Table 3 Cohen’s kappa (%) for the categorical scoring between synthetic CT (sCT) and CT

Lumbosacral transitional anomaly:

100

Fusion of the growth plates of the sacrum S1/S2:

83.9

Fusion of the growth plates of the sacrum S2/S3:

84.8

Cortical delineation of the joint space of the iliac side:

100^a

100^a

Cortical delineation of the joint space of the sacral side:

100^a

100^a

Joint facet defect (≥ 3 mm) on the iliac side:

100^a

61.5

Joint facet defect (≥ 3 mm) on the sacral:

100^a

100^a

Presence of ossified nuclei of the SI joint:

67.2

67.2

Bony bridges of the SI joint:

100^a

0