Evaluation of a Prototype PET-Based Biology-Guided Therapy (BGRT) System with Anchor Point Tracking Treatment Planning and Delivery Using Software Emulation
Abstract
Purpose
This work demonstrates the dosimetric performance of the developmental Anchor Point Tracking algorithm using phantom data acquired on the RefleXion X2 system with wide field-of-view PET detectors and software emulation of treatment planning and delivery.
Methods
Experiments were performed using an FDG-filled target inside an ArcCHECK or an FDG-filled target that moves freely inside a torso-shaped water phantom. PET data for treatment planning and delivery were acquired using an X2 system. One treatment plan was created using the previous X1 algorithm and a corresponding plan was created using the X2 Anchor Point Tracking algorithm that is in development. Plan quality, treatment time, and emulated delivery accuracy of the two algorithms were compared.
Results
For all twelve experiments involving stationary or moving targets, the median treatment time using the Anchor Point Tracking algorithm was shorter by 31.5% (P = 0.00001). Plan quality improved over X1 algorithm (median CI50 = 6.3 vs. 4.4, respectively; P = 0.00001), particularly in the superior-inferior extent of an oscillating target. The 3%/3mm absolute dose gamma inside the prescription dose was significantly better with the Anchor Point Tracking algorithm (P = 0.05). Of note, the Anchor Point Tracking algorithm also performed better than the X1 algorithm when the target suddenly shifted 1 cm during treatment (gamma = 40 vs. 100%). For targets undergoing periodic motion (N = 6), delivery accuracy was evaluated using PTV margin loss, which is the radial loss of PTV coverage (mm) relative to the 97% isodose line. There was no difference in margin loss between the two algorithms (P = 0.7).
Conclusion
This work demonstrated the Anchor Point Tracking algorithm’s ability to better spare normal tissue with more conformal BgRT plans without sacrificing delivery accuracy, and it was also better at responding to sudden shifts of the target during treatment.