Diffusion-weighted imaging and variable flip angle T1 mapping: a supplement for image-guided biopsy in follow-up analysis of liver fibrosis

Purpose To evaluate the performance of diffusion-weighted imaging (DWI) and variable flip angle (VFA) T1 mapping as a supplement to image-guided biopsy in follow-up analysis of liver fibrosis.Materials and Methods This prospective study was approved by the institution’s committee on human research, and written informed consent was provided from the enrolled patients. We investigated five MRI parameters of DWI and VFA T1 mapping, collected from 11 patients who underwent serial ultrasound image-guided biopsy with follow-up MRI within 1.5 years after treatment for liver fibrosis/cirrhosis. For each patient, four consecutive MRI examinations were conducted, including baseline MRI before treatment and three follow-up MRI examinations after treatment at each 0.5-year interval. ADC values at four b values and T1 relaxation times were correlated to pathology-confirmed liver fibrosis stages, which were subsequently divided into two groups, stages F2–3 and F4. The receiver operating characteristic (ROC) analysis and repeated measurement analysis of variance were used for statistical analysis.Results Among these ADC parameters, ADC value (b = 500 s/mm2) was the most consistent in differentiating between stage F2–3 and F4 liver fibrosis. Repeated measurement analysis showed that the intra-group and inter-group differences were 0.447 and 0.024, respectively. T1 relaxation time could not consistently differentiate between the F2–3 and F4 groups; however, it was repeatable, and the intra-group and inter-group differences were 0.410 and 0.042, respectively.Conclusion MRI-ADC value at a b value of 500 s/mm2 can be a promising biomarker for differentiating stages F2–3 and F4 liver fibrosis. A combination of this biomarker with repeatable T1 relaxation time may function as a non-invasive tool for follow-up liver fibrosis in patients who reject repeated image-guided biopsy. Keywords: image-guided biopsy, MRI T1 mapping, diffusion-weighted imaging