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Objective To investigate the relationship between the body mass index (BMI)/body mass index improved (BMIIMPd) and the dose of the small intestine as well as the acute radiation colitis in the intensity-modulated radiation therapy after cervical cancer surgery.Methods Thirty-nine cervical cancer patients underwent postoperative adjuvant radiotherapy.All patients received Philips large bore CT scan for enhanced CT scan,target delineation and organ at risk.All patients were treated with a single arc 10 MV VMAT plan.The correlation between the radiation dose of the small intestine and the acute radiation enteritis and BMI/BMIIMPd was analyzed.Results The BMI was calculated as (22.23±2.80) kg/m2,BMIIMPd was (21.49±3.95) kg/m2,the small intestine volume VSI was (1 155.71 ± 419.33)cc3.The volume of the small intestine received more than 10 Gy (V10_SI) VMAT was (66.50± 27.01) ％,and the equivalent uniform dose (EUD) and normal tissue complication probability (NTCP) were (4 098.87± 184.93) cGy and (7.98±8.73)％.One way ANOVA demonstrated that under the VMAT technology,the BMIIMPd,V30,V40,EUD (or=50) and NTCP in the small intestine were the influencing factors of the occurrence of acute radiation enteritis.Conclusions If the improved BMIIMPd is utilized to distinguish the BMI,the high dose area of the small intestine will be larger and the incidence of acute radiation enteritis will be higher for patients with BMIIMPd between 10.1 and 16.9(normal and thin).Conventional BMI cannot be utilized as a basis for the prediction of the incidence of acute radiation enteritis in patients with cervical carcinoma.
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Objective To investigate the clinical effect of lung equivalent uniform dose (LEUD)-based predictive model for radiation pneumonitis (RP) induced by volumetric modulated arc therapy (VMAT) and to determine the optimal a value.Methods A total of 65 patients with primary lung cancer who received VMAT from July 2015 to February 2016 were divided into RP group and non-RP group according to the presence or absence of RP after radiotherapy.Their dose-volume histogram (DVH) data and other data were obtained and analyzed by the self-compiled numerical analysis program.The LEUD values in the two groups were calculated at a=[-50, 50], and then the a value was identified when the relative difference of LEUD between the two groups was maximal.The paired t test was used for analyzing the differences in V5, V20, V30, minimum lethal dose (MLD), and LEUD (aoptimal) between the two groups.A Pearson correlation analysis was used to determine the correlation of Vdose and LEUD (aoptimal) with RP.The logistic regression method was used to establish the predictive model of RP.Results The maximum relative difference in LEUD between RP group and non-RP group was obtained at a=0.3(627.94 cGy vs.510.23 cGy, relative difference[R]=23.07%).R decreased slowly at t=[-50,-5], increased sharply at t=[-5, 0], and reached the maximum value at a=0.3.After a rapid decrease at a=[0.3, 4], R decreased slowly at a=[4, 50].The correlation analysis of the traditional physical volume dose threshold also showed that the LEUD (at a=0.3) was correlated with V5, V10, V20, and MLD (r=0.929, P<0.05).Conclusions For patients receiving VMAT for thoracic cancer, LEUD (at a=0.3) can distinguish between patients with and without RP.Therefore, LEUD is recommended to be<510 cGy.A combination of LEUD and conventional physical dose has a good clinical predictive value for RP under non-uniform irradiation.
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Objective To study the geometric difference between six different ITV generation methods from 4DCT for patients with non?small cell lung cancer ( NSCLC) treated with stereotactic ablative radiotherapy technique ( SABR) . Methods Between Dec. 2013 and Mar. 2014,16 patients were enrolled in this retrospective study. All patients underwent imaging with 4DCT scans. The MI and DI index were evaluated between six ITV generation methods:combining GTV from all 10 respiratory phases ( ITV10 );combining GTV from four respiratory phases, including two extreme phases ( 0% and 50%) plus two intermediate phases ( 20% and 70%) ( ITVYeo ) which was proposed by Seung?Gu Yeo of Soonchunhyang University;combining GTV from two extreme phases ( ITVEI+EE ) . And combining GTV from five odd phases (10%,30%,50%,70%,90%)(ITVodd).Accordingly the ITVEVEN which was combined from the remaining five even phases (20%,40%,60%,80%,0%),and ITVAVG,ITVMIP were contoured from two reconstructed 4DCT sequences,finally,a method which was not sensitive to the tumor volume and motion characteristic was selected for clinical use. Data were compared using a variance analysis followed by Student?Newman?Keulsa test both in same group or between groups. At the same time, the volume and the three dimensional movements of the tumor, the relativity of MI and DI were analyzed by Multi?parameter regression analysis. Results The mean (range) tumor motion (RLR,RAP,RCC,and R3D) are 3. 5 mm (1. 4?8. 4 mm),4. 5 mm (1. 1?8. 6 mm),9. 5 mm (0?10 mm),12. 3 mm (2. 5?55. 3 mm) respectively. The IGTVx volume are Underestimated by 25. 7%,35. 6%,17. 9%,12. 8%,3. 6%,4. 8%( P=0. 000) respectively. The MI index comparisons between six ITV generation methods and ITV10 showed statistical significance:0. 69,0. 62,0. 80, 0. 86,0. 93,0. 91 ( P=0. 006 ) . The DI index showed no statistical significance:0. 98, 0. 98, 0. 97, 0. 97, 0. 99,0. 98(P=0. 130).The tumor size and motion amplitude were certified not the independent factors for the MI index of ITVodd and ITVEVEN . Conclusions IGTVODD/EVEN based on odd or even 4DCT phases is not sensitive to the tumor size or motion characteristic and is proved to have a good marching with ITV10 meanwhile maintaining a reasonable contouring efficiency,it can be recommend to the institutions which was not equipped with the deformable registration systems.