performing 129xe mri scan of lung ventilation to assess pulmonary function

A Standardized Workflow for Hyperpolarized &lt;sup&gt;129&lt;/sup&gt;Xe MRI to Study Pulmonary Function

Hyperpolarized 129Xe MRI is an exciting tool for non-invasive, spatially-resolved characterization and quantification of specific aspects of pulmonary function1,2,3. Acquisition and reconstruction approaches similar to those used in anatomical proton MRI yield images of inhaled 129Xe in the lungs, permitting visualization of non-ventilated lung regions and region-resolved quantification of ventilation distribution4,5,6,7,8. More advanced pulse sequence and analysis techniques yield further complementary information, including quantification of gas-exchange efficacy between alveoli and pulmonary capillaries via spectroscopic MRI9,10,11,12,13 and characterization of alveolar microstructure integrity via diffusion-weighted MRI14,15,16.
Inhaled 129Xe has been proven safe and tolerable in adult and pediatric subjects, including those with pulmonary disease17,18. Measurements of lung function derived from 129Xe MRI have shown sensitivity to structural and functional alterations in many pulmonary disease contexts, including chronic obstructive pulmonary disease6,10,19, cystic fibrosis20,21,22, idiopathic pulmonary fibrosis23,24,25, and asthma7,10,26. Given the high safety and tolerability of 129Xe MRI, the lack of ionizing radiation in MRI compared with other common imaging approaches, and the high reproducibility of 129Xe MRI results27,28, 129Xe MRI holds significant promise, in particular for precise serial monitoring of individuals receiving a time course of therapy for chronic pulmonary disease.
The safety and clinical promise of 129Xe MRI have led to its FDA approval in December 2022 for lung ventilation imaging in persons aged 12 years and older29. Given this, it is anticipated that the number of research and clinical sites capable of performing 129Xe MRI (currently ~20 worldwide) will increase significantly over the coming years. As 129Xe MRI spreads to new institutions, it is important that robust methodological resources exist to allow sites to build out clinically relevant 129Xe MRI techniques quickly and to perform scans and generate results that are closely comparable with those of existing sites.
In this work, we will outline the current best practices for human hyperpolarized 129Xe MRI of lung ventilation, as agreed upon by member institutions of the 129Xe MRI Clinical Trials Consortium (Xe MRI CTC) and summarized in a recent position paper30. Topics will include the preparation of tailored pulse sequences ideal for a complete 129Xe MRI workflow, preparation, and administration of hyperpolarized 129Xe gas, an optimized workflow for human 129Xe MRI sessions, and best practices for monitoring subject safety and comfort during MRI sessions.

Author Spotlight: Standardization and Best Practices for Advancing Lung Imaging Using &lt;sup&gt;129&lt;/sup&gt;Xe MRI

Acquiring Hyperpolarized 129Xe Magnetic Resonance Images of Lung Ventilation

Our research seeks to establish Xenon MRI as a clinical tool for characterizing lung function. Xenon MRI allows us to directly visualize ventilation defects in patients with obstructive lung diseases like COPD, asthma, and cystic fibrosis. It offers information that can't be obtained from standard MRI and pulmonary function test.Xenon MRI was recently approved by the FDA for clinical evaluation of lung ventilation. This represents a culmination of a huge amount of effort by the people in our field and it's an exciting opportunity to show how Xenon MRI can improve patient care and outcomes in pulmonary disease. Xenon MRI is still a relatively new family of techniques, and standardization is still an ongoing process.This protocol distills the existing standards for Xenon ventilation MRI into a form that we hope will be useful to research in clinical sites who are trying to perform these scans for the first time. Common clinical readouts of lung function, like pulmonary function tests, only give a single number for the entire lung with no spatial information included. Xenon MRI can make regional assessments of several aspects of lung health and function, which we believe will be very useful in the clinic.Only a few institutions are currently performing Xenon MRI, but we expect there will be many more sites soon considering the recent FDA approval. We hope that this Xenon ventilation MRI protocol will serve as a blueprint for new sites and help em to ramp up their Xenon MRI operations more quickly.

Performing 129Xe MRI Scan of Lung Ventilation to Assess Pulmonary Function

After making the final xenon-129 pre-scan adjustments and ensuring the subject is ready for the xenon-129 dose, proceed to perform the xenon-129 ventilation scan. First, load the xenon-129 ventilation sequence from the prepared protocol. Ensure all pulse sequence parameters are as desired and set proper scan execution settings.Select the field of view, or FOV size, and center location based on the localizer results. Aim for the center of the FOV to coincide with the center of the lungs in all three dimensions and the FOV to be large enough to comfortably contain the entire chest cavity, including the entirety of both lungs. Bring the xenon-129 dose bag intended for the ventilation scan from the polarization measurement station into the scanner room.Hold or place the dose bag near the subject. Avoid regions near the bore opening where the magnetic field strength changes rapidly. Assist the subject in inhaling the xenon-129 dose from the bag, following the already-coached inhalation procedure.Execute the scan immediately upon hearing the signal go"from the individual assisting the subject. Monitor the subject while the scan proceeds. Following the scan, monitor the subject's heart rate and SPO2 using the pulse oximeter and monitor for transient central nervous system effects via verbal communication with the subject.If no significant deviations from baseline occur, then after waiting for at least two minutes, another xenon-129 dose can be administered. The ventilation images from a healthy individual are shown here. A high xenon-129 signal can be observed throughout the lungs in these images, and no ventilation impairment is evident in this individual.This figure depicts an individual with alpha-1 antitrypsin deficiency in which severe ventilation impairment can be easily detected by observing the patchy appearance of the xenon-129 images. Similarly, severe ventilation impairment can be seen in this figure depicting an individual with severe cystic fibrosis. The images shown here depicts an individual with chronic obstructive pulmonary disease in which more subtle ventilation defects can be noted.

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Research

JoVE Journal

Medicine

28 Views.  University of Virginia. After making the final xenon-129 pre-scan adjustments and ensuring the subject is ready for the xenon-129 dose, proceed to perform the xenon-129 ventilation scan. First, load the xenon-129 ventilation sequence from the prepared protocol. Ensure all pulse sequence parameters are as desired and set proper scan execution settings.Select the field of view, or FOV size, and center location based on the localizer results. Aim for the center of the FOV to coincide with the center of the lungs...