Reproducibility of measurement of apparent diffusion coefficients of malignant hepatic tumors: Effect of DWI techniques and calculation methods

Purpose: To evaluate the effect of diffusion‐weighted imaging (DWI) methods, apparent diffusion coefficient (ADC) calculation methods, and selection of b‐values on the ADCs and the measurement reproducibility of malignant hepatic tumors. Materials and Methods: Nineteen patients with pathologically confirmed malignant hepatic tumors underwent breath‐hold DWI (b‐values = 0, 50, 500 s/mm2) and respiratory‐triggered DWI (0, 50, 300, 500, 1000 s/mm2) twice on a 1.5 T magnetic resonance imaging (MRI) scanner. ADCs were calculated using a two b‐value and/or a multiple b‐value method. The reproducibility of the ADC measurements was evaluated from the intraclass correlation coefficients (ICCs) and the 95% Bland–Altman limit‐of‐agreement (LOA). Results: The ADCs were different according to the DWI methods (P = 0.040–0.282), ADC calculation methods (P = 0.003–0.825), and the choice of b‐values (P < 0.001). The ADC tended to be more reproducible with use of breath‐hold DWI (ICC: 0.898–0.933; LOA, 18.8%–24.0%) than respiratory‐triggered DWI (ICC: 0.684–0.928; LOA, 15.0%–31.9%) (P = 0.008–0.122). For respiratory‐triggered DWI, the multiple b‐value method using five b‐values had better reproducibility than the two b‐value method for measurement of ADC (P = 0.009–0.221). Conclusion: The DWI method, ADC calculation method, and selection of b‐values potentially influence the ADCs and the reproducibility of malignant hepatic tumors. ADCs calculated from breath‐hold DWI are more reproducible than from respiratory‐triggered DWI. A multiple b‐value method may improve the reproducibility of respiratory‐triggered DWI. J. Magn. Reson. Imaging 2012;36:1131–1138. © 2012 Wiley Periodicals, Inc.