Figure 3.

(a) Contrast-enhanced T₁ weighted fat-suppressed sagittal image of a lumbar spine showing enhancement at the posterosuperior corner of the L4 and L5 vertebral bodies (arrowheads). These active lesions are not evident on (b) the short tau inversion–recovery (STIR) imaging (arrowheads), with poor agreement between the two images. With the spine units L3–S1, Reader 1 had an ankylosing spondylitis spine MRI-activity score of 2 for contrast-enhanced images and 0 for STIR images, whereas Reader 2 had a score of 1 for contrast-enhanced images and 0 for STIR images.