Objective To observe the variation of apparent diffusion coefficient(ADC) and sum up the feasibility of diffusion weighted imaging(DWI) after enhancement by employing the multi-b value model of liver DWI before and after injection of gadolinium-ethoxibenzyl-diethylene triaminepentaacetic acid(Gd-EOB-DTPA).

Methods Data from 126 patients with Gd-EOB-DTPA were collected. Among these patients, 30 had normal liver, 25 had liver cancer, 20 had metastatic carcinoma, 28 had hemangioma, and 23 had cysts, as confirmed by clinical and pathological examination. Philips Achieva 1.5T dual-gradient superconducting magnetic resonance scanner was used for in-phase, in-and-out phase T1 weighted breath hold axial scan, and axial respiratory gated DWI. 0.025 mmol/kg dose of Gd-EOB-DTPA was injected into the patients, temporal high resolution isotropic volume examination(THRIVE) and T1 weighted breath hold axial scan were conducted at arterial phase, venous phase and 3, 10, 20, and 30 min phases. Axial T2 weighted fat saturation respiratory gated scan was conducted at 5 min phase. Axial respiratory gated DWI was conducted at 15 min phase, followed by coronal T2 weighted breath hold scan. Axial respiratory gated DWI was conducted at 25 min phase. The plain, 15 min phase and 25 min phase scan had the same DWI parameter which was single-excitation spin echo-echo planar imaging sequence, the b value was 0, 50, 300, 600 s/mm², respectively, with a scan time of 196 s. The b=50, 300, and 600 s/mm² ADC diagram of plain scan, 15 and 25 min scan were generated on an EWS workstation by ADC analysis function. The ADC values of normal liver, liver cancer, metastasis, hemangioma, and cyst were measured. At the same b values, the ADC values of the same type of disease were statistically analyzed by t test at plain scan, 15 and 25 min scan.

Results For the same b value and disease, the ADC values of the plain scan were the largest. The ADC values began to decrease and finally increase with the injection of Gd-EOB-DTPA. These values at the 25 min scan were consistent with the result of the plain scan, and the 15 min scan were the lowest. The ADC values had no significant difference in the plain scan, 15 min scan and 25 min scan(t=0.25~1.29, all P>0.05). For the DWI of the same disease and phase, the b value increased and the ADC values decreased; the smaller the b value, the greater the ADC values. Conclusion After intravenous injection of Gd-EOB-DTPA, the decrease of the ADC values in the liver was minimal, and DWI was feasible after enhancement.