One-dimensional quantitative evaluation of peripheral lung adenocarcinoma with or without ground-glass opacity on thin-section CT images using profile curves

The purpose of our investigation was to compare the usefulness of the subjective visual assessment of ground-glass opacity (GGO) with a quantitative method that used a profile curve to determine prognosis. 96 adenocarcinomas were studied. Three diameters ([D1]-[D3]) were defined for estimating the diameter of tumours on the monitor: the distance between two points was measured using software that displays a CT density profile across the tumour. One experienced and one less experienced radiologist independently evaluated the following six parameters: the three diameters [D1]-[D3]; the solid portion of total tumour in the two different ratios ([D2]/[D1], [D3]/[D1]); and the area ratio of GGO for total opacity to subjective visual evaluation. Interobserver agreement between the two radiologists of the diameters (mean bias +/- 1.96 standard deviations) was as follows: [D1], -0.7 +/- 6 mm; [D2], 0.4 +/- 4.4 mm; and [D3], -0.1 +/- 4.2 mm (Bland and Altman's method). Interobserver agreement was fair in evaluating the area ratio of GGO (kappa test, kappa = 0.309). Univariate logistic regression analysis revealed that two ratios ([D2]/[D1], [D3]/[D1]) might be significantly useful in estimating lymph node metastasis (p < 0.026), lymph duct invasion (p < 0.001) and recurrence (p < 0.015). Observation of the area ratio of GGO by an experienced radiologist would be necessary for estimating lymph node metastasis (p = 0.04) and lymph duct invasion (p < 0.001). We concluded that the ratio of solid component to total tumour, which is obtainable in a more objective and simple way using profile curves obtained by software, is a more useful method of estimating prognosis than is visual assessment.