Sixty-four slice spiral CT low-dose chest two-phase scanning for lung density measurement in assessing the pulmonary function in patients with chronic obstructive pulmonary disease

Abstract

To explore the value of 64 slice spiral CT (SCT) low-dose chest scanning at full inspiration and full expiration for lung density measurement in assessing the pulmonary function in patients with chronic obstructive pulmonary disease (COPD). Totally 36 COPD patients (the COPD group) underwent pulmonary function tests (PFT) and were essentially verified COPD; 30 healthy people (the control group) were selected whose 64 slice SCT chest scanning was normal. The 2 groups underwent chest 64 slice SCT low-dose scanning at full inspiration and full expiration. After the scanning, the lung was measured by CT Pulmo software. The lung was divided into 3 regions by scanning layers. We measured and calculated the density indexes of each region (including the upper, middle, lower field, and the total lung) of the 2 groups. All density indexes were lung density at full inspiration and full expiration (Din, Dex), density difference (Dex-Din), density ratio (Dex/ Din), density variation percentage (Din-Dex)/Din. All patients underwent PFT and 64 slice SCT within 3 days, whose pulmonary function was tested by Master Lab ( Jaeger, Germany). The indexes were the percentage of actual value and expected value of forced expiratory volume at the first second (FEV1%) and the ratio of first second forced expiratory volume to forced vital capacity (FEV1/FVC). Then we compared with the CT indexes between the COPD group and the control group. The relevant indicators of lung densities were analyzed in comparison with the indicators of FEV1% and FEV1/FVC by Pearson correlation analysis. The density indexes of each region and total lung, and the Din in the control group and the COPD group were compared. The difference between them was statistically significant (P<0.05). The difference among other indexes was also statistically significant (P<0.01). Excellent correlation was found between Dex, Dex-Din, Dex/ Din and (Din-Dex)/ Din indexes with FEV1% and FEV1/FVC (r=0.566, 0.686, 0.568, 0.580, -0.565, -0.598, 0.565 and 0.598; P<0.01) Sixty-four slice SCT low-dose two-phase scanning density indexes are closely related to the indicators (FEV1% and FEV1/FVC) of clinical lung function tests, which can be used to evaluate the lung function in COPD patients conventiently and accurately.