Ventilation abnormalities in obstructive airways disorder: detection with pulmonary dynamic densitometry by means of spiral CT versus dynamic Xe-133 SPECT.

Abstract

To evaluate pulmonary dynamic densitometry (PDD) by means of spiral computed tomography (CT) for detection of ventilation abnormalities in obstructive airways disorders compared with dynamic xenon-133 single photon emission CT. Eight-second spiral CT was performed during two to three respiratory cycles in six healthy volunteers, 19 patients with airways disorder, and six patients with restrictive lung disease. The data sets were reconstructed as 36 1-second temporally overlapping images at 0.2-second intervals, and regional PDD curves were displayed. Regional ventilation was assessed by means of Xe-133 clearance time. Normal lungs showed smooth, sinusoidal PDD curves with maximal amplitude in lung attenuation change (MALAC) of 54.9 HU +/- 24.5, whereas lungs with obstructive airways disorders with prolonged Xe-133 clearance showed significantly diminished MALAC (31.6 HU +/- 20.1, P < .0001), accompanied by irregularity, asynchronous phase, and deterioration of normal ventral-to-dorsal gradients in MALAC and lung attenuation. Lungs with restrictive diseases without prolonged Xe-133 clearance did not show statistically significant reduction in MALAC. In a total of 251 lung regions, regional MALAC correlated inversely with Xe-133 clearance time (r = -.842). PDD by means of spiral CT is acceptable for the detection of ventilation abnormalities in obstructive airways disorder.