[Quantitative comparison of diffusion weighted image in liver at two field strengths for chronic hepatitis B]

Objective: To evaluate whether there were differences between apparent diffusion coefficient (ADC) values derived from 3.0 T and 1.5 T MR diffusion-weighted imaging (DWI) in liver of patients with chronic hepatitis B. Methods: From January 2016 to November 2016, a total of 40 chronic hepatitis B prospectively underwent both 1.5 T and 3.0 T DWI before liver biopsy, the interval between two scans was within 15 minutes, the protocol was respiratory-triggered DWI(RT-DWI). The ADC values were measured at both field strengths using ROI method. Bland-Altman tests and paired t-tests were used to compare ADC values obtained at 1.5 T and 3.0 T. Results: The ADC values of different b values for patients with mild inflammation at 1.5 T were(1.22-1.48(1.35±0.08)×10(-3) mm(2)/s), the ADC values of different b values for patients with mild inflammation at 3.0 T were(1.18-1.45(1.30±0.08)×10(-3) mm(2)/s); the ADC values of different b values for patients with moderate to severe inflammation at 1.5 T were(1.11-1.37(1.25±0.06)×10(-3) mm(2)/s), the ADC values of different b values for patients with moderate to severe inflammation at 3.0 T were(1.08-1.31(1.20±0.06)×10(-3) mm(2)/s). There were significantly differences between the ADC values of different b values for patients with chronic hepatitis B obtained at two field strengths (P<0.01). Conclusions: Different field strengths have influence on ADC values in liver, the ADC values derived from 3.0 T are lower than the ADC values derived from 1.5 T.