Objective:To investigate the influence of the complexity metrics of the multi-leaf collimator (MLC) on the γ-pass rate of volumetric modulated arc therapy (VMAT) plans for nasopharyngeal carcinoma (NPC).Methods:A total of 60 VMAT plans for NPC were selected to measure the γ-pass rate. The MLC data across all control points (CPs) in each VMAT plan were analyzed to calculate the mean field area (MFA), average leaf gap (ALG), small aperture score (SAS), and their corresponding weighted metrics including MFAW, ALGW, and SASW, considering dose weight (W). Pearson′s bivariate correlation analysis was conducted to examine the correlations between MLC complexity metrics and the γ-pass rate. Moreover, the receiver operating characteristic (ROC) analysis was employed to assess the predictive efficacy of MLC complexity metrics on dose verification result.Results:Under the 3%/3 mm, 3%/2 mm, and 2%/2 mm criteria, the MFA in the 60 VMAT plans exhibited a positive correlation with the γ-pass rate ( r=0.82, 0.79, 0.72, P<0.05), and the MFAW was also positively correlated with the γ-pass rate ( r=0.83, 0.81, 0.75, P<0.05). The ALG manifested a positive correlation with the γ-pass rate ( r=0.82, 0.79, 0.74, P<0.05), as did the ALGW ( r=0.83, 0.81, 0.77, P<0.05). The SAS(0-1 cm), SAS(1-2 cm), SAS(2-3 cm), and SAS(3-4 cm) displayed negative correlations with the γ-pass rate ( r= -0.86, -0.82, -0.71, -0.84, -0.82, -0.72, -0.79, -0.79, -0.73, -0.30, -0.35, -0.42, P<0.05), whereas the SAS(4-5 cm), SAS(5-6 cm), and SAS(6-40 cm) showed positive correlations with the γ-pass rate ( r=0.49, 0.45, 0.33, 0.73, 0.71, 0.59, 0.79, 0.79, 0.76, P<0.05). The outcomes of SASW reveal slightly stronger correlations than those of SAS. In terms of correlations among complexity metrics, a positive correlation was observed between MFA and ALG ( r=0.98, P<0.05). ALG was negatively correlated with SAS(0-1 cm), SAS(1-2 cm), SAS(2-3 cm), and SAS(3-4 cm) ( r= -0.95, -0.94, -0.89, -0.39, P<0.05), and positively correlated with SAS(4-5 cm), SAS(5-6 cm), and SAS(6-40 cm) ( r=0.51, 0.77, 0.92, P<0.05). The weighted result mirrored these correlations. The ROC-derived analytical result indicate that MFA, MFAW, ALG, ALGW, SAS(0-1 cm), SAS(1-2 cm), SAS(2-3 cm), SAS(6-40 cm), SASW(0-1 cm), SASW(1-2 cm), SASW(2-3 cm), and SASW(6-40 cm) demonstrated exceptional predictive efficacy for dose verification result [Area under the curve (AUC) > 0.9, P<0.05]. Conclusions:The γ-pass rate of VMAT plans for NPC is strongly correlated with MLC complexity metrics, which demonstrate excellent predictive efficacy for dose verification result. The increased uncertainty in dose calculations and measurements caused by narrow fields generated by the MLC is a significant factor contributing to the reduced γ-pass rate of VMAT plans. This finding is associated with discrepancies in the precision of treatment planning system (TPS) modeling and the accuracy of dose verification tools, providing a reference for similar challenges.

