Opposed Phase Imaging as a Diagnostic Biomarker for Differentiating Malignant from Benign Bone Marrow Lesions

Abstract

Background: The real dilemma in diagnosing osseous lesions, is that benign or even nonneoplastic marrow lesions can demonstrate signal changes similar to malignant lesions. Consequently, biopsy is often demanded for conclusive diagnosis. Hence, the advancement of strong objective methods, such as quantitative biomarkers, is vital clinically for characterization and the follow-up of any bone marrow lesion.Opposed phase imaging is an example of MR quantitative biomarker technique, being able to detect microscopic fat, and characterizing any marrow lesion based on the amount of fatty marrow infiltrated or preserved. Aim of Study:To assess the diagnostic efficiency of opposed phase MR imaging and signal intensity ration (SIR) in differentiating as well as characterizing benign and malignant bone marrow lesion, by setting an optimal cut-off value.Patients and Methods: This was a prospective noncontrolled randomized study, including 65 patients (35 men and 30 women, mean age 32 years old), with focal bone marrow lesions. All lesions were studied by conventional, contrast enhanced and opposed phase MR imaging. Chemical shift imaging was carried out by axial in-phase [repetition time (TR), 500ms; echo time (TE), 4.6ms; flip angle, 80 °] and out of-phase (TR, 500 ms, TE, 2.3ms, flip angle, 80 °). Signal intensity ratio (SIR) was calculated by dividing the out of-phase signal intensity on the in-phase signal intensity.Results: There was a significant difference ( p<0.001, independent t-test) in the mean SIR for the benign lesions (mean, 0.59; SD, 0.28) compared with the malignant lesions (mean, 0.99; SD, 0.08). ROC analysis yielded optimal cut off values at >0.93 correctly differentiating malignant from benign lesions (sensitivity, 94.7%; specificity, 86.6%), area under the curve (AUC, 0.888), (positive predictive value, 81.8%), (negative predictive value, 96.3%) and (95% confidence interval, 0.765-0.960).Conclusion: SIR values calculated from opposed phase imaging is a useful diagnostic biomarker for quantitative differentiation of benign from malignant bone marrow lesions, SIR in malignant lesions were higher than benign lesion, with a value of 0.93 can be used as a cut off to differentiate both entities.