Protocols for multi‐site trials using hyperpolarized ¹²⁹Xe MRI for imaging of ventilation, alveolar‐airspace size, and gas exchange: A position paper from the ¹²⁹Xe MRI clinical trials consortium

Abstract

Hyperpolarized (HP) 129Xe MRI uniquely images pulmonary ventilation, gas exchange, and terminal airway morphology rapidly and safely, providing novel information not possible using conventional imaging modalities or pulmonary function tests. As such, there is mounting interest in expanding the use of biomarkers derived from HP 129Xe MRI as outcome measures in multi‐site clinical trials across a range of pulmonary disorders. Until recently, HP 129Xe MRI techniques have been developed largely independently at a limited number of academic centers, without harmonizing acquisition strategies. To promote uniformity and adoption of HP 129Xe MRI more widely in translational research, multi‐site trials, and ultimately clinical practice, this position paper from the 129Xe MRI Clinical Trials Consortium (https://cpir.cchmc.org/XeMRICTC) recommends standard protocols to harmonize methods for image acquisition in HP 129Xe MRI. Recommendations are described for the most common HP gas MRI techniques—calibration, ventilation, alveolar‐airspace size, and gas exchange—across MRI scanner manufacturers most used for this application. Moreover, recommendations are described for 129Xe dose volumes and breath‐hold standardization to further foster consistency of imaging studies. The intention is that sites with HP 129Xe MRI capabilities can readily implement these methods to obtain consistent high‐quality images that provide regional insight into lung structure and function. While this document represents consensus at a snapshot in time, a roadmap for technical developments is provided that will further increase image quality and efficiency. These standardized dosing and imaging protocols will facilitate the wider adoption of HP 129Xe MRI for multi‐site pulmonary research.

Pediatric 129Xe Gas‐Transfer MRI—Feasibility and Applicability

“…This study implemented the one-point Dixon approach with a 16-second breath hold duration to compare the data to published data in adults. 9,16,23,24 Multiecho, IDEAL (iterative decomposition of water and fat with echo asymmetry and least-squares estimation), and chemical-shift imaging approaches are promising and more robust as these techniques avoid the one-point Dixon decomposition assumptions but are more sophisticated and typically require more compromise between breath hold duration, more undersampling artifacts, or coarser resolutions. 10,[25][26][27][28] Additionally, there are limited references/data published for these emerging approaches especially if comparisons to multiple sites are needed.…”

“…The calibration dose permitted accurate flip angles, echo time (TE), and frequencies when imaging xenon. 16 Practice inhalations of air were performed outside and inside the scanner, prior to the Xe breath hold, to improve compliance.…”

Standalone portable xenon-129 hyperpolariser for multicentre clinical magnetic resonance imaging of the lungs

“…12 It is worth noting that to facilitate multicentre applications of 129 Xe MRI, as well as increasing a site’s accessibility to polariser technology, it is important to standardise xenon dosing and imaging protocols as outlined in ref. 17 and to also consider the additional outlay on 129 Xe RF coils and broadband RF amplifiers on the scanner itself.…”

Noninvasive diagnosis of pulmonary hypertension with hyperpolarised129Xe magnetic resonance imaging and spectroscopy

“…Both bags were expanded to the desired total inhalation volume using the xenon flow gas blend (1% Xe/10% N 2 /89% He). 28 subjects received a standard total gas volume of 1 L, while four subjects received a gas volume tailored to 20% of their forced vital capacity (FVC) as per the recent recommended guidelines [ 17 ]. Thus, the mean gas volume delivered across the 32 subjects was 954±152 mL.…”

“…Thus, the mean gas volume delivered across the 32 subjects was 954±152 mL. 129 Xe spectroscopy and imaging were acquired on either a 1.5 T (GE 15M4 EXCITE (GE Healthcare, Waukesha, WI, USA), training cohort) or a 3 T (SIEMENS MAGNETOM Trio (Siemens, Erlangen, Germany), training and testing cohort) scanner during two separate breath-holds of 129 Xe [ 17 ]. For each scan, subjects were coached to inhale the 129 Xe from functional residual capacity (FRC).…”