Assessing Particle Deposition in the Respiratory Tract

Methods of Assessing Particle Deposition in the Respiratory Tract 

Radioactive aerosols are frequently used in deposition or medical application studies because they allow noninvasive measurements of high sensitivity and reasonable spatial resolution. The fraction of aerosols deposited in the body is derived from radioactivity balance considerations. 

Inhaled particles can be labeled with a variety of radionuclides, emitting P-rays or y-rays. The P-rays are highly absorbed from tissue, so that they are almost undetectable from outside the body. With P-emitting radionuclides (e.g., or C), particle deposition in the respiratory system or in the mouth can be assessed only from radioactivity recovered on expired-air filters or in lavage fluid from mouth washings. 

Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016 

For stable y-labeling of inhaled aerosols, different radioisotopes (e.g., C, Co, Co, Ga, In, or Tc) are available, providing a wide spectrum of energies, types of radiation, half-lives, and doses. Unfortunately, it is technically difficult to label pharmaceutical agents directly, so that in most medical deposition studies a surrogate of radiolabeled particles or a mixture of drug substance and labeled particles is employed. 

---