Self-refocused spatial-spectral pulse for positive contrast imaging of cells labeled with SPIO nanoparticles.
Self-refocused spatial-spectral pulse for positive contrast imaging of cells labeled with SPIO nanoparticles.
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DOI：
10.1002/mrm.21973
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发表时间：
2009-07
影响因子：
3.3
通讯作者：
Spielman, Daniel
中科院分区：
文献类型：
--
作者：
Balchandani, Priti;Yamada, Mayumi;Pauly, John;Yang, Phillip;Spielman, Daniel
核磁共振已被广泛应用于体内非侵入性追踪超顺磁性氧化铁纳米颗粒(SPIO)标记细胞的位置。通常，SPIO被用作阴性对比剂，这使得很难区分标记细胞与图像中不均匀和实际空洞的无关来源。因此，人们提出了几种新的方法来从SPIO中获得积极的对比。坎宁安等人提出的一种技术。利用光谱选择性脉冲来激发和重新聚焦SPIO附近的自旋。虽然这种技术的频率选择性提供了有效的正对比度，但缺乏切片选择性会导致来自感兴趣切片之外的非共振源的干扰信号。我们开发了一种自重聚焦空间光谱(SR-SPSP)脉冲，以实现对非共振自旋的切片选择性自旋回波成像。使用自聚焦脉冲在回波时间选择中提供了灵活性，因为自旋回波可以在脉冲结束之后的任何时间放置。SR-SPSP射频脉冲实现的空间选择性消除了片外区域的背景信号，并降低了对共振水抑制的要求。体模和活体数据表明，使用这种新的RF脉冲可以实现正对比度和切片选择性。
MRI has been used extensively to noninvasively track the location of cells labeled with superparamagnetic iron-oxide nanoparticles (SPIOs) in vivo. Typically, SPIOs are employed as a negative contrast agent which makes it difficult to differentiate labeled cells from extraneous sources of inhomogeneity and actual voids in the image. As a result, several novel approaches have been put forth to obtain positive contrast from SPIOs. One technique proposed by Cunningham et al. utilizes spectrally selective pulses to excite and refocus spins in the vicinity of the SPIOs. Although the frequency selectivity of this technique provides effective positive contrast, the lack of slice selectivity results in interfering signal from sources of off-resonance outside the slice of interest. We have developed a self-refocused spatial-spectral (SR-SPSP) pulse to achieve slice-selective spin-echo imaging of off-resonant spins. Using a self-refocused pulse affords flexibility in echotime selection since the spin echo may be placed at any time after the end of the pulse. The spatial selectivity achieved by the SR-SPSP RF pulse eliminates background signal from out-of-slice regions and reduces the on-resonant water suppression requirements. Phantom and in vivo data demonstrate that positive contrast and slice-selectivity are achieved using this novel RF pulse.
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