In patients with COPD, the VDP obtained with hyperpolarized 29Xe MR imaging was significantly greater than that with 3He MR imaging, suggesting incomplete or delayed filling of lung regions that may be related to the different properties of 129Xe gas and physiologic and/or anatomic abnormalities in COPD.

ADC values for emphysematous lungs were significantly increased compared with healthy lungs in age-matched subjects, and all values were comparable to those reported previously at 1.5 Tesla. Ventilation defect score and ventilation defect volume results were also comparable to results previously reported in COPD subjects Reproducibility of ADC for same-day scan-rescan and 7-day rescan was high and similar to previously reported results.

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Diffusion-weighted hyperpolarized (129) Xe MRI is a promising technique for mapping changes in human lung morphology and may be useful for early detection of emphysema associated with COPD.

In subjects with chronic obstructive pulmonary disease (COPD), hyperpolarized xenon-129 ((129)Xe) magnetic resonance imaging (MRI) reveals significantly greater ventilation defects than hyperpolarized helium-3 ((3)He) MRI. The physiological and/or morphological determinants of ventilation defects and the differences observed between hyperpolarized (3)He and (129)Xe MRI are not yet understood. Here we aimed to determine the structural basis for the differences in ventilation observed between (3)He and (129)Xe MRI in subjects with COPD using apparent diffusion coefficients (ADC) and computed tomography (CT). Ten COPD ex-smokers provided written, informed consent and underwent MRI, CT, spirometry, and plethysmography. (3)He and (129)Xe MRI ventilation volume was generated using semiautomated segmentation, and ADC maps were registered to generate ADC values for lung regions of interest ventilated by both gases (ADCHX) and by (3)He gas only (ADCHO). CT wall area percentage and the lowest 15th percentile point of the CT lung density histogram (HU15%) were also evaluated. For lung regions accessed by (3)He gas only, mean (3)He ADCHO was significantly greater than for regions accessed by both gases (ADCHO = 0.503 ± 0.119 cm(2)/s, ADCHX = 0.470 ± 0.125 cm(2)/s, P < 0.0001). The difference between (3)He and (129)Xe ventilation volume was significantly correlated with CT HU15% (r = -65, P = 0.04) and (3)He ADCHO (r = 0.70, P = 0.02), but not CT wall area percentage (r = -0.34, P = 0.33). In conclusion, in this small study in COPD subjects, we observed significantly decreased (129)Xe MRI ventilation compared with (3)He MRI, and these regions of decreased (129)Xe ventilation were spatially and significantly correlated with regions of increased pulmonary emphysema, but not airway wall thickness.

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease characterized by both small airway and parenchymal abnormalities. There is increasing evidence to suggest that these two morphologic phenotypes, although related, may have different clinical presentations, prognosis, and therapeutic responses to medications. With the advent of novel imaging modalities, it is now possible to evaluate these two morphologic phenotypes in large clinical studies using noninvasive or minimally invasive methods such as computed tomography (CT), magnetic resonance imaging (MRI), and optical coherence tomography (OCT). In this article, we provide an overview of these imaging modalities in the context of COPD and discuss their strengths as well as their limitations for providing quantitative COPD phenotypes.

The dependence of rotating frame spin-lattice relaxation, T1 rho on locking field frequency, f1, was measured for phantom materials and human breast tissues. These data were used to predict the relative signal strengths obtainable in a spin-locking imaging sequence. This imaging sequence was implemented on a 0.15-T imaging system and measurements of phantom and tissue signal strength for various imaging parameters agreed with predicted signal strengths. Compared to T1 and T2, T1 rho appears to have unique capability to distinguish tumor from normal fat and fibrous breast tissues. The applications of T1 rho to tissue characterization and imaging at high static field strengths are discussed.

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