patient preparation and subject training for hyperpolarized xenon mri

使用超极化氙 129 MRI 评估肺功能

Hyperpolarized Xenon-129 (HXe) magnetic resonance imaging (MRI)1 is a technique that offers unique insights into lung structure, function, and gas exchange processes. By dramatically amplifying the magnetization of Xenon gas through spin-exchange optical pumping, HXe MRI achieves an order-of-magnitude improvement in signal-to-noise ratio compared to thermally polarized Xenon MRI2,3,4,5,6. This hyperpolarization enables the direct visualization and quantification of Xenon gas uptake into lung tissue and blood, which would otherwise be undetectable with conventional thermally polarized MRI7.
Chemical shift saturation recovery (CSSR) MR spectroscopy8,9,10,11,12,13 has proven to be one of the most valuable HXe MRI techniques. CSSR involves selectively saturating the magnetization of Xenon dissolved in lung tissue and blood using frequency-specific radiofrequency (RF) pulses. The subsequent recovery of the dissolved-phase (DP) signal as it exchanges with fresh hyperpolarized Xenon gas in the airspaces on a timescale of ms offers important functional information about the lung parenchyma.
Since its development in the early 2000s, the techniques behind CSSR spectroscopy have been progressively refined14,15,16,17,18,19,20,21,22,23. Further, advances in modeling Xenon uptake curves have enabled the extraction of specific physiological parameters, such as alveolar wall thickness and pulmonary transit times10,24,25,26. Studies have shown CSSR&#39;s sensitivity to subtle changes in lung microstructure and gas exchange efficiency in the form of pulmonary abnormalities found in clinically healthy smokers27, as well as in a range of lung diseases, including chronic obstructive pulmonary disease (COPD)18,27,28, fibrosis29, and radiation-induced lung injury30,31. CSSR spectroscopy has also been demonstrated to be sensitive to detect oscillations in the DP signal corresponding to pulsatile blood flow during the cardiac cycle32.
While significant progress has been made, practical challenges remain in implementing CSSR spectroscopy on clinical MRI systems. Scan times requiring single-dose breath holds approaching 10 s may be too long for pediatric subjects33,34 or patients with severe lung disease35,36. Additionally, the technique is susceptible to measurement biases if acquisition parameters such as the order of the saturation delay times or the efficacy of the dissolved-phase saturation are not properly optimized21. To address these limitations and make CSSR more accessible to the broader research community, clear, step-by-step protocols for both conventional breath hold and free-breathing acquisitions, currently under development, are needed.
The objective of this paper is to present a detailed methodology for performing optimized CSSR MR spectroscopy using HXe gas. The protocol will cover polarization and delivery of the Xenon gas, RF pulse calibration, sequence parameter selection, subject preparation, data acquisition, and key steps in data analysis. Examples of experimental results will be provided. It is hoped that this comprehensive guide will serve as a foundation for CSSR implementations across sites and help realize the full potential of this technique for quantifying lung microstructural changes in a range of pulmonary diseases.

作者聚焦：利用自由呼吸超极化氙 129 MRI 推进肺病研究

通过超偏振氙光谱法获得的肺结构和功能的定量测量

Our research focuses on using hyperpolarizing on 129 MRI technology to assess pulmonary function and to investigate lung diseases. The main objective is to see how this imaging technique can lead to better detection, understanding, and tracking of different lung conditions. Most hyperpolarized lung MR imaging is performed during a breath hold.We believe that pulmonary function quantified under such an artificial condition, may not fully reflect gas exchange during regular respiration, and we are testing new free breathing measurements that do not require any breath hold. Current challenges include the optimization of the CSSR acquisition technique for consistency and accuracy in the face of physiological variation and patient compliance. Severely ill or pediatric patients struggle with maintaining lengthy breath holds.The CSSR heart technique appears particularly sensitive to changes in alveolar septal wall thickness. As we and others in the field of demonstrated, alveolar wall thickening can indicate the presence of interstitial edema, inflammation, or pulmonary fibrosis. All metrics derived from CSSR spectroscopy acquisitions are currently based on the temporal dynamics of the signal amplitudes.In the future though, we hope to include changes in peak shape and center frequency in the analysis to obtain a more complete picture of the ongoing gas exchange processes.

超极化氙气 MRI 的患者准备和受试者培训

首先，设置生理监测系统，在成像过程中记录呼吸曲线和实时气体分析。使用使用吸气-呼气录音引导受试者的音频信号连接并测试 MRI 室内耳机。调整音轨的播放速度。吸气.呼气。基于每个受试者的正常呼吸频率。接下来，为扫描仪床准备一个干净的头枕、腿部支撑枕头和毯子。将解开的 Xenon 129 胸背心线圈放在 MRI 扫描仪的桌子上，然后插入线圈的连接器插头。对于自由呼吸研究，向受试者介绍吸气-呼气语音记录，以便在成像过程中实现同步呼吸。将受试者带入 MRI 室，将他们放在扫描仪床上，躺在敞开的氙气背心线圈的顶部。一旦受试者被定位，就系好威扣带，使背心线圈闭合，但不要收缩受试者的胸部。对于自由呼吸研究，将带有气动杆的面罩放在患者的脸上。拉紧带子，使面罩紧贴鼻子和嘴巴，而不会太紧。安装后，取下面罩并将其放在一边以备后用，将带子留在受试者的头部后面。然后在两个食指上放置两个脉搏血氧仪，以在研究过程中持续监测心率和血氧饱和度。将兼容 MRI 的耳机戴在受试者的耳朵上。将 MRI 扫描仪台移入磁体孔中，使受试者的肺部位于视野的中心。

Research

JoVE Journal

Medicine

Patient Preparation and Subject Training for Hyperpolarized Xenon MRI

Quantitative Measure of Lung Structure and Function Obtained from Hyperpolarized Xenon Spectroscopy

Hyperpolarized Xenon-129 (HXe) magnetic resonance imaging (MRI) provides tools for obtaining 2- or 3-dimensional maps of lung ventilation patterns, gas ...

科研

医学

Polarizing Xenon-129 for Hyperpolarized Xenon Spectroscopy

偏振氙-129用于超偏振氙光谱

Performing Hyperpolarized Xenon-129 Inhalation for Chemical Shift Saturation Recovery (CSSR) Measurement

执行超极化氙 129 吸入以测量化学位移饱和恢复 （CSSR）