Objective To investigate the accuracy and reliability of the image automatic matching using X-ray volumetric image (ⅩⅥ) system with the accelerator Elekta Synergy and to compare the matches with different methods and area.Methods A simulation plan using the head and neck phantom was designed and sent to ⅩⅥ system for CBCT scanning.During the scanning,the couch for certain distance was moved and the data of ⅩⅥ image automatic Matching in different matching methods and area was collected.Results The result of ⅩⅥ image automatic matching is consistent and correct to direction and distance which the couch had been moved (x:(0.11 ± 0.41) mm,y:(-0.04± 2.6) mm,z:(0.28 ± 0.74 mm)).There are not significant differences between the results that matching in different matching methods and different matching area.Conclusions The automatic image Matching of ⅩⅥ is accuracy and high reliability in recognition of offset error.But there are some significant differences on the automatic image Matching in different matching methods and different matching area.

Objective To investigate an appropriate megavoltage computed tomography ( MVCT ) protocol to guide helical tomotherapy ( HT) for multiple metastases. Methods According to the location of target volume, 48 patients with multiple metastases undergoing HT were divided into head/chest group ( n=15), head/pelvis group (n=15), and chest/pelvis group (n=18). Each target volume received MVCT scans during the treatment. The obtained MVCT images were registered to CT images and the setup errors were recorded. The CTV?PTV margins were calculated. Comparison was made by paired t test. Results In the head/chest group, there was no significant difference in the setup error in x?axis between the head and chest (-0.15±1?25 vs. -0.21±2?34, P=0?71), while the head had significantly smaller setup errors in y?and z?axis than the chest (0.73±1?22 vs. 1.56±2?54, P=0?00;0.93±1?44 vs. 2.65±1?88, P=0?00). In the head/pelvis group, the head had significantly smaller setup errors in x?, y?, and z?axis than the pelvis (-0.16±1?31 vs. -1.29±3?72, P=0?00;0.81±1?34 vs. 3.20±3?90, P=0?00;1.24±1?75 vs. 5.49±2?80, P=0?00) . In the chest/pelvis group, there were no significant differences in setup errors in x?or y?axis between the chest and pelvis (-0.25± 2?90 vs. -0.22± 3?65, P=0?06;0.35± 3?60 vs. 0.38± 3?78, P=0?87), while the chest had a significantly smaller setup error in z?axis than the pelvis (1.95±2?81 vs. 3.35± 3?05, P=0?00) . In the three groups, the CTV?PTV margins of lower target volume were reduced in three dimensions after the correction of upper target volume, in which y?axis showed the largest reduction of CTV?PTV margins (5?13 vs. 4?01;9?17 vs. 8?30;8?52 vs. 7?13). Conclusions The setup error of individual target volume should not be used for correction of the overall setup error in HT for multiple metastases with isolated target volume. An MVCT protocol that provides image?based guidance for multiple target volumes is recommended.

Objective To discuss the application value of DWI and ADC on predicting therapeutic effect of radiotherapy treatment in NPC. Methods Twenty four local recurrent cases and 38 non-recurrent cases after radiotherapy treatment in NPC were reviewed. MRI and DWI-MRI were performed at pre-radiotherapy and 3, 6, 12 months after treatment, the ADC values of the lesions were analyzed by SPSS 18.0 statistical software. ROC curves based on the ADC values were measured in 3, 6, 12 months after treatment plotted to analyze the threshold ADC value for confirming recurrence. Results The recurrent group and newly diagnosed group showed significantly high signal on DWI, while the non-recurrent group acquired low or mixed signal. The ADC values of the primary tumor in the recurrent group and the non-recurrent group were (0.709 ± 0.078) × 10-3 and (0.693 ± 0.089) × 10-3mm2/s, respectively, t=-0.717,P>0.05, respectively.The ADC values of the primary and recurrent tumor in the recurrent group were (0.730± 0.068) × 10-3mm2/s and (0.709 ± 0.078) × 10-3mm2/s, t=-1.000,P>0.05 , respectively.There were statistical differences between the recurrent group and the non-recurrent group for ADC in 3, 6, 12 months after treatment:(1.128 ± 0.179) × 10-3 and (1.358 ± 0.145) × 10-3mm2/s, t=5.567,P<0.01;(1.164 ± 0.174) and (1.450 ± 0.102) × 10-3mm2/s, t=7.310,P<0.01;(1.107 ± 0.180) × 10-3 and (1.584 ± 0.125) × 10-3mm2/s, t=11.189,P<0.01;respectively. Take 1.29 × 10-3 mm2/s,1.32 × 10-3mm2/s,1.37 × 10-3mm2/s respectively in 3, 6, 12months after treatment as the diagnostic threshold to predict tumor recurrence. The sensitive , specificity, and accuracy were (83.3%, 73.7%, 77.4%), (83.3%, 89.5%, 87.1%), (100.0%, 94.7%, 96.3%).Conclusions Both DWI and ADC value are important for diagnosing and predicting recurrent NPC after radiotherapy treatment, DWI and ADC can be used to regular follow-up after radiotherapy, to further improve the rate of early diagnosis of recurrent NPC.

