99mTc-MIBI Scintigraphy to differentiate malignancies from benign lesions detected on Planar bone scans

The aim of study was to evaluate the effectiveness of 99mTc-MIBI (hexakis 2-methoxyisobutyl isonitrile) scintigraphy to differentiate malignant from benign lesions, detected on 99mTc-MDP planar bone scans. 59 patients with bony lesions were studied prospectively and compared with histopathology. Each patient underwent a 99mTc-MDP scan, and if evidence of lesion found, patient underwent 99mTc-MIBI scintigraphy after three to four days. 99mTc-MIBI scans were evaluated visually and quantitatively. For quantitative analysis count ratio of lesion to contralateral normal side (L/C) was taken and Student T test was applied.99mTc-MDP scans showed increase tracer uptake but no significant difference between benign and malignant uptake was seen. Significant difference (p value 0.015), was seen in malignant (L/C 3.51 ± 1.02) and benign lesions (L/C 2.50 ± 0.42) on 99mTc-MIBI scan. Three of thirty benign lesions did not show significant 99mTc-MIBI uptake. Six malignant lesions appeared as false negatives. Specificity of 99mTc-MIBI was 86.66%, Negative Predictive Value (NPV) 81.25% whereas the sensitivity was 79.31%.99mTc-MIBI scintigraphy provides its usefulness by distinguishing malignant from benign lesions along with correct identification of metastatic lesions. NPV points toward its ability to correctly diagnose the normal (benign) cases. However biopsy still remains the gold standard and a definitive diagnostic modality.