Investigation of the optimal b-value to detect breast tumors with diffusion weighted imaging by 1.5-T MRI

BACKGROUND: Previous studies have reported that the signal attenuation of diffusion-weighted magnetic resonance imaging (DWI) for normal breast tissue and tumor were well fitted by a monoexponential and a biexponential function, respectively. The aim of this study was to investigate the optimal b-value to detect breast tumors from DWI signal attenuations. METHODS: Sixty-four subjects with breast cancer underwent DWI using six b-values up to 3500 s/mm(2). The signal attenuations of normal breast and tumor were fitted by mono- and biexponential functions, respectively. The maximum contrast b-values were estimated and compared in terms of frequency. RESULTS: In almost all cases, the contrast increased with a b-value from 0 to approximately 1500 s/mm(2). For b > 1500 s/mm(2), the contrast decreased. The highest contrast b-value in the range of 0 to 2500 s/mm(2) most frequently was b = 1500 and the next most frequent was 1400 s/mm(2). Comparing sensitivity and specificity between b = 700 and b = 1400 s/mm(2), b =1400 s/mm(2) was slightly superior. CONCLUSION: Based on these results, DWI with a b-value of approximately 1400-1500 s/mm(2) is recommended for optimizing breast tumor detectability.