Ramped hybrid encoding for improved ultrashort echo time imaging.
Ramped hybrid encoding for improved ultrashort echo time imaging.
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DOI：
10.1002/mrm.25977
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发表时间：
2016-09
影响因子：
3.3
通讯作者：
McMillan AB
中科院分区：
文献类型：
--
作者：
Jang H;Wiens CN;McMillan AB
我们提出了一种新的采集方法，以最大限度地减少每次激发编码持续时间并提高短 T2* 物种的成像能力。在所提出的斜坡混合编码 (RHE) 技术中，梯度在 RF 脉冲之前应用，如通过径向采集 (PETRA) 和零 TE (ZTE) 成像减少逐点编码时间。然而，在 RHE 中，RF 激励后梯度迅速倾斜至最大幅度，以最大限度地缩短编码持续时间。为了获取 RF 死区期间未测量的中心 k 空间数据，RHE 采用类似于 PETRA 的混合编码方案。开发了一种基于单点成像的新梯度校准方法来估计 k 空间轨迹并实现稳健且高质量的重建。 RHE 可缩短每激励编码时间，并提供超短 T2* 成像方法中最高的空间分辨率。在体模和体内实验中，RHE 表现出强大的成像，化学位移或由 T2* 衰减和不需要的切片选择引起的模糊可以忽略不计。 RHE 允许超短 T2* 成像的每激励编码时间最短，从而减轻编码过程中发生的快速 T2* 衰减的影响，并提高空间分辨率。
We propose a new acquisition to minimize the per-excitation encoding duration and improve the imaging capability for short T2* species. In the proposed ramped hybrid encoding (RHE) technique, gradients are applied before the RF pulse as in pointwise encoding time reduction with radial acquisition (PETRA) and Zero TE (ZTE) imaging. However, in RHE, gradients are rapidly ramped after RF excitation to the maximum amplitude to minimize encoding duration. To acquire central k-space data not measured during RF deadtime, RHE utilizes a hybrid encoding scheme similar to PETRA. A new gradient calibration method based on single-point imaging was developed to estimate the k-space trajectory and enable robust and high quality reconstruction. RHE enables a shorter per-excitation encoding time and provides the highest spatial resolution among ultrashort T2* imaging methods. In phantom and in vivo experiments, RHE exhibited robust imaging with negligible chemical shift or blurriness caused by T2* decay and unwanted slice selection. RHE allows the shortest per-excitation encoding time for ultrashort T2* imaging, which alleviates the impact of fast T2* decay occurring during encoding, and enables improved spatial resolution.