Objective:To investigate the differences in dosimetric parameters for target volumes and organs at risk (OARs), radiation doses to reconstructed tissues, and beam-on time in radiotherapy among helical tomotherapy (HT), volumetric modulated arc therapy (VMAT), and fixed-field intensity-modulated radiotherapy (F_IMRT) following immediate breast reconstruction for breast cancer, thereby providing a reference for the selection of clinical radiotherapy techniques.Methods:This study retrospectively investigated 15 breast cancer patients who underwent radiotherapy following modified radical mastectomy and immediate breast reconstruction at the Liuzhou Worker′s Hospital from August 2018 to July 2023. During target volume delineation, precautions were taken to avoid the reconstructed tissues, which were delineated separately. Customized HT, VMAT, and F_IMRT treatment plans were designed for each patient. The plans were categorized into the HT, VMAT, and F_IMRT groups based on different radiotherapy techniques employed. They were comparatively analyzed through one-way analysis of variance (ANOVA), with multiple comparisons further conducted in the case of significant differences.Results:Statistical analyses reveal significant differences in various parameters of target volumes among the three groups of plans ( F = 38.73, 14.95, 37.01, 48.05, 35.55, 22.56, 34.30, P < 0.05). Pairwise comparisons indicate that the maximum dose ( D2%), minimum dose ( D98%), mean dose ( Dmean), and the proportion of high-dose volumes within the target volume ( V107%and V110%) in both the HT and VMAT groups were significantly better than those in the F_IMRT group. The HT group demonstrated the optimal conformity index (CI), while the VMAT group displayed the superior homogeneity index (HI) compared to the other two groups. In terms of OAR, the V20 of the ipsilateral lung was the lowest in the HT group ( F = 14.31, P < 0.05) and the highest in the F_IMRT group ( F = 14.31, P < 0.05). However, the V5 and Dmean for both the ipsilateral and contralateral lungs in the HT group significantly surpassed those of the other groups ( F = 39.16, 31.91, P < 0.05). The mean dose Dmean ( F = 5.57, P < 0.05) of the contralateral breast was significantly reduced in the VMAT group compared to the other two groups. No statistically significant differences were observed for other OARs, including the heart, spinal cord PRV, thyroid, and humeral head ( P > 0.05). The radiation doses to reconstructed tissues ( Dmax, V53.5, Dmean) ascended in the order of HT, VMAT, and F_IMRT groups ( F = 17.69, 17.53, 15.11, P < 0.05). The HT and F_IMRT groups showed similar beam-on times ( P > 0.05), both exceeding that of the VMAT group by several folds ( F = 28.72, P < 0.05). Conclusions:The comparative analysis indicates that the three radiotherapy techniques exhibit distinct advantages and limitations, with F_IMRT demonstrating the least comprehensive advantage. HT can enhance the conformity of target volumes while reducing the overall radiation doses to reconstructed tissues and the crucial indicator V20 in the ipsilateral lung. VMAT demonstrates the highest treatment efficiency, yielding improved dose uniformity in the target volume and reduced radiation doses to the contralateral breast. It is advisable to prioritize HT or VMAT based on actual clinical conditions.

Objective:To investigate the influence of the complexity metrics of the multi-leaf collimator (MLC) on the γ-pass rate of volumetric modulated arc therapy (VMAT) plans for nasopharyngeal carcinoma (NPC).Methods:A total of 60 VMAT plans for NPC were selected to measure the γ-pass rate. The MLC data across all control points (CPs) in each VMAT plan were analyzed to calculate the mean field area (MFA), average leaf gap (ALG), small aperture score (SAS), and their corresponding weighted metrics including MFAW, ALGW, and SASW, considering dose weight (W). Pearson′s bivariate correlation analysis was conducted to examine the correlations between MLC complexity metrics and the γ-pass rate. Moreover, the receiver operating characteristic (ROC) analysis was employed to assess the predictive efficacy of MLC complexity metrics on dose verification result.Results:Under the 3%/3 mm, 3%/2 mm, and 2%/2 mm criteria, the MFA in the 60 VMAT plans exhibited a positive correlation with the γ-pass rate ( r=0.82, 0.79, 0.72, P<0.05), and the MFAW was also positively correlated with the γ-pass rate ( r=0.83, 0.81, 0.75, P<0.05). The ALG manifested a positive correlation with the γ-pass rate ( r=0.82, 0.79, 0.74, P<0.05), as did the ALGW ( r=0.83, 0.81, 0.77, P<0.05). The SAS(0-1 cm), SAS(1-2 cm), SAS(2-3 cm), and SAS(3-4 cm) displayed negative correlations with the γ-pass rate ( r= -0.86, -0.82, -0.71, -0.84, -0.82, -0.72, -0.79, -0.79, -0.73, -0.30, -0.35, -0.42, P<0.05), whereas the SAS(4-5 cm), SAS(5-6 cm), and SAS(6-40 cm) showed positive correlations with the γ-pass rate ( r=0.49, 0.45, 0.33, 0.73, 0.71, 0.59, 0.79, 0.79, 0.76, P<0.05). The outcomes of SASW reveal slightly stronger correlations than those of SAS. In terms of correlations among complexity metrics, a positive correlation was observed between MFA and ALG ( r=0.98, P<0.05). ALG was negatively correlated with SAS(0-1 cm), SAS(1-2 cm), SAS(2-3 cm), and SAS(3-4 cm) ( r= -0.95, -0.94, -0.89, -0.39, P<0.05), and positively correlated with SAS(4-5 cm), SAS(5-6 cm), and SAS(6-40 cm) ( r=0.51, 0.77, 0.92, P<0.05). The weighted result mirrored these correlations. The ROC-derived analytical result indicate that MFA, MFAW, ALG, ALGW, SAS(0-1 cm), SAS(1-2 cm), SAS(2-3 cm), SAS(6-40 cm), SASW(0-1 cm), SASW(1-2 cm), SASW(2-3 cm), and SASW(6-40 cm) demonstrated exceptional predictive efficacy for dose verification result [Area under the curve (AUC) > 0.9, P<0.05]. Conclusions:The γ-pass rate of VMAT plans for NPC is strongly correlated with MLC complexity metrics, which demonstrate excellent predictive efficacy for dose verification result. The increased uncertainty in dose calculations and measurements caused by narrow fields generated by the MLC is a significant factor contributing to the reduced γ-pass rate of VMAT plans. This finding is associated with discrepancies in the precision of treatment planning system (TPS) modeling and the accuracy of dose verification tools, providing a reference for similar challenges.

