Effect of Attenuation Correction on Lesion Detectability in FDG PET of Breast Cancer

The aim of this study was to compare the visual analysis of attenuation-corrected and noncorrected 18F-fluoro-2-deoxy-D-glucose (FDG) PET images in patients with primary or metastatic breast cancer using standardized film documentation and to evaluate the influence of attenuation correction on lesion detectability. Standard FDG PET of the breasts and of the axillary regions was performed on 28 women with breast cancer. Transmission scans were acquired for attenuation correction after administration of FDG. Transverse and coronal slices and maximum intensity projections both with and without attenuation correction were documented in a standardized manner on film. Noncorrected images were displayed with an upper threshold of five times the mean activity in normal lung tissue. Attenuation-corrected images were documented with an upper threshold of a standardized uptake value of five. Two independent nuclear medicine physicians, who were unaware of the results of clinical investigation, other imaging modalities and histopathologic findings, interpreted the images visually, noncorrected images first. One hundred eighty-four of 189 lesions in 28 of 28 patients were found on attenuation-corrected and noncorrected images. Seventeen lesions were found in the breasts of 12 patients. In 18 patients, 31 axillary lesions were found. Moreover, 141 lesions representing distant metastases were detected in 18 patients. Attenuation-corrected images showed the same lesions in all patients but 2, in whom 5 of 189 small pulmonary lesions (2.6%) were not detected. Iterative reconstruction did not improve detectability of these lesions on attenuation-corrected images. These lesions were confirmed by CT, which revealed diameters of