High-intensity zone (HIZ) In 1992, Aprill and Bogduk first described what is now known as the High-intensity zone (HIZ) seen on MRI of the lumbar spine. HIZ was a 'high-intensity signal' (bright white) located in the posterior annulus fibrosus. It is clearly dissociated from the signal of the nucleus pulposus in that it is surrounded superiorly, inferiorly, posteriorly, and anteriorly by the low-intensity (black) signal of the annulus fibrosus and is appreciably brighter than the signal of the nucleus 1).