Positron emission tomography in pulmonary edema.

Positron emission tomography (PET) enables the concentration of positron-emitting isotopes to be measured quantitatively in vivo. It is also possible to measure the physical density of the lung with an external source of radiation. Several investigative procedures have been described for studying the distribution of the intravascular and extravascular water pools in the lung with PET. Clinical applications of these procedures have shown that acute hydrostatic pulmonary edema in humans has characteristics similar to experimentally induced hydrostatic edema. In chronic interstitial pulmonary edema, on the other hand, the relationship between the intravascular and extravascular water pools is different, and experimental models of acute pulmonary edema may not be relevant to this category of patients. The possible effects of these differences on lung function, such as gas exchange, may be studied with PET in the future. Microvascular permeability to proteins may also be studied.