[Objective]To compare and contrast the dosimetry between Tomo planning and BrainLab planning for lung metasta-ses in stereotactic body radiation therapy(SBRT).[Methods]Four Patients with one,two,three and four metastases were selected. The PTV is 2.89 ± 1.15 cm3. Two plannings with total dose of 50 Gy to cover 95% of PTV ,5 Gy/Fraction and 10 fractions were designed using Tomo planning system and BrainLab planning system respectively. The DVH curves of spinal cord ,both lungs and normal tissue were compared. The conformity index andhomogeneityindex were analyzed as well.[Results]The homogeneity index (HI)and conformity index(CI)of the targets in Tomo planning system were 1.0314 ± 0.0700 and 0.687 ± 0.075,respectively. In BrainLab planning system the HI and CI of the targets were 1.0764 ± 0.1241 and 0.571 ± 0.042,respectively. To HI the P value in T test was less than 0.01 and the HI was better in Tomo than BrainLab and so was CI. The dose to spinal cord was higher in BrainLab planning system than that in Tomo. The dose to nomal tissue and both lungs were not different in the two planning systems and V20 of lung is as small as 10%.[Conclusions]For small volume lung metastases which longest diameter were less than 4 cm,the tomotherapy should be better choice.

Objective To evaluate the feasibility of keeping the consistency of bladder filing by a Bladderscan ( BS ) device during radiotherapy for rectal cancer. Methods The bladder volume was measured using a BS device and recorded. To verify the reliability of the BS measurement, the urinary output was determined by a measuring glass after complete urinary discharge. The bladder volume of 42 patients determined by the planning computed tomography ( CT) scans was used as the standard urinary volume. The bladder volume was measured using the BS device before radiotherapy every day. The chief complaint urinary volume was determined as the bladder volume when a patient felt a strong urge to urinate. The controlled urinary volume was determined as the urinary output intervened by the BS device to reach the standard urinary volume. Comparison was made by t test and data was assessed by Pearson correlation analysis. Results There was no significant difference in obtained urinary volume between the BS device and the planning CT scan ( P=0?84) . The urinary volume measured by the measuring glass was correlated with that measured by the BS device ( P=0?00 ) . The ability to hold urine in all patients was gradually weakened during treatment. The controlled urinary volume had a significantly smaller decrease after 1, 2, 3, 4, and 5 weeks of treatment than the chief complaint urinary volume ( 5% vs. 21%;6% vs. 20%;6% vs. 20%, 4% vs. 21%;11% vs. 26%;all P=0?00) . Conclusions Patients have a gradually decreased urinary volume during treatment. The intervention by the BS device gives a bladder volume close to that in the planning system, which results in a consistent bladder filling.

