PVDR of two grid collimators

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GRID collimator based SFRT has greater PVDR at the shallower depth, even at 10 cm depth, it is still greater than that of Lattice therapy. In the past, when the GRID therapy was used, avoiding the hot dose beamlets passing through part of the normal structures were not considered as a decision-making point, and they were not even documented. The reported toxicity of GRID therapy was still very low. This may imply the GRID therapy has a very small or minimal toxicity, may or may not related its greater PVDR,