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Objective:To preliminarily investigate the effects of tumor treating field (TTF) arrays on the positioning accuracy of radiotherapy setup in the treatment of glioblastoma.Methods:The kilovolt cone-beam CT (CBCT) and an X-ray volumetric imaging (XVI) system were used to verify the radiotherapy setup of 29 patients treated with conventional radiotherapy and 12 patients treated with TTF concurrent radiotherapy, respectively. The errors of radiotherapy position isocenter and treatment plan isocenter were evaluated in six directions, namely lateral (Lat), head pin (Lng), dorsoventral (Vrt), roll, pitch, and rotation (Rtn). Then, the plan isocenter was redetermined according to the setup error data. Moreover, the dose distribution was recalculated without changing the radiation field parameters. Finally, the V40, Dmean, D98% and D2% of both PTV and CTV and the Dmean, D20 cm 3, and D30 cm 3 of scalp tissue were evaluated. Results:When patients were treated with TTF concurrent radiotherapy wearing TTF arrays, the setup errors increased by 2 mm and 1.3 mm on average (maximum: 3.5 mm and 2.7 mm) toward the foot and dorsal directions, respectively. In addition, the setup errors in both Roll and Rtn directions increased by about 1.1° toward one side. The V40 and D98% of PTV decreased by up to 4.78% and 6%, respectively. The Dmean, D20 cm 3, and D30 cm 3 to scalp tissue increased by up to 2.6%, 3.2%, and 3.5%, respectively. The errors of other dose parameters for both CTV and PTV were within 2%. Conclusions:TTF arrays have significant effects on the setup errors of patients in the Lng and Vrt directions and increase the setup difficulty in the Roll and Rtn directions, while there is no significant error in the Lat and Pitch directions. Moreover, too large setup errors can significantly reduce the dose to PTV.
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ObjectiveThis study aimed to analyze the difference in setup error before and after correction of systematic error. To determine the most appropriate image-guided strategy during HT treatment， we use different scanning ranges and image-guidance frequencies in patients with nasopharyngeal carcinoma （NPC） treated with helical tomotherapy （HT）. MethodsFifteen patients with NPC who received HT treatment in Sun Yat-sen University Cancer Center from October 2019 to February 2020 were selected. Megavoltage computed tomography （MVCT） scanning was performed before each treatment. After five times of radiotherapy， system-error correction was performed to adjust the setup center. The setup errors before and after the correction of systematic errors， as well as the setup errors of different scanning ranges and different scanning frequencies， were collected for analysis and comparison. ResultsWhen comparing the setup errors before and after the correction of systematic error， the differences in setup errors in the left–right （LR）， superior–inferior （SI）， and anterior–posterior （AP） directions were statistically significant （P<0.05）.The different scanning ranges of "nasopharynx + neck" and "nasopharynx" were compared， and a statistically significant difference was found in yaw rotational errors （P<0.05）. In the comparison of daily and weekly scan frequency after system-error correction， a significant difference was found in AP direction （P<0.05）. ConclusionDuring radiotherapy for NPC， the systematic error can be corrected according to the first five setup errors， and then small-scale scanning was selected for image-guided radiotherapy every day.
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@#Performing external beam radiotherapy alone without chemotherapy or brachytherapy for locally advanced cervical cancer with multiple lymph node metastases is challenging. The purpose of this case report is to present the efficacy of high‑dose adaptive extended‑field intensity‑modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) in treating locally advanced cervical cancer with multiple lymph node metastases. A 67‑year‑old woman with locally advanced squamous cell carcinoma of the uterine cervix was treated by external beam radiotherapy alone due to the refusal of chemotherapy and intracavitary brachytherapy. In order to maximize the efficacy of treatment, extended‑field radiotherapy that includes the paraaortic lymph nodes as well as an adaptive IMRT‑SIB plan, was applied. The treatment was successful, resulting in complete tumor disappearance without severe adverse events. In conclusion, high‑dose adaptive IMRT‑SIB may be an alternative treatment option for locally advanced cervical cancer with multiple lymph node metastases.
