Accurate IVIM model-based liver lesion characterisation can be achieved with only three b-value DWI

Objective The objective of this study was to evaluate a simplified intravoxel incoherent motion (IVIM) approach of diffusion-weighted imaging (DWI) with four b-values for liver lesion characterisation at 1.5 T. Methods DWI data from a respiratory-gated MRI sequence with b = 0, 50, 250, 800 s/mm 2 were retrospectively analysed in 173 lesions and 40 healthy livers. The apparent diffusion coefficient ADC = ADC(0,800) and IVIM-based parameters D 1 ′ = ADC(50,800), D 2 ′ =ADC(250,800), f 1 ′, f 2 ′, D*′, ADC low = ADC(0,50), and ADC diff =ADC low -D 2 ′ were calculated voxel-wise without fitting procedures. Differences between lesion groups were investigated. Results Focal nodular hyperplasias were best discriminated from all other lesions by f 1 ′ with an area under the curve (AUC) of 0.989. Haemangiomas were best discriminated by D 1 ′ (AUC of 0.994). For discrimination between malignant and benign lesions, ADC(0,800) and D 1 ′ were best suited (AUC of 0.915 and 0.858, respectively). Discriminatory power was further increased by using a combination of D 1 ′ and f 1 ′. Conclusion IVIM parameters D and f approximated from three b-values provided more discriminatory power between liver lesions than ADC determined from two b-values. The use of b = 0, 50, 800 s/mm 2 was superior to that of b = 0, 250, 800 s/mm 2 . The acquisition of four instead of three b-values has no further benefit for lesion characterisation. Key Points • Diffusion and perfusion characteristics are assessable with only three b-values . • Association of b = 0, 50, 800 s/mm 2 is superior to b = 0, 250, 800 s/mm 2 . • A fourth acquired b-value has no benefit for differential diagnosis . • For liver lesion characterisation, simplified IVIM analysis is superior to ADC determination . • Simplified IVIM approach guarantees numerically stable, voxel-wise results and short acquisition times .