Use of biexponential and stretched exponential models of intravoxel incoherent motion and dynamic contrast-enhanced magnetic resonance imaging to assess the proliferation of endometrial carcinoma

BACKGROUND: It is important to assess the proliferation of endometrial carcinoma (EC) noninvasively using imaging methods. This prospective diagnostic study investigated the value of biexponential and stretched exponential models of intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in predicting the Ki-67 status of EC. METHODS: In all, 70 patients with EC underwent pelvic MRI. The diffusion coefficient (D), pseudo diffusion coefficient (D*), perfusion fraction (f), distributed diffusion coefficient (DDC), water molecular diffusion heterogeneity index (α), volume transfer constant (K(trans)), rate transfer constant (K(ep)), and volume of extravascular extracellular space per unit volume of tissue (V(e)) were compared. The area under the receiver operating characteristic (ROC) curve (AUC) was used to quantify diagnostic efficacy. Multivariate logistic regression and bootstrap (1,000 samples) analyses were used to establish and evaluate, respectively, the optimal model to predict Ki-67 status. RESULTS: D, K(trans), and K(ep) were lower while α was higher in the high-proliferation group as compared with low-proliferation group (all P values<0.05). D and K(ep) were independent predictors of Ki-67 status in EC, and the combination of these parameters had optimal diagnostic efficacy (AUC =0.920; sensitivity 85.71%; specificity 89.29%), which was significantly better than that of D (AUC =0.753; Z=2.874; P=0.004), α (AUC =0.715; Z=3.505; P=0.001), K(trans) (AUC =0.808; Z=2.741; P=0.006), and K(ep) (AUC =0.832; Z=2.147; P=0.032) alone. The validation model showed good accuracy (AUC =0.882; 95% confidence interval 0.861–0.897) and consistency (C-statistic =0.902). D, K(ep), K(trans), and α showed a slightly negative (r=−0.271), moderately negative (r=−0.534), slightly negative (r=−0.409), and slightly positive (r=0.488) correlation with the Ki-67 index, respectively (all P values <0.05). CONCLUSIONS: IVIM- and DCE-MRI-derived parameters, including D, α, K(trans), and K(ep), were associated with Ki-67 status in EC, and the combination of D and K(ep) may serve as a superior imaging marker for the identification of low- and high-proliferation EC.