Physical and Biological Dosimetry Study on the Optimization of Intensity-Modulated Radiotherapy Plan for Head and Neck Tumors Based on Accurate Segmentation of Pharyngeal Constrictor Muscles with MR/CT Fusion Image
Abstract
Purpose
The purpose of this study was to explore the difference between the two plans of intensity modulated radiotherapy (IMRT) for head and neck tumors, which did not limit the dose of pharyngeal constrictor and protected the pharyngeal constrictor, the dose of pharyngeal constrictor, the probability of tumor control (TCP) and the probability of normal tissue complications (NTCP).
Methods
240 patients with head and neck tumors treated by radiotherapy in our hospital were selected, and the target area was delineated on the patient's localized CT image and an IMRT plan was designed, named Plan1. On the basis of the original planned CT (pCT), the entire pharyngeal constrictor is sketched based on the fusion image of MRI and CT, and the dose limit is set for the pharyngeal constrictor, then an IMRT plan is designed, named Plan2. Both groups plan to meet the planned target area (PTV) coverage and other OARs dose limits at the same time.
Results
D98 and V100% of Plan 2 were higher than that of Plan 1, the difference was statistically significant (p<0.001). The target area fitness index of Plan2 is also good, and the difference is also statistically significant, p=0.016. However, there was no significant difference in Dmean (p=0.328), D2 (0.172) and HI (p=0.143) between the two. The difference of Dmax, Dmean, V40 and V50 of the upper, middle and lower pharyngeal constrictors of Plan1 and Plan2 was statistically significant (p<0.05).
Conclusion
The target dose of protecting pharyngeal constrictor and not limiting the dose plan of pharyngeal constrictor in patients with head and neck tumors meet the clinical requirements. Compared with the plan that does not limit the dose of the pharyngeal constrictor, the radiotherapy plan that protects the pharyngeal constrictor reduces the Dmax, Dmean and NTCP of the pharyngeal constrictor.