[Magnetic resonance myelography with a fast-spin-echo sequence]

A major application of Magnetic Resonance Imaging (MRI) consists in the "myelographic effect", characterized by high signal intensity of the CSF, which permits to visualize spinal subarachnoid spaces and nerve root sheaths. Such new ultrafast pulse sequences as fast spin echo (FSE) further enhance CSF high signal intensity. In addition, suppressing background with the fat suppression technique and with maximum intensity projection (MIP), a particular algorithm already used in MR angiography, FSE sequences yield 3D myelography-like images. Our study was aimed at assessing the clinical role and the reliability of this technique. Our preliminary experience is based on 21 patients with pain in the lower back and legs and on 5 healthy volunteers; all the myelography-like images were obtained with a 1.5-T MR system (Signa, General Electric). The parameters for FSE myelography-like images included: TR = 6000, TE = 200, ETL = 32, thickness = 3 mm, matrix = 256 x 224, Nex = 4, FOV = 20 cm, fat presaturation, no phase wrap, acquisition time = 2 min 58 s. MR myelography sequences were acquired after a standard FSE T1/T2-weighted exam. MR-myelography results confirmed the diagnosis of disk herniation made on conventional T1/T2-weighted images, especially in thecal sac compression and/or amputation of nerve root sheaths. MR myelography appeared to be especially useful in migrated disk herniation or in abnormal origin of nerve roots. Moreover, it allowed full and panoramic visualization of the subarachnoid spaces and excellent definition of the thecal sac, nerve roots and nerve root sheaths. In one patient only movement artifacts affected image quality. To conclude, even though it fails to yield any functional information, MR myelography appears to be an easy, rapid and noninvasive support to conventional MRI of the lumbar spine, to replace conventional myelography.