ABSTRACT
Objective To investigate the dosimetric difference between inverse planning simulated annealing(IPSA)and manual optimized plan for isodose line in interstitial brachytherapy for locally advanced cervical cancer and to provide a better optimization method for clinical application. Methods A total of 104 patients with cervical cancer were enrolled in this study. They received pelvic external beam radiotherapy and interstitial brachytherapy in five fractions. Both IPSA and manual optimized plan for isodose line were used to optimize the dose in each fraction. Dose volume parameters of the two plans were compared to analyze the dosimetric outcome by paired t-test. Results There were no significant differences in mean D 90and D 100for high-risk clinical target volume(HR-CTV)and D 90for intermediate-risk clinical target volume(IR-CTV)between the two groups(P>0.05). The IPSA group had a significantly higher D 100for IR-CTV than the manual optimized group(58.36±2.06 Gy vs. 53.99±2.17 Gy, P=0.025). For organs at risk,the IPSA group had a significantly lower mean rectum D 2ccand a significantly higher bladder D 2ccthan the manual optimized group(68.53± 2.85 Gy vs. 71.77± 1.79 Gy, P=0.002;80.49± 3.36 Gy vs. 78.71± 2.64 Gy,P=0.034). There was no significant difference in sigmoid D 2ccbetween the two groups(P>0.05). The IPSA group had significantly higher relative dose homogeneity index(HI)and conformity index (CI)of radiation dose for target volume than the manual optimized group(P<0.05), and there was no significant difference in overdose volume index(OI)between the two groups(P= 0. 1 0 7).Conclusions Compared with manual optimized plan for isodose line, IPSA can improve the dose distribution of tumor tissue,reduce mean rectum D 2cc,and increase CI and HI,so it is a preferable optimized treatment planning method in clinical application.
ABSTRACT
Objective To investigate the differences in dosimetry between conformal radiotherapy (CRT),field-in-field intensity-modulated radiotherapy (FIF-IMRT),and intensity-modulated radiotherapy (IMRT) after breast-conserving surgery for left-sided breast cancer.Methods A total of 31 patients who underwent breast-conserving surgery for left-sided breast cancer were randomly selected,and the plans for CRT,FIF-IMRT,and IMRT were developed.The dose-volume histogram (DVH) was used for self-control study,and the non-parametric test was used to compare the differences in target volume and doses to organs at risk (OARs).Results All the three methods met the requirements of the prescribed doses.The CRT group had a higher V105 of the target volume and higher heart V30 and Dmax (P=0.000,0.000,0.000).The IMRT group had higher V5 and Dmean (P=0.000,0.000),as well as a higher lung V5 and a lower lung V40 (P=0.000,0.000).The FIF-IMRT group had the lowest Dmean (P=0.000),and the IMRT group had significantly higher Dmean and Dmax of the right lung and the spinal cord than the other two groups (P=0.000,0.000,0.000,0.000).The FIF-IMRT group had a significantly lower single hop count than the other two groups (P=0.000).Conclusions CRT has a good dose distribution in the target volume,but greatly injures the surrounding tissues.FIF-IMRT can well protect OARs and cause less damage to the device.