Lung Dose Reduction From Patient Specific 4D Motion Based Non-Uniform Dose Prescription in Lung IMRT Treatment
W Zou*, M Zhang, X Xu, T Chen, B Haffty, S Jabbour, N Yue, Cancer Institute of New Jersey, New Brunswick, NJSU-E-J-132 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Motion of the tumor target in lung can be significant in patients. Traditionally lung dose is uniformly prescribed to the entire Internal Tumor Volume (ITV) with certain setup margin. Such uniform dose prescription may deliver quite high dose to the normal tissue surrounding the target volume due to tumor motion. This study explores patient specific motion based non-uniform dose prescription that is to deliver prescription dose to the target while maximizing the sparing of the surrounding normal tissue.
Patient 4D CT images were collected during simulation. CT phases were deformably registered. The spatial tracks of the tumor and surrounding tissue voxels were extracted from the transform matrix. The voxel dose to the tumor target and the surrounding tissue was evaluated at each phase and then summed together. Simulated Annealing algorithm was used to search for the spatial dose prescription distribution that delivers sufficient tumor voxel dose while minimizing the surrounding normal tissue dose.
Simple phantom and patients studies were included. The optimization process generally converged within 60 seconds to obtain a solution for non-uniform dose prescription. The result has shown a reduction in the adjacent lung tissue as great as 18% while maintaining the tumor dose.
This study proposed a methodology for a non-uniform dose prescription that would deliver sufficient dose to the moving lung tumor target while maximizing the sparing of the surrounding lung tissue. The beam delivery and the interplay effect are being further studied.