Influence of RF spoiling on the stability and accuracy of <i>T</i>₁ mapping based on spoiled FLASH with varying flip angles

Abstract

There is increasing interest in quantitative T(1) mapping techniques for a variety of applications. Several methods for T(1) quantification have been described. The acquisition of two spoiled gradient-echo data sets with different flip angles allows for the calculation of T(1) maps with a high spatial resolution and a relatively short experimental duration. However, the method requires complete spoiling of transverse magnetization. To achieve this goal, RF spoiling has to be applied. In this work it is investigated whether common RF spoiling techniques are sufficiently effective to allow for accurate T(1) quantification. It is shown that for most phase increments the apparent T(1) can deviate considerably from the true value. Correct results may be achieved with phase increments of 118.2 degrees or 121.8 degrees. However, for these values the method suffers from instabilities. In contrast, stable results are obtained with a phase increment of 50 degrees. An algorithm is presented that allows for the calculation of corrected T(1) maps from the apparent values. The method is tested both in phantom experiments and in vivo by acquiring whole-brain T(1) maps of the human brain.