Single breath‐hold measurement of pulmonary gas exchange and diffusion in humans with hyperpolarized ¹²⁹Xe MR

Abstract

Pulmonary diseases usually result in changes of the blood-gas exchange function in the early stages. Gas exchange across the respiratory membrane and gas diffusion in the alveoli can be quantified using hyperpolarized 129 Xe MR via chemical shift saturation recovery (CSSR) and diffusion-weighted imaging (DWI), respectively.Generally, CSSR and DWI data have been collected in separate breaths in humans.Unfortunately, the lung inflation level cannot be the exactly same in different breaths, which causes fluctuations in blood-gas exchange and pulmonary microstructure. Here we combine CSSR and DWI obtained with compressed sensing, to evaluate the gas diffusion and exchange function within a single breath-hold in humans. A new parameter, namely the perfusion factor of the respiratory membrane (SVR d/g ), is proposed to evaluate the gas exchange function. Hyperpolarized 129 Xe MR data are compared with pulmonary function tests and computed tomography examinations in healthy young, age-matched control, and chronic obstructive pulmonary disease human cohorts. SVR d/g decreases as the ventilation impairment and emphysema index increase. Our results indicate that the proposed method has the potential to detect the extent of lung parenchyma destruction caused by age and pulmonary diseases, and it would be useful in the early diagnosis of pulmonary diseases in clinical practice.

In vivo methods and applications of xenon-129 magnetic resonance

“…Thus, for hyperpolarised gases, there is no SNR penalty proportional to 1/√R as is observed in thermally-polarised parallel imaging (where R is the “acceleration” factor by which the number of phase encoding steps is reduced compared to full Fourier encoding) [86] , enabling high acceleration factors with little degradation of the image quality [90] , [91] , [92] , [93] . Compressed sensing has the advantage that it does not require multiple receiver coils and has been successfully implemented to accelerate 129 Xe imaging and enable: acquisition of 129 Xe images and 1 H anatomical MR images in a single breath-hold which aids their registration [94] ; high-resolution multiple b -value diffusion-weighted imaging [95] , [96] ; increased temporal resolution in dynamic 129 Xe imaging [94] , [97] ; and combined acquisition of diffusion-weighted and gas-exchange 129 Xe imaging in a single breath-hold [98] . Furthermore, prior knowledge can be used to improve image reconstruction and achieve higher acceleration, for instance by using knowledge of the magnetisation decay or structural information from 1 H MR images [99] , or the sparsity of complex difference images for gas flow applications [100] .…”

Investigating biases in the measurement of apparent alveolar septal wall thickness with hyperpolarized 129Xe MRI

“…The DP imaging techniques currently in use can be divided into two general types: (1) static measurements of the regional xenon distribution within the lung parenchyma as dictated by the structure and physiology of the lung, [9][10][11][12][13][14][15][16][17][18][19] and the MR acquisition parameters, in particular the flip angle and the TR [20][21][22] ; and (2) dynamic measurements that capture the xenon gas uptake by the lung tissue and transport by the pulmonary circulation as a function of time. 3,9,[23][24][25][26][27][28][29][30] Both approaches have already been shown to be sensitive to various forms of lung disease. [31][32][33][34][35][36][37][38][39][40][41][42] More recently, efforts have been made to combine these methods by adding 2D or 3D spatial information to dynamic gas uptake measurements at the expense of lengthened scan times.…”

“…The DP imaging techniques currently in use can be divided into two general types: (1) static measurements of the regional xenon distribution within the lung parenchyma as dictated by the structure and physiology of the lung, 9‐19 and the MR acquisition parameters, in particular the flip angle and the TR 20‐22 ; and (2) dynamic measurements that capture the xenon gas uptake by the lung tissue and transport by the pulmonary circulation as a function of time 3,9,23‐30 . Both approaches have already been shown to be sensitive to various forms of lung disease 31‐42 .…”

Magnetic resonance imaging: progresses and perspective

“…超高场MRI系统在具有显著优势的同时 [37] , 也带 来了许多在低场磁共振成像仪上不具有的技术挑 战 [38,39] . 例如, 由于组织的介电效应导致图像极不均 [41,42,43] ; 超极化 13 C磁共振成像可以对 生物体内的代谢过程, 特别是肿瘤的代谢过程进行可 视化研究, 为相关疾病的早期诊断研究提供了方法和 工具 [44,45] .…”