3-D volume scanning. A new technique for lumbar MR imaging.

A 3-D volume magnetic resonance (MR) acquisition utilizing a T1-weighted gradient-echo sequence provides an excellent image of the intradural nerve roots. In a 6 1/2 minute acquisition, 64 overlapping 2 mm slices can be obtained. High-quality reformats into other planes can be performed creating an "MR radiculogram" in considerably less time than necessary at present for a lumbar MRI study. In 30 patients with sciatica, the volume scan was compared to our standard lumbar MR protocol, consisting of sagittal and transverse spin-echo T1-weighted sequences and a long-TR sequence. The image sets were rated on a 5-point scale for disk herniation and nerve root compression at L 3-4, L 4-5, and L 5-S 1 on both sides; thus 180 locations were assessed. The volume scan invariably produced a better nerve root image than the standard examination, but the smaller signal to noise ratio affected especially the image of the vertebral body. Significant disagreement in ratings between the two techniques was seen at 7 locations for disk herniation, and at 6 locations for root compression. Review of the two studies upheld the verdict of the volume scan in 6 cases of herniation and 3 cases of root compression. Clear-cut verdicts (definitely normal or abnormal) were possible in over 90% with both techniques. Lumbar 3-D volume scanning thus appears to be at least equivalent to MR scanning protocols as currently used. Additionally, the nerve root is much better depicted with the volume scan, and examination time is considerably reduced.