SELF-REFOCUSED SPATIAL-SPECTRAL RF PULES FOR IMAGING CELLS LABELED WITH SPIOS

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 简介： 我们已经开发了一种自重聚焦空间光谱（SPSP）脉冲对，以实现非共振自旋的切片选择性，短回波时间，自旋回波成像。自重聚焦SPSP脉冲对实质上是相位匹配的90 SPSP脉冲和180 SPSP脉冲，通过一系列 近似，导致比两个单独脉冲可能的回波时间短得多的回波时间。当与标准成像序列一起使用时，SPIO纳米颗粒导致信号失相并充当阴性造影剂。 然而，阴性造影剂不能与图像中的空隙区分开，并且可能遭受部分体积效应。 为SPIO标记的细胞的正对比度成像提出的技术之一使用光谱选择性脉冲来对标记的细胞附近的非共振水进行成像。我们开发的SPSP自重聚焦脉冲对能够实现非共振频率的切片选择性成像，从而消除来自感兴趣切片外部的非共振源的背景信号。 方法和讨论： 使用Shinnar Le-Roux（SLR）算法[6]设计了带宽（BW）为164 Hz的最小相位180脉冲。最终的自重聚焦SPSP脉冲对由53个常规小倾角子脉冲组成，所述子脉冲由自重聚焦脉冲对包络的采样值缩放。从具有不同浓度SPIO标记的人基质细胞的琼脂体模获得数据。体内数据从小鼠获得，将100万和300万SPIO标记的细胞注射到后腿中。图像显示使用自聚焦SPSP自旋回波序列获得阳性对比。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: We have developed a self-refocused spatial-spectral (SPSP) pulse pair to achieve slice-selective, short-echo-time, spin-echo imaging of off-resonant spins. A self-refocused SPSP pulse pair is essentially a phase-matched 90 SPSP pulse and 180 SPSP pulse combined into one pulse through a series of approximations, resulting in a considerably shorter echo time than possible with two separate pulses. When used with standard imaging sequences, the SPIO nanoparticles lead to signal dephasing and act as a negative contrast agent. However, negative contrast agents cannot be distinguished from voids in the image and can suffer from partial volume effects. One of techniques proposed for positive contrast imaging of SPIO-labeled cells uses spectrally selective pulses to image off-resonant water near the labeled cells. The SPSP self-refocused pulse pair we have developed enables slice-selective imaging of off-resonant frequencies, hence eliminating background signal from sources of off-resonance outside the slice of interest. Methods and Discussion: A minimum-phase 180 pulse with a bandwidth (BW) of 164 Hz was designed using the Shinnar Le-Roux (SLR) algorithm [6]. The final self-refocused SPSP pulse pairs were comprised of 53 conventional small tip-angle subpulses scaled by the sampled values of the self-refocused pulse pair envelopes. Data were obtained from an agar phantom with varying concentrations of SPIO-labeled human stromal cells. In vivo data were obtained from a mouse, with 1 million and 3 million SPIO-labeled cells injected into the hind legs. Images showed positive contrast was obtained using the self-refocused SPSP spin-echo sequence.