Chapter 19: Xenon Septal Uptake

The main function of the lungs, gas exchange, is accomplished through diffusion processes driven by concentration gradients: after filling the lungs with air, oxygen diffuses into the lung parenchyma and blood, while carbon dioxide is driven from the blood out into the gas state, and exhaled. The efficiency of this process is high due to the large surface area available for gas exchange and the extreme thinness of the gas–blood barrier. However, lung diseases can affect both, the surface area and the thickness of the barrier, thus decreasing the efficiency. Therefore, any method capable of evaluating the different sub-components of gas exchange will be valuable both in assessing the specific cause of any lung dysfunction and in evaluating efficacy of therapeutic intervention. Measurement of pulmonary septal uptake of hyperpolarized xenon offers the opportunity to obtain such information. Over the last two decades a significant body of research has been done in this direction, developing several models of the uptake of hyperpolarized xenon by the pulmonary tissue and blood. In this chapter we introduce these theoretical treatments of the xenon uptake in the lung and review the up to date research in the area.