Biophysical Basis of Brain iDQC MR Imaging

该应用的广泛、长期目标是开发分子间双量子相干（iDQC）磁共振成像，特别是在大脑中的应用。这是基于iDQC提供新颖和独特的成像对比的主要假设，这与各种重要的MRI应用相关，并可能有用，包括脑功能磁共振成像、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，在iDQC成像应用成为现实之前，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至关重要。因此，本提案的具体目的是根据固有参数（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）来量化新型iDQC图像对比度。这些目标是通过研究设计和方法来开发具有高信噪比和独特对比度特性的最佳iDQC成像技术，以理论分析和计算机模拟为指导，并通过在1.5 t和14T下的大鼠和大鼠大脑以及1.5 t下的正常人类志愿者的大脑进行测量来验证。基于iDQC信号的独特特性，我们将从信号激励、信号检测和图像后处理三个方面进行脉冲序列优化。这项研究的结果将导致iDQC成像对比度的基本因素的定量，以及适用于不同场强的各种新应用的成像技术的大大改进。

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.