Reverse radioaerosol/radioperfusion distribution in pulmonary endobronchial obstruction.

A characteristic image pattern of diminished radioaerosol penetration and reduced radioparticle perfusion has been observed in endobronchial obstruction. This reverse mismatch has a variety of etiologies, with the most common being mucus plugging. The regional hypoxia created by the obstruction causes the blood to shunt from the affected lung. Eleven patients from a group of 178 patients referred with a working diagnosis of pulmonary embolism showed the reversed mismatch. All presented with sudden dyspenea, chest pain and hypoxia. Bronchoscopy was recommended from the image results and nine patients demonstrated mucus plugs that were subsequently aspirated, one patient had a partially obstructing endobronchial carcinoma and one patient had a traumatic fractured bronchus that became occluded with healing granulation tissue. All improved following bronchoscopy. The incompleteness of the airway obstruction accounted for the variations of the perfusion images. Because of the radioaerosol's ability to sharply image the pulmonary airway distribution in contrast to the poor resolution of the radiogases such as xenon-133, it is recommended that radioaerosol lung imaging be substituted for radiogas ventilation imaging since it can accurately detect endobronchial obstruction as well as pulmonary embolism.