Imaging sensitivity of dedicated positron emission mammography in relation to tumor size

Positron emission mammography (PEM) has been reported to have higher sensitivity than whole-body positron emission tomography (PET)due to higher spatial resolution. However, no direct evidence exists regarding the imaging sensitivity of PEM related to lesion size. In the present study, imaging sensitivity of PEM was investigated in relation to pathologically confirmed tumor size.A total of 113 breast lesions from 101 patients were included in the analysis. The patients underwent 18F-fluorodeoxyglucose (FDG) PEM and whole-body PET/computed tomography (CT) before surgical resection, and images were analyzed visually and quantitatively using the tumor-to-normal-tissue uptake ratio (TNR). Tumors were classified into four groups based on size using pathologic results, and sensitivities of PEM and PET/CT were compared in the overall subjects and in each size group.In visual analysis, PEM showed significantly higher imaging sensitivity than PET/CT (95% vs. 87%; P = 0.004), which was more definite in the small-tumor groups. In quantitative analysis, the TNR of PEM was significantly higher than that of PET/CT in the small-tumor groups, whereas no difference was found in the overall group. With a cutoff TNR of 2.5, PEM showed significantly higher sensitivity than PET/CT in the overall and small-tumor groups.In conclusion, PEM had higher imaging sensitivity than PET/CT, particularly in small tumors. The results suggest that PEM may be used for diagnosis and characterization of small lesions as a supplementary imaging modality for PET/CT.