Troubleshooting and Quality Assurance in Hyperpolarized Xenon Magnetic Resonance Imaging: Tools for High-Quality Image Acquisition

Summary

Here, we present a protocol for obtaining high-quality hyperpolarized xenon-129 magnetic resonance images, covering hardware, software, data acquisition, sequence selection, data management, k-space utilization, and noise analysis.

Abstract

Hyperpolarized (HP) xenon magnetic resonance imaging (¹²⁹Xe MRI) is a recently federal drug administration (FDA)-approved imaging modality that produces high-resolution images of an inhaled breath of xenon gas for investigation of lung function. However, implementing ¹²⁹Xe MRI is uniquely challenging as it requires specialized hardware and equipment for hyperpolarization, procurement of xenon imaging coils and coil software, development and compilation of multinuclear MR imaging sequences, and reconstruction/analysis of acquired data. Without proper expertise, these tasks can be daunting, and failure to acquire high-quality images can be frustrating, and expensive. Here, we present some quality control (QC) protocols, troubleshooting practices, and helpful tools for¹²⁹Xe MRI sites, which may aid in the acquisition of optimized, high-quality data and accurate results. The discussion will begin with an overview of the process for implementing HP ¹²⁹Xe MRI, including requirements for a hyperpolarizer lab, the combination of ¹²⁹Xe MRI coil hardware/software, data acquisition and sequence considerations, data structures, k-space and image properties, and measured signal and noise characteristics. Within each of these necessary steps lies opportunities for errors, challenges, and unfavorable occurrences leading to poor image quality or failed imaging, and this presentation aims to address some of the more commonly encountered issues. In particular, identification and characterization of anomalous noise patterns in acquired data are necessary to avoid image artifacts and low-quality images; examples will be given, and mitigation strategies will be discussed. We aim to make the ¹²⁹Xe MRI implementation process easier for new sites while providing some guidelines and strategies for real-time troubleshooting.

Introduction

For over a century, lung function assessment has primarily relied on global measurements from spirometry and body plethysmography. However, these traditional pulmonary function tests (PFTs) are limited in their ability to capture early-stage disease's regional nuances and subtle changes in lung tissue¹. Nuclear medicine with inhaled radiotracers has been used widely for the assessment of ventilation/perfusion mismatches commonly associated with pulmonary emboli, but this involves ionizing radiation and yields lower resolution. In contrast, computed tomography (CT) has emerged as the gold standard for lung imaging, offering exceptional spati....

Protocol

The protocol outlined below adheres to the guidelines and standards established by the University of Missouri Human Research Ethics Committee, ensuring the ethical conduct of the study and the protection of participants' rights, safety, and well-being.

NOTE: To ensure the reliability and accuracy of hyperpolarized xenon MRI studies, it is crucial to perform rigorous characterization of acquired images, follow a comprehensive protocol, and employ effective troubleshooting strategies. The im.......

Discussion

The ability to troubleshoot ¹²⁹Xe MRI issues is a necessary skill and may help mitigate problems in real time. Until a hyperpolarized gas infrastructure can be purchased from a single party and garner support from scanner manufacturers, these quality control tasks are the sole responsibility of the individual laboratories. The goal of this manuscript is to provide the reader with helpful practices and suggestions for the inevitable event of poor data acquisition. While we attempt to address as many potential i.......

Materials

Name	Company	Catalog Number	Comments
Polarization measurement station	Polerean	42881	https://polarean.com/
Pressure vessele with plunger valve	Ace glass	8648-85	https://www.aceglass.com/html/3dissues/Pressure_Vessels/offline/download.pdf
Tedlar bag	Jensen inert	GST381S-0707TJO	http://www.jenseninert.com/
Xenon Hyperpolarizer 9820	Polerean	49820	https://polarean.com/
Xenon loop coil	Clinical MR Solutions	Custom device	https://www.sbir.gov/sbc/clinical-mr-solutions-llc
Xenon vest coil	Clinical MR Solutions	Custom device	https://www.sbir.gov/sbc/clinical-mr-solutions-llc