Objective To investigate the diagnostic value of proton density fat fraction (PDFF) and in phase and out of phase imaging (OP/IP) for thoracic and lumbar multiple myeloma bone disease (MMBD). Methods All patients underwent spinal MRI, including sagittal T1WI, sagittal STIR, sagittal mDxion quant and sagittal mDxion FFE. The normal vertebrae and benign lesion vertebrae were non-MMBD lesion group, and the MMBD lesion vertebrae was MMBD lesion group, and the PDFF and OP/IP value were measured

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... ctively. Two independent sample t-tests were performed, and the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic performance of the two parameters for MMBD; the Pearson test was used to analyze the correlation between the two parameters. The diagnostic cutoff value of OP/IP and PDFF were calculated by Youden index method. Results The PDFF of the MMBD lesion group was lower while the OP/IP was higher than those of the non-MMBD lesion group (both P < 0.05). The diagnostic cutoff values, the area under the ROC curve (AUC), the sensitivity, the specificity of PDFF and OP/IP were 8.45% and 0.66, 0.969 and 0.922, 96.64% and 85.71%, 96.35% and 90.41%, respectively. The difference in AUC between two groups was statistically significant (P=0.007). MMBD was moderately negatively correlated with OP/IP. Conclusion PDFF and OP/IP have certain value for the diagnosis of MMBD. The diagnostic performance of PDFF is better than OP/IP.