TABLE 1.

Validation of digitally reconstructed radiographs (DRR) generator accuracy with landmark analysis

	Phantom				Patient 1				Patient 2
DRR	1‐pre	2‐pre	1‐post	2‐post	1‐pre	2‐pre	1‐post	2‐post	1‐pre	2‐pre	1‐post	2‐post
mean	0.764	0.865	1.034	0.911	0.871	0.900	1.013	1.102	0.871	0.862	1.071	0.828
SD	0.575	0.786	0.740	0.500	0.530	0.623	0.671	0.677	0.635	0.444	0.534	0.530
median	0.697	0.841	0.985	0.976	0.824	0.785	1.002	0.851	0.727	0.948	0.976	0.948
IQR	0.551	0.855	0.901	0.884	0.780	0.847	0.670	0.976	0.996	0.713	0.727	0.788
min	0	0	0	0	0	0.325	0	0.325	0	0	0	0
max	2.203	2.956	3.305	1.658	2.082	2.540	3.316	2.602	2.057	1.626	2.057	1.626
(a)

	Phantom				Patient 1				Patient 2
DRR	1‐pre	2‐pre	1‐post	2‐post	1‐pre	2‐pre	1‐post	2‐post	1‐pre	2‐pre	1‐post	2‐post
mean	1.423	1.157	1.298	1.597	1.606	1.455	1.600	1.477	1.615	1.149	1.097	0.988
SD	0.754	0.600	0.773	0.905	0.797	0.835	0.610	0.632	1.254	0.547	0.568	0.675
median	1.326	1.088	1.140	1.481	1.622	1.340	1.570	1.650	1.197	1.158	0.983	0.910
IQR	1.058	0.774	1.302	1.268	0.941	1.406	0.973	0.841	1.722	0.767	0.610	0.873
min	0.321	0.121	0.269	0.354	0.165	0.148	0.728	0.261	0.153	0.309	0.231	0.113
max	3.334	2.566	2.777	3.399	3.294	3.119	2.673	2.812	4.593	2.170	2.855	2.753
(b)

Note: Identifiable landmark points ($N=20$) were manually selected in each image for the known ExacTrac DRRs and DRRs generated by (a) our customized Insight Segmentation and Registration Toolkit (ITK) script; (b) our ray tracing algorithm built from scratch. Displacement statistics between matching landmarks are recorded in units of mm.

Abbreviations: IQR, interquartile range; max, maximum; min, minimum; SD, standard deviation.