Use of Hyperpolarized 129Xe MR Lung Imaging in Infants

Abnormalities of the lungs are common in newborns and can include aspiration or infectious pneumonia, respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), pulmonary hypertension (PH), congenital diaphragmatic hernia (CDH), and other abnormalities of lung development. Diagnostic radiography is commonly used in this population to differentiate diagnosis and to assess changes after treatment. While X-ray and CT provide quality imaging, they also expose infants to ionizing radiation. MR imaging offers a safe, non-ionizing alternative. However, imaging lungs via 1H MR is intrinsically difficult due to multiple air-tissue interfaces within the lungs causing local gradients and severe magnetic field susceptibility, which leads to an exceedingly short effective transverse relaxation time (T2\*). Additionally, the lungs have low proton density, which along with the short T2\* results in low signal to noise ratio, and the physiological motion caused by respiration and cardiac pulsation further reduces lung signal. The development of more powerful hardware, along with faster MRI techniques, has enabled detailed noninvasive 1H MR imaging of pulmonary tissues. Additionally, the development of inhaled hyperpolarized gas MRI has led to breakthroughs in the ability to visualize and quantify regional ventilation and alveolar size.