Abstract: Objective To explore the optimal b value in diffusion-weighted 3.0T MRI scanning to diagnose multiple myeloma.Methods Fifty patients with multiple myeloma by clinical diagnostic criteria and twenty healthy volunteers were enrolled into this study. Following routine MRI scanning, sensitivity for diagnosis of multiple myeloma with different b values diffusion-weighted image (DWI) was 95% on 3.0-T MR unit. The image quality with different b values was analyzed and compared qualitatively by three scales system and quantitatively by signal-to-noise ratio (SNR). Apparent diffusion coefficient (ADC) between the MM group and the normal group was also measured.Results The smaller the b value was, the better the DWI image quality would be. Mean SNR of images obtained with b value 50, 600 and 1 000 s/mm² were 22.28±14.40,11.85±7.78,7.57±4.72 respectively. The difference among them was statistically significant (F=19.523, P<0.01) There was no significant difference between the mean ADC values on DWI with b value 600 s/mm²[(1.52±0.81)×10^-3 mm²/s] and 1000s/mm²[(1.32±0.74)×10^-3 mm²/s] (P>0.05). The mean ADC values of the normal volunteers group[(0.28±0.11)×10^-3 mm²/s] were significantly lower than that of the MM group[(1.32±0.74)×10^-3mm²/s] on DWI with b value 600 s/mm² (P<0.01).Conclusion A b value about 600 s/mm² is recommended when diffusion-weighted MRI scanning is used to diagnose multiple myeloma at 3.0 T MRI.

Key words: multiple myeloma, magnetic resonance, diffusion-weighted image