Voxel-Wise Comparison of Co-Registered Quantitative CT and Hyperpolarised Gas Diffusion-Weighted MRI Measurements in IPF.

The patterns of idiopathic pulmonary fibrosis (IPF) lung disease that directly correspond to elevated hyperpolarised gas diffusion-weighted (DW) MRI metrics are currently unknown. This study aims to develop a spatial co-registration framework for a voxel-wise comparison of hyperpolarised gas DW-MRI and CALIPER quantitative CT patterns. Sixteen IPF patients underwent He DW-MRI and CT at baseline, and eleven patients had a 1-year follow-up DW-MRI.

Hyperpolarised xenon-129 diffusion-weighted magnetic resonance imaging for assessing lung microstructure in idiopathic pulmonary fibrosis.

Background: Hyperpolarised 129-xenon (Xe) magnetic resonance imaging (MRI) shows promise in monitoring the progression of idiopathic pulmonary fibrosis (IPF) due to the lack of ionising radiation and the ability to quantify functional impairment. Diffusion-weighted (DW)-MRI with hyperpolarised gases can provide information about lung microstructure. The aims were to compare Xe DW-MRI measurements with pulmonary function tests (PFTs), and to assess whether they can detect early signs of disease progression in patients with newly diagnosed IPF.

Longitudinal Lung Function Assessment of Patients Hospitalized With COVID-19 Using H and Xe Lung MRI.

Background: Microvascular abnormalities and impaired gas transfer have been observed in patients with COVID-19. The progression of pulmonary changes in these patients remains unclear.

Research Question: Do patients hospitalized with COVID-19 without evidence of architectural distortion on structural imaging exhibit longitudinal improvements in lung function measured by using H and Xe MRI between 6 and 52 weeks following hospitalization?

Study Design And Methods: Patients who were hospitalized with COVID-19 pneumonia underwent a pulmonary H and Xe MRI protocol at 6, 12, 25, and 51 weeks following hospital admission in a prospective cohort study between November 2020 and February 2022.

Implementable Deep Learning for Multi-sequence Proton MRI Lung Segmentation: A Multi-center, Multi-vendor, and Multi-disease Study.

Background: Recently, deep learning via convolutional neural networks (CNNs) has largely superseded conventional methods for proton ( H)-MRI lung segmentation. However, previous deep learning studies have utilized single-center data and limited acquisition parameters.

Purpose: Develop a generalizable CNN for lung segmentation in H-MRI, robust to pathology, acquisition protocol, vendor, and center.

Image Phenotyping of Preterm-Born Children Using Hyperpolarized Xe Lung Magnetic Resonance Imaging and Multiple-Breath Washout.

Preterm birth is associated with low lung function in childhood, but little is known about the lung microstructure in childhood. We assessed the differential associations between the historical diagnosis of bronchopulmonary dysplasia (BPD) and current lung function phenotypes on lung ventilation and microstructure in preterm-born children using hyperpolarized Xe ventilation and diffusion-weighted magnetic resonance imaging (MRI) and multiple-breath washout (MBW). Data were available from 63 children (aged 9-13 yr), including 44 born preterm (⩽34 weeks' gestation) and 19 term-born control subjects (⩾37 weeks' gestation).

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

Hyperpolarized (HP) Xe 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 Xe MRI as outcome measures in multi-site clinical trials across a range of pulmonary disorders. Until recently, HP Xe MRI techniques have been developed largely independently at a limited number of academic centers, without harmonizing acquisition strategies.

An asymmetrical whole-body birdcage RF coil without RF shield for hyperpolarized Xe lung MR imaging at 1.5 T.

Purpose: This study describes the development and testing of an asymmetrical xenon-129 ( Xe) birdcage radiofrequency (RF) coil for Xe lung ventilation imaging at 1.5 Tesla, which allows proton ( H) system body coil transmit-receive functionality.

Methods: The Xe RF coil is a whole-body asymmetrical elliptical birdcage constructed without an outer RF shield to enable H imaging.

Gallium-67 Scan with Single Photon Emission Computed Tomography for the Evaluation and Monitoring of Infected Abdominal Aortic Aneurysms: A 10-Year Case Series.

Purpose: This study aimed to evaluate the role of gallium-67 single photon emission computed tomography (SPECT) with contrast computed tomography (CT) in the evaluation and monitoring of infected abdominal aortic aneurysms (IAAA).

Materials And Methods: A retrospective cohort analysis was performed using prospectively collected data of consecutive patients with IAAA in Princess Margaret Hospital in Hong Kong between January 2010 and December 2020. The patients were identified using the Radiology Information System.

Lung MRI with hyperpolarised gases: current & future clinical perspectives.

