Diffusion‐weighted hyperpolarized ¹²⁹Xe MRI in healthy volunteers and subjects with chronic obstructive pulmonary disease

Abstract

129Xe apparent diffusion coefficient (ADC) MRI offers an alternative to 3He ADC MRI, given its greater availability and lower cost. To demonstrate the feasibility of HP 129Xe ADC MRI, we present results from healthy volunteers (HV), chronic obstructive pulmonary disease (COPD) subjects, and age-matched healthy controls (AMC). The mean parenchymal ADC was 0.036±0.003 cm2/s for HV, 0.043±0.006 cm2/s for AMC, and 0.056±0.008 cm2/s for COPD subjects with emphysema. In healthy individuals, but not the COPD group, ADC decreased significantly in the anterior-posterior direction by ~22% (p = 0.006, AMC; 0.0059, HV), likely due to gravity-induced tissue compression. The COPD group exhibited a significantly larger superior-inferior ADC reduction (~28%) than the healthy groups (~24%) (p = 0.00018 HV; p = 3.45×10-5 AMC), consistent with smoking-related tissue destruction in the superior lung. Superior-inferior gradients in healthy subjects may result from regional differences in xenon concentration. ADC was significantly correlated with pulmonary function tests (FEV1, r=-0.77, p=0.0002; FEV1/FVC, r=-0.78, p=0.0002; DLCO/VA, r=-0.77, p=0.0002), and in healthy groups, increased with age by 0.0002 cm2/s/yr (r=0.56, p=0.02). This study shows 129Xe ADC MRI is clinically feasible, sufficiently sensitive to distinguish HV from subjects with emphysema, and detects age and posture-dependent changes.

Assessment of Regional Lung Function with Multivolume1H MR Imaging in Health and Obstructive Lung Disease: Comparison with3He MR Imaging

“…The IQR decrease from healthy volunteers is strictly related to the decrease or loss of gravity dependence with disease. These results are consistent with data in recent studies on apparent diffusion coefficient, reporting a gradient in alveolar expansion in the direction of gravity in healthy subjects (33)(34)(35)(36) and the near absence of anterior-posterior apparent diffusion coefficient gradient in patients with emphysema, to be attributed to the presence of tissue loss in diseased lung parenchyma (34,35) or to the decreased compressibility of the lung tissue due to air trapping (36). In patients with severe asthma, proton signal difference decreased from healthy volunteers with larger spatial variation in relation to the simultaneous presence of obstructed and wellventilated regions.…”

Direct comparison of 129Xe diffusion measurements with quantitative histology in human lungs

“…This was the result of both the scarcity of healthy control lungs rejected for lung transplant during the project period (none, in fact) and temporary limitations on xenon polarizer availability (we have subsequently built our own polarizer to avoid this in future studies (38)(39)(40)). Nevertheless, with the collected seven IPF samples here, we were able to demonstrate strong statistical significance compared with COPD samples, and measurements in these IPF specimens are consistent with nonemphysematous alveolar spaces in vivo (27,30,34). Our measurements of L m in these samples are slightly larger than we have measured in past studies in healthy lungs; this is likely the result of variations in tissue processing between the two studies and the fact that subtle airspace enlargement may be present in IPF.…”

Emerging Imaging Tools for Use with Traumatic Brain Injury Research

“…Hyperpolarization techniques enable the signal from a given number of nuclear spins to be raised by > 100,000 times, allowing imaging of nuclei other than protons, such as C 13 , N 15 and Xe 29. Feasibility has already been demonstrated in a clinical setting (Kaushik et al, 2010). Because the natural occurrence of C 13 in the human body is so low, there is essentially no background noise.…”

“…Consequently, distribution patterns may be mapped by injection and imaging of several hyperpolarized C 13 molecules simultaneously giving valuable information about membrane structure and permeability. There has already been proof of concept in the pulmonary system in adults using Xe 29 (Kaushik et al, 2010) and translation into the pediatric population is anticipated, allowing us to enter the world of molecular imaging, proteomics, and genomics.…”