Objective:To explore the diagnostic efficacy and clinical value of the signal ratio of MRI conventional sequences and the apparent diffusion coefficient(ADC)value in multiple myeloma(MM).Methods:35 patients with newly diagnosed MM and 43 normal controls were recruited.Lumbar MRI conventional sequences(T1 WI,T2WI,SPAIR)and DWI scans were performed.The differ-ences in sequence signal ratios and ADC values between MM(including subgroups of MM at different stages)and the normal control group were compared.Sensitivity and specificity were analyzed using ROC curves.The ADC cutoff value was obtained.The differences in the area under the ROC curves were compared.Results:The T1 WI signal ratio of the MM group was lower than that of the normal control group(P＜0.01),with the sensitivity and specificity of 0.97 and 0.93 respectively.The SPAIR signal ratio was higher than that of the normal control group(P＜0.01),with the sensitivity and specificity of 0.68 and 0.97 respectively.The ADC value was higher than that of the normal control group(P＜0.05),with the sensitivity and specificity of 0.93 and 0.95 respectively.The ADC cutoff value was 0.52(×10-3mm2/s).The area under the ROC curve(AUC)was:ADC value＞T1WI signal ratio＞SPAIR signal ratio.Pairwise analysis of AUC showed that there was no statistically significant difference between the T1WI signal ratio and the ADC value(P＞0.05),and both had the same evaluation efficacy,which was superior to that of the SPAIR signal ratio,and the difference was statistically significant(P＜0.05).Conclusion:The T1 WI signal ratio and ADC value have high sensitivity and specificity,and their diagnostic efficacy is better than that of the SPAIR signal ratio.There is a significant difference when the ADC value is higher than 0.52.The combined application of T1WI and ADC value is conducive to the diagnosis of MM.