GK	Gamma Knife
BM	Brain metastasis
GAN	Generative adversarial network
HD-U-Net	Hierarchically densely connected U-Net
DSC	Dice similarity coefficient
MSE	Mean squared error
IRB	Institutional Review Board
GI	Gradient index
CI50	Conformity index at 50% of prescription dose
ReLU	Rectified linear unit
DRL	Deep reinforcement learning
IQR	Interquartile range
OAR	Organs at risk