Table 1 Imaging parameters

(a) Anteroposterior diameter of the pelvic entrance

The line connecting the midline of the superior border of the symphysis pubis to the sacral promontory (Fig. 1)

[6, 19,20,21]

(b) Pelvic entrance transverse diameter

The maximum distance between the iliopubic lines on both sides (Fig. 2)

[6, 20]

(c) Anteroposterior diameter of the middle pelvis

The line connecting the midpoint of the inferior border of the pubic symphysis to the middle of the anterior border of the sacrococcygeal junction (Fig. 1)

[19, 22]

(d) Anteroposterior diameter of the pelvic outlet

The line connecting the midpoint of the inferior border of the pubic symphysis to the tip of the coccyx (Fig. 1)

[19, 20, 23]

(e) Pelvic outlet diameter

The line between the sciatic spines on both sides (Fig. 3)

[6, 15, 20, 22,23,24,25,26,27,28,29]

(f) Pubic symphysis height

The line in the middle of the upper and lower edges of pubic of symphsis (Fig. 1)

[19, 22, 29]

(g) Sacrococcygeal distance

The line connecting the midline of the anterior border of the sacral promontory to the tip of the coccyx (Fig. 1)

[19, 23, 29, 30]

(h) Sacrococcygeal curvature depth

A vertical line from the deepest part of the sacrococcygeal hollow to the sacrococcygeal distance (Fig. 1)

[19]

(i) Sacrococcygeal–pubic angle

The angle between the extension line of the anteroposterior diameter of the pelvic inlet and the extension line of the anteroposterior diameter of the pelvic outlet (Fig. 1)

[19]

(j) Pelvic depth

The line connecting the midpoint of the anteroposterior diameter of the pelvic entrance to the tip of the coccyx (Fig. 1)

[7, 19]

(k) Mesorectal fat area

The area of mesangium and fat around the rectum at the level of the tip of the sciatic spine (Fig. 3)

[13, 23, 25, 26]

(l) Angle T4

The angle between the upper and lower borders of the pubic symphysis with the lower border of the tumor as the vertex (Fig. 4)

[31]

(m) Angle A5

The angle between the line connecting the upper and lower borders of the pubic symphysis and the line connecting the midpoint of the upper border of the pubic symphysis to the sacral promontory (Fig. 1)

[16]