Improved sensitivity and limit-of-detection using a receive-only coil in magnetic particle imaging
Improved sensitivity and limit-of-detection using a receive-only coil in magnetic particle imaging
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DOI：
10.1088/1361-6560/aacb87
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发表时间：
2018-07-01
影响因子：
3.5
通讯作者：
Wiekhorst, Frank
中科院分区：
文献类型：
--
作者：
Paysen, Hendrik;Wells, James;Wiekhorst, Frank
磁性粒子成像 (MPI) 是一种能够定量确定磁性纳米粒子 (MNP) 整体 3D 分布的成像方式。在这项工作中，我们提出了一种通过采用新的仅接收线圈（Rx-线圈）进行信号采集来降低 MNP 检测限的方法。新的信号检测器旨在提高灵敏度，从而提高重建图像的质量。我们展示了使用安装在临床前 MPI 扫描仪中的原型 Rx 线圈进行的表征测量。 Rx 线圈的梯度设计可减弱激励场产生的不需要的信号贡献，与传统的两用线圈（TxRx 线圈）相比，背景水平降低 17 dB，这对于检测少量 MNP 至关重要。网络分析仪对频率相关线圈灵敏度的测量以及记录的 MPI 数据的频谱分析表明，Rx 线圈的线圈灵敏度总体增加了约 +12 dB。灵敏度分布的比较表明，在 6 x 3 x 3 cm(3) 的成像体积中，与 TxRx 线圈相比，Rx 线圈的均匀性没有显着下降。最后，使用 MNP 的系列稀释通过实验确定每种线圈类型的检测限，使用 2 s 的采集时间，传统 TxRx 线圈的铁值为 133 ng，新 Rx 线圈的铁值为 20 ng。观察到重建信号强度与样品中铁质量之间的线性关系，在检测限至 3·10(3)ng(Fe) 的范围内，确定系数 (R-2) 高于 99%。这些结果为提高临床前 MPI 扫描仪的图像质量和加快采集时间开辟了道路。
Magnetic partide imaging (MPI) is an imaging modality capable of quantitatively determining the 3D distribution of a magnetic nanoparticle (MNP) ensemble. In this work, we present a method for reducing the MNP limit of detection by employing a new receive-only coil (Rx-coil) for signal acquisition. The new signal detector is designed to improve the sensitivity and thus quality of reconstructed images. We present characterization measurements conducted with the prototype Rx-coil installed in a preclinical MPI scanner. The gradiometric design of the Rx-coil attenuates the unwanted signal contributions arising from the excitation field, leading to a 17 dB lower background level compared to the conventional dual-purpose coil (TxRx-coil), which is crucial for detecting low amounts of MNP. Network analyzer measurements of the frequency-dependent coil sensitivity, as well as spectral analysis of recorded MPI data demonstrate an overall increase of the coil sensitivity of about +12 dB for the Rx-coil. Comparisons of the sensitivity distributions revealed no significant degradations in terms of homogeneity for the Rx-coil compared to the TxRx-coil in an imaging volume of 6 x 3 x 3 cm(3). Finally, the limit of detection was determined experimentally for each coil type using a serial dilution of MNPs, resulting in values of 133 ng of iron for the conventional TxRx-coil and 20 ng for the new Rx-coil, using an acquisition time of 2 s. A linear relationship between the reconstructed signal intensities and the iron mass in the samples was observed with coefficients of determination (R-2) of above 99% in the range of the limit of detection to 3 10(3)ng(Fe). These results open the way for improved image quality and faster acquisition time in pre-clinical MPI scanners.