[Comparison of lumbar spinal canal measurements on MRI and CT]

To compare AP diameter measurements of spinal canal and thecal sac on MRI and CT.

The AP diameter of the spinal canal at L4 and thecal sac at L4-5 were measured on both MRI and CT performed on patients at less than one month interval. Measurements were obtained from axial CT images of the abdomen on CT and sagittal T1W (n = 98) and T2W (n = 78) MR images of the spine. The examinations were reviewed at more than 24 hours interval. Radiologists were blinded. Inter-observer agreement evaluation was performed prior to this study. Measurements were compared using a t test for paired variables.

For the spinal canal, mean measurements were 0.4 +/- 1.5mm inferior on CT compared to MRI. For the thecal sac, mean measurements were 0.1 +/- 1.4mm inferior on CT compared to MRI.

Measurements on CT and MRI for lumbar spinal canal and thecal sac are fairly comparable, with mean measurement differences inferior to the degree of precision of the measurement technique itself.