Hyperpolarized (3)He MRI of mouse lung

Hyperpolarized (3)He images of mouse lung are presented. Ventilation images and measurements of (3)He apparent diffusion coefficient (ADC) are reported in healthy mice, and preliminary studies of emphysema and lung cancer in mice are described using these techniques. The design and operation of an electronically controlled small-animal ventilator to deliver the hyperpolarized gas and control animal respiration are described. Images are acquired using an asymmetric gradient echo imaging method to enhance the signal-to-noise ratio of the rapidly diffusing (3)He. In mice with elastase-induced emphysema, the whole-lung average ADC is greater by approximately 25%, a statistically significant difference, compared to healthy animals. By contrast, mice exposed to cigarette smoke for up to 12 months reveal no statistically relevant increases in ADC, although emphysema was not confirmed in these mice. A study of lung cancer (melanoma) in mice is also presented. While tumors are shown to cause substantial ventilation defects in the lung, these defects appear confined to the cancerous regions and do not extend to large-scale regions of the lung distal to the tumors.