Spirometric-gated computed tomography quantitative evaluation of lung emphysema in chronic obstructive pulmonary disease - A comparison of 3 techniques

Objective: To compare the quantitative assessment of pulmonary emphysema with spirometric-gated computed tomography (gated CT) using 3 different acquisition techniques and to determine if low-current spiral CT could be used effectively to quantitate emphysema. Methods: Eleven patients with chronic obstructive pulmonary disease (COPD) underwent gated CT and pulmonary function tests (PFTs). Spiral whole-lung 10-mm collimation acquisitions at standard (146 mAs) and low (43 mAs) current and sequential 3-slice 1-mm collimation high-resolution computed tomography (HRCT) acquisitions at standard current were obtained at 90% of the patient's vital capacity. The mean lung density (MLD) and the pixel index (PI) derived from the 3 data sets were compared using one-way analysis of variance and correlated with PFTs using linear regression. Moreover, the radiation dose associated with each technique was measured. Results: The MLDs were not significantly different. The Pls calculated from the standard- and low-current spiral acquisitions were similar, and both were significantly different from that of HRCT. The MLDs correlated with the PFTs in standard-current spiral and HRCT but not in low-current spiral acquisitions, whereas the Pls correlated with the PFTs in all 3 techniques. High-resolution computed tomography implied the lowest dose (0.08 mSv) compared with low-current (1.2 mSv) and standard-current (4 mSv) spiral techniques. Conclusions: Low- and standard-dose spiral CT provides similar lung density data in COPD. The combination of low-dose whole-lung spiral CT and 3-slice HRCT represents the best compromise between the amount of information provided and radiation exposure to the patient and could be substituted for standard-dose spiral CT for quantitative evaluation of COPD.