MRI-based Quantitative Susceptibility Mapping of Hepatic Iron Overload

项目总结/摘要 该提案的总体目标是开发和验证一种新的磁共振技术 基于成像（MRI）的腹部定量敏感性成像（QSM），用于非侵入性 评估肝脏铁沉积。在这项工作中，我们将开发和优化先进的数据采集， 图像重建方法，以实现腹部的QSM。此外，我们将确定准确性， 重复性和重复性腹部QSM的铁定量与肝脏铁超载患者。 铁在各种器官中过度积累，包括肝脏，影响成人和儿童 人群，是有毒的，需要治疗，旨在减少身体铁储存。准确评估肝脏 铁浓度对于铁过载的检测和分级以及纵向监测至关重要 在治疗期间。 MRI是一种广泛使用的技术，对铁的存在高度敏感。不幸的是，目前的核磁共振成像 弛豫测定法基本上受限于它们与铁浓度的关系知之甚少， 这取决于铁超载的类型，并且在治疗期间也会变化。MRI也是 对组织的磁化率非常敏感，这与铁有很好的关系 浓度.磁化率以一种很好的方式扭曲了主磁场， 可以在体内测量磁场失真。基于MRI的QSM方法估计 基于测量由组织自身产生的磁场失真来测量组织。核磁共振- 基于QSM的方法已经在大脑中开发和验证。然而，将QSM翻译为 腹部一直不成功。我们已经确定了QSM发展的四个主要技术障碍 1）整个腹部脂肪的存在，这引入了额外的相移， 混淆了敏感性估计，2）肝脏中极高铁浓度的可能性（与 大脑），这导致快速的信号衰减，3）呼吸和其他生理运动，这引入了 所获取的图像和估计的磁化率图中的伪影，以及4）最近识别的空间分辨率 效应，当获得的空间分辨率不足时，会在QSM中引入偏差。 通过解决这四个障碍，我们将开发一种新的基于MRI的QSM方法，用于 腹部定量肝脏铁超载。初步验证研究非常有希望， 对患者中LIC的定量具有极好的前景。在本提案中，我们的目标是[1]完成 开发用于测量LIC的基于MRI的腹部QSM，[2]确定重复性， 肝脏铁超载患者在1.5T和3 T下QSM的重现性，[3]确定 应用超导量子共振技术对肝铁超载患者1.5T和3 T腹部QSM的研究 干扰装置（SQUID）生物磁肝电阻测量法作为参考标准。 总之，该项目将开发一种新的基于MRI的QSM技术， 将在患有肝脏铁超载的儿童和成人患者中验证它。成功验证后，QSM将 基于组织的基本性质提供准确、可重复和可再现的LIC定量。

PROJECT SUMMARY / ABSTRACT The overall goal of this proposal is to develop and validate a novel technique for Magnetic Resonance Imaging (MRI)-based Quantitative Susceptibility Mapping (QSM) of the abdomen, for non-invasive assessment of liver iron deposition. In this work, we will develop and optimize advanced data acquisition and image reconstruction methods to enable QSM of the abdomen. Further, we will determine the accuracy, repeatability, and reproducibility of abdominal QSM for iron quantification in patients with liver iron overload. Excessive accumulation of iron in various organs, including the liver, which affects both adult and pediatric populations, is toxic and requires treatment aimed at reducing body iron stores. Accurate assessment of liver iron concentration is critical for the detection and staging of iron overload as well as for longitudinal monitoring during treatment. MRI is a widely available technology and highly sensitive to the presence of iron. Unfortunately, current MRI relaxometry methods are fundamentally limited by their poorly understood relationship to iron concentration, which depends on the type of iron overload and also varies during treatment. In contrast, MRI is also exquisitely sensitive to the magnetic susceptibility of tissue, which has a well-understood relationship to iron concentration. Magnetic susceptibility distorts the main magnetic field in a well-characterized manner, and this magnetic field distortion can be measured in-vivo. MRI-based QSM methods estimate the susceptibility of tissues based on measuring the magnetic field distortion produced by the tissues themselves. MRI- based QSM methods have been developed and validated in the brain. However, translation of QSM to the abdomen has been unsuccessful. We have identified four major technical barriers for development of QSM of the abdomen: 1) the presence of fat throughout the abdomen, which introduces additional phase shifts and confounds the susceptibility estimates, 2) the potential for very high iron concentration in the liver (compared to the brain), which results in rapid signal decay, 3) respiratory and other physiological motion, which introduces artifacts in the acquired images and estimated susceptibility maps, and 4) recently identified spatial resolution effects, which introduce bias in QSM when insufficient spatial resolution is acquired. By addressing these four barriers, we will develop a novel MRI-based QSM method for use in the abdomen to quantify liver iron overload. Preliminary validation studies are very promising and have shown excellent promise for the quantification of LIC in patients. In this proposal, we aim to [1] complete development of MRI-based abdominal QSM for measurement of LIC, [2] determine the repeatability and reproducibility of QSM at 1.5T and 3T in patients with liver iron overload, [3] determine the accuracy of abdominal QSM at 1.5T and 3T in patients with liver iron overload using superconducting quantum interference device (SQUID) biomagnetic liver susceptometry as the reference standard. In summary, this project will develop a novel MRI-based QSM technique designed for the abdomen and will validate it in pediatric and adult patients with liver iron overload. Upon successful validation, QSM will provide accurate, repeatable, and reproducible quantification of LIC based on a fundamental property of tissue.