Comparison between Intravoxel Incoherent Motion and Splenic Volumetry to Predict Hepatic Fibrosis Staging in Preoperative Patients

Abstract

Intravoxel incoherent motion (IVIM) and splenic volumetry (SV) for hepatic fibrosis (HF) prediction have been reported to be effective. Our purpose is to compare the HF prediction of IVIM and SV in 67 patients with pathologically staged HF. SV was divided by body surface area (BSA). IVIM indices, such as slow diffusion-coefficient related to molecular diffusion (D), fast diffusion-coefficient related to perfusion in microvessels (D*), apparent diffusion-coefficient (ADC), and perfusion related diffusion-fraction (f), were calculated by two observers (R1/R2). D (p = 0.718 for R1, p = 0.087 for R2) and D* (p = 0.513, p = 0.708, respectively) showed a poor correlation with HF. ADC (p = 0.034, p = 0.528, respectively) and f (p < 0.001, p = 0.007, respectively) decreased as HF progressed, whereas SV/BSA increased (p = 0.015 for R1). The AUCs of SV/BSA (0.649-0.698 for R1) were higher than those of f (0.575-0.683 for R1 + R2) for severe HF (≥F3-4 and ≥F4), although AUCs of f (0.705-0.790 for R1 + R2) were higher than those of SV/BSA (0.628 for R1) for mild or no HF (≤F0-1). No significant differences to identify HF were observed between IVIM and SV/BSA. SV/BSA allows a higher estimation for evaluating severe HF than IVIM. IVIM is more suitable than SV/BSA for the assessment of mild or no HF.

Keywords: computed tomography (CT); diffusion-weighted imaging; hepatic fibrosis; intravoxel incoherent motion; magnetic resonance imaging (MRI).

Figure 1

Intravoxel incoherent motion measurement. By measuring three regions of the liver (anterior and posterior segments of the right lobe and lateral segment of the left lobe), IVIM parameters were measured in this patient (F1). This case showed images with an ROI placed in the anterior region of the right lobe of the liver. A model of signal strength variation in IVIM analysis was made from Synapse Vincent software. White line is actual data obtained. Red line is the IVIM nonlinear regression fit providing slow diffusion-coefficient related to molecular diffusion (true diffusion-coefficient) as D, fast diffusion-coefficient related to perfusion in micro-vessels (pseudodiffusion-coefficient) as D*. Yellow line is the monoexponential fit providing apparent diffusion-coefficient (ADC).

Figure 2

Three-dimensional reconstruction image of the spleen. Splenic hilum view; The volume of the spleen was 74 mL in this patient (F1).

Figure 3

Patient flowchart. A total of 88 patients with liver surgery received both IVIM of MRI and liver dynamic CT. Twenty patients with image deficiency and long intervals between IVIM and surgery were excluded. One of the remaining 68 patients was excluded from the study because he had a splenectomy. Finally, 67 patients were included in the study.

Figure 4

Box-and-whisker diagrams for each parameter measurement. Box-and-whisker diagrams for each parameter measurement of IVIM and SV/BSA were shown. R1, Observer 1; R2, Observer 2; D, molecular diffusion; D*, fast diffusion-coefficient related to perfusion in microvessels; ADC, apparent diffusion-coefficient; f, perfusion-related diffusion fraction; SV/BSA, ratio of splenic volume to body surface area; F grade, hepatic fibrotic grade.