Objective To evaluate the effect of helical tomotherapy (HT) megavoltage CT (MVCT) under different acquisition pitch and registration conditions upon the accuracy of radiotherapy for used nasopharyngeal carcinoma,aiming to provide reference for image-guided radiotherapy (IGRT) for nasopharyngeal carcinoma.Methods MVCT scans were performed on an anthropomorphic head& neck phantom which was simulated the positioning errors in the x,y and z direction.The obtained images were registered with the planning CT images.Acquisition pitch was set as the coarse,normal and fine modes.Registration conditions were set as bone registration,bone and soft tissue registration and full-image registration.Registration accuracy was determined by comparing the measured value with the preset value.The accuracy of radiotherapy under different acquisition pitch and registration conditions was statistically compared.Results The 3D errors of bone,bone and soft tissue and full-image registration under different acquisition pitch (coarse,normal and fine) were (1.51±0.47,1.54±0.35,1.81±0.53) mm and (1.41± 0.37,1.53±0.36,1.56±0.39) mm and (1.51±0.27,1.57±0.32,1.73±0.33) mm,respectively.The bone registration yielded the highest accuracy (P＜0.05).When the registration condition was set as bone registration,the accuracy of three acquisition pitch did not significantly differ (all P＞0.05).The fine mode of acquisition pitch possessed the highest stability,whereas required the longest time.Conclusion The acquisition pitch and registration conditions should be selected during HT MVCT based on the clinical requirement of each patient with nasopharyngeal carcinoma.

Objective:To investigate and analyze the basic occupational situation of Chinese radiotherapists and to provide references for the development and construction of the radiation therapist team in China.Methods:Between May 7, 2021 and June 15, 2021, this survey was conducted using a self-designed questionnaire, which was distributed and collected in the form of online survey to conduct a statistical analysis of the basic situation of radiotherapists in 30 provincial-level administrative regions in China.Results:A total of 2 928 valid questionnaires were collected from 30 provincial-level administrative regions. The ratio of male to female and average age of the participants were 69∶31 and 35 years (18-65), respectively. According to the survey result, 84.7% of the participants came from Tertiary A-level hospitals. In terms of educational background, the participants with doctoral, master, undergraduate, junior-college, and technical-secondary degrees accounted for 0.2%, 6.9%, 76.6%, 14.9%, and 1.4%, respectively. In terms of title, full senior technologists, associate senior technologist, technologist-in-charge, technologist, and technician in the participants accounted for 0.5%, 5.8%, 32.5%, 52.2%, and 8.2%, respectively. The participants with years of employment of 0-, 5-, 10-, 20-y accounted for 33.74%, 25.79%, 25.51%, and 14.96%, respectively. The majors of the participants included medical imaging/imaging technology (45.9%), clinical medicine (19.1%), and biomedical engineering (11.9%).Conclusions:Chinese radiotherapists tend to be younger and are rapidly increasing in number. Employers should attach importance to the career planningand continuing education of radiotherapists to improve their technical skills, in order to fully satisfy the demand for radiotherapists in the new era.

Objective:To preliminarily observe the feasibility of different immobilization techniques for total skin irradiation (TSI) using helical tomotherapy.Methods:Three eczema scrophuloderma patients treated with TSI in Sun Yat-sen University Cancer Center were immobilized with low-temperature thermoplastic in a prone position, diving suit combined with negative pressure vacuum bag in a supine position, low-temperature thermoplastic combined with vacuum bag in a supine position, respectively. Different immobilization effects were observed. The conformity index (CI) of the target area, heterogeneity index (HI) of the target area, and the mean dose (D mean) of the target area were calculated. Results:Three immobilization methods could achieve satisfactory immobilization effects, and all the dosimetric parameters of radiation treatment plans met the clinical requirements. The average set-up errors in the left and right, head and foot, and abdomen and back directions of three patients were (0.26±3.40) mm, (-2.63±4.63) mm and (6.13±4.86) mm, respectively. The CI, HI andD mean were0.56±0.09, 1.186±0.059 and (2586.56±63.28) cGy. Conclusions:Low-temperature thermoplastic or diving suits can be combined with vacuum bags for immobilization in TSI. The epidermal dose can be increased with bolus through the dose-building effect, which can provide a safe and reliable method for TSI in helical tomotherapy.

