Two‐point T1 measurement: Wide‐coverage optimizations by stochastic simulations

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Abstract
Stochastic reliability of T1 measurement from image signal ratios is examined in the ideal case by stochastic simulations in the context of wide‐coverage optimizations. Precise measurements prove to be accurate, and accurate ones precise. Sign‐preserved inversion‐recovery (IR)/non‐IR techniques are the best ration method, reciprocal non‐IR/IR ones being equivalent, but inconvenient. Wide‐coverage optima are relatively unsharp. Suggested guidelines for covering the 150‐ to 1500‐ms T1 band are minimal relevant TE; T1 about 400 ms; effective repetition times about in the ratio, TR2(IR)/TR1 (non‐IR) = 2.5–3.0, and in a sum as long as possible up to about TR1 + TR2 = 3.5–4.0 s; signal‐averaging after and only after TR1 + TR2 has been lengthened to the said region. Also suggested are different guidelines for covering T1 bands, 120–1200 and 200–1800 ms. Typically, precisions and accuracies improve linearly or faster with increasing S/N and (S/N)2, respectively. Unnecessarily high pixel resolutions or thin slicings exact great penalties in accuracies. Progressively shortening TR1 eventually transforms a wide coverage into a sharp targeting with small potential gains in a narrow T1 locality and large compromises almost everywhere else. The simulations yield an insight into applicabilities of standard error propagation analyses in two‐point T1 measurement. © 1986 Academic Press, Inc.