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Radiation Dosage , Uterine Cervical NeoplasmsABSTRACT
Objective:To compare the comprehensive performance of three Varian on-board image (OBI) image systems (KV-CBCT, KV-planar and MV-EPID) and to explore the value of the combined application of these three systems in daily image-guided radiotherapy for nasopharyngeal cancer.Methods:KV-CBCT, KV-planar and MV-EPID scanning and registration were carried out in the left and right/abdominal and back/head and foot direction on human head and neck phantom. The set-up error, registration time, additional radiation dose and image quality of the three systems were compared by F-test.Results:KV-CBCT, kV-planar and MV-EPID were scanned for 55 times, respectively, and the set-up errors in the left and right/abdominal and back/head and foot direction of the three image-guided systems were (0.00±5.43)/(-0.02±5.49)/(0.02±5.58) mm, (0.04±5.49)/(0.02±5.56)/(0.02±5.54) mm, (0.02±5.22)/(0.11±5.34)/(-0.04±5.33) mm, respectively ( P=0.999, 1.000, 0.989). The average time consuming was (200±45) s, (120±36) s and (115±42) s; the additional radiation dose from low to high was kV-planar, KV-CBCT and MV-EPID; the image quality from low to high was MV-EPID, kV-planar and KV-CBCT. Conclusions:Three image-guided systems can meet the requirements of image-guided radiotherapy for nasopharyngeal cancer. Based on the overall performance of the three systems, 1 CBCT+ 4 kV planar per week is recommended and EPID should be used as a backup system in daily image-guided radiotherapy for nasopharyngeal cancer. This scheme makes full use of the high image quality of CBCT and the low radiation of kV planar to realize the regular detection of nasopharyngeal cancer volume change and the implementation of high-precision radiotherapy.
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Objective:To analyze the effects of two decomposition algorithms of dual-energy cone beam CT (DECBCT) (direct decomposition and iterative decomposition) on the image quality and material decomposition accuracy of different sizes of phantoms.Methods:Different sizes of imaging parts of patients were simulated using the combination of CatPhan604 phantoms and customized annuluses. CBCT with high energy of 140 kVp and low energy of 100 kVp were acquired using the Varian Edge CBCT system. Then the material decomposition of DECBCT images was performed using the two algorithms. The electron density (ED) and contrast-to-noise ratio (CNR) of each material in the CTP682 module were calculated. They were used to assess the decomposition accuracy and image quality of the two algorithms.Results:Based on the values in the Catphan604 manual, both algorithms have high ED accuracy. Only the ED accuracy of four materials of the smallest sized phantom showed statistical difference ( z = -4.21, 4.30, 2.87, 5.45, P < 0.05), but the average relative error was less than 1%. The CNR of the iterative decomposition algorithm was significantly higher than that of the direct decomposition, increasing by 51.8%-703.47%. The increase in the phantom size significantly reduced the accuracy of ED, and the increased amplitude of the relative error was up to a maximum of 2.52%. The large phantom size also reduced the image quality of iterative decomposition, and the decreased amplitude of CNR was up to a maximum of 39.71. Conclusions:Compared with the direct decomposition, the iterative decomposition algorithm can significantly reduce the image noise and improve the contrast without losing the accuracy of electron density in the DECBCT construction of different sizes of phantoms.
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Since the application of image-guided radiotherapy in clinical practice, cone-beam CT (CBCT) has become the most widely employed image-guided device. However, some problems remain to be cautioned in the application of CBCT, such as certain errors in the setup errors before and after the correction of CBCT, the failure of CBCT to correct dynamic changes, whether the influence of application frequency of CBCT on patients’ boundary of clinical target volume can be reduced, imaging conditions of CBCT lack of a certain degree of flexibility, and the effect of clinical value and application cost on the practicality of CBCT. Only by fully understanding the problems in CBCT application can CBCT be applied more reasonably and scientifically.
