Limits of normality of quantitative thoracic CT analysis

Introduction: Quantitative CT scan analysis has been widely studied in ARDS patients, while, data on healthy population are scanty. Reference values, however, would be of clinical relevance when assessing, i.e., the excess lung weight or edema, or whatever change in CT anatomy/physiology induced by disease. Methods: We retrospectively included patients who underwent a spiral CT scan for clinical reasons and whose images were considered normal by radiologists. Lungs were outlined on each CT image with a dedicated software; lung weight, volume and tissue fraction were computed with a dedicated software. Results: We enrolled 52 patients (25 males), age 65±12 years, height 1.67±0.09 m, BMI 26±4 kg/m 2 . The table summarizes the main CT scan characteristics of patients, with CT taken at near total lung capacity. While the gas values are dependent on inflation, the lung weight is not. Therefore, of particular note the significant correlation between height and total lung weight (p 2 =0.40) according to the equation: total lung weight = –1268 + height$*$1311. The correlation between height and total lung volume is statistically significant (p 2 =0.51) according to the equation: total lung volume = –15250 + height$*$12001. Conclusions: Lung weight and volume are related to height in a healthy population.