The use of pulmonary MRI in a clinical setting has historically been limited. Whilst CT remains the gold-standard for lung imaging in many clinical indications, technical developments in ultrashort and zero echo time MRI techniques are beginning to help realise non-ionising imaging in certain lung disorders. In this invited review, we discuss a complementary technique - hyperpolarised (HP) gas MRI with inhaled He and Xe - a method for and imaging of the lung that has great potential as a clinical tool for early detection and improved understanding of pathophysiology in many lung diseases.

Airspace Dimension Assessment (AiDA) by inhaled nanoparticles: benchmarking with hyperpolarised Xe diffusion-weighted lung MRI.

Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking. Airspace Dimension Assessment with inhaled nanoparticles (AiDA) is a new method developed for in vivo measurement of distal airspace dimensions. The aim of this study was to benchmark the AiDA method against quantitative measurements of distal airspaces from hyperpolarised Xe diffusion-weighted (DW)-lung magnetic resonance imaging (MRI).

In vivo methods and applications of xenon-129 magnetic resonance.

Hyperpolarised gas lung MRI using xenon-129 can provide detailed 3D images of the ventilated lung airspaces, and can be applied to quantify lung microstructure and detailed aspects of lung function such as gas exchange. It is sensitive to functional and structural changes in early lung disease and can be used in longitudinal studies of disease progression and therapy response. The ability of Xe to dissolve into the blood stream and its chemical shift sensitivity to its local environment allow monitoring of gas exchange in the lungs, perfusion of the brain and kidneys, and blood oxygenation.

Finite element simulations of hyperpolarized gas DWI in micro-CT meshes of acinar airways: validating the cylinder and stretched exponential models of lung microstructural length scales.

Purpose: This work assesses the accuracy of the stretched exponential (SEM) and cylinder models of lung microstructural length scales that can be derived from hyperpolarized gas DWI. This was achieved by simulating He and Xe DWI signals within two micro-CT-derived realistic acinar airspace meshes that represent healthy and idiopathic pulmonary fibrosis lungs.

Methods: The healthy and idiopathic pulmonary fibrosis acinar airway meshes were derived from segmentations of 3D micro-CT images of excised human lungs and meshed for finite element simulations of the Bloch-Torrey equations.

MR properties of F C F gas in the lungs of healthy volunteers: and apparent diffusion coefficient at 1.5T and at 3T.

Purpose: To measure the transverse relaxation time ( ) and apparent diffusion coefficient (ADC) of F-C F gas in vivo in human lungs at 1.5T and 3T, and to determine the representative distribution of values of these parameters in a cohort of healthy volunteers.

Methods: Mapping of ADC at lung inflation levels of functional residual capacity (FRC) and total lung capacity (TLC) was performed with inhaled F-C F (eight subjects) and Xe (six subjects) at 1.

Tc-99m sulfur colloid SPECT-CT and assessment of functional liver reserve after Y90 radioembolization: A case report.

Introduction: Quantitative assessment is an essential tool in determining the proportion of liver to be reserved before lobectomy. Technetium-99 m sulfur colloid single-photon emission computed tomography (Tc-99 m SC SPECT-CT) can help in the quantitative assessment of functioning liver tissues and percentage of liver reserve before segmentectomy and lobectomy Matesan et al. (2017), Bowen et al.

Single breath-held acquisition of coregistered 3D Xe lung ventilation and anatomical proton images of the human lung with compressed sensing.

Purpose: To develop and assess a method for acquiring coregistered proton anatomical and hyperpolarized Xe ventilation MR images of the lungs with compressed sensing (CS) in a single breath hold.

Methods: Retrospective CS simulations were performed on fully sampled ventilation images acquired from one healthy smoker to optimize reconstruction parameters. Prospective same-breath anatomical and ventilation images were also acquired in five ex-smokers with an acceleration factor of 3 for hyperpolarized Xe images, and were compared to fully sampled images acquired during the same session.

Airway Microstructure in Idiopathic Pulmonary Fibrosis: Assessment at Hyperpolarized He Diffusion-weighted MRI.

Background MRI with inhaled hyperpolarized helium 3 (He) allows for functional and structural imaging of the lungs. Hyperpolarized gas diffusion-weighted (DW) MRI provides noninvasive and quantitative assessment of microstructural acinar changes in the lungs. Purpose To investigate whether microstructural imaging metrics from in-vivo hyperpolarized He DW MRI are sensitive to longitudinal changes in a cohort of participants with idiopathic pulmonary fibrosis (IPF) and to evaluate the reproducibility of these metrics and their correlation with existing clinical measures of IPF disease severity.

