Biophysical Basis of Brain iDQC MR Imaging

这项应用的广泛和长期目标是开发分子间双量子相干(IDQC)磁共振成像，特别关注在大脑中的应用。这是基于一个基本假设，即iDQC提供新颖和独特的成像对比度，这与各种重要的MRI应用相关，并具有潜在的用途，包括脑功能磁共振成像、检测肿瘤中的缺氧、弥散加权成像和小梁骨的表征。然而，由于这项技术的早期性质，我们认为在iDQC成像应用于实际之前，更好地了解iDQC成像对比机制的基本原理，并确定成像优化的关键因素是至关重要的。因此，该建议的具体目的是根据内在参数(包括弛豫、扩散、对磁化率分布的敏感性以及iDQC信号对微结构的依赖性)和实验参数(场强、脉冲定时、相干选择、检测方法)来量化新的iDQC图像对比度。这些目标是通过开发具有高信噪比和独特对比度特性的最佳iDQC成像技术的研究设计和方法来实现的，以理论分析和计算机模拟为指导，并通过在1.5、9.4和14T的模体和大鼠大脑以及1.5T的正常人类志愿者的大脑中的测量来验证。根据iDQC信号的特点，从信号激励、信号检测、图像后处理三个方面对脉冲序列进行优化。这项研究的结果应该能够量化iDQC成像对比度的基本因素，并大大改进成像技术，使其适用于不同场强下的各种新应用。

The broad, long-term objective of this application is to develop intermolecular double-quantum coherence (iDQC) MR imaging with particular focus on applications in the brain. This is based on the primary hypothesis that iDQC provides novel and unique imaging contrast which is relevant to and potentially useful in a wide variety of important MRI applications, including brain fMRI, detection of hypoxia in tumors, diffusion-weighted imaging, and characterization of trabecular bones. However, owing to the early nature of the technique, we believe that it is crucial to gain a better understanding of fundamentals of iDQC imaging contrast mechanisms, and to determine the key factors for imaging optimization before applications of iDQC imaging become practical. The specific aims of this proposal are therefore to quantify the novel iDQC image contrast in terms of intrinsic parameters (including relaxation, diffusion, sensitivity to magnetic susceptibility distributions, and dependence of iDQC signals on microstructures) and experimental parameters (field strength, pulse timing, coherence selection, detection method). These aims are achieved via research designs and methods in development of optimal iDQC imaging techniques with high SNR and unique contrast characteristics, guided by theoretical analyses and computer simulations, and validated with measurements in phantoms and rat brains at 1.5 9.4 and 14T, and brains of normal human volunteers at 1.5T. Our pulse sequence optimization will be approached from signal excitation, signal detection, and image post-processing, based on the unique characteristics of iDQC signals. The outcome of this study should lead to quantitation of essential factors for iDQC imaging contrast, and much improved imaging techniques applicable for a variety of novel applications at different field strengths.