TriTone: a radiofrequency field (B₁)-insensitive T₁ estimator for MRI at high magnetic fields

详细信息	查看全文 | 推荐本文 |

• 作者：Roman Fleysher ; Lazar Fleysher ; Songtao Liu ; Oded Gonen
• 关键词：T₁ mapping ; Fast volumetric imaging ; High-field MRI ; Quantitative MRI ; RF inhomogeneity ; Optimization methods
• 刊名：Magnetic Resonance Imaging
• 出版年：2008
• 期刊代码：188_0730725x
• 类别：med
• 出版时间：July 2008
• 卷：26
• 期：6
• 页码：781-789
• 文件大小：577 K

摘要

Fast, high-resolution, longitudinal relaxation time (T₁) mapping is invaluable in clinical and research applications. It has been shown that two spoiled gradient recalled echo (SPGR) images acquired in steady state with variable flip angles is an attractive alternative to the multi-image sets previously acquired with inversion or saturation recovery. The known sensitivity of the two-point method to transmit radiofrequency field (B₁) inhomogeneity exacerbated at 3 T and above, however, mandates its combination with an additional, time-consuming and possibly specific-absorption-rate-intensive B₁ measurement, preventing direct migration of the method to these fields. To address this, we introduce a method designed to be free of systematic errors caused by B₁ inhomogeneity in which the value of T₁ is extracted from three SPGR images acquired with echo planar imaging (EPI) readout. The precision of the T₁ maps produced is found to be comparable to the two-point method, while the accuracy is greatly improved in the same time and spatial resolution. A welcome byproduct of the method is a map of B₁ that can be used to correct other acquisitions in the same session. Tables of the optimal acquisition protocols are provided for several total imaging times.