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Objective@#To investigate the correlation between skin elasticity and setup error in optical surface image-guided radiotherapy.@*Methods@#The skin elasticity (R7) data of the head, chest and abdomen were extracted and analyzed its correlation with age by systematic literature review. Fifty-four patients diagnosed with nasopharyngeal carcinoma, breast cancer and cervical cancer were recruited in this study. Firstly, the patients were positioned based on the room laser and markers. Subsequently, the patient position was verified by the Varian On-Board Imager, and then C-Rad Catalyst was adopted to obtain surface images in two states (mask or non-mask) as reference images. In the subsequent fraction treatment, after initial positioning, the local calibration was performed by Catalyst, and setup errors in three directions were recorded. Meanwhile, the patient setup was verified by CBCT twice a week. The Pearson correlation analysis was performed to analyze the correlation between setup error and age.@*Results@#The skin elasticity was negatively correlated with aging (P<0.01). The correlation coefficient between random error and age in head-and-neck cancer were 0.645, 0.624 and 0.866 in the AP, SI and LR directions (all P<0.05) for male patients without mask, respectively. The system error was significantly correlated with age in the LR direction (P<0.05) for male patients, and in the AP direction (P<0.05) for female patients with head-and-neck cancer without mask. The setup error had a significant correlation with skin elasticity in male patients with head-and-neck cancer, and the sequence of absolute value of correlation coefficient was LR>SI>AP.@*Conclusion@#In optical surface-guided radiotherapy of head and neck cancer, skin elasticity may be a significant index for assessing the setup errors in male patients.
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Objective To investigate the correlation between skin elasticity and setup error in optical surface image-guided radiotherapy.Methods The skin elasticity (R7) data of the head,chest and abdomen were extracted and analyzed its correlation with age by systematic literature review.Fifty-four patients diagnosed with nasopharyngeal carcinoma,breast cancer and cervical cancer were recruited in this study.Firstly,the patients were positioned based on the room laser and markers.Subsequently,the patient position was verified by the Varian On-Board Imager,and then C-Rad Catalyst was adopted to obtain surface images in two states (mask or non-mask) as reference images.In the subsequent fraction treatment,after initial positioning,the local calibration was performed by Catalyst,and setup errors in three directions were recorded.Meanwhile,the patient setup was verified by CBCT twice a week.The Pearson correlation analysis was performed to analyze the correlation between setup error and age.Results The skin elasticity was negatively correlated with aging (P＜0.01).The correlation coefficient between random error and age in headand-neck cancer were 0.645,0.624 and 0.866 in the AP,SI and LR directions (all P＜0.05) for male patients without mask,respectively.The system error was significantly correlated with age in the LR direction (P＜0.05) for male patients,and in the AP direction (P＜ 0.05) for female patients with head-and-neck cancer without mask.The setup error had a significant correlation with skin elasticity in male patients with head-and-neck cancer,and the sequence of absolute value of correlation coefficient was LR ＞ SI ＞ AP.Conclusion In optical surface-guided radiotherapy of head and neck cancer,skin elasticity may be a significant index for assessing the setup errors in male patients.
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In order to improve the speed and accuracy of cone beam CT image quality assurance, an automatic image quality assurance software based on feature extraction is designed and implemented. This paper introduces how the software can realize the positioning of Catphan500 phantoms and the selection of ROI in each module through Canny algorithm and Hough transform circle detection. For the different modules in the Catphan500 phantom, this paper describes the calculation methods of HU accuracy, spatial linearity, HU uniformity and spatial linearity in the software. Finally, the article verifies the feasibility of the software through experiments.
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Algorithms , Automation , Cone-Beam Computed Tomography , Phantoms, Imaging , Quality Control , SoftwareABSTRACT
Stereotactic body radiotherapy (SBRT) is an advanced form of radiotherapy (RT) with a growing interest on its application in the treatment of hepatocellular carcinoma (HCC). It can deliver ablative radiation doses to tumors in a few fractions without excessive doses to normal tissues, with the help of advanced modern RT and imaging technologies. Currently, SBRT is recommended as an alternative to curative treatments, such as surgery and radiofrequency ablation. This review discusses the current status of SBRT to aid in the decision making on how it is incorporated into the HCC management.
