Clinical ventilation imaging with 113mIn aerosol

Functional images of ventilation can be obtained following inhalation of small radioactive aerosols. To this end, a method has recently been proposed for removing the larger droplets from a polydispersed aerosol preparation. We have modified this method in order to make it suitable for clinical routine, especially regarding the diagnostic strategy of pulmonary embolism, and we have compared it with regional ventilation assessed with continuous inhalation of 81mKr. Normal subjects, patients with pulmonary embolism and patients with various degrees of airflow obstruction underwent the aerosol procedure immediately after a routine 81mKr ventilation/99mTc perfusion lung scan. A solution of 113mIn-albumin is nebulized, using a disposable device, in a large reservoir settling bag. Then the patient inhales the aerosol from the bag during 5 minutes of tidal breathing. This is followed by multiple view lung imaging on the gamma camera (equipped with a high energy collimator). The use of 113mIn allows one to perform a ventilation scan in multiple views (anterior posterior, obliques) following the routine 99mTc perfusion scan. Qualitative (image inspection) and quantitative (penetration index) comparison with 81mKr scans indicates that this readily available aerosol technique provides ventilation images of good statistical quality and with relatively little central deposition, even in patients with severe airflow obstruction.