Multi-modal Pulmonary Imaging: Using Complementary Information from CT and Hyperpolarized 129Xe MRI to Evaluate Lung Structure-Function

Podsumowanie

CT and ¹²⁹Xe MRI provide complementary lung structure-function information that can be exploited for regional analysis using image registration. Here, we provide a protocol that builds from the existing literature for ¹²⁹Xe MR to CT image registration using open-source platforms.

Streszczenie

Hyperpolarized ¹²⁹Xe gas MRI is an emerging technique to evaluate and measure regional lung function including pulmonary gas distribution and gas exchange. Chest computed tomography (CT) still remains the clinical gold standard for imaging of the lungs, though, in part due to the rapid CT protocols that acquire high-resolution images in seconds and the widespread availability of CT scanners. Quantitative approaches have enabled the extraction of structural lung parenchymal, airway and vascular measurements from chest CT that have been evaluated in many clinical research studies. Together, CT and ¹²⁹Xe MRI provide complementary information that can be used to evaluate regional lung structure and function, resulting in new insights into lung health and disease. ¹²⁹Xe MR-CT image registration can be performed to measure regional lung structure-function to better understand lung disease pathophysiology, and to perform image-guided pulmonary interventions. Here, a method for ¹²⁹Xe MRI-CT registration is outlined to support implementation in research or clinical settings. Registration methods and applications that have been employed to date in the literature are also summarized, and suggestions are provided for future directions that may further overcome technical challenges related to ¹²⁹Xe MR-CT image registration and facilitate broader implementation of regional lung structure-function evaluation.

Wprowadzenie

Hyperpolarized gas magnetic resonance imaging (MRI) first emerged as a novel functional pulmonary imaging modality to evaluate pulmonary ventilation distribution nearly three decades ago¹. Since then, research studies using hyperpolarized gas MRI have revealed numerous insights into the nature of lung function in patients with chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis^2,3,4,5,6. Both hyperpolarized ³He and ¹

Protokół

The imaging cases shown here were approved by the University of British Columbia Providence Health Care Research Ethics Board (REB# H21-01237, H21-02149, H22-01264). Participants provided written informed consent prior to completing imaging. The overall pipeline from image acquisition to registration is outlined in Figure 2, and the protocol details here focus on the MR-CT image registration only. Image acquisition and segmentation are dependent on available or preferred imaging hardware, imaging protocols, and image analysis software tools and, therefore, are left to readers' preference. The protocol is designed to be agnostic to tho

Wyniki

This study prospectively acquired paired CT and ¹²⁹Xe MRI in a research setting for regional lung structure-function characterization and image-guided bronchoscopy across a range of lung diseases and conditions. Figure 3 shows registered ¹²⁹Xe MRI ventilation and CT in coronal and sagittal planes for four representative participants with a range of MRI ventilation patterns (for the same participants of Figure 1). The registered ¹²⁹

Dyskusje

CT and ¹²⁹Xe MRI provide complementary information to evaluate regional lung structure and function that is best facilitated using image registration. Multi-modal image registration can be non-trivial to implement, and so the protocol provided here is intended to provide the tools for readers to register ¹²⁹Xe MRI to CT. The provided protocol uses ANTsPy for easier implementation for users with a broad range of image processing experience using Python rather than C++, as in conventional ANTs. Overal...

Materiały

Name	Company	Catalog Number	Comments
3D Slicer	Brigham and Women's Hospital (BWH)	https://www.slicer.org/	Image analysis/visualization software; open source
ANTsPy	NA	https://github.com/ANTsX/ANTsPy	Coding infrastructure; open source
ITK-SNAP	NA	http://www.itksnap.org/pmwiki/pmwiki.php	Image analysis/visualization software; open source
MAGNETOM Vida 3.0T MRI	Siemens Healthineers	NA	Can be any 1.5 T or 3.0 T scanner with broadband imaging capability
MATLAB	Mathworks	https://www.mathworks.com/products/matlab.html	General software, good for image analysis; available by subscription
reg.py	NA	NA	Registration script (Supplementary File 1)
Revolution HD CT scanner	GE Healthcare	NA	Can be any CT scanner with ≥64 detectors
VIDA Insights	VIDA Diagnostics Inc.	NA	CT analysis software; can be any to generate masks