Objective:To investigate the differences in dosimetric parameters for target volumes and organs at risk (OARs), radiation doses to reconstructed tissues, and beam-on time in radiotherapy among helical tomotherapy (HT), volumetric modulated arc therapy (VMAT), and fixed-field intensity-modulated radiotherapy (F_IMRT) following immediate breast reconstruction for breast cancer, thereby providing a reference for the selection of clinical radiotherapy techniques.Methods:This study retrospectively investigated 15 breast cancer patients who underwent radiotherapy following modified radical mastectomy and immediate breast reconstruction at the Liuzhou Worker′s Hospital from August 2018 to July 2023. During target volume delineation, precautions were taken to avoid the reconstructed tissues, which were delineated separately. Customized HT, VMAT, and F_IMRT treatment plans were designed for each patient. The plans were categorized into the HT, VMAT, and F_IMRT groups based on different radiotherapy techniques employed. They were comparatively analyzed through one-way analysis of variance (ANOVA), with multiple comparisons further conducted in the case of significant differences.Results:Statistical analyses reveal significant differences in various parameters of target volumes among the three groups of plans ( F = 38.73, 14.95, 37.01, 48.05, 35.55, 22.56, 34.30, P < 0.05). Pairwise comparisons indicate that the maximum dose ( D2%), minimum dose ( D98%), mean dose ( Dmean), and the proportion of high-dose volumes within the target volume ( V107%and V110%) in both the HT and VMAT groups were significantly better than those in the F_IMRT group. The HT group demonstrated the optimal conformity index (CI), while the VMAT group displayed the superior homogeneity index (HI) compared to the other two groups. In terms of OAR, the V20 of the ipsilateral lung was the lowest in the HT group ( F = 14.31, P < 0.05) and the highest in the F_IMRT group ( F = 14.31, P < 0.05). However, the V5 and Dmean for both the ipsilateral and contralateral lungs in the HT group significantly surpassed those of the other groups ( F = 39.16, 31.91, P < 0.05). The mean dose Dmean ( F = 5.57, P < 0.05) of the contralateral breast was significantly reduced in the VMAT group compared to the other two groups. No statistically significant differences were observed for other OARs, including the heart, spinal cord PRV, thyroid, and humeral head ( P > 0.05). The radiation doses to reconstructed tissues ( Dmax, V53.5, Dmean) ascended in the order of HT, VMAT, and F_IMRT groups ( F = 17.69, 17.53, 15.11, P < 0.05). The HT and F_IMRT groups showed similar beam-on times ( P > 0.05), both exceeding that of the VMAT group by several folds ( F = 28.72, P < 0.05). Conclusions:The comparative analysis indicates that the three radiotherapy techniques exhibit distinct advantages and limitations, with F_IMRT demonstrating the least comprehensive advantage. HT can enhance the conformity of target volumes while reducing the overall radiation doses to reconstructed tissues and the crucial indicator V20 in the ipsilateral lung. VMAT demonstrates the highest treatment efficiency, yielding improved dose uniformity in the target volume and reduced radiation doses to the contralateral breast. It is advisable to prioritize HT or VMAT based on actual clinical conditions.

