Fig. 4

Comparison of different images: Panel a1, b1, and c1 represented a slice of CBCT, pCT, and sCT, respectively; panel a2, b2, and c2 showed soft tissue and bony structure comparisons in the green boxed region under the soft tissue window; panel a3, b3, and c3 showed tumor tissue comparisons in the pink boxed region under the lung window; panel d1 showed the HU value differences between CBCT and pCT, while panel d2 showed the HU value differences between sCT and pCT