Role of Raman spectroscopy and surface enhanced Raman spectroscopy in colorectal cancer

Table 2 A summary of the different clinical applications of Raman spectroscopy to colorectal cancer

Method	Sampling type	Sample number	Ref.	Year	Spectral region (cm-1)	Laser excitation (nm)	Data analysis
Probe	In vivo (tissue)	20	Shim et al[42]	2000	450-1800	785	PCA, PLS, ANN
Probe	In vivo and ex vivo (tissue)	9	Molckovsky et al[44]	2003	900-1800	785	PCA, LDA, LOOCV
Micro-spectrometer	In vitro (primary tissue)	10	Chen et al[38]	2006	500-1900	782.5	PCA
Probe	Ex vivo (tissue)	59	Widjaja et al[45]	2008	800-1800	785	PCA, SVM, LOOCV
Micro-spectrometer	Ex vivo (tissue)	54	Beljebbar et al[47]	2009	600-1800	785	SVM, PCA
Micro-spectrometer	In vitro (serum)	120	Li et al[37]	2012	800-1800	785	PCR, PLSR, LDA
Micro-spectrometer	In vitro (cell lines)	N/A	Ranc et al[39]	2013	400-1800	532	PCA
Probe	In vitro (tissue)	177	Wood et al[43]	2014	800-1800	830	PCA, LDA, LOOCV
Micro-spectrometer	In vivo (tissue)	50	Bergholt et al[78]	2014	800-1800 and 2900-3600	785	PLS, LDA

PCA: Principle component analysis; LDA: Linear differential analysis; PLS/PLSR: Principle least squares regression analysis; LOOCV: Leave one out cross validation; ANN: Artificial neural network; SVM: Support vector machine; PCR: Principle component regression.