Objective To summarize the relationship between the transverse dimension of the target volume and the most optimized X jaw size in volumetric modulated arc therapy(VMAT) plan for cervical cancer radiotherapy.
Methods The VMAT plans were made by modifying X jaw size on CT images in 12 postoperative patients with cervical cancer. On each image, the best X jaw size was identified. The relationship between the best X jaw size and the transverse width of planning target volume (PTV) was determined.
Results The change in the transverse dimension of the target volume was accompanied with the changes of the optimized X jaw size. The relationship between X jaw size (y) and the PTV's transverse width (x) could be expressed as the following equation:y=-0.0033x2+0.7132x+3.6322.
Conclusions There is a relationship between X jaw size and PTV's transverse width, which can be used for the postoperative VMAT plan design in patients with cervical cancer.