Answer to Question #10870 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
Will a nuclear medicine test tell if there is fluid in the lungs?
Over many, many years and in millions of patients, nuclear medicine has proven to be safe and extremely useful in the diagnosis and even treatment of human disease.
Its utility is based on the specific localization of radiopharmaceuticals (i.e., radiotracers and radionuclide-based therapeutic agents) in organs and abnormal structures such as tumors. In principal, therefore, a radiotracer that filled the so-called fluid space of the body would likely localize to some extent in fluid in the lungs (among other sites in the body) and, therefore, might be useful for noninvasively visualizing such fluid.
In practice, however, there are simpler and more effective diagnostic imaging procedures—most notably, a chest x ray—for testing if there is fluid in the lungs. The lungs are largely air, of course, and like air are relatively radiolucent, meaning that most incident x rays pass right through them and onto the x-ray film or other detector. Soft tissue such as muscle (which is very much like water in many respects) and, in particular, bone are much denser and many fewer x rays will pass through these tissues.
Therefore, if there is an abnormal accumulation of relatively radiopaque fluid in or near the lungs, it will be readily apparent on an x ray next to the radiolucent, air-filled normal lung. Moreover, the spatial resolution, or sharpness, of a chest x ray is excellent and the radiation dose very, very low. Thus, a chest x ray, rather than a nuclear medicine test, would be the imaging modality of choice for detecting fluid in the lungs.
Pat Zanzonico, PhD