Rapid Fetal HASTE MR Imaging

快速胎儿 HASTE MR 成像

• 批准号: 10193491
• 负责人: Berkin Bilgic
• 金额: $ 9.67万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-04-15 至 2023-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10193491
• 关键词: Acceleration; Anatomy; Benign; Cerebrum; Data; Deposition; Diagnostic; Ensure; Environment; Heating; Image; Magnetic Resonance Imaging; Modernization; Modification; Morphologic artifacts; Motion; Noise; Phase; Physiologic pulse; Play; Positioning Attribute; Pregnant Women; Procedures; Relaxation; Resolution; Running; Safety; Sampling; Scanning; Scheme; Signal Transduction; Slice; Speed; T2 weighted imaging; Technology; Time; Training; Ultrasonography; Uncertainty; Vendor; absorption; brain parenchyma; cost; design; fetal; image reconstruction; imaging modality; improved; in utero; millisecond; radio frequency; reconstruction; stem

Project Summary Single-shot T2-weighted (SST2w) imaging is the most common acquisition sequence in fetal MRI. Its popularity stems from its ability to supply excellent T2 contrast, and encode information from each imaging slice in <2 seconds. Despite these advantages, the unmet need for technical improvements renders SST2w highly under- developed, and constrains the acquisition to run at a fraction of its potential speed. Such inefficient acquisition makes SST2w vulnerable to fetal motion and necessitates a large number of repeat scans, during which pregnant women have to tolerate being inside a confined environment and remain motionless in uncomfortable positions. These inefficient acquisitions fail to provide the desired image quality and suffer from severe resolution loss during the long readout window, which incurs strong signal decay and requires aggressive partial Fourier sampling. We propose optimized acquisition and reconstruction technology to speed up SST2w acquisition by 5-fold, while providing sharper images with reduced voxel blurring. To make these possible, we will begin by tailoring our radiofrequency (RF) refocusing pulses to reduce their energy deposition dramatically. This is important because SST2w acquisition plays a large number of refocusing pulses in rapid succession, which requires a long “cool-off” period to keep RF heating within safety limits. This dead time prolongs the acquisition time of standard SST2w by 3–4-fold. We will replace this train of constant flip angle refocusing pulses with a variable refocusing flip (vrf) angle scheme, which will reduce the energy deposition by 3-fold while matching the contrast and SNR of the standard acquisition. Not only this will allow us to decrease the unused sequence time to improve scan efficiency, but also reduce the energy deposition to low enough levels to permit additional simultaneous multislice (SMS) encoding. vrf will also allow for prolonging the echo time to reduce the partial Fourier factor, thereby decreasing voxel blurring by ~35%. Using low-energy multiPINS pulse design for SMS refocusing will let us incorporate 3-fold SMS acceleration. Combination of vrf and multiPINS refocusing will thus provide a 5-fold net speed up over standard SST2w, while remaining within RF heating safety levels. We will use our wave-CAIPI extreme controlled aliasing k-space trajectory to ensure high image quality when 3-fold SMS acceleration is introduced. Augmenting wave encoded image reconstruction with LORAKS phase- constraint will better compensate partial Fourier sampling and further reduce blurring. Finally, we will evaluate the ability of the developed acquisition and reconstruction technologies to improve the acquisition speed and apparent resolution of fetal SST2w imaging while closely matching the contrast and SNR of the standard acquisition by scanning 10 pregnant women at 3T.

项目摘要 单发T2加权（SST2W）成像是胎儿MRI中最常见的采集序列。它很受欢迎 源于其提供出色的T2对比的能力，并从<2中的每个成像切片中编码信息 秒。尽管有这些优势，但对技术改进的需求却使SST2W高度不足 开发并解释了以其潜在速度一小部分运行的采集。这种效率低下的收购 使SST2W容易受到胎儿运动的影响，并需要大量重复扫描的必要点，在此期间怀孕 妇女必须忍受在狭窄的环境中，并保持不舒服的位置。 这些效率低下的收购无法提供所需的图像质量，并且遭受了严重的分辨率损失 在长的读数窗口中，会产生强信号衰减，需要侵略性的部分傅立叶 采样。 我们提出了优化的采集和重建技术，以加快SST2W的收购5倍， 同时提供较尖锐的体素模糊的图像。为了使这些成为可能，我们将从裁缝开始 我们的射频（RF）重新聚焦脉冲以大大减少其能量沉积。这很重要 因为SST2W采集在快速连续中播放大量的重新聚焦脉冲，这需要长时间 “冷静”时期可将RF加热保持在安全极限之内。这段时间延长了标准的收购时间 SST2W乘3–4倍。我们将用可变重新聚焦的恒定翻转角度重新聚焦的恒定翻转角度重新聚焦的火车 翻转（VRF）角度方案，在与对比度和SNR相匹配时，它将减少3倍的能源沉积 标准收购。这不仅可以使我们减少未使用的序列时间以改进扫描 效率，但也可以将能量沉积降低到足够低的水平，以允许额外的多层次 （SMS）编码。 VRF还将允许延长回声时间以减少部分傅立叶因素，从而 将体素模糊减少〜35％。使用低能多型脉冲设计进行SMS重新集中，将使我们 结合3倍SMS加速度。因此，VRF和重新聚焦的乘数组合将提供5倍的净 在标准的SST2W上加快速度，同时保持在RF加热安全水平范围内。 我们将使用Wave-Caipi极限控制的混叠K-空间轨迹，以确保高图像质量 引入了3倍SMS加速度。通过Loraks相 - 增强波的编码图像重建 约束将更好地补偿部分傅立叶采样并进一步减少模糊。最后，我们将评估 开发的采集和重建技术提高采集速度和 胎儿SST2W成像的明显分辨率与标准的对比度和SNR紧密匹配 通过扫描10名孕妇在3T上获得收购。