Short-lived radionuclides and regional lung function

Abstract

Short-life γ-emitting radionuclides are particularly suitable for studies of the function of different regions of the lung. All the important constituents of the gas in the lungs (oxygen, carbon dioxide and nitrogen) can be labelled with these isotopes. Their distribution can be sensed by detectors placed externally so that the procedures are non-invasive. Because of their short physical half-lives (less than 20 min), cyclotron-produced gaseous isotopes give little radiation exposure. The healthy lung achieves its function, the exchange of oxygen and carbon dioxide, by maintaining an approximately equal flow of air and blood into each of the 300 million air sacs or alveoli. For each unit, the ratio of alveolar ventilation to blood flow , the ratio, approaches unity. Nearly all cases of hypoxaemia (low arterial P.O2, breathing air) are associated with a wide dispersion of ratios through the lung. This can be studied in two ways using short-life radionuclides: (1) the distribution of oxygen (as 15O) or carb...