Improving the differentiating of malignant tumors and benign lesions using 199t1-T1oride scintigraphy

Introduction. 199Tl-chloride scintigraphy is used for visualization of malignant tumors and benign lesions including inflammation. Differentiating of them is performed by permanent and independent retention index, but not always effective. Purpose: improve the differentiating of malignant tumors from benign lesions using 199Tl-chloride scintigraphy. Materials and methods. Results of 97 patients’ 199Tl-chloride scintigraphy with 119 regions of hyperfixation in malignant tumors (n=68) and benign lesions (n=51) were studied. Lesions were localized in musculoskeletal system (n=89), in lungs and mediastinum (n=25) and other organs (n=5). Results. Sensitivity, specificity, positive, negative predictive value and accuracy 199Tl-chloride scintigraphy in differentiating of malignancies from benign lesions were 75.0%, 86.3%, 58.1%, 93.2% and 84.0%, respectively using optimal value of permanent and independent retention index RI=0.89 (RI=DR/ER). Significant correlations between retention index (RI) and 199Tl-chloride hyperfixation in early phase of scintigraphy (ER) in group with malignancies (r=-0.70, p=0.00001) and benign lesions (r=-0.76, p=0.00001) were revealed. As a consequence, method for differentiating malignant tumors from benign lesions with optimal dependent relative retention index RI(relative)=RI+0.055-ER and cut-off value RI(relative)=0.98 4 was proposed (sensitivity, specificity, positive, negative predictive value and accuracy 199Tl-chloride scintigraphy in differentiating of malignancies from benign lesions were 83.8%, 86.3%, 73.8%, 92.0% and 85.5%, respectively). Statistically significant (p=0.01) improvement of efficiency of 199Tl-chloride scintigraphy diagnostics in differentiating of malignant tumors from benign lesions using relative retention index (RI(relative)) compared with independent retention index (RI) were revealed by ROC-analysis. Conclusion. The optimal value of permanent and independent retention index for differentiating of malignant tumors from benign lesions are RI=0.89. Efficiency of 199Tl-chloride scintigraphy diagnostic in differentiating of these processes improves using of relative retention index.