Objective:To evaluate the effect of different reconstruction points of intrauterine applicator on the source dwell positions and plan dosimetry in intracavitary brachytherapy for cervical cancer.Methods:Clinical data of 43 patients with cervical cancer who had completed radical radiotherapy in Liuzhou Workers' Hospital from May 2020 to October 2022 were retrospectively analyzed. Among 43 patients, aged 32-79 years, 40 cases were diagnosed with squamous carcinoma and 3 cases of adenocarcinoma. All patients received external irradiation for 50.4 Gy / 28 fractions and CT-guided intracavitary brachytherapy (45° intrauterine applicator) was 36 Gy / 6 fractions. Brachytherapy was performed by using Fletcher applicator, the curvature of intrauterine applicator were 15°, 30°and45°. Two sets of brachytherapy plans were simulated for each patient. One set of plans extracted the simulated CT positioning images and the original plan of the patient's brachytherapy. The reconstruction point of the curved part of the 45° intrauterine applicator was adjusted to slice-by-slice reconstruction. The plan was optimized to meet clinical requirements according to the prescription, which was called the slice-by-slice group. In the other set of plans, slice-by-slice group was used as a template. The reconstruction points of the curved section of the 45° intrauterine applicator were adjusted to 1, 3, 5, and 7, without modifying the applicator weights and other parameters, which was called the average group 1, 3, 5 and 7. The deviation analysis of 15°, 30° and 45° intrauterine applicator with different number of reconstruction points was carried out, the reconstruction deviation of 45°, 30° and 15° intrauterine applicator at different reconstruction points was compared. Paired-sample t-test or Wilcoxon signed rank test were used to compare the differences in high-risk clinical target volume (HR-CTV) D 50%, D 90%, D 100%, V 100%, V 150%, V 200% and conformity index (CI) as well as D 2 cm3, D 1 cm3 and D 0.1 cm3 in bladder, rectum, and small intestine between two groups of 45° intrauterine applicator. Results:The reconstruction deviation in the average group was mainly from the vertical direction of the 45° intrauterine applicator. The mean reconstruction deviations of 45° (1, 3, 5, 7 reconstruction points), 30° (1, 3, 5 reconstruction points) and 15° (1, 2 reconstruction points) were 1.30 mm, 0.32 mm, 0.14 mm and 0.08 mm; 0.57 mm, 0.14 mm and 0.06 mm; 0.14 mm and 0.06 mm, respectively. There was no significant difference in the parameters of high-risk clinical target volume (HR-CTV) in the slice-by-slice group compared with the average group 5 and 7 (all P>0.005), and no significant difference was found between the average group 5 and 7 (all P>0.005). There were no statistically significant differences in bladder and rectum doses between the slice-by-slice group and the average groups or within the average groups (all P>0.005). The parameters of small intestine in the slice-by-slice group were higher than those of the average group 1, the difference was statistically significant ( P=0.002,<0.001,<0.001). The dose of small intestine in the slice-by-slice group was not statistically significant compared with those in the average group 5 and 7 (both P>0.005). The dose of small intestine in the average group 5 was not statistically significant compared with that in the average group 7 ( P>0.005). The small intestine dose deviations of D 0.1 cm3, D 1 cm3 and D 2 cm3 in the average groups at 1 reconstruction point were 2.41%±1.70%, 1.95%±1.27% and 1.71%±1.10%, respectively. Conclusion:The number of reconstruction points is recommended to be no less than 1, 3 and 5 of the curved part of the 15°, 30°and 45° Fletcher intrauterine applicator, respectively, during intracavitary brachytherapy for cervical cancer.

Objective:To analyze the correlation between the monitor units and pass rate of plan dose verification in the volumetric intensity modulated arc therapy (VMAT) plan.Methods:VMAT plans for 20 patients with nasopharyngeal carcinoma (NPC) and 30 patients with cervical cancer who underwent radiotherapy at Liuzhou Workers' Hospital from January to October 2020 were retrospectively chosen. The Detector 1500 array and Octavius 4D phantom from German PTW company were used for dose measurement. The pass rates of dose verification of relevant plans were analyzed under the conditions of 3%/2 mm and 2%/2 mm. The correlation between the monitor units and pass rate of plan dose verification in VMAT plans was assessed by Pearson's bivariate correlation analysis.Results:Under the condition of 3%/2 mm, the correlation coefficients between the monitor units and gamma pass rate were -0.873 ( P<0.001), -0.800 ( P<0.001), -0.781 ( P<0.001), -0.493 ( P=0.006) for NPC_1Arc, NPC_2Arc, NPC_1Arc+NPC_2Arc and Cervix_2Arc, respectively. Under the condition of 2%/2 mm, the correlation coefficients between the monitor units and gamma pass rate were -0.842 ( P<0.001), -0.770 ( P<0.001), -0.748 ( P<0.001) and -0.531 ( P=0.003) for NPC_1Arc, NPC_2Arc, NPC_1Arc+NPC_2Arc and Cervix_2Arc, respectively. Conclusion:Significant negative correlation can be observed between the monitor units and plan dose verification pass rate in VMAT plan.

