Interactions of regional respiratory mechanics and pulmonary ventilatory impairment in pulmonary emphysema: assessment with dynamic MRI and xenon-133 single-photon emission CT.

Study objectives Dynamic MRI and 133 Xe single-photon emission CT (SPECT) were used to directly evaluate the interaction of regional respiratory mechanics and lung ventilatory function in pulmonary emphysema. Methods Respiratory diaphragmatic and chest wall (D/CW) motions were analyzed by sequential MRI of fast-gradient echo pulse sequences during two to three respiratory cycles in 28 patients with pulmonary emphysema, including 9 patients undergoing lung volume reduction surgery (LVRS). The extent of air trapping in the regional lung was quantified by the 133 Xe retention index (RI) on three-dimensional 133 Xe SPECT displays. Results By contrast to healthy subjects (n = 6) with regular, synchronous D/CW motions, pulmonary emphysema patients showed reduced, irregular, or asynchronous motions in the hemithorax or location with greater 133 Xe retention, with significant decreases in the maximal amplitude of D/CW motions (MADM and MACWM; p 133 Xe retention sites by LVRS effectively and regionally improved D/CW motions in nine patients, with significant increases in MADM and MACWM (p 1 ( r = 0.881, p r = 0.906, p 133 Xe RI in each hemithorax ( r = −0.871, p r = −0.901, p Conclusions This direct comparison of regional respiratory mechanics with lung ventilation demonstrated a close interaction between these impairments in pulmonary emphysema. The present techniques provide additional sensitivity for evaluating pathophysiologic compromises in pulmonary emphysema, and may also be useful for selecting resection targets for LVRS and for monitoring the effects.