Comparison of in vivo lung morphometry models from 3D multiple b-value He and Xe diffusion-weighted MRI.

Purpose: To compare in vivo lung morphometry parameters derived from theoretical gas diffusion models, the cylinder model and stretched exponential model, in a range of acinar microstructural length scales encountered in healthy and diseased lungs with He and Xe diffusion-weighted MRI.

Methods: Three-dimensional multiple b-value He and Xe diffusion-weighted MRI was acquired with compressed sensing at 1.5 T from 51 and 31 subjects, respectively, including healthy volunteers, ex-smokers, idiopathic pulmonary fibrosis, and chronic obstructive pulmonary disease patients.

Assessment of the influence of lung inflation state on the quantitative parameters derived from hyperpolarized gas lung ventilation MRI in healthy volunteers.

In this study, the effect of lung volume on quantitative measures of lung ventilation was investigated using MRI with hyperpolarized He and Xe. Six volunteers were imaged with hyperpolarized He at five different lung volumes [residual volume (RV), RV + 1 liter (1L), functional residual capacity (FRC), FRC + 1L, and total lung capacity (TLC)], and three were also imaged with hyperpolarized Xe. Imaging at each of the lung volumes was repeated twice on the same day with corresponding H lung anatomical images.

Hyperpolarised xenon magnetic resonance spectroscopy for the longitudinal assessment of changes in gas diffusion in IPF.

Prognosticating idiopathic pulmonary fibrosis (IPF) is challenging, in part due to a lack of sensitive biomarkers. A recent article in described how hyperpolarised xenon magnetic resonance spectroscopy may quantify regional gas exchange in IPF lungs. In a population of patients with IPF, we find that the xenon signal from red blood cells diminishes relative to the tissue/plasma signal over a 12-month time period, even when the diffusion factor for carbon monoxide is static over the same time period.

Spatial Comparison of CT-Based Surrogates of Lung Ventilation With Hyperpolarized Helium-3 and Xenon-129 Gas MRI in Patients Undergoing Radiation Therapy.

Purpose: To develop and apply an image acquisition and analysis strategy for spatial comparison of computed tomography (CT)-ventilation images with hyperpolarized gas magnetic resonance imaging (MRI).

Methods And Materials: Eleven lung cancer patients underwent xenon-129 (Xe) and helium-3 (He) ventilation MRI and coregistered proton (H) anatomic MRI. Expiratory and inspiratory breath-hold CTs were used for deformable image registration and calculation of 3 CT-ventilation metrics: Hounsfield unit (CT), Jacobian (CT), and specific gas volume change (CT).

Comparison of He and Xe MRI for evaluation of lung microstructure and ventilation at 1.5T.

Background: To support translational lung MRI research with hyperpolarized Xe gas, comprehensive evaluation of derived quantitative lung function measures against established measures from He MRI is required. Few comparative studies have been performed to date, only at 3T, and multisession repeatability of Xe functional metrics have not been reported.

Purpose/hypothesis: To compare hyperpolarized Xe and He MRI-derived quantitative metrics of lung ventilation and microstructure, and their repeatability, at 1.

3D diffusion-weighted Xe MRI for whole lung morphometry.

Purpose: To obtain whole lung morphometry measurements from Xe in a single breath-hold with 3D multiple b-value Xe diffusion-weighted MRI (DW-MRI) with an empirically optimized diffusion time and compressed sensing for scan acceleration.

Methods: Prospective three-fold undersampled 3D multiple b-value hyperpolarized Xe DW-MRI datasets were acquired, and the diffusion time (Δ) was iterated so as to provide diffusive length scale (Lm ) estimates from the stretched exponential model (SEM) that are comparable to those from He. The empirically optimized Xe diffusion time was then implemented with a four-fold undersampling scheme and was prospectively benchmarked against He measurements in a cohort of five healthy volunteers, six ex-smokers, and two chronic obstructive pulmonary disease patients using both SEM-derived Lm and cylinder model (CM)-derived mean chord length (Lm).

Whole lung morphometry with 3D multiple b-value hyperpolarized gas MRI and compressed sensing.

Purpose: To demonstrate three-dimensional (3D) multiple b-value diffusion-weighted (DW) MRI of hyperpolarized He gas for whole lung morphometry with compressed sensing (CS).

Methods: A fully-sampled, two b-value, 3D hyperpolarized He DW-MRI dataset was acquired from the lungs of a healthy volunteer and retrospectively undersampled in the k and k phase-encoding directions for CS simulations. Optimal k-space undersampling patterns were determined by minimizing the mean absolute error between reconstructed and fully-sampled He apparent diffusion coefficient (ADC) maps.