[Alteration ratio of lung field CT numbers of full inspiration to end expiration scans in chronic obstructive pulmonary diseases].

The alteration ratio of lung field CT numbers in different respiratory phases was studied in 52 patients with chronic pulmonary obstructive disease (COPD) and 20 subjects with normal lung. The 52 patients with COPD consisted of 30 with clinically diagnosed chronic pulmonary emphysema (CPE), 15 with suspected CPE (sCPE) and seven with bronchial asthma (BA). The 20 subjects with normal lung were divided into two groups according to age. CT images were obtained in each case under different respiratory conditions, i.e., full inspiration and end expiration. The following parameters were employed for numerical evaluation: %(I-E)Apex = (MLDApexI-MLDApexE/MLDApexE x 100 %(I-E)Mid = (MLDMidI-MLDMidE)/MLDMidE x 100 %(I-E)Base = (MLDBaseI-MLDBaseE)/MLDBaseE x 100 %(I-E)Whole = (MLDWholeI-MLDWholeE)/MLDWholeE x 100 where MLD is mean lung density and the letters I and E stand for full inspiration and end expiration, respectively. The small letters Apex, Mid, Base and Whole stand for apex cut, mid-thorax cut, base cut and whole lung, respectively. The values of %(I-E)Whole were significantly different between disease groups except for those between the sCPE and BA groups. The values of %(I-E)Whole showed a good positive correlation with FEV1.0% (r = 0.79) and V25/H (r = 0.80) and a good negative correlation RV/TLC (r = -0.75). Diagnostic differentiation of COPDs by %(I-E)Whole values identified 80% of CPE cases and 91% of normal lung cases. In the sCPE group, the values of %DLco in patients with %(I-E)Whole above 9% were smaller than those in patients with %(I-E)Whole under 9%.(ABSTRACT TRUNCATED AT 250 WORDS)