A simplified framework to optimize MRI contrast preparation
A simplified framework to optimize MRI contrast preparation
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DOI：
10.1002/mrm.27417
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发表时间：
2019-01-01
影响因子：
3.3
通讯作者：
Sugny，Dominique
中科院分区：
文献类型：
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作者：
Van Reeth，Eric;Ratiney，Helene;Sugny，Dominique
PurposeThis article提出了一个严格的最优控制框架的准备计划，优化MRI对比度的基础上弛豫时间differentials.MethodsCompared到以前的最优对比度准备计划的设计，优化参数的数量大幅减少。该制备方案被定义为几个块脉冲的翻转角，相位项和脉冲间延迟的组合进行了优化，以控制磁化evolution.ResultsThe所提出的方法减少了计算时间的强大的制备方案，以大约一分钟（而几个小时，需要与以前的计划），可以忽略不计的性能损失。所选择的参数化允许将总制备持续时间公式化为约束，这改善了对比性能和制备时间之间的总体折衷。模拟，在体外和体内的结果验证了这一改进，说明了所提出的方法的直接适用性，并指出其灵活性方面的可实现的对比。主要的改善尤其是在短T2增强方面，如通过在大鼠大脑上获得非平凡对比度所示，其中短T2白质结构（胼胝体）与周围灰质组织相比增强结论这种方法提出了设计最佳对比剂制备序列的关键进展，强调了它们产生非标准对比剂的能力，它们在临床环境中的潜在受益，以及它们在任何MR系统上的直接适用性。
PurposeThis article proposes a rigorous optimal control framework for the design of preparation schemes that optimize MRI contrast based on relaxation time differences.MethodsCompared to previous optimal contrast preparation schemes, a drastic reduction of the optimization parameter number is performed. The preparation scheme is defined as a combination of several block pulses whose flip angles, phase terms and inter‐pulse delays are optimized to control the magnetization evolution.ResultsThe proposed approach reduces the computation time of ‐robust preparation schemes to around a minute (whereas several hours were required with previous schemes), with negligible performance loss. The chosen parameterization allows to formulate the total preparation duration as a constraint, which improves the overall compromise between contrast performance and preparation time. Simulation, in vitro and in vivo results validate this improvement, illustrate the straightforward applicability of the proposed approach, and point out its flexibility in terms of achievable contrasts. Major improvement is especially achieved for short‐T2enhancement, as shown by the acquisition of a non‐trivial contrast on a rat brain, where a short‐T2white matter structure (corpus callosum) is enhanced compared to surrounding gray matter tissues (hippocampus and neocortex).ConclusionsThis approach proposes key advances for the design of optimal contrast preparation sequences, that emphasize their ability to generate non‐standard contrasts, their potential benefit in a clinical context, and their straightforward applicability on any MR system.