Abstract:Objective To study the differences of physical parameters between external multi-leaf collimator (MLC) and internal MLC in intensity-modulated radiotherapy (IMRT) for cervical cancer, and to provide necessary reference for the rational application of IMRT technology in clinical practice. Methods A total of 29 postoperative patients with cervical cancer who received radiotherapy in Cangzhou People’s Hospital of Hebei Province from June 2020 to June 2021 were selected. Two IMRT plans were designed on the Pinnacle3 9.11 planning system using external MLC and internal MLC, and were divided into external group and internal group. The target area and organ at risk dose (D2, D50, D95, D98, Dmin, Dmax, and Dmean), volume parameters (V20%, V30%, V40%, V45%, V95%, V100%, V105%, and V110%), treatment plan validation pass rate, machine units (MU), and treatment time of two groups were compared. Results The conformal index of planned target volume (PTV) in external group was higher than that in internal group, and the homogeneity index was lower than that in internal group (P<0.05). The D95, D98, Dmin, V95%, and V100% of target PTV in external group were higher than those in internal group, while Dmax, D2, D50, Dmean, V105%, and V110% were lower than those in internal group (P<0.05). D2, Dmean, V30%, V40%, V45% of rectum, Dmean, V30%, V40% of bladder, D2 of small intestine, Dmean, D98 of left femoral head and D98 of right femoral head in external group were lower than those in internal group (P<0.05); V20% of small intestine was higher than that in external group (P<0.05). The MU and pass rate of external group were lower than those in internal group, the treatment time was longer than that in internal group (P<0.05). Conclusion The dose parameters of the external collimator plan are better than those of the internal collimator plan, but the verification pass rate is low and the treatment time is long. Both plans can meet the clinical needs. It is feasible to conduct postoperative radiotherapy for cervical cancer.
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