2D	Two-dimensional
3D	Three-dimensional
DSA	Digital Subtraction Angiography
CT	Computed Tomography
MRI	Magnetic Resonance Imaging
DRR	Digitally Reconstructed Radiographs
NCC	Normalized cross-correlation
PCA	Principal Component Analysis
CNN	Convolutional Neural Network
GPU	Graphic Processing Unit(GPU)
3D Attu	3D Attention-U-net
MI	Mutual Information
TPS	Thin plate spline
mTRE	Mean Target Registration Error