The use of the single-pulse RARE sequence in the study of the cerebrospinal axis [Uso della sequenza "RARE" a singola eccitazione nello studio dell'asse cerebrospinale.]

The authors describe a fast MR sequence allowing to obtain a myelographic-like, markedly T2-weighted, image quite similar to conventional myelographies. Relative to conventional spin-echo sequences, in which echoes are encoded so as to achieve the same phase, each echo of the sequence here employed is given a different phase encoding. The sequence, called MYUR (myelography-urography) is based on the generation, after a 90 degrees pulse, of a "train" of 256 echoes, each one phase-encoded differently, by multiple 180 degrees pulses, producing a single image. The total duration of such a sequence, with 2 repetitions, is 21 seconds. The MR myelographic sequence allows to univocally study tissues with a very long T2 relaxation time; under normal conditions, only cerebrospinal fluid, urine and bile are demonstrated. A resistive MR unit operating at 0.28 T was employed in the present study. MR myelography is capable of pointing out an eventual dural sac compression or a space-occupying mass, thus allowing an effective scout-view to center the subsequent pulse sequences; all MR-myelographic exams need to be completed with other short and long TR sequences.