNA reduced the proliferation and increased the radiosensitivity of A549 cell line,probably by affecting the cell cycle,promoting cell apoptosis and suppressing DNA damage repair.
		2019 Vol. 28 (2): 131-135 [Abstract] ( 393 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	136	Effect of CCR4 on sorafenib radiosensitivity and tumorigenesis of hepatocellular carcinoma cells in nude mice
		Wang Wei, Ke Shanbao, Liu Mingbo, Li Baiyu, Wang Zhaojie
		Objective To investigate the effect of CC chemokine receptor 4(CCR4) on sorafenib radiosensitivity and tumorigenesis of hepatocellular carcinoma cells in nude mouse models. Methods Western blot was used to detect the expression of CCR4 in hepatocellular carcinoma cell line. Lentivirus was utilized to construct PLC/PRF/5 and SMMC-7721 cell lines stably overexpressing and silencing CCR4,which were verified by Western blot. The influence of CCR4 on the radiosensitivity of hepatocellular carcinoma cells was assessed by plate clone formation assay. The effect of CCR4 on the tumorigenesis in hepatocellular carcinoma cells in vivo was evaluated by tumorigenesis assay in nude mice. Results CCR4 was highly expressed in highly-metastatic hepatocellular carcinoma cells and lowly expressed in hepatocellular carcinoma cells with low metastases. The PLC/PRF/5 and SMMC-7721 cells,which stably overexpressed and silenced CCR4,were successfully established. Overexpression of CCR4 reversed the inhibitory effect of sorafenib radiotherapy on PLC/PEF/5,whereas knockdown of CCR4 could increase the radiosensitivity of SMMC-7721 to sorafenib. Overexpressing CCR4 could promote the tumorigenicity of PLC/PEF/5,whereas knockdown of CCR4 could inhibit the tumorigenicity of SMMC-7721 in nude mice. Conclusion CCR4 overexpression significantly reduces the radiosensitivity of PLC/PRF/5 and increases the tumorigenicity in nude mice,whereas knockdown of CCR4 considerably increases the chemosensitivity and radiosensitivity of SMMC-7721 and suppresses the tumorigenicity in nude mice.
		2019 Vol. 28 (2): 136-139 [Abstract] ( 393 ) [HTML 1KB] [ PDF 0KB] ( 0 )

Review Articles

	140	Interpretation of ICRU Report No.89(prescribing, recording, and reporting brachytherapy for cancer of the cervix)—radiobiology
		He Mingyuan, Tang Yuhuan, Zhao Hongfu, Cheng Guanghui
		This paper made a detailed interpretation about the radiobiology-related contents in the ICRU report No.89, aiming to provide reference to resolve the problems related to radiobiology for the colleagues occupied in the brachytherapy for cervical cancer.
		2019 Vol. 28 (2): 140-145 [Abstract] ( 503 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	146	Research status of prophylactic irradiation to para-aortic lymph nodes in cervical cancer
		Liu Yehong, Guo Qi, Tian Ye
		The recurrence rate of para-aortic lymph nodes in patients with cervical cancer undergoing concurrent pelvic chemoradiotherapy is approximately 10%,which seriously affects the prognosis of patients with cervical cancer. Some researchers suggest that high-risk patients with locally advanced cervical cancer undergo prophylactic irradiation to the para-aortic lymph nodes based on pelvic chemoradiotherapy. In this article, the clinical efficacy, the applicable population, the upper margin of the target volume, the preventive dose and the side effects of prophylactic irradiation to the para-aortic lymphatic nodes were analyzed.
		2019 Vol. 28 (2): 146-150 [Abstract] ( 447 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	151	Research advances in the prevention and treatment of radiation-induced dermatitis
		Ou Dan, Wang Xiaoshen, Hu Chaosu
		Radiation-induced dermatitis (RD) is one of the most common complications induced by radiotherapy in cancer patients. The incidence and severity of RD are largely associated with the risk factors of patients. RD can severely affect the quality of life, even discontinue the treatment and reduce the tumor control rate in severe patients. Currently, randomized control trials evaluating the preventive measures for acute RD have been rarely conducted. The clinical interventions for acute RD significantly vary. In this article, the pathogenesis, risk factors, clinical manifestations, evaluation, prevention and treatment of RD were investigated.
		2019 Vol. 28 (2): 151-154 [Abstract] ( 719 ) [HTML 1KB] [ PDF 0KB] ( 0 )

Symposium

	155	Analysis of failure of helical tomotherapy multi-leaf collimator system
		Li Hongming, Yu Lang, Sun Xiansong, Wang Xinhai, Hu Ke, Zhang Fuquan, Qiu Jie
		Objective To analyze the failure and processing methods of helical tomotherapy multi-leaf collimator (MLC) and summarize relevant maintenance experience, aiming to accurately identify the faulty parts, shorten the downtime and enhance the work time. Methods The failure data of the helical tomotherapy MLC system in the past 48 months were analyzed to identify the common faulty parts, causes and processing methods. Results During the previous 48 months, the MLC failure occurred for 20 times, 11 times for air compressor failure, 4 times for position verification board failure, twice for leaf driver failure, twice for cushion valve failure and once for the slip of leaf position verification rod. The MLC failure was significantly correlated with the humidity of high-pressure gas. The work time of machine exerted significant effect upon the service time of MLC parts. Conclusions The structure of the helical tomotherapy MLC system is complex. The high-intensity work increases the failure rate. The humidity of high-pressure gas affects the normal operation of the MLC equipment. The faulty parts can be identified, the downtime can be reduced and the work time can be enhanced by summarizing the experience of MLC maintenance.
		2019 Vol. 28 (2): 155-157 [Abstract] ( 366 ) [HTML 1KB] [ PDF 0KB] ( 0 )

	158	Varian IX accelerator kV class CBCT image ring-shaped artifact troubleshooting
		Liu Yinliang, Zhai Fushan, Lyu Shuzhuang, Niu Weitao
		The hardware and software faults in the image guidance system may cause ring-shaped artifacts, which is more commonly induced by the aging of the hardware. During troubleshooting, the first step should be checking whether there are obvious faults in the basic hardware. Subsequently, OBI background image is collected to confirm the bad point status. If the bad point is not shielded, it can be compensated by updating the image processing bad point. The invoked Pixel Correction Maps are adopted compensate for the bad point and calibrate the image. If it is still unable to repair, replacing the detection board can be considered. Cone-beam CT (CBCT) image guidance system is an important approach to verify the position orientation and positioning accuracy in modern radiotherapy, which effectively guarantees for the safety and accuracy of radiotherapy. We should fully understand its law of aging, maintain the equipment on a regular basis and verify the image quality to ensure the normal operation of the equipment.
		2019 Vol. 28 (2): 158-160 [Abstract] ( 477 ) [HTML 1KB] [ PDF 0KB] ( 0 )

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