Objective:To explore the effects of bladder volumes from CT simulation on bladder volume consistency and set-up errors during radiotherapy for prostate cancer, aiming to provide a reference for clinical practice.Methods:A retrospective analysis was conducted for of 66 prostate cancer patients treated with intensity-modulated radiation therapy in the Sun Yat-sen University Cancer Center from August 2015 to November 2020. They underwent CT scan or radiotherapy after voluntarily holding in urine. Cone beam computed tomography (CBCT) scans were performed for them to measure their set-up errors in left-right (L-R), superior-inferior (S-I), and anterior-posterior (A-P) directions before each treatment. The bladder contours of the patients were delineated on CT simulation images and CBCT images. Accordingly, bladder volumes were calculated. Based on the calculated bladder volumes derived from the CT simulation images, the patients were divided into three groups: 18 cases in the 200-300 ml group, 24 cases in the 300-400 ml group, and 24 cases in the >400 ml group. Finally, this study analyzed the effects of bladder volumes derived from CT simulation on set-up errors and the changes of CBCT-derived bladder volumes relative to planned volumes during radiotherapy.Results:The bladder volumes in the 200-300 ml, 300-400 ml, and >400 ml groups during radiotherapy were reduced by 15%, 26%, and 32%, respectively. The pairwise comparison indicates statistically significant differences in the changes of bladder volumes among the three groups ( Z=3.43, 7.97, 4.83, P<0.05). Regarding the three-dimensional set-up errors, there were statistically significant differences in S-I set-up errors among the three groups ( H=26.72, P<0.05), but there was no statistically significant difference in L-R and A-P set-up errors ( P>0.05) among these groups. The 200-300 ml, 300-400 ml, and >400 ml groups exhibited S-I set-up errors of 0.00 (-0.20, 0.20) cm, 0.00 (-0.20, 0.30) cm, and -0.10 (-0.30, 0.20) cm, respectively. Therefore, the >400 ml group displayed larger the S-I set-up errors than other two groups, with statistically significant differences ( Z=4.17, 4.66, P< 0.05), while there was no statistically significant differences in S-I set-up errors between other two groups ( P> 0.05). Conclusions:Controlling the bladder filling volumes at 200-300 ml in CT simulation is beneficial for maintaining bladder volume consistency and reducing set-up errors of patients during radiotherapy.

Objective To investigate the relationships of pre-radiotherapy body weight,gender,age,EBVDNA,hemoglobin,plasma albumin,and induction chemotherapy regimen with the changes of target area and lymph node volume in adaptive radiotherapy,so as to provide a reference for the timing and population selection of adaptive radiotherapy.Methods A retrospective analysis was conducted on 34 patients who received the first course of radiotherapy at Sun Yat-sen University Cancer Center from January 2022 to November 2022.All patients underwent CT scans again after 20 sessions of radiotherapy for developing the secondary radiotherapy plans.The body weight,gender,age,tumor stage,hemoglobin,plasma albumin,induction chemotherapy regimen,and EBVDNA were collected.Results The tumor volume reduction in the primary focus was more evident in patients with pre-treatment plasma albumin≥40 g/L than in those with pre-treatment plasma albumin<40 g/L(t=3.971,P=0.001),and in patients with pretreatment EBVDNA≤4000 copies/mL than in those with pretreatment EBVDNA>4000 copies/mL(t=4.080,P=0.001).Pearson analysis showed that GTVnx volume difference was positively correlated with pre-radiotherapy GTVnx volume(r=0.444,P=0.009),right parotid gland volume difference(r=0.737,P<0.001),left parotid gland volume difference(r=0.435,P=0.010),and hemoglobin(r=0.722,P<0.001).Conclusion The reduction in tumor volume during radiotherapy is more pronounced in nasopharyngeal cancer patients with normal plasma albumin level and those with pretreatment EBVDNA≤4000 copies/mL.The pre-radiotherapy treatment volume of primary focus,parotid gland volume change before and after radiotherapy,and pre-radiotherapy EBVDNA,hemoglobin and plasma albumin levels can be used to predict the degree of tumor volume shrinkage during radiotherapy,providing a reference for the selection of the timing of adaptive radiotherapy for nasopharyngeal carcinoma.