A semi-automatic method of modifying a three dimensional volume visualization image of an anatomical structure in real time to separate desired portions thereof comprising: providing a two dimensional image slice (10, 12, 14) of a 3D volume visualization image of an anatomical structure; identifying by a user a desired region of the 2D image slice with an anatomical structure of interest; providing a prototype image of the 2D image slice with the desired region of the anatomical structure of interest; using a genetic algorithm employing a neural network model to evolve parameters of an algorithm that employs a transfer function to map intensity values coinciding with the desired region of the anatomical structure of interest to color and transparency values to generate an image by: creating a LH histogram of the said 2D image slice corresponding to the prototype image, the LH histogram including intensity values of the desired region of the said 2D image slice; using the genetic algorithm, marking selected regions of the LH histogram with one or more graphical elements (41, 42, 43), each of the graphical elements comprising a genotype of the genetic algorithm; using a multi dimensional transfer function, MDTF, mapping color and transparency values to the intensity values in the marked regions of the LH histogram to generate an image; using the NN model of the genetic algorithm, comparing the MDTF-generated image of the marked regions with the prototype image to determine whether the MDTF-generated image of the genotype sufficiently matches the prototype image; and if the transfer function generated image sufficiently matches the prototype image, applying the transfer function to additional 2D image slices of the 3D volume visualization image to generate a modified 3D volume visualization image of the anatomical structure. providing a two dimensional image slice (10, 12, 14) of a 3D volume visualization image of an anatomical structure; identifying by a user a desired region of the 2D image slice with an anatomical structure of interest; providing a prototype image of the 2D image slice with the desired region of the anatomical structure of interest; using a genetic algorithm employing a neural network model to evolve parameters of an algorithm that employs a transfer function to map intensity values coinciding with the desired region of the anatomical structure of interest to color and transparency values to generate an image by: creating a LH histogram of the said 2D image slice corresponding to the prototype image, the LH histogram including intensity values of the desired region of the said 2D image slice; using the genetic algorithm, marking selected regions of the LH histogram with one or more graphical elements (41, 42, 43), each of the graphical elements comprising a genotype of the genetic algorithm; using a multi dimensional transfer function, MDTF, mapping color and transparency values to the intensity values in the marked regions of the LH histogram to generate an image; creating a LH histogram of the said 2D image slice corresponding to the prototype image, the LH histogram including intensity values of the desired region of the said 2D image slice; using the genetic algorithm, marking selected regions of the LH histogram with one or more graphical elements (41, 42, 43), each of the graphical elements comprising a genotype of the genetic algorithm; using a multi dimensional transfer function, MDTF, mapping color and transparency values to the intensity values in the marked regions of the LH histogram to generate an image; using the NN model of the genetic algorithm, comparing the MDTF-generated image of the marked regions with the prototype image to determine whether the MDTF-generated image of the genotype sufficiently matches the prototype image; and if the transfer function generated image sufficiently matches the prototype image, applying the transfer function to additional 2D image slices of the 3D volume visualization image to generate a modified 3D volume visualization image of the anatomical structure.