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Hyperpolarized 3He MR Imaging of the Lung: Normal Range of Ventilation Defects and PFT Correlation in Young Adults

Objective To prospectively investigate the number, location, and size of ventilation defects and correlate these findings with pulmonary function tests (PFTs) when performing hyperpolarized helium-3 (HP 3He) magnetic resonance imaging (MRI) of the lung in healthy young adults. Materials and Methods Six healthy adult female volunteers underwent standard PFT and MRI of the lungs after inhalation of HP 3He. HP 3He MR images were evaluated by 4 reviewers in consensus. Number, location, and size of ventilation defects were recorded. Locations of ventilation defects included the right upper lobe, right middle lobe, right lower lobe, left upper lobe, left lower lobe, and lingula. Ventilation defects were localized into central, middle, or peripheral portions of the lungs. Size of ventilation defects was categorized with a maximum diameter of either ≤3 cm or >3 cm. HP 3He MRI findings were correlated with PFT results. Results The study cohort comprised 6 healthy, young adult female volunteers (mean age 22.5 y, range: 20-25 y) who underwent both PFT and HP 3He MRI. Five (83.3%) out of 6 volunteers had at least 1 ventilation defect (mean=2.3; range: 1-4; 95% confidence interval: 1.3-3.8 defects/patient). Among a total of 14 ventilation defects observed from 5 healthy, young adult volunteers, ventilation defects were observed in left lower lobe in 6 (42.9%), right lower lobe in 3 (21.4%), right upper lobe in 3 (21.4%), and left upper lobe in 2 (14.3%) patients. No ventilation defects were observed in the right middle lobe and lingula. All observed ventilation defects were less than 3 cm in size and peripherally located. There was no correlation between number, location, or size of ventilation defects and PFT results. Conclusions Small (≤3 cm) peripherally located ventilation defects can be seen in the majority of healthy, young adult volunteers, and should not be mistaken as abnormalities when evaluating HP 3He MRI. These ventilation defects are located in the peripheral upper lobes and lower lobes (lower lobes>upper lobes) while sparing right middle lobe and lingula. The number, location, and size of ventilation defects on HP 3He MRI were not correlated with PFT results in the normal range, which suggests HP 3He MRI may be more sensitive than PFT for evaluating small ventilation defects in young adults.