The value of volume doubling time in diagnosis of solitry pulmonary nodules by 64-slice spiral CT

Objective: To discuss the value of volume doubling time (DTV) in diagnosis of solitary pulmonary nodules (SPN) by 64-slice spiral CT. Methods: There were 46 cases which were underwent repeated follow-up CT at the first month and at the third month after the initial chest CT. We evaluated the value of DTV calculated by LungCARE volumetry software and diameter doubling time (DTD) calculated by diameter method in the diagnosis of SPN. We compared the difference of DTV in different kinds of SPN and in different follow-up periods by Mann-Whitney U test. Results: Twenty-nine malignant nodules and seventeen benign nodules were confirmed in forty-six SPN cases. The sensitivity, specificity, positive predictive value, negative predictive value and Youden index of DTV and DTD in the diagnosis of malignant nodules were 93.10%, 94.11%, 96.42%, 88.89% and 0.87 vs.79.31%, 70.59%, 82.14%, 66.67% and 0.50. The diagnostic value of DTV was better than DTD (χ2 =10.211, P<0.05). Furthermore, there were no differences in DTV between different follow-up periods (U=0.127 and U=0.066, P>0.05) but significant differences between adenocarcinomas and squamous cell carcinomas (U=-3.193 and U=-2.810, P<0.01 ). Conclusions: The value of DTV in diagnosis of malignant nodule was superior to DTD. The evaluation of DTV may be helpful in assessing the growth characteristic of SPN and its follow-up. (authors)