Methodology for identifying threshold criteria. From each image set, the image at 2 or 4 revolutions was extracted (A) and sequentially binarized with a decreasing grayscale value, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover (B, C). The threshold value for the gel was set as the maximum grayscale value that produced a complete clover structure with no interruptions in the 4 leaves (D). Bar: 1 mm.