Three-dimensional analysis of lumbar intervertebral foramina using MRI and CT: a comparison study

Objective: To improve the measurement accuracy of lumbar intervertebral foramen by analyzing the three-dimensional data obtained from MRI and CT. Methods: The MRI and CT data of 56 patients with lumbar degenerative diseases (24 men, 32 women; age 56.5 ± 7.6 years, range 39 ∼ 72 years) and 41 healthy adults (18 men, 23 women; age 31.4 ± 5.2 years, range 25 ∼ 36 years) were collected from August 2013 to August 2016. Lumbar foramen three-dimensional models of MRI and CT were created using mimics 19.0 software. The volume, sagittal minimum area, and coronal length of lumbar foramina were measured and compared between MRI and CT using t-test. Intra class correlation coefficient (ICC) was used to evaluate the agreements of the measurements from MRI and CT models. Results: There was high agreement between different measurers (ICC > 0.9). In the healthy group, the foramina volume on L₁ ∼ S₁ levels and sagittal minimum area on L₁/L₂, L₂/L₃, L₃/L₄ and L₄/L₅ levels in MRI models was significantly smaller than that in CT models (P < 0.05). In the degenerative lumber group, the foramina volume on L₁-S₁ levels and sagittal minimum area on L₁/L₂ and L₂/L₃ in MRI models was significantly smaller than that in CT models (P < 0.05). The other data between two groups existed no statistical difference (P > 0.05). Conclusions: The measurements of lumbar foramen obtained from the MRI and CT differs significantly. The main cause is that posterior soft tissue of lumbar foramen cannot be accurately identified on CT in people without degeneration. (authors)