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Carcinoma, Hepatocellular , Catheter Ablation , Decision Making , Radiosurgery , Radiotherapy , Radiotherapy, Image-GuidedABSTRACT
Objective To investigate the accuracy and application value of optical surface monitoring system in intensity modulated radiotherapy for thoracic tumors patients.Methods Twenty-eight patients with thoracic tumors were included.During each treatment fraction,the patients were immobilized with body surface markers and laser lamps.The surface images obtained by the optical surface monitoring system were registered with the reference images and recorded during the CBCT scan.The translation and rotation errors of x (left-right),y (craniocaudal) and z (anterior-posterior) axes were recorded.After scanning,the CBCT images were registered with the planned CT images and the translation and rotation errors of x,y and z axes were recorded.The setup errors of these two image systems were analyzed and corrected before each treatment.The correlation between the two sets of setup errors were analyzed with Pearson test,and systematic error (∑) and random error (σy) were also calculated.The consistency of the two image systems was evaluated with the Bland-Altman method and the 95％ limits of agreement were calculated.Results There was a good correlation between these two groups,and the correlation coefficients were 0.79,0.62,and 0.53 in x,y and z axes,respectively.The ∑/σr of the optical surface monitoring system were 0.7 mm/1.5 mm,0.9 mm/1.8 mm and 0.9 mm/1.5 mm in x,y and z axes,respectively.The ∑/σ of CBCT were 0.8 mm/1.6 mm,1.3 mm/1.9 mm and 0.7 mm/1.5 mm in x,y and z axes,respectively.The 95％ limits of agreement of translations direction were (-2.0-2.3),(-3.4-3.6) and (-3.3-2.4) mm,and the 95％ limits of agreement of rotation direction were (-2.0 to 1.6)°,(-2.0 to 1.4)° and (-1.6 to 1.6)° inx,y and z axes,respectively.Conclusions The optical surface monitoring system is an effective image guide tool,which can quickly and accurately verify the patient's position and improve the position accuracy.It can be applied for positioning in the intensity modulated radiation treatments for the thoracic tumor patients.
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PURPOSE: The aim of this study was to identify volume changes and dose variations of rectum and bladder during radiation therapy in prostate cancer (PC) patients. MATERIALS AND METHODS: We analyzed 20 patients with PC treated with helical tomotherapy. Daily image guidance was performed. We re-contoured the entire bladder and rectum including its contents as well as the organ walls on megavoltage computed tomography once a week. Dose variations were analyzed by means of Dmedian, Dmean, Dmax, V₁₀ to V₇₅, as well as the organs at risk (OAR) volume. Further, we investigated the correlation between volume changes and changes in Dmean of OAR.
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Humans , Organs at Risk , Prostate , Prostatic Neoplasms , Radiotherapy, Image-Guided , Radiotherapy, Intensity-Modulated , Rectum , Urinary BladderABSTRACT
PURPOSE: The aim of this retrospective study was to investigate the use of a radiopaque tissue fiducial marker (TFM) in the treatment of prostate cancer patients who undergo post-prostatectomy radiotherapy (PPRT). TFM safety, its role and benefit in quantifying the set-up uncertainties in patients undergoing PPRT image-guided radiotherapy were assessed. MATERIALS AND METHODS: A total of 45 consecutive PPRT patients underwent transperineal implantation of TFM at the level of vesicourethral anastomosis in the retrovesical tissue prior to intensity-modulated radiotherapy. Prostate bed motion was calculated by measuring the position of the TFM relative to the pelvic bony anatomy on daily cone-beam computed tomography. The stability and visibility of the TFM were assessed in the initial 10 patients. RESULTS: No postoperative complications were recorded. A total of 3,500 images were analysed. The calculated prostate bed motion for bony landmark matching relative to TFM were 2.25 mm in the left-right, 5.89 mm in the superior-inferior, and 6.59 mm in the anterior-posterior directions. A significant 36% reduction in the mean volume of rectum receiving 70 Gy (rV₇₀) was achieved for a uniform planning target volume (PTV) margin of 7 mm compared with the Australian and New Zealand Faculty of Radiation Oncology Genito-Urinary Group recommended PTV margin of 10 mm. CONCLUSION: The use of TFM was safe and can potentially eliminate set-up errors associated with bony landmark matching, thereby allowing for tighter PTV margins and a consequent favourable reduction in dose delivered to the bladder and rectum, with potential improvements in toxicities.
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Humans , Clothing , Cone-Beam Computed Tomography , Fiducial Markers , New Zealand , Postoperative Complications , Prostate , Prostatectomy , Prostatic Neoplasms , Radiation Oncology , Radiotherapy , Radiotherapy, Image-Guided , Radiotherapy, Intensity-Modulated , Rectum , Retrospective Studies , Urinary BladderABSTRACT
Currently,image-guided radiation therapy (IGRT) is the most advanced technique in the field of radiation oncology.However,the most commonly used image-guided techniques,such as cone beam computed tomograhpy (CBCT) and electronic portal imaging device (EPID) are limited due to extra radiation,poor image quality and failure of real-time monitoring.Optical surface imaging technique generates no additional radiation and can conduct real-time monitoring.Multiple researches have demonstrated that it has significant advantages in terms of guiding positioning,real-time monitoring of the fractionated and divided motion,reducing the frequency of CBCT scanning,breathing door control,etc.In this paper,this novel technique and its application prospect in radiotherapy are reviewed.
