Table 3.

List of 16 ANN model input variables.

#	ANN Input Variables	#	ANN Input Variables
1	% of all voxels within 5 mm occupied by OAR5 mm	9	Square root of min distance to GTV surface
2	% of all voxels within 10 mm occupied by OAR5 mm	10	Min distance to OAR5 mm (>=0 only) b
3	% of all voxels within 15 mm occupied by OAR5 mm	11	Min distance to OAR5mm (<=0 only)
4	% of all voxels within 20 mm occupied by OAR5 mm	12	Square root of min distance to OAR5mm
5	% of GTV occupied by OAR5 mm a	13	Min distance to PTVOPT (>=0 only)
6	Distance to GTV centroid	14	Min distance to PTVOPT (<=0 only)
7	Max distance from GTV centroid to GTV surface a	15	Min distance to (OAR5 mm‐OARCRIT) (>=0 only)
8	Min distance to GTV surface	16	Min distance to (OAR5 mm‐OARCRIT) (<=0 only)

Each variable was calculated for all voxels inside the GTV for each plan unless indicated otherwise. Some ANN model input variables could have both positive and negative values, with negative values corresponding to an overlap between the GTV and the OAR structure associated with the variable.

^aEvery voxel for the GTV had the same value.

^bA linear correlation was observed between this distance metric and dose but only up to a distance of ~ 16 mm. So this metric has a maximum value of 16 mm for any voxel.