Effects of jaw tracking technique on the absorb dose of PTV and OARs in intensity-modulated radiation therapy for nasopharyngeal carcinoma / 国际生物医学工程杂志

ABSTRACT

Objective To study the effects of using jaw tracking technique with Smart LMC algorithm on the absorbing dose of planning target volume (PTV) and organs at risk (OARs) in dynamic intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC).Methods Field fluencies of 10 cases of NPC patients were optimized using DVO algorithm on Eclipse TPS (11.0),and according to the same optimal fluence,MLC operation files were calculated using jaw tracking technique and jaw fixing technique respectively,dose distribution was calculated with AAA algorithm and jaw tracking IMRT plan (JT-IMRT) and jaw fixing IMRT plan (JF-IMRT) were generated respectively.Collimators' position at the plan implementation was observed,and the total number of plans' monitor units (MU),the dose of PTV,the absorb dose of OARs,and the actual fluence verification pass rate were compared.Results The collimators' opening gap distances in 166 control points of the JT-IMRT reduced in both X and Y directions in the field,compared to that of the JF-IMRT.Total number of the JT-IMRT's MU increased by 3.59％-11.63％.There was no statistical significant difference between the doses of the PTV.Statistical significance was found in the differences between maximum dose (Dmax) of brainstem,spinal cord,crystal,optic nerve,the mean dose (Dmean) and D50％ of parotid and their decreased values after therapy (t=5.70-8.66,P＜0.05).The actual fluence verification pass rate of the JT-IMRT was higher than that of the JF-IMRT.There was a significant difference between the results (t=5.18,P＜0.05).Conclusions The JT-IMRT plan of the smart LMC algorithm is more tolerant to the radiation leakage between inter-and intra-leaf.The dose of OARs is lower,while the dose calculation precision and the verification pass rate are higher,the actual radiation dose is more accurate and reliable.Therefore it is more suitable for clinical applications.