Rapid Free-Breathing 3D High-Resolution MRI for Volumetric Liver Iron Quantification

项目摘要 动机：在美国，大约每300名非西班牙裔高加索人中就有1人具有遗传性 血色素沉着症在其他种族和种族中的发病率各不相同。输血型含铁血黄素沉着症常发生在 曾多次输血治疗癌性贫血的癌症患者。铁 超负荷，如果不治疗，可能会导致致命的器官损伤。铁超载的治疗旨在降低体内的铁 使用静脉切开术或螯合疗法来维持足够低的体内铁水平，同时将不良反应降至最低 效果。肝铁浓度被广泛认为是全身铁储存的最佳指标；因此， 准确的肝铁定量改善了铁超载的临床管理，最大限度减少了 螯合剂给药。基于MRI的R2*弛豫测量法(R2*-MRI)是一种无创性的肝铁临床标准 由于它对组织铁的存在很敏感，所以没有电离辐射进行定量。R2*-MRI收购 多个时间点的图像以估计每个体素的R2*(=1/T2*)弛豫率。然而，在临床上， 现有的R2*-MRI易于患者运动，如屏气常见的呼吸运动 在扫描过程中练习。屏息对儿童和一些成年人来说是具有挑战性的，而不能令人满意的呼吸- 持有会导致较差的R2*值。当前R2*-MRI的另一个挑战是由于以下原因导致的信号丢失 在高浓度铁存在的情况下，T2*迅速衰变。严重的铁负荷在患者中很常见。 与输血引起的铁负荷有关，而目前的R2*-MRI不能可靠地捕捉到如此快速的信号 衰变，导致R2*测量不准确。该项目解决了这些挑战，以提供新颖的 R2*-MRI方法用于准确和一致的肝铁定量。 方法：该项目有两个开发目标，并在临床研究中得到了验证。AIM 1将实现快速 自由呼吸超短TE MRI，可在多个时间点采集图像以进行R2*测量。是这样的 采集是通过将3D中心向外的k空间轨迹与多个数据读出相结合来实现的 无需扫描时间开销的导航器，便于并行成像压缩感知。AIM 2将实现 利用低阶张量结构的回溯式运动校正图像重建 获取三维时空体积数据。我们将制定数据并行和分布式策略 计算量大的张量多维重建的计算。目标3将决定 创新在临床环境中的表现。 意义：这项工作将导致快速、健壮、自由呼吸的腹部磁共振成像，以便更准确地评估 儿童和成人的肝脏铁超载。这些技术将促进定量技术的广泛应用。 身体成像。

Project Summary Motivation: In the United States, approximately 1 in 300 non-Hispanic Caucasians have hereditary hemochromatosis with varying rates in other ethnicities and races. Transfusion hemosiderosis often develops in cancer patients who have received repeated blood transfusions for cancer-related anemia treatment. Iron overload, if left untreated, can cause fatal organ damage. Treatment of iron overload aims at reducing body iron stores with phlebotomy or chelation therapy to maintain sufficiently low body iron levels while minimizing adverse effects. Liver iron concentration is widely accepted for the best indicator of total body iron stores; therefore, accurate liver iron quantification improves clinical management of iron overload and minimizes side effects of chelator administration. MRI-based R2* relaxometry (R2*-MRI) is a noninvasive clinical standard for liver iron quantification with no ionizing radiation due to its sensitivity to the presence of tissue iron. R2*-MRI acquires images at multiple time points to estimate R2* (= 1/T2*) relaxation rates at each voxel. However, clinically available R2*-MRI is prone to patient movement such as respiratory motion that breath-holding is commonly practiced during scan. Breath-holding is challenging for children and some adults, and unsatisfactory breath- holding leads to poor R2* values. The other challenge with the current R2*-MRI is caused by signal loss due to rapid T2* decay in the presence of a high concentration of iron. Severe iron loading is commonly seen in patients with transfusion-induced iron overload, and the current R2*-MRI does not reliably capture such a rapid signal decay, resulting in inaccuracy in R2* measurements. This project addresses these challenges to provide novel R2*-MRI methods for accurate and consistent liver iron quantification. Approach: The project has two development aims that are validated on clinical studies. Aim 1 will enable rapid free-breathing ultrashort TE MRI, which acquires images at multiple time points for R2* measurements. Such acquisition is achieved by incorporating a 3D center-out k-space trajectory with multiple data readouts with self- navigator without scan time overhead, facilitating parallel imaging compressed sensing. Aim 2 will enable retrospectively motion-corrected image reconstruction that makes use of a low-rank tensor structure of the acquired 3D spatiotemporal volumetric data. We will develop strategies for data parallelism and distributed computing for computationally demanding tensor-based multidimensional reconstruction. Aim 3 will determine the performance of the innovations in a clinical setting. Significance: This work will lead to rapid, robust, free-breathing abdominal MRI for more accurate assessment of liver iron overload in children and adults. The techniques will facilitate widespread application in quantitative body imaging.