Diagnostic performances of double-phase Tc-99m MIBI scintimammography in patients with indeterminate ultrasound findings: visual and quantitative analyses

The aim of the study was to compare the diagnostic performances of visual and quantitative analyses of double-phase Tc-99m methoxyisobutylisonitrile (MIBI) scintimammography (SMM) in patients with ultrasonographically indeterminate findings. SMM (early: 10 min; delayed: 3 h) was performed on 78 patients (malignant 66, benign 12). For visual analysis, the five-scoring method was used. For quantitative analysis, ratios of early and delayed lesions to non-lesion (L/Ns) were calculated. When a visual grade of over 3 was used as the cut-off value for the detection of primary breast cancer, the sensitivity and specificity were 86.4% and 100%, respectively. The area under the curve (AUC) was 0.972. The optimal L/N ratios were 1.22 for early and 1.1 for delayed images. When early L/N 1.22 was used as the cut-off point, the sensitivity and specificity of SMM were 92.4% and 91.7%, respectively. The AUC was 0.952. When delayed L/N 1.1 was used as the cut-off value, the sensitivity and specificity were 78.8% and 91.7%, respectively. The AUC was 0.863. Visual interpretation and early L/N were superior to delayed L/N for the detection of breast cancer. This study suggests the possible diagnostic role of visual and quantitative analyses of double-phase SMM for differentiating malignant breast lesions in patients with ultrasonographically indeterminate findings.