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Targeting Accuracy of Image-Guided Radiosurgery for Intracranial Lesions

Y Huang

Y Huang*, N Wen , B Zhao , J Kim , J Gordon , I Chetty , Henry Ford Health System, Detroit, MI


SU-E-J-123 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

To evaluate the setup accuracies of image-guided intracranial radiosurgery across several different linear accelerator platforms.

A CT scan with a slice thickness of 1.0 mm was acquired of a Rando head phantom (The Phantom Laboratory) in a U-frame mask (BrainLAB AG). The phantom had three embedded BBs, simulating a central, left, and anterior lesion. The phantom was setup with each BB placed at the radiation isocenter under image guidance. Four different setup procedures were investigated: (1) NTX_ExacTrac: 6 degree-of-freedom (6D) correction on a Novalis Tx (BrainLAB AG) with ExacTrac localization (BrainLAB AG); (2) NTX_CBCT: 4D correction on the Novalis Tx with cone-beam computed tomography (CBCT); (3) TrueBeam_CBCT: 4D correction on a TrueBeam (Varian) with CBCT; (4) Edge_CBCT: 6D correction on an Edge (Varian) with CBCT. The experiment was repeated 5 times with different initial setup error at each BB location on each platform, and the mean (μ) and one standard deviation (σ) of the residual error was compared.

The congruence between radiation and imaging isocenters on each platform was evaluated by acquiring Winston Lutz (WL) images of a WL jig followed by imaging using ExacTrac or CBCT. The difference in coordinates of the jig relative to radiation and imaging isocenters was then recorded.

Averaged over all three BB locations, the residual vector setup errors (μ±σ) of the phantom in mm were 0.6±0.2, 1.0±0.5, 0.2±0.1, and 0.3±0.1 on NTX_ExacTrac, NTX_CBCT, TrueBeam_CBCT, and Edge_CBCT, with their ranges in mm being 0.4~1.1, 0.4~1.9, 0.1~0.5, and 0.2~0.6, respectively. And imaging isocenter was found stable relative to radiation isocenter, with the congruence to radiation isocenter in mm being 0.6±0.1, 0.7±0.1, 0.3±0.1, 0.2±0.1, respectively, on the four systems in the same order.

Millimeter accuracy can be achieved with image-guided radiosurgery for intracranial lesions based on this set of experiments.

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