Accuracy of CT Attenuation Measurement for Differentiating Treated Osteoblastic Metastases From Enostoses

The objective of our study was to assess whether the maximum and mean CT attenuations are accurate for differentiating between enostoses and treated sclerotic metastases.

We retrospectively reviewed CT studies of 165 patients (167 lesions) that included 49 patients with 49 benign lesions, 69 patients with 71 sclerotic treated lesions, and 47 patients with 47 untreated lesions, and calculated the mean and maximum CT attenuations of each lesion. ROC curves were used to identify thresholds for differentiating enostoses from treated sclerotic metastases and from untreated sclerotic metastases.

The maximum CT attenuation of enostoses (1212.0 HU) was higher from that of untreated (754.7 HU) (p = 9.7 × 10^-16) and that of treated (891.7 HU) (p = 9.9 × 10^-10) sclerotic metastases. The maximum CT attenuation of treated sclerotic metastases (891.7 HU) was higher than that of untreated sclerotic metastases (754.7 HU) (p = 0.003). Enostoses had higher mean CT attenuation (1123.0 HU) than untreated (602.0 HU) (p < 2.2 × 10^-16) and treated (731.7 HU) (p = 9.6 × 10^-15) sclerotic metastases. A threshold mean CT attenuation of 885 HU had an accuracy of 91.7% and 81.7% to differentiate enostoses from untreated and treated metastases, respectively, whereas a threshold maximum CT attenuation of 1060.0 HU had an accuracy of 81.3% and 72.5% to differentiate enostoses from untreated and treated metastases.

The mean and maximum CT attenuations can differentiate between enostoses and sclerotic metastases; however, the accuracy of both metrics decreases after treatment.