Objective:To study the differences in the dosimetry and delivery time between helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) in postoperative radiotherapy of synchronous bilateral breast cancer (SBBC) and to explore the feasibility of clinical application of the HT technology.Methods:A retrospective analysis was conducted for nine SBBC patients who underwent modified radical postoperative radiotherapy in the Fourth Affiliated Hospital of Guangxi Medical University from February 2017 to May 2022. For each patient, the Precision planning system was used to formulate the HT plan, and the RayStation planning system was employed to develop the VMAT plan. All plans obtained were divided into HT group and VMAT group according to plan type. The paired sample t-test was used to compare the dosimetric parameters of the target volume and organ at risk (OAR) and delivery time between the two radiotherapy technologies. Results:The plans of both groups could meet the clinical treatment requirements. The coverage ( D95% and V100%), conformity index (CI), average dose ( Dmean), and median dose ( D50%) of the target volumes in the HT group were better than those in the VMAT group, and the differences were statistically significant ( t=-3.21, -3.39, -5.03, 3.76, 4.97, P < 0.05). The differences in the maximum dose ( D2%), minimum dose ( D98%), high dose volumes ( V107% and V110%), and homogeneity index (HI) of the target volumes between the two groups were not statistically significant ( P > 0.05). Regarding the OAR, the V20 and Dmean of both lungs in the HT group were significantly lower than those in the VMAT group, but the irradiation volume V5 of both lungs in the HT group was significantly higher than that in the VMAT group ( t=-3.01, 3.83, -2.81, P < 0.05). Moreover, V20, V30, V40, and Dmean of heart and the V20 and Dmean of liver in the HT group were significantly lower than those in the VMAT group, with statistically significant differences ( t=3.76, -2.83, -2.74, 5.93, 4.57, 4.48, P < 0.05). There was no significant difference in the radiation doses to other OARs (spinal cord, thyroid gland, and humerus head, P > 0.05). The delivery time of the HT group was significantly higher than that of the VMAT group ( t = 11.32, P < 0.05). Conclusions:Compared with VMAT, HT has greater dosimetric advantages, and can provide higher target coverage, conformability and average dose, and significantly reduce the overall radiation doses to both lungs, heart, and liver in OARs. However, the irradiation volume V5 at low-dose areas of both lungs and the delivery time in the HT group are higher than those in the VMAT group, but still meet the clinical treatment requirements. Therefore, it is feasible to apply the HT technology to the modified radical postoperative radiotherapy of SBBC.

【Objective】 To investigate the effect of autologous blood transfusion(ABT) drainage system and simple drainage(using drainage bags) on the prognosis of patients after lumbar surgery. 【Methods】 The patients admitted to the Department of Orthopedics of our hospital from August 2018 to September 2020 who underwent posterior open lumbar internal fixation and fusion were divided into two groups according to different drainage methods adopted after surgery: 50 patients were randomly selected from the patients who received postoperative ABT system for drainage as ABT group, and 50 patients were randomly selected from the patients who received postoperative drainage by drainage bag as simple drainage bgroup(the control group). The postoperative drainage volume, actual postoperative drainage, total dominant blood loss, total autologous blood transfusion volume, as well as the postoperative anemia indexes, infection indexes and albumin levels in d1, d3 and d7 of the 2 groups were retrospectively analyzed. 【Results】 The gender, age, operation duration and operation segment of the 2 groups were comparable (P>0.05), and preoperative Hb, Hct, ALB, WBC, NE%, intraoperative blood loss, intraoperative autologous blood transfusion volume and actual postoperative drainage volume were similar (P>0.05). There were no significant differences in Hb, Hct, ALB, WBC, NE% and CRP in postoperative d1, d3 and d7, as well as in preoperative and postoperative Hb, Hct and ALB, and in postoperative and preoperative WBC, NE% and CRP (P>0.05). The postoperative drainage volume (mL) and total dominant blood loss (mL) in ABT group and the control group were 554.40±176.82 vs 337.80±102.43, and 1 048.40±282.87 vs 791.80±277.02, respectively (P<0.05). 【Conclusion】 The use of ABT drainage system after lumbar surgery increased the drainage volume compared with simple drainage, but the improvement of anemia, albumin and infection was not obvious. ABT system should not be used routinely for drainage after lumbar surgery.

