Comparison of 1.5 Tesla and 0.35 Tesla field strength magnetic resonance imaging scans in the morphometric evaluation of the lumbar intervertebral foramina.

ABSTRACT

OBJECTIVE: To compare magnetic resonance imaging (MRI) scans obtained from 1.5 Tesla (T) MRI units with scans obtained from 0.35T MRI units in the morphometric evaluation of the lumbar intervertebral foramina (IVF). DESIGN: Three dimensions of lumbar IVFs were measured on a cadaveric lumbar spine by using Vernier calipers. The spine was embedded in gelatin to simulate soft tissue and scanned twice in a 1.5T MRI unit (3-mm and 5-mm slice thicknesses) and once in a 0.35T MRI unit (5-mm slice thickness). Measurements from the scans were made independently by three observers. The results obtained from the two units were compared to the actual IVF size (as measured by calipers) and to one another. RESULTS: The greatest superior-to-inferior distance had the strongest statistically significant correlation to the actual cadaver measurements for both the 0.35T and 1.5T imaging units [r = 0.986 (0.35T); r = 0.985 (1.5T at 3 mm) and r = 0.981 (1.5T at 5 mm); p < .0001 in all cases]. Mean differences and standard errors were minimal between measurements made from MRI scans of both 1.5T and 0.35T units and measurements made directly from the cadaveric spine. CONCLUSION: Both imaging units produced images that accurately depicted the actual size of the IVF. The MRI units of 0.35T field strength produced images of high morphometric accuracy. In addition, the potential for side effects and the operating costs are less with 0.35T units. Therefore, 0.35T MRI units may be a prudent choice as a clinical and research imaging tool in the evaluation of the lumbar IVF.