Biophysical Basis of Brain iDQC MR Imaging

本申请的广泛长期目标是开发分子间双量子相干（iDQC）MR成像，特别关注大脑中的应用。 这是基于以下主要假设：iDQC提供了新型和独特的成像对比度，这与各种重要的MRI应用相关并可能有用，包括脑fMRI、肿瘤缺氧检测、弥散加权成像和骨小梁表征。 然而，由于该技术的早期性质，我们认为，这是至关重要的，以获得更好地了解iDQC成像对比度机制的基本原理，并确定成像优化的关键因素之前，iDQC成像的应用变得实用。 因此，本提案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、相干性选择、检测方法）来量化新型iDQC图像对比度。这些目标是通过研究设计和方法，在开发最佳的iDQC成像技术，具有高信噪比和独特的对比度特性，指导理论分析和计算机模拟，并验证与测量幻影和大鼠大脑在1.5 - 9.4和14 T，和大脑的正常人类志愿者在1.5 T。 我们将根据iDQC信号的独特特性，从信号激励、信号检测和图像后处理三个方面进行脉冲序列优化。 本研究的结果应导致iDQC成像对比度的基本因素的定量，以及适用于不同场强下各种新应用的更好的成像技术。

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.