Fig. 1. Determination of initial seed points. (a) NIR image; (b) image after Gabor filtering; (c) grid lines and candidate initial seed points; (d) effective initial seed points

Fig. 2. Dynamic search area of kth iteration

Fig. 3. Partial initial seed points and their corresponding local vessel directions

Fig. 4. Three types of vessel structures. (a) Normal; (b) bifurcation; (c) crossing

Fig. 5. Gaussian model of vessel cross section

Fig. 6. dm1 and dm2 corresponding to normal vessel

Fig. 7. Tracking results. (a) NIR image; (b) image processed with Gabor filter; (c) tracked vessel edge points; (d) edge points of normal vessel; (e) edge points of bifurcation vessel; (f) edge points of crossing vessel

Fig. 8. Comparison of results of three methods. (a) NIR image 1; (b) NIR image 2; (c) image 1 processed with Gabor filter; (d) image 2 processed with Gabor filter; (e) image 1 processed with proposed method; (f) image 2 processed with proposed method; (g) image 1 processed with RLT; (h) image 2 processed with RLT; (i) image 1 processed with LAT; (j) image 2 processed with LAT

Fig. 9. ROC images extracted by three methods. (a) Proposed method; (b) RLT method; (c) LAT method

Fig. 10. Comparison of detection rate of three methods with different SNR. (a) Precision; (b) recall; (c) F-measure

Table 1. Comparison of detection rate of three methods