Characterization of breast lesion using double phase Tc-99m Tetrofosmin scintimammography: Comparison of visual and quantitative analyses

To compare the diagnostic performances of visual and quantitative indices of double phase Tc-99m Tetrofosmin scintimammography (TF-SMM) for the detection of breast cancer. Double phase TF-SMM (early, 10 min; delayed, 3 h) were performed after injection of 925 MBq of Tc-99m Tetrofosmin in 75 highly suspected breast cancer patients (malignant: 49, benign: 26). For visual analysis, five scoring method was used. For quantitative analysis, early, delayed lesions to non-lesion ratios (L/Ns) and washout rate (%, WR) were calculated. Receiver operating characteristic curve (ROC) analyses were performed to determine the optimal visual grade, to calculate cut-off values of quantitative indices, and to compare visual and quantitative diagnostic performances. When over grade 3 of visual grade was used as cut-off value in the defection of primary breast cancer, the sensitivity and specificity were 75.5 and 80.8%, respectively. The positive and negative predictive values were 88.1 and 63.6%, respectively. The area under curve was 0.824 (95% CI, 0.719–0.902) and standard error (S.E.) was 0.047. The optimal L/N ratios were 3.13 for early and 2.56 for delayed image. When early L/N 3.13 was used as cut-off point, the sensitivity and specificity of TF-SMM were 61.2 and 96.2%, respectively. The positive and negative predictive values were 96.8 and 56.8%, respectively. The AUC was 0.809 (95% CI, 0.702–0.890) and S.E. was 0.049. When delayed L/N 2.56 was used as cut-off value, the sensitivity and specificity were 46.9 and 96.2%, respectively. The positive and negative predictive values were 95.8 and 49%, respectively. The AUC was 0.741 (95% CI, 0.627–0.835) and S.E. was 0.057. No statistical differences between visual assessment and quantitative analysis of early image (difference between area, 0.015; S.E., 0.044; 95% CI, −0.072 to 0.102; p = 0.736) and delayed image (difference between area, 0.083; S.E., 0.054; 95% CI, −0.023 to 0.060; p = 0.189) was noted. However, early L/N was superior to delayed L/N ratio for the detection of breast cancer (difference between area, 0.068; S.E., 0.033; 95% CI, 0.004–0.132; p = 0.038). In conclusion, TF-SMM showed a favorable diagnostic accuracy in differentiating benign from malignant breast lesions. The optimal visual interpretation grades for the detection of primary breast cancer of double phase TF-SMM were grade 4 and 5. The optimal quantitative indices for the detection of breast cancer were 3.12 for early L/N and 2.56 for delayed L/N.