Differentiating between pulmonary adenocarcinoma and squamous cell carcinoma by spectral CT volumetric quantitative analysis: a comparative study with conventional spectral analysis

BACKGROUND: Unlike the conventional spectral analyses of spectral computed tomography (CT) that cannot fully represent the whole lesion, the volumetric quantitative analysis reveals the information of the whole lesion and is of more accurate. So this study sought to evaluate the value of volumetric quantitative analysis in the differential diagnosis of pulmonary adenocarcinoma (ADC) and squamous cell carcinoma (SQCC). METHODS: Fifty-seven patients with lung cancer confirmed by pathology, including 35 ADC and 22 SQCC patients, were retrospectively analyzed. Calcium concentration and effective-Z (Eff-Z) in plain scan (PS), iodine concentration, and water concentration in the arterial phase (AP) were measured. The Student t-test or rank-sum test was used to determine the statistically significant parameters. Receiver operating characteristic (ROC) curve was used, and the corresponding area under the curve (AUC), sensitivity and specificity was calculated to evaluate the diagnostic efficacy in differential diagnosis of ADC and SQCC. RESULTS: In the volumetric quantitative analysis of spectral CT, the concentration of calcium [(6.97±2.83) mg/cm(3)], Eff-Z (7.90±0.14), and iodine [1.42 (0.84) mg/cm(3)] was significantly higher in ADC than SQCC [(5.14±2.39) mg/cm(3), (7.80±0.10), 1.16 (0.65) mg/cm(3), t=2.513, 2.860, Z=–2.246, P=0.015, 0.006, 0.025], but the concentration of water was significantly lower in ADC [995.00 (38.70) mg/cm(3)] than SQCC [1,007.00 (14.38) mg/cm(3), Z=–2.082, P=0.037]. Moreover, whether it’s ADC or SQCC, the concentrations of calcium [(8.51±4.28) mg/cm(3), (5.96±2.50) mg/cm(3)], Eff-Z (7.97±0.20, 7.86±0.13), and water [1,007.00 (14.38) mg/cm(3), 1,029.28 (10.49) mg/cm(3)] were lower in the volumetric spectral analysis than the conventional spectral analysis, while the concentration of iodine [1.33 (0.80) mg/cm(3), 0.94 (0.63) mg/cm(3)] was significantly higher in the volumetric spectral analysis than the conventional spectral analysis. The ROC curve analysis showed that the areas under the curves (AUC) (0.76, 0.76, 0.75, 0.71), sensitivity (66.7%, 66.7%, 66.7%, 85.2%), and specificity (92.3%, 84.6%, 86.9%, 69.2%) of the volumetric spectral analysis parameters for the differential diagnosis of ADC and SQCC were higher than those of the conventional spectral analysis [(0.65, 0.66, 0.73, 0.63), (44.4%, 48.1%, 59.3%, 66.7%), (69.2%, 69.2%, 84.6%, 53.8%)] parameters. CONCLUSIONS: The volumetric quantitative analysis has a promising advantage in the observation range of whole lesions, it may be invaluable in the differential diagnosis of ADC and SQCC, and is worthy of clinical recommendation.