With its ability to assess regional pulmonary gas exchange, hyperpolarized ¹²⁹Xe MRI may be valuable for both diagnosing and monitoring idiopathic pulmonary fibrosis (IPF) [1]. However, the use of ¹²⁹Xe MRI to characterize ventilation has received little attention because IPF patients exhibit remarkably few ventilation defect regions (VDR) compared to those with obstructive lung diseases. We have recently developed a linear binning method to quantify ventilation distribution that also reports on low and high-intensity regions (LIR, HIR). The objective of this work was therefore to test whether ¹²⁹Xe ventilation MRI, quantified in this manner, exhibits features that can differentiate early-stage from later-stage IPF. To do so we compared ¹²⁹Xe MRI binning with the GAP index [2], which stages IPF using gender, age and physiology. ¹²⁹Xe ventilation MRI scans were acquired in 10 young controls (25.7±3.4 yrs) and 10 IPF patients (67.1±7.6 yrs, FVC=66.9±21.4%, and DLCO 49.7±12.1%). MRI used a multi-slice GRE scan: FOV = 40 cm, 12.5 mm slice, matrix = 128×128, BW = 8 kHz, α = 7-10°, TR/TE = 8.9/2.1ms. To enable semi-automated quantification, the thoracic cavity was delineated using a breath-hold ¹H FIESTA (SSFP) image: FOV = 40 cm, 12.5 mm slice, matrix = 192×192, α = 45°, TR/TE = 2.8/1.2 ms, BW = 125 kHz. These were registered to the ¹²⁹Xe MRI using affine transformations. The ¹²⁹Xe MRI and registered ¹H image were segmented by region growing to create a combined mask that included both the thoracic cavity and the airways. This mask was eroded by 1 pixel and vascular structures were removed using Frangi’s vessel-enhancing algorithm. ¹²⁹Xe images were corrected for B1 inhomogeneity, and then rescaled by the 99^th percentile of their cumulative intensity distribution so that the resulting pixel values ranged from 0-1. The distribution in healthy young volunteers had a mean = 0.52 and standard deviation SD = 0.18. These were used to define 6 bins for mapping ventilation distribution, and to quantify defects, low and high-intensity regions as follows: VDR—[0, mean-2SD], LIR—[mean-2SD, mean-1SD], and HIR—[mean+1SD, 1]. In younger controls VDR = 2.6±1.8%, LIR = 17.5±5.7%, HIR = 16.7±3.3%, and thoracic cavity volume was TCV = 3.8±0.6L. By comparison, IPF subjects had a smaller thoracic cavity volume (TCV = 2.9±0.3L), modestly increased VDR (8.9±5.4%), LIR (25.4±9.7%), and HIR (19.2±12.9%). However, HIR varied significantly among IPF patients, and exhibited a significant negative correlation with GAP staging index (r=-0.66, p=0.04). For patients with GAP<2, HIR=29.9±11.7%. By contrast, for patients with GAP>3 HIR decreased to 8.3±3.4%. Thus, in patients with more advanced disease, as characterized by GAP>3, HIR was more than 3-fold lower than in patients with early disease.Although ¹²⁹Xe gas exchange metrics will likely remain the primary focus in IPF, this study shows that ¹²⁹Xe ventilation MRI may help in further staging the disease. The dramatic reduction in high-intensity pixels for patients with more advanced disease suggests that the fibrosis progressed sufficiently to compromise lung compliance. By contrast, it appears that earlier in the disease process, there are still pockets of compliant lung that receive proportionally more ventilation. Thus, loss of HIR may be a useful marker of disease progression in IPF.