1. A method for visualizing and demarcating tumors by performing photodynamic methods and analysis of a multispectral fluorescent image, the method comprising: recording a first multispectral image with a multispectral camera, the first multispectral image being represented by a linear mixture model defined by the equation: 
 X=AS wherein A is an unknown matrix of spectral profiles, and S is an unknown matrix of spatial maps of classes present in the first multispectral image, wherein the classes present in the first multispectral image comprise a first class corresponding to a tumor or unhealthy tissue, a second class corresponding to healthy tissue, and a third class corresponding to other tissue types present in the first multispectral image; transforming the first multispectral image into a second multispectral image with extended dimensionality by using nonlinear dimensionality expansion, the second multispectral image being represented by the equation: 
 X =ĀS wherein Ā is an unknown matrix of spectral profiles with extended dimensionality; linearly transforming the second multispectral image into a first innovation representation of the second multispectral image according to the equation: 
 T[ X ]=ĀT[S] wherein T[S] is a second innovation representation of the matrix S; performing independent component analysis on the first innovation representation to estimate at least one of the unknown matrix of spectral profiles with extended dimensionality, Ā, and its inverse, Ā −1 ; estimating the unknown matrix of spatial maps of classes present in the first multispectral image S by multiplying the second multispectral image X by Ā −1 ; extracting data of interest comprising at least one of a tumor map, the first class, the second class and the third class according to selected criteria; and visualizing the tumor.