Non-invasive quantification of functional parameters of the cardiovascular system, in particular the heart, remains very challenging with current imaging techniques. This aspect is mainly due to the fact, that the spatio-temporal resolution of current imaging methods, such as Magnetic Resonance Imaging (MRI) or Positron Emission Tomography (PET), does not offer the desired data repetition rates in the context of real-time data acquisition and thus, can cause artifacts and misinterpretations in accelerated data acquisition approaches. We present a fast non-invasive and quantitative dual-modal in situ cardiovascular assessment using a hybrid imaging system which combines the new imaging modality Magnetic Particle Imaging (MPI) and MRI. This pre-clinical hybrid imaging system provides either a 0.5 T homogeneous ${B}_{{0}}$ field for MRI or a 2.2 T/m gradient field featuring a Field-Free-Point for MPI. A comprehensive coil system allows in both imaging modes for spatial encoding, signal excitation and reception. In this work, 3-dimensional anatomical information acquired with MRI is combined with in situ sequentially acquired time-resolved 3D (i.e. 3D + t) MPI bolus tracking of superparamagnetic iron oxide nanoparticles. MPI data were acquired during a 21 $\mu \text{l}$ (40 $\mu $ mol(Fe)/kg _BW ) bolus tail vein injection under free-breathing with an ungated and non-triggered MPI scan with a repetition rate of 46 volumes per seconds. We successfully determined quantitative hemodynamics as 3D + t velocity vector estimations of a beating rat’s heart by analyzing 3 seconds of 3D + t MPI image data. The used hybrid system allows for MR-based MPI Field-of-View planning and cardiac cross-sectional anatomy analysis, precise co-registration of dual-modal datasets, as well as for MPI-based hemodynamic functional analysis using an optical flow technique. We present the first in-vivo results of a new methodology, allowing for fast, non-invasive, quantitative and in situ hybrid cardiovascular assessment, showing its potential for future clinical applications.

中文翻译：

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混合MPI-MRI系统，用于实时3D血流定量的双模态心血管评估-临床前体内可行性研究。

利用当前的成像技术，心血管系统尤其是心脏的功能参数的非侵入性量化仍然非常具有挑战性。这方面主要是由于以下事实：当前的成像方法（如磁共振成像（MRI）或正电子发射断层扫描（PET））的时空分辨率在真实环境下无法提供所需的数据重复率。时间数据采集会因此而在加速数据采集方法中造成伪影和误解。我们提出了一种快速的非侵入性和定量双模式原位使用混合成像系统进行心血管评估，该系统结合了新的成像方式电磁粒子成像（MPI）和MRI。该临床前混合成像系统可提供0.5 T均质 $ {B} _ {{0}} $ 用于MRI的场或具有MPI的无场点的2.2 T / m梯度场。全面的线圈系统允许在两种成像模式下进行空间编码，信号激励和接收。在这项工作中，将MRI获得的3维解剖学信息与原位顺序获取超顺磁性氧化铁纳米粒子的时间分辨3D（即3D + t）MPI推注跟踪。MPI数据是在21 $ \ mu \ text {l} $ （40 $ \亩$ mol（Fe）/ kg _BW ）在无呼吸且未触发的MPI扫描下进行的自由呼吸下推注尾静脉推注，重复速率为每秒46卷。通过分析3秒的3D + t MPI图像数据，我们成功地将定量的血液动力学确定为跳动大鼠心脏的3D + t速度矢量估计。使用的混合系统允许基于MR的MPI视野规划和心脏横截面解剖分析，双模式数据集的精确共配准，以及使用光流技术的基于MPI的血液动力学功能分析。我们提出第一个体内 新方法的结果，可以实现快速，无创，定量和快速 原位 混合心血管评估，显示出其在未来临床应用中的潜力。