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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 analyze the effect of image guidance on the doses to the rectum and bladder in radical external beam radiotherapy for cervical cancer, and to investigate the reasonable application mode of image-guided radiotherapy (IGRT) in the treatment of cervical cancer. Methods A total of 20 patients with cervical cancer who underwent helical tomotherapy(HT) in PLA Army General Hospital from 2012 to 2016 were enrolled in this study. A megavoltage computed tomography(MVCT) scan was performed before each treatment. The obtained MVCT images were used for dose reconstruction in the adaptive module of HT to obtain the actual dose (Plan-1) and the non-image-guided dose was simulated (Plan-2). Each single dose distribution and the corresponding fused CT image were sent to the software MIM 6.0 to obtain the total radiation dose by dose superposition. The radiation doses and volumes of the rectum and bladder were compared between the two therapeutic plans. Results The radiation doses to the rectum and bladder in Plan-2 were significantly higher than those in Plan-1. There were significant differences in Dmaxand V50of the rectum and V50of the bladder between Plan-1 and Plan-2(P=0.040;P=0.000;P=0.047). Compared with Plan-1, there were statistical differences in inter-fractional Dmaxand V50during the initial treatment (P=0.047,0.037), and V50of the rectum within the 13thto 21stradiotherapy, respectively (P=0.009, 0.017, 0.028). Besides, differences regarding Vmaxand V50in the initial treatment and the 21stto 23rdradiotherapy were close to the statistical significance when compared to those in Plan-1, respectively (P= 0.061,0.053; P= 0.072,0.058). Conclusions IGRT can reduce the radiation doses and volumes of the rectum and bladder, especially the rectum. The therapeutic plan should be rescheduled when tumor retraction is evident at half of the total radiation dose (around 13thfraction) in external beam radiotherapy. If it is difficult to achieve image guidance in each treatment,selective image guidance could be performed to effectively reduce the injuries of the rectum and bladder.
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Objective:To determine the law of dose variation in nasopharyngeal carcinoma patients treated with helical tomotherapy by observing the difference between the actual and planned doses of targets and at-risk organs in these patients. Methods:Ten naso-pharyngeal carcinoma patients were treated with helical tomotherapy. Each single dose distribution and the corresponding computed tomography (CT) images were transmitted to the commercial software MIMvista 6.50, which was used to perform deformable image registration on the CT images. The sum of the actual dose was then obtained by accumulating the single doses. The image-guided actu-al dose was denoted as Plan 2, and the initial plan was called Plan 1. The dose-volume histogram of the dose distribution of targets and at-risk organs in Plans 1 and 2 were compared. Results:The D98 and D95 doses of the planning gross target volume (PGTV) in Plan 2 were significantly lower than those in Plan 1. Compared with Plan 1, the Dmean and D50 doses of double parotids in Plan 2 were higher by 42.23%and 63.82%(P<0.001, P=0.001) on average, respectively, for the left parotid, as well as by 38.64%and 66.76%(P=0.002, 0.004), respectively, for the right parotid. The D2 dose of spinal cord in Plan 2 was significantly higher than that in Plan 1. The doses were higher by 16.49%on average (P=0.026). Conclusion:To achieve precise and individually adaptive radiotherapy, correcting the error between anatomy and placement during tomotherapy for nasopharyngeal carcinoma patients is necessary.
