(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: image guidance during radiotherapy delivery (RT-IGRT) is a trend in IGRT advancing. Low-frequency X-ray RT-IGRT (LFX-RT-IGRT) is promising because it ensures the intrafractional localization accuracy based on patient anatomy with a reasonable low imaging dose. This work is to develop an LFX-RT-IGRT technique using single panel X-ray imaging system.
Methods: images are captured at different gantry angles during rotational treatments. The angle interval is between 45° to 135°, and the default setting is at 90°. The 3D displacements are derived from image registration with DRR for the two images taken at adjacent gantry angles. A head anthropomorphic phantom and an inhouse-designed box phantom were setup with cone beam CT based positioning. The derived displacements in 3D during treatment were recorded and analyzed statistically for both still phantoms with and without a man-set offset.
Results: the head phantom, LFX-RT-IGRT yields average biases of {-0.16mm, 0.08mm, -0.3mm} in lateral, longitudinal and vertical directions, respectively. The standard deviations are {0.04mm, 0.11mm, 0.10mm}. The average and maximum biases in 3D are 0.56mm and 0.81mm. For the box phantom, the average biases are 0.23mm, 0.13mm and 0.35mm in three directions. The standard deviations are {0.11mm, 0.12mm, 0.05mm}. The average and maximum biases in 3D are 0.65mm and 1.12mm, respectively. The displacement calculation time is less than 2.3 seconds using an Intel Core i7-7700HQ processor (4 CPU cores, 2.8 GHz) with 16GB of DRR3 memory.
Conclusion: A new RT-IGRT system using the single panel X-ray image system has been developed for intrafractional position check. These results indicate that LFX-RT-IGRT system is precise and efficient for monitoring target motion during patient treatment.
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