TABLE 3.

Traditional KBP studies aimed to predict voxel‐level doses for providing a starting point for the plan optimization process

Ref.	Method	Approach/Model	Key features	Purpose
92	AB	Direct	BEV projections	To identify similar patient cases by matching 2D BEV projections of structures
93	AB	Direct	BEV projections	To adapt the best match plan parameters from one institute to optimize the query case of an outside institution
94, 95	MB	Multivariate analysis Slice weight function	Distance‐to‐PTV, Slice level	To determine the relationship between the position of voxels and corresponding doses to predict the sparing of OARs
96	MB	Active shape model, active optical flow model	PTV locations in relation to spinal cord	To study the effect of PTV contours on dose distribution at the spinal cord. Five subgroups were created according to the PTV locations in relation to spinal cords.
97	AB	Direct	Target‐OAR overlap Shell creation surrounding the match target volume	To adapt the matched case from the database for query case by deforming the match beam fluences, warping the matched primary/boost dose distribution, and distance scaling factor
98	AB	Direct	Target‐OAR overlap	To transfer the beam settings and multileaf collimator positions of the best match case to the new case
99	AB	Direct	The PTV and Seminal vesicles (SV) concaveness angle and % distance from SV to the PTV	To transfer treatment parameters of the atlas case to the new case
100	AB	Indirect	Multi‐scale image appearance features	To use contextual atlas regression forest (cARF) augmented with density estimation over the most informative features to learn an automatic atlas‐selection metric for dose prediction
101	AB	Indirect	Features based on the spatial dose distribution and features derived from DVHs	To extend CRF by introducing the conditional random field model (cARF‐CRF) to transform the probabilistic dose distribution into a scalar dose distribution that adheres to desired DVHs.
102	AB	Indirect	Multi‐scale image appearance features	To converts a predicted per voxel dose distribution into a complete radiotherapy plan through a fully automated pipeline using cARF‐CRF.

Abbreviations: AB, atlas‐based (Direct or Indirect method); DTH, distance‐to‐target histogram; MB, model‐based; OVH, overlap volume histogram.