Optimizing the precision in T1 relaxation estimation using limited flip angles

Abstract

In this article we describe the precision in the estimation of the spin-lattice relaxation time T1 from MRI signals acquired for various flip angles with the repetition time TR held constant. We review the estimation procedure itself and present a model for the propagation of noise in the signal into the calculated T1. This model is verified by both Monte Carlo simulations and experimental data taken on image phantoms. Based on this model, we find that for a given TR/T1 there exist two optimal flip angles that will minimize the uncertainty in the estimated T1. We also show how two optimal angles can be selected for a given range of TR/T1 values. In addition, T1 estimation using the two optimal angles can be comparable to or better than using multiple evenly spaced angles. Finally, in an initial comparison with the two-point saturation recovery method of calculating T1, results for equal total scanning time TRTot suggest that for T1 greater than 0.5 TRTot, the limited flip angle approach gives better T1 precision whereas for T1 less than 0.5 TRTot the saturation recovery approach is better.

Rapid high‐resolution T1 mapping by variable flip angles: Accurate and precise measurements in the presence of radiofrequency field inhomogeneity

“…Advantages of this approach include low power deposition compared to spin echo techniques and low spatial distortion compared to rapid echo planar imaging. Most importantly, the accuracy has been shown to be similar to that achieved with conventional and accelerated techniques but with a significant reduction in imaging time (5,6).…”

“…However, a couple of key results from previous work on this topic (5,6,11,14,15) serve as useful guidelines. When imaging for a single T 1 , precision can be optimized using two "ideal" angles, defined as those whose signals are 71% of the Ernst angle signal (6).…”

Quantitative evaluation of liver cirrhosis using T1 relaxation time with 3 tesla MRI before and after oxygen inhalation

“…Third, there was a wide standard deviation in the T1 relaxation time. We used two different flip angles to measure T1 relaxation time, a simple method and one of the generic methods, which were reported to give similar data from sampling of an inversion curve (5). Further investigation of T1 relaxometry in the liver and comparison among the different methods are needed.…”

“…The T1 map of the liver was automatically obtained by using the MapIT processing tool (MapIT software, Siemens Healthcare, Germany). The processing tool is based on the driven equilibrium single pulse observation of T1 (DESPOT) (5,17).…”

“…Therefore, noninvasive quantitative markers or diagnostic tests are required for assessing the presence and severity of liver cirrhosis. MR elastography, diffusionweighted MRI, and perfusion CT or MR imaging have been investigated as noninvasive quantitative imaging markers for the staging of liver cirrhosis (3)(4)(5)(6)(7).…”