Small Pulmonary Nodules: Evaluation with Repeat CT—Preliminary Experience

PURPOSE: To assess the use of early repeat computed tomography (CT) of solitary pulmonary nodules to determine nodule growth. MATERIALS AND METHODS: The authors performed repeat CT of nodule phantoms to assess the accuracy of their measurement technique. They then used this technique to assess nodule growth (nine malignant, six benign) in 15 patients (nine men, six women; age range, 60-79 years; average age, 66 years) who underwent repeat CT as part of their routine clinical protocol. The final diagnosis was established with surgical resection or follow-up for more than 2 years after an indeterminate biopsy. RESULTS: Results of phantom experiments revealed that the method used to determine area change is sensitive enough to help detect nodule growth if one pixel is added around the entire circumference of a nodule. With use of standard exponential growth curves and known tumor growth rates, malignant growth could be detected in vivo within 30 days. All 15 in vivo nodules were correctly classified with early repeat CT. CONCLUSION: Preliminary experience with early repeat CT suggests that a single repeat CT scan obtained 30 days after the first scan can depict growth in most malignant tumors as small as 5 mm.