Figure 1.

Procedure for extracting genuine blood flow signals and tumour contours from intraoral ultrasonography images. (a) Original Doppler ultrasonography image (256 colours). The velocity range scale is shown to the left of the image. (b) The original Doppler ultrasonography image (a) has been converted into 64 colours. Colour reduction processing has been used to show the velocity range scale in nine stages of yellow–red. (c) The noise signals of three of nine stages in the velocity range scale. The noise signals are dark red, whereas genuine blood flow signals are shown in white. (d) Extracted blood flow signals. (e) An original B-mode ultrasonography image. (f) Median, mean and low-path filters have been applied to the original B-mode ultrasonography image (e) for noise reduction. (g) The image (f) was binarized by discriminant function analysis. (h) The tumour boundaries extracted using a Laplacian filter. (i) The extracted blood flow signals image (d) and tumour contour extracted tumour invasion front from image (h) have been superimposed.