A multislice single breath-hold scheme for imaging alveolar oxygen tension in humans

Reliable, noninvasive, and high-resolution imaging of alveolar partial pressure of oxygen (p_AO₂) is a potentially valuable tool in the early diagnosis of pulmonary diseases. Several techniques have been proposed for regional measurement of p_AO₂ based on the increased depolarization rate of hyperpolarized ³He. In this study, we explore one such technique by applying a multislice p_AO ₂-imaging scheme that uses interleaved-slice ordering to utilize interslice time-delays more efficiently. This approach addresses the low spatial resolution and long breath-hold requirements of earlier techniques, allowing p_AO₂ measurements to be made over the entire human lung in 10-15 s with a typical resolution of 8.3 × 8.3 × 15.6 mm ³. PO₂ measurements in a glass syringe phantom were in agreement with independent gas analysis within 4.7 ± 4.1% (R = 0.9993). The technique is demonstrated in four human subjects (healthy nonsmoker, healthy former smoker, healthy smoker, and patient with COPD), each imaged six times on 3 different days during a 2-week span. Two independent measurements were performed in each session, consisting of 12 coronal slices. The overall p _AO₂ mean across all subjects was 95.9 ± 12.2 Torr and correlated well with end-tidal O₂ (R = 0.805, P < 0.0001). The alveolar O₂ uptake rate was consistent with the expected range of 1-2 Torr/s. Repeatable visual features were observed in p_AO ₂ maps over different days, as were characteristic differences among the subjects and gravity-dependent effects.