A computer-implemented method for generating an image of a patient's internal anatomy in a surgical field during a medical procedure, comprising: acquiring a full dose 2D baseline image of the surgical field including the patient's internal anatomy in a baseline orientation (step 200); digitally manipulating the full dose 2D baseline image to produce a baseline image set (step 204) including representative images of the baseline image at a plurality of permutations of movements of the baseline image from the baseline orientation (step 206); acquiring a new 2D image of the surgical field at a lower dose than the full dose 2D baseline image; comparing the new 2D image to the representative images in the baseline image set and selecting the representative image having an acceptable degree of correlation with the new image (step 210); and merging the selected representative image with the new 2D image (step 212) and displaying the merged image; wherein the step of comparing the new image to the representative images of the baseline image set includes: performing a principal component analysis, PCA, on the pixels of the representative images in the baseline image set to generate one or more PCA vectors; producing a PCA matrix of PCA vectors for each pixel in a representative image; generating a column vector for each representative image and the new image of pixel data for each pixel in the image; performing a matrix multiplication of the PCA matrix and each column vector to generate a new column vector for each representative image and the new image; obtaining the dot product of the column vector for the new image and the column vector for each of the representative image; and selecting a representative image for which the dot product is within a predetermined threshold, wherein: the comparing step includes generating an image difference from the differences between the representative image and the new image; and the merging step includes selectively overlaying the difference image to one or more of the merged image, representative image and new image, to remove the difference image from the merged image. acquiring a full dose 2D baseline image of the surgical field including the patient's internal anatomy in a baseline orientation (step 200); digitally manipulating the full dose 2D baseline image to produce a baseline image set (step 204) including representative images of the baseline image at a plurality of permutations of movements of the baseline image from the baseline orientation (step 206); acquiring a new 2D image of the surgical field at a lower dose than the full dose 2D baseline image; comparing the new 2D image to the representative images in the baseline image set and selecting the representative image having an acceptable degree of correlation with the new image (step 210); and merging the selected representative image with the new 2D image (step 212) and displaying the merged image; wherein the step of comparing the new image to the representative images of the baseline image set includes: performing a principal component analysis, PCA, on the pixels of the representative images in the baseline image set to generate one or more PCA vectors; producing a PCA matrix of PCA vectors for each pixel in a representative image; generating a column vector for each representative image and the new image of pixel data for each pixel in the image; performing a matrix multiplication of the PCA matrix and each column vector to generate a new column vector for each representative image and the new image; obtaining the dot product of the column vector for the new image and the column vector for each of the representative image; and selecting a representative image for which the dot product is within a predetermined threshold, wherein: performing a principal component analysis, PCA, on the pixels of the representative images in the baseline image set to generate one or more PCA vectors; producing a PCA matrix of PCA vectors for each pixel in a representative image; generating a column vector for each representative image and the new image of pixel data for each pixel in the image; performing a matrix multiplication of the PCA matrix and each column vector to generate a new column vector for each representative image and the new image; obtaining the dot product of the column vector for the new image and the column vector for each of the representative image; and selecting a representative image for which the dot product is within a predetermined threshold, wherein: the comparing step includes generating an image difference from the differences between the representative image and the new image; and the merging step includes selectively overlaying the difference image to one or more of the merged image, representative image and new image, to remove the difference image from the merged image.