[en] 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. (authors)

[en] 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. (authors)

[en] Objective: To study the superiority of polyurethane foam sealing agent immobilization with KV-CBCT for the patients with nasopharyngeal carcinoma (NPC). Methods: 36 NPC patients were divided into two groups. Group A was immobilized using standard plastics pillow with the head-and-neck thermoplastic masks, and so do individualized polyurethane foam sealing agent pillow as group B. CBCT was weekly carried out weekly, and the setup errors of the head and neck position (axial (x, y, z)) were analyzed by paired t-test. The marginal was calculated using 2.52Σ + 0.7σ. Results: On x-, y-, z-axial, the average setup errors values of head and neck position were (-0.27 ± 1.33) mm, (-0.31 ± 1.50) mm, (0.54 ± 0.90) mm and (-0.59 ± 2.76) mm, (-0.11 ± 2.23) mm, (0.66 ± 1.60) mm; and the marginal were 3.28 mm, 3.64 mm, 1.86 mm and 6.17 mm, 5.17 mm, 3.52 mm, respectively in Group A; with (-0.44 ± 0.87) mm, (-0.18 ± 1.06) mm, (0.13 ± 0.72) mm and (-0.07 ± 1.58) mm, (-0.04 ± 2.11) mm, (0.03 ± 1.31) mm, and 2.07 mm, 2.46 mm, 1.71 mm and 3.57 mm, 5.03 mm, 3.16 mm, respectively in Group B. Compared with Group A to Group B, P value were 0.315, 0.011, 0.000 and 0.045, 0.630, 0.002 On x-, y-, z-axial. Conclusions: The application of polyurethane foam sealing agent in the immobilization of NPC patients is better than standard plasthetics pillow, and especially for the positioning of neck. Compared to head position, the setup errors of neck are larger, so it is suggested to make the outer margin separately. (authors)

[en] 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. (authors)

[en] 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 and 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. (authors)

[en] Objective: To investigate a simple and easy method to maintain a stable urine volume and consistent bladder filling during immobilization, CT scanning, plan designing, and radiotherapy using an ultrasonic bladder capacity scanner (BS). Methods: A total of 66 patients with pelvic tumor who were admitted to our hospital and received radiotherapy from 2013 to 2014 were enrolled and required to drink 500 ml water after emptying the bladder. BS was used to measure bladder capacity at four time points. Before radiotherapy, 62 patients with pelvic tumor were randomly divided into two groups in a single-blind trial. Both groups were asked to empty the bladder, drink 500 ml water, and wait for a subjective feeling of urgency of urination. The 42 patients in group 1 were asked to hold urine, and bladder capacity was measured and urine volume was recorded when patients complained of 'urgency of urination'. The patients in group 2 were told that urine volume should reach the standard in plan designing, and BS was used to determine whether the standard was reached. Results: The time from bladder emptying to the subjective feeling of urgency of urination ranged from 0.5 to 1.5 hours; when the patients had a subjective feeling of urgency of urination, the urine volume ranged from 30 to 500 ml. In group 1, when the patients had a subjective feeling of urgency of urination, the difference between the bladder capacity measured and that in plan designing was 30.6%, while in group 2, the difference was 12.6%. Conclusions: The use of BS in monitoring bladder capacity helps patients to develop a stable feeling of urgency of urination and reach the bladder capacity in plan designing and thus maintain a consistent degree of bladder filling. (authors)

[en] 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^-3 mm²/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^-3 mm²/s and (0.709 ± 0.078) × 10^-3 mm²/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^-3 mm²/s, t = 5.567, P < 0.01; (1.164 ± 0.174) and (1.450 ± 0.102) × 10^-3 mm²/s, t = 7.310, P < 0.01;(1.107 ± 0.180) × 10^-3 and (1.584 ± 0.125) × 10^-3 mm²/s, t= 11.189, P < 0.01; respectively. Take 1.29 × 10^-3 mm²/s, 1.32 × 10^-3 mm²/s, 1.37 × 10^-3 mm²/s respectively in 3, 6, 12 months 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. (authors)