剂量跌落环联合虚拟限量环在鼻咽癌同步推量调强放疗中的应用研究OA

Objective To analyze the application value of combining a dose fall-off ring(DFOR)with a virtual dose-limiting ring(VDLR)in optimizing the dose distribution of simultaneous integrated boost intensity-modulated radiotherapy(SIB-IMRT)plans for nasopharyngeal carcinoma(NPC).Methods Twenty newly diagnosed NPC patients treated at some hospital with SIB-IMRT were selected.For each patient,two SIB-IMRT plans were designed based on Monaco planning system:SIB-IMRT1 which utilized VDLR alone to restrict dose distribution outside the target volumes and SIB-IMRT2 which combined DFOR with VDLR to restrict dose distribution outside the target volumes.The two types of SIB-IMRT plans were compared in terms of dosimetric parameters for the planning target volume(PTV)and organs at risk(OAR),as well as treatment delivery parameters such as number of segments,monitor units(MU)and delivery time.Statistical analysis was carried out with SPSS 26.0 software.Results The dosimetric parameters of both the SIB-IMRT plans met the requirements for clinical treatment.The SIB-IMRT1 plan had the D2%,Dmean and homogeneity index(HI)of PTVp,PTVn and PTV2,D2%,Dmean and D98%of PTVp1,D2%and HI of PTVn1,V6 006-6 996,6 600 of PTV6 006-6 996 and V2-6 006,6 006 of PTV2-6 006 inferior to those of the SIB-IMRT2 plan,with the differences being statistically significant(P<0.05);the D98%and conformity index(CI)of PTVn1 in the SIB-IMRT1 plan were slightly better than those in the SIB-IMRT2 plan,with the differences being statistically significant(P<0.05);the SIB-IMRT1 plan had the Dmean of the parotid gland,oral cavity,and larynx and Vbody-2,4000 of body-PTV2 inferior to those of the SIB-IMRT2 plan,with the differences being statistically significant(P<0.05).The SIB-IMRT1 plan had the numbers of segments and MU higher than those of the SIB-IMRT2 plan,with the differences being statistically significant(P<0.05);the two types of plans had no significant differences in the delivery time(P>0.05).The dose-volume histogram showed that the SIB-IMRT2 plan behaved better than the SIB-IMRT1 plan in some dosimetric parameters of PTVs,OARs and body-PTV2.Conclusion Compared to the SIB-IMRT1relying solely on VDLR,the SIB-IMRT2 plan combining DFOR and VDLR without significantly altering the beam delivery time optimizes some PTV dosimetric parameters,and demonstrates superior dosimetric performance in sparing some OARs and body-PTV2.[Chinese Medical Equipment Journal,2026,47(5):50-56]