“…As a popular multivariate statistical technique, principal component analysis (PCA) can be used to extract spatial information from the original data by computing principal components (PCs) which are linear combinations of the original data [16]. PCA has been widely used in various imaging technologies, such as computed tomography (CT) [17,18], positron emission tomography (PET) [19,20] and magnetic resonance imaging (MRI) [21]. In optical molecular imaging, PCA was used to analyze optical data varying with times [22,23], spectrums [12] and energies [7,8].…”