1. An image registration method, comprising steps of: obtaining a Dual-Spectrum spectrogram of a long-wave Infra-red (LIR) image and a middle-wave Infra-red (MIR) image; detecting a first plurality of feature points on the target image and a second plurality of feature points on the source image, wherein the first plurality of feature points has a first plurality of cross-points of the vessel middle lines and the second plurality of feature points has a second plurality of cross-points of the vessel middle lines; searching a plurality of corresponding point pairs to determine corresponding relationships between the first plurality of feature points on the target image and the second plurality of feature points on the source image, wherein the corresponding point pair includes a pair of feature points; and correcting locations of the plurality of corresponding point to obtain a registered source image.