Lateral decubitus HRCT: a simple technique to replace expiratory CT in children with air trapping

OBJECTIVE: To evaluate the effectiveness of lateral decubitus high-resolution CT (HRCT) in detecting air trapping in children. MATERIALS AND METHODS: HRCT scans of 21 children with heterogeneous lung attenuation caused by air trapping (n = 10) or with infiltrative lung disease (n = 11) were reviewed retrospectively. The air-trapping disease included bronchiolitis obliterans (n = 7), bronchial obstruction due to mediastinal lymphoma (n = 1), endobronchial haemangioma (n = 1) and foreign body aspiration (n = 1). HRCT was performed in both lateral decubitus positions as well as the supine position. The attenuation (Hounsfield units; HU) was measured in both the hypo- and adjacent hyper-attenuating areas of the heterogeneous lung portion, and the difference of attenuation between these two areas was calculated in the supine and both lateral decubitus scans, respectively. The attenuation differences of the three scans were compared in each group. RESULTS: The attenuation difference was larger in the ipsilateral decubitus (207.95 +/- 105.24 HU) scans than in the contralateral (121.25 +/- 90.05 HU) or supine (162 +/- 94.01 HU) scans in the air-trapping group (P < 0.05). There were no significant differences among the three scans in the infiltrative lung disease group (P > 0.05). CONCLUSIONS: Lateral decubitus HRCT is an effective adjunct to standard HRCT in the evaluation of air trapping as a cause of mosaic lung attenuation in uncooperative paediatric patients.