Pulmonary hamartomas: CT pixel analysis for fat attenuation using radiologic-pathologic correlation.

INTRODUCTION: To assess the accuracy of CT pixel analysis for fat attenuation in pulmonary hamartomas.

METHODS: Retrospective review identified 32 patients in three separate groups; pathologically proven hamartoma (n = 11), hamartoma diagnosed on imaging (n = 9) and a control group (n = 14) of pathology-proven non-hamartomatous smoothly marginated solitary pulmonary nodules. All lesions were assessed using: visual assessment for fat, pixel analysis of the inner 2/3rds and mean attenuation of the entire lesion, using an internal reference for fat. Fat percentages on CT and at histology were compared.

RESULTS: Visual assessment for macroscopic fat was the most reliable method for diagnosing pulmonary hamartoma. Combining percentage of fat-attenuation pixels in the inner 2/3rds of the lesion improved specificity to 100%. Mean attenuation or pixel analysis in isolation were not helpful in lesional characterization.

CONCLUSION: Combining percentage fat-attenuating pixels in the inner 2/3rds with visual assessment for macroscopic fat improves specificity for diagnosing pulmonary hamartomas.