Diagnostic value of different patient positions during expiratory low-dose thin-layer MDCT for evaluating air trapping after allogeneic hematopoietic stem cell transplantation.

OBJECTIVE To investigate the diagnostic value of different patient positions during expiratory low-dose thin-layer multidetector computed tomography (MDCT) for detecting air trapping after allogeneic hematopoietic stem cell transplantation (allo-HSCT). PATIENTS AND METHODS Expiratory lung MDCT scanning was done for 51 post-allo-HSCT patients in both the supine and prone positions to determine if they had air trapping lesions. We assessed the volume fraction of an air trapping region (CT value of ≤700HU at expiratory phase) against the whole lung area with a GE workstation and graded these results. RESULTS In the supine position, multiple air trapping lesions were found in 16 of 51 patients, which were scattered and mainly distributed in the dorsal sides of both lower lobes. In the prone position, in addition to these 15 patients, air trapping lesions were also found in 11 other patients, which were mainly distributed in the anterior load-bearing area of the lung lower lobes and lobe-connected areas. Compared with that in the supine position, the graded score of air trapping in the prone position was significantly different (p = 0.006). CONCLUSIONS When performing expiratory thin-layer MDCT for patients with chronic rejection reactions after allo-HSCT, scanning in the prone position should also be performed, not only to more accurately observe lesions, but also for a preliminary evaluation of air trapping severity. This provides a basis for an early clinical diagnosis and treatment.