Fast spin-echo MR imaging of the cervical spine: influence of echo train length and echo spacing on image contrast and quality.

PURPOSE To examine the interaction of echo train length and interecho spacing and their effects on image quality and contrast in fast spin-echo sequences of the cervical spine. METHODS Forty-three patients with suspected cervical disk disease were prospectively evaluated with fast spin-echo with varying echo train lengths and interecho spacing. A flow phantom was used to confirm findings related to cerebrospinal fluid pulsation. Parameters were manipulated to adjust contrast, signal-to-noise ratio, the effects of artifacts, and the speed of acquisition. RESULTS In general, increasing echo train length increased homogeneity and high intensity of cerebrospinal fluid signal and reduced acquisition time; however, it decreased the signal-to-noise ratio of cerebrospinal fluid and cord and increased blurring, and, to a lesser extent, edge enhancement, and "truncation-type" artifact. Increasing interecho space permitted the use of longer echo times but minimally decreased contrast and signal-to-noise ratio of cord and cerebrospinal fluid. In addition, increasing echo spacing increased blurring, edge enhancement, truncation-type, magnetic susceptibility, and motion artifacts. CONCLUSIONS For cervical spine imaging, a long echo train length and short echo spacing partially compensate for cerebrospinal fluid flow and produce the best myelographic effect but must be modulated by other constraints, such as artifact production or technical capabilities.