Alignments conducted between the MV X-ray beam isocenter and the CBCT image-guidance system, and a comprehensive evaluation of the manual image matching accuracy.

<p>Alignments conducted between the MV X-ray beam isocenter and the CBCT image-guidance system, and a comprehensive evaluation of the manual image matching accuracy.</p

Spatial discrepancies between the steel ball and MV X-ray beam for gantry rotation values of 0°, 90°, 180°, and 270°, and ring rotation values of 0°, 20°, and 340°.

<p>Spatial discrepancies between the steel ball and MV X-ray beam for gantry rotation values of 0°, 90°, 180°, and 270°, and ring rotation values of 0°, 20°, and 340°.</p

Spatial discrepancy between the MV X-ray beam isocenter and CBCT center.

<p>The center of the MV beam and CBCT were calculated from the mean discrepancy between the MV beam or CBCT and the steel ball, respectively. The dotted line markings show the original data points of these discrepancies. The double arrows indicate the mean discrepancy of the MV beam isocenter and CBCT center.</p

Histogram illustrating discrepancies in manual image matching with respect to image blurring for (a) the left-right (LR) direction, (b) the anterior-posterior (AP) direction, and (c) the superior-inferior (SI) direction.

<p>Histogram illustrating discrepancies in manual image matching with respect to image blurring for (a) the left-right (LR) direction, (b) the anterior-posterior (AP) direction, and (c) the superior-inferior (SI) direction.</p

Alignments conducted between the MV X-ray beam isocenter and the CBCT image-guidance system, and a comprehensive evaluation of the manual image matching accuracy, with an overall deviation of <i>D</i>_<i>all</i>.

<p>Alignments conducted between the MV X-ray beam isocenter and the CBCT image-guidance system, and a comprehensive evaluation of the manual image matching accuracy, with an overall deviation of <i>D</i>_<i>all</i>.</p

Spatial discrepancies between the steel ball and CBCT corresponding to changes in CBCT imaging parameters between Tube 1 and Tube 2, or switching rotation direction between clockwise (CW) or counterclockwise (CCW).

<p>Spatial discrepancies between the steel ball and CBCT corresponding to changes in CBCT imaging parameters between Tube 1 and Tube 2, or switching rotation direction between clockwise (CW) or counterclockwise (CCW).</p

The Vero4DRT system with dual implementation of the kV imaging system and electronic portal imaging device (EPID).

<p>Exposure by non-coplanar MV beams was enabled by gantry and ring rotation. Dynamic tumor motion tracking was conducted through exposure to the gimbaled MV X-ray head. The lock-on system was used to correct sagging by the X-ray beam axis.</p

Tumor shadow consistency measurements showing a comparison between the theoretical tumor shadow size and averaged intensity (AI) and cone-beam computed tomography (CBCT) images.

<p>Tumor shadow consistency measurements showing a comparison between the theoretical tumor shadow size and averaged intensity (AI) and cone-beam computed tomography (CBCT) images.</p

The consistency of tumor shadow volumes between the theoretical volumes and the volumes in averaged intensity (AI)-CT and CBCT images.

<p>The consistency of tumor shadow volumes between the theoretical volumes and the volumes in averaged intensity (AI)-CT and CBCT images.</p

Mean manual matching error and standard deviation using AI-CT images and CBCT images, which were obtained by five independent operators.

<p>Mean manual matching error and standard deviation using AI-CT images and CBCT images, which were obtained by five independent operators.</p