polarizing xenon-129 for hyperpolarized xenon spectroscopy

Hyperpolarized Xenon-129 MRI를 이용한 폐 기능 평가

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.

저자 스포트라이트: 자유 호흡 과분극 Xenon-129 MRI를 통한 폐 질환 연구 발전

Quantitative Measure of Lung Structure and Function Obtained from Hyperpolarized Xenon Spectroscopy(과분극 크세논 분광법에서 얻은 폐 구조 및 기능의 정량적 측정)

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.

Hyperpolarized Xenon Spectroscopy를 위한 Polarizing Xenon-129

시작하려면 연구가 시작되기 약 2.5시간 전에 크세논 편광판을 가열하십시오. 250 밀리리터 특수 폴리비닐 플루오라이드 또는 PVF 백의 커넥터 2개를 천장 클립에 끼웁니다. 백을 사용 가능한 4개의 편광판 분배 포트 중 하나에 부착합니다.편광판 터치스크린에서 enriched xenon tank를 선택합니다. 유속을 중간으로 설정하고 편광 부피를 250밀리리터로 설정합니다. 그런 다음 시작 버튼을 눌러 편광 과정을 시작합니다.편광된 크세논 가스가 주입되면 편광판의 터치스크린에 백을 제거하라는 메시지가 표시됩니다. 천장 클립으로 닫은 특수 PVF 백의 커넥터 튜브를 집은 다음 백을 분리하여 MRI 스캐너의 구멍 내부에 넣습니다.

Research

JoVE Journal

Medicine

Polarizing Xenon-129 for Hyperpolarized Xenon Spectroscopy

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 ...

연구

의학

Patient Preparation and Subject Training for Hyperpolarized Xenon MRI

Hyperpolarized Xenon MRI에 대한 환자 준비 및 피험자 교육

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

CSSR(Chemical Shift Saturation Recovery) 측정을 위한 Hyperpolarized Xenon-129 흡입 수행