Dissolved ¹²⁹Xe lung MRI with four‐echo 3D radial spectroscopic imaging: Quantification of regional gas transfer in idiopathic pulmonary fibrosis

Abstract

Purpose Imaging of the different resonances of dissolved hyperpolarized xenon‐129 (129Xe) in the lung is performed using a four‐echo flyback 3D radial spectroscopic imaging technique and is evaluated in healthy volunteers (HV) and subjects with idiopathic pulmonary fibrosis (IPF). Theory and Methods 10 HV and 25 subjects with IPF underwent dissolved 129Xe MRI at 1.5T. IPF subjects underwent same day pulmonary function tests to measure forced vital capacity and the diffusion capacity of the lung for carbon monoxide (DLCO). A four‐point echo time technique with k‐space chemical‐shift modeling of gas, dissolved 129Xe in lung tissue/plasma (TP) and red blood cells (RBC) combined with a 3D radial trajectory was implemented within a 14‐s breath‐hold. Results Results show an excellent chemical shift separation of the dissolved 129Xe compartments and gas contamination removal, confirmed by a strong agreement between average imaging and global spectroscopy RBC/TP ratio measurements. Subjects with IPF exhibited reduced imaging gas transfer when compared to HV. A significant increase of the amplitude of RBC signal cardiogenic oscillation was also observed. In IPF subjects, DLCO% predicted was significantly correlated with RBC/TP and RBC/GAS ratios and the correlations were stronger in the inferior and periphery sections of the lungs. Conclusion Lung MRI of dissolved 129Xe was performed with a four‐echo spectroscopic imaging method. Subjects with IPF demonstrated reduced xenon imaging gas transfer and increased cardiogenic modulation of dissolved xenon signal in the RBCs when compared to HV.

Hyperpolarized 129Xe MRI Abnormalities in Dyspneic Patients 3 Months after COVID-19 Pneumonia: Preliminary Results

“…Using the healthy volunteers as a comparator group, our results to are similar to the published literature (14). The low RBC:TP we are reporting is similar to reports in patients with interstitial lung disease such as idiopathic pulmonary fibrosis but these patients have significantly abnormal CT scans (14), whereas here we demonstrate damage effectively only seen using XeMRI in patients with normal or near normal CT scans. On subjective assessment, our patients demonstrated normal ventilation on XeMRI confirming that the main abnormality and damage caused by the SARS-CoV-2 virus is in areas of pulmonary gas exchange and is present diffusely throughout the lungs as shown by the wide coefficient of variation.…”

“…The XeMRI technique we have used has been previously reported (14), and demonstrates good reproducibility for patients and volunteers (0.82 and 0.88, respectively) (24). Using the healthy volunteers as a comparator group, our results to are similar to the published literature (14). The low RBC:TP we are reporting is similar to reports in patients with interstitial lung disease such as idiopathic pulmonary fibrosis but these patients have significantly abnormal CT scans (14), whereas here we demonstrate damage effectively only seen using XeMRI in patients with normal or near normal CT scans.…”

In vivo methods and applications of xenon-129 magnetic resonance

“…An alternative approach is based on iterative decomposition with echo asymmetric and least-squares estimation (IDEAL) [245] , which involves acquisition of images at multiple echo times to improve the separation of gaseous, TP- and RBC-dissolved 129 Xe [104] . Both radial [104] , [318] and spiral [246] , [247] read-outs have been reported. The single-point Dixon method is sensitive to regional gas-exchange impairment in IPF, and dissolved-phase 129 Xe MRI biomarkers show agreement with T LCO [248] , [318] .…”

“…Both radial [104] , [318] and spiral [246] , [247] read-outs have been reported. The single-point Dixon method is sensitive to regional gas-exchange impairment in IPF, and dissolved-phase 129 Xe MRI biomarkers show agreement with T LCO [248] , [318] . Recent data demonstrate the sensitivity of dissolved-phase 129 Xe MRI to IPF disease progression [249] , and distinct gas-exchange features in asthmatics and COPD patients [104] , [232] and a range of cardiopulmonary pathologies [250] .…”

“…(a) 1 H anatomical SPGR image, (b) 129 Xe ventilation image and (c) 129 Xe RBC/TP map acquired with an IDEAL sequence [318] of a coronal mid-posterior slice in a patient with acute COVID-19. For this slice, ventilated volume percentage = 99.6% and RBC/TP = 0.188 (mean RBC/TP in healthy volunteers = 0.47 [318] ). RBC/TP = red blood cells to tissue and blood plasma ratio.…”