Objective: To evaluate the dosimetric effects of set-up errors on nasal NK/T cell lymphoma by introducing set-up errors into the radiotherapy planning system for dose reconstruction. Methods: Ten patients with nasal NK/T cell lymphoma were recruited. A non-coplanar volumetric modulated arc therapy plan was designed for CT image and clinical target area of each patient. After the completion of the plan, the set-up errors were introduced into the radiotherapy plan by changing the ISO of the treatment, and dose calculation was performed to reconstruct the dose distribution. Results: With the increase of system set-up errors, the dose of target was decreased and the order affected by set-up errors in different directions was: left-right direction> head-foot direction> front-rear direction. When the translational set-up errors in each direction were -3 mm to 3 mm and the rotating set-up errors were -3° to 3°, the range of dose change in all targets was less than ±3%. When the set-up errors in all directions were ≤ 3 mm, the dose of organ at risk was less than or similar to the prescribed dose. When the set-up errors were> 3 mm, the doses of lens, spinal cord, parotid gland and optic nerve gradually exceeded the prescribed dose. Only when the rotating set-up errors were ≥ 3°, the dose of lens exceeded the prescribed dose. Special attention should be paid to the influence of the greater set-up errors in the left and right direction on lens, spinal cord and parotid gland, as well as on the spinal cord due to the larger set-up errors in the front and rear direction. After the actual set-up errors were introduced from our department, it exerted slight effect on the irradiation dose of GTV and CTV, which was less than ±2%. In a few cases, the dose of organ at risk potentially exceeded the prescribed dose limit, and special attention should be diverted to overdose of the lens and optic nerve. Conclusions The set-up errors will result in target dose deficiency and overdose of organ at risk in nasal NK/T cell lymphoma, especially upon the set-up errors in the left and right direction. The effect of 3 mm and 3° set-up errors on target and organ at risk is limited. Therefore, it is recommended to maintain the single direction set-up errors within 3 mm and 3°. The actual set-up errors introduced from our department exert little effect on the target dose, but a small number of organs are at risk of exceeding the prescribed dose limit. It is necessary to increase the evaluation of the extension region of organ at risk.

Objective To compare the dosimetric characteristics of the VMAT plans between the flattening-filter-free (FFF) and flattening filter (FF) modes for nasopharyngeal carcinoma and analyze the feasibility of VMAT plans in the FFF model applied in clinical practice.Methods Ten patients diagnosed with stage Ⅱ nasopharyngeal carcinoma between 2016 and 2017 were recruited in this investigation.For the CT image and clinical target volume (CTV) of the identical patient,FFF-and FF-mode VMAT plans were established with the identical prescription dose of 6 975 cGy and the identical modified parameters on the RayStation platform (6 MV X-ray).The dosimetric characteristics,the number of machine hops and the time of beam were recorded and statistically compared between the FFF and FF modes.Results The minimum dose D98％ target,target coverage,conformal index (CI) did not significantly differ between the FF and FFF plans (P=0.262-0.975),whereas the maximum dose of D2％,the average dose of D and target homogeneity index (HI) of the FF plans were slightly advantageous to those of the FFF plan (P=0.004-0.038).The acceptable dose of bilateral lenses,the volume of the left parotid gland with an acceptable dose of＞ 30 Gy and the average dose of the left temporal lobe in the FFF mode were declined compared with those in the FF mode (P=0.002-0.025).The volume of normal tissues (Body) within the dose range of 2-30 Gy in the FFF mode was less than that in the FF mode (P=0.000-0.003).In the FFF mode,the mean number of machine hops was 1.188 times (P=0.000) and the average time of beam was 91.2％ of the FF plan (P=0.024).Conclusions Both the FF and FFF plans qualify the dosimetric requirements in clinical settings.FF plan is advantageous in terms of the dose distribution in the target area,whereas FFF plan yields better OAR protection and low-dose irradiation.In spite of the increasing quantity of machine hops,the time of beam is declined in the FFF plan.Consequently,FFF mode probably contributes to enhance the clinical efficacy.