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Patients with locally advanced lung cancer and very limited pulmonary function (forced expiratory volume in 1 second [FEV1] ≤ 1 L) have dismal prognosis and undergo palliative treatment or best supportive care. We describe two cases of locally advanced node-positive non-small cell lung cancer (NSCLC) patients with very limited lung function treated with induction chemotherapy and moderate hypofractionated image-guided radiotherapy (Hypo-IGRT). Hypo-IGRT was delivered to a total dose of 45 Gy to the primary tumor and involved lymph nodes. Planning was based on positron emission tomography-computed tomography (PET/ CT) and four-dimensional computed tomography (4D-CT). Internal target volume (ITV) was defined as the overlap of gross tumor volume delineated on 10 phases of 4D-CT. ITV to planning target volume margin was 5 mm in all directions. Both patients showed good clinical and radiological response. No relevant toxicity was documented. Hypo-IGRT is feasible treatment option in locally advanced node-positive NSCLC patients with very limited lung function (FEV1 ≤ 1 L).
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Humans , Carcinoma, Non-Small-Cell Lung , Electrons , Four-Dimensional Computed Tomography , Induction Chemotherapy , Lung Neoplasms , Lung , Lymph Nodes , Palliative Care , Prognosis , Radiotherapy , Radiotherapy, Image-Guided , Tumor BurdenABSTRACT
Many cancer patients will develop spinal metastases. Local control is important for preventing neurologic compromise and to relieve pain. Stereotactic body radiotherapy or spinal radiosurgery is a new radiation therapy technique for spinal metastasis that can deliver a high dose of radiation to a tumor while minimizing the radiation delivered to healthy, neighboring tissues. This treatment is based on intensity-modulated radiotherapy, image guidance and rigid immobilization. Spinal radiosurgery is an increasingly utilized treatment method that improves local control and pain relief after delivering ablative doses of radiation. Here, we present a review highlighting the use of spinal radiosurgery for the treatment of metastatic tumors of the spine. The data used in the review were collected from both published studies and ongoing trials. We found that spinal radiosurgery is safe and provides excellent tumor control (up to 94% local control) and pain relief (up to 96%), independent of histology. Extensive data regarding clinical outcomes are available; however, this information has primarily been generated from retrospective and nonrandomized prospective series. Currently, two randomized trials are enrolling patients to study clinical applications of fractionation schedules spinal Radiosurgery. Additionally, a phase I clinical trial is being conducted to assess the safety of concurrent stereotactic body radiotherapy and ipilimumab for spinal metastases. Clinical trials to refine clinical indications and dose fractionation are ongoing. The concomitant use of targeted agents may produce better outcomes in the future.
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Humans , Radiosurgery/methods , Radiotherapy, Image-Guided/methods , Radiotherapy, Intensity-Modulated/methods , Spinal Neoplasms/surgery , Clinical Trials as Topic , Immobilization , Pain/radiotherapy , Radiosurgery/trends , Spinal Neoplasms/secondaryABSTRACT
Objective To evaluate the effect of popliteal fossa fixed method to reduce the setup errors in patients with postoperative cervical carcinoma by CBCT of TrueBeam Linear accelerator.Methods 30 cases of postoperative cervical cancer patients were randomly divided into two groups,group A with popliteal fossa fixed method by trapezoidal fixation,group B with traditional vacuum pad fixation.CBCT was used to record both setup errors and rotational errors,Stroom extension formula was used to calculate the PTV expansion value coming from the two different fixation methods.Results There was significant difference in setup errors between group A and group B.The setup errors in the left-right direction (X),cranial-caudal direction (Y) and anterior-posterior direction (Z) were (0.19±0.14) cm,(0.17±0.12) cm and (0.13±0.11) cm in group A,respectively.On the contrary,the setup errors in X,Y and Z were (0.24±0.19) cm,(0.25±0.21) cm and (0.22±0.18) cm in group B,respectively.The rotational errors were 0.05°±0.02° in group A,comparing with 0.5°±0.21° in group B (P =0.00).The PTV expanded margin in group A was 0.56 cm in X direction,0.51 cm in Y direction,0.40 cm in Z direction,in comparing with 0.73 cm,0.78 cm and 0.67 cm in group B,respectively.Group A remarkably reduced the PTV,pelvis,small intestine,bladder and rectum irradiated volumes [(1 167±271) mm3 vs (1 379±297) mm3,(84±12) mm3 vs (130±17) mm3,(81±51) mm3 vs (117±64)mm3,(62±40) mm3 vs (75±47) mm3,(21±16) mm3 vs (31±21) mm3].Conclusion Popliteal fossa fixed method can reduce setup errors and improve the stability of positioning,more suitable in precise radiotherapy for postoperative cervical cancer patients,which has the value of further validation.