Fig. 1. Algorithm flow diagram

Fig. 2. Rotating nuclear templates with different rotation angles. (a) 45°; (b) 30°; (c) 15°; (d) 0°; (e) 165°; (f) 150°; (g) 135°; (h) 120°; (i) 105°; (j) 90°; (k) 75°; (l) 60°

Fig. 3. Filter templates in horizontal direction under different rotation angles. (a) 135°; (b) 90°; (c) 45°; (d) retain center of rotation

Fig. 4. Filter templates in vertical direction under different rotation angles. (a) 135°; (b) 0°; (c) 45°; (d) retain center of rotation

Fig. 5. Filter templates in diagonal direction under different rotation angles. (a) 0°; (b) 90°

Fig. 6. Decomposition and reconstruction process of secondary algorithm. (a) Original intracranial cortical blood vessel PT-OCT cross-sectional image; (b) PT-OCT cross-sectional image processed by proposed algorithm; (c) image after first-level wavelet decomposition; (d) after second-level wavelet decomposition image; (e) enhanced secondary low-frequency image; (f) filtered secondary horizontal detail image; (g) filtered secondary vertical detail image; (h) filtered secondary diagonal detail image; (i)

Fig. 7. Comparison of filtering results of 89^th frame and 106^th frame OCT cross-sectional images by different algorithms. (a) Effect of traditional RKT algorithm after processing 89^th frame; (b) effect of improved RKT algorithm after processing 89^th frame; (c) effect of traditional RKT algorithm after processing 106^th frame; (d) effect of improved RKT algorithm after processing 106^th frame

Fig. 8. PT-OCT 3D image and its side view processed by different algorithms. (a) Unprocessed image; (b) traditional RKT algorithm; (c) improved RKT algorithm; (d) side view of Fig. (a); (e) side view of Fig. (b); (f) side view of Fig. (c)

Fig. 9. Tomography images at different imaging depths. (a) 1.16mm; (b) 1.35mm; (c) 1.46mm; (d) 1.57mm; (e) 1.66mm; (f) 1.90mm; (g) 2.07mm

Fig. 10. Parameter curves of filtered tomographic images at different depths. (a) RMSE; (b) PSNR

Table 1. Comparison of objective parameters of different algorithms on OCT intracranial cortical blood vessel images