Radiologists' Rating for Comparative Qualitative Assessment of Intravoxel Incoherent Motion Using Novel Analysis Methods

Abstract

Objective The objective was to assess qualitative interpretability and quantitative precision and reproducibility of intravoxel incoherent motion (IVIM) parametric images evaluated using novel IVIM analysis methods for diagnostic accuracy. Methods Intravoxel incoherent motion datasets of 55 patients (male/female = 41:14; age = 17.8 ± 5.5 years) with histopathology-proven osteosarcoma were analyzed. Intravoxel incoherent motion parameters—diffusion coefficient (D), perfusion fraction (f), and perfusion coefficient (D*)—were estimated using 5 IVIM analysis methods—(i) biexponential (BE) model, (ii) BE-segmented fitting 2-parameter (BESeg-2), (iii) BE-segmented fitting 1-parameter (BESeg-1), (iv) BE model with total variation penalty function (BE + TV), and (v) BE model with Huber penalty function (BE + HPF). Qualitative scoring in a 5-point Likert scale (uninterpretable: 1; poor: 2; fair: 3; good: 4; excellent: 5) was performed by 2 radiologists for 4 criteria: (a) tumor shape and margin, (b) morphologic correlation, (c) noise suppression, and (d) overall interpretability. Interobserver agreement was evaluated using Spearman rank-order correlation (r s). Precision and reproducibility were evaluated using within-subject coefficient of variation (wCV) and between-subject coefficient of variation (bCV). Results BE + TV and BE + HPF produced significantly (P < 10−3) higher qualitative scores for D (fair–good [3.3–3.8]) than BE (poor [2.3]) and for D* (poor–fair [2.2–2.7]) and f (fair–good [3.2–3.8]) than BE, BESeg-2, and BESeg-1 (D*: uninterpretable–poor [1.3–1.9] and f: poor–fair [1.5–3]). Interobserver agreement for qualitative scoring was r s = 0.48–0.59, P < 0.009. BE + TV and BE + HPF showed significantly (P < 0.05) improved reproducibility in estimating D (wCV: 24%–31%, bCV: 21%–31% improvement) than the BE method and D* (wCV: 4%–19%, bCV: 5%–19% improvement) and f (wCV: 25%–49%, bCV: 25%–47% improvement) than BE, BESeg-2, and BESeg-1 methods. Conclusions BE + TV and BE + HPF demonstrated qualitatively and quantitatively improved IVIM parameter estimation and may be considered for clinical use further.