Answer to Question #10870 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

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

Answer posted on 15 January 2014. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.