Fig. 3.

Calculation of collagen volume fraction. a Collagen is stained by picrosirius red on a myocardial specimen; the yellow counter stain represents myocytes. In a first step, all pixels in the image were counted. b In a second step, all white background pixels were counted and subtracted from the total myocardial area quantified in the image (a). After converting varying shades of red to black, using a thresholding algorithm, all black pixels were counted. This number was divided by the total number of pixels (minus the white ones) in the image to calculate the collagen volume fraction