MR sequence parameter optimization: an algorithmic approach.

The MR pulsing sequence is often described by terms such as spatial resolution, signal-to-noise, coverage, acquisition time, and contrast. These might be considered "secondary" parameters because they are not set directly but are instead specified indirectly by setting the "primary" parameters: field of view; projections (phase-encoded or readout); slice thickness and gap; number of excitations; and the sequence parameter times--repetition, echo delay, and inversion. Together, the primary and secondary parameters specify the MR pulsing sequence. Many of these parameters are interrelated such that setting one parameter indirectly affects another. Parameter specification is thus an iterative procedure that involves compromises to achieve an optimum relative to some predefined criteria. In this article, we examine the interrelationships between the primary and secondary parameters that specify the spin-echo pulsing sequence and suggest an algorithmic approach for selecting the best sequence parameters.