Application of a Simplified Method for Estimating Perfusion Derived from Diffusion-Weighted MR Imaging in Glioma Grading

Abstract

Purpose: To evaluate the feasibility of a simplified method based on diffusion-weighted imaging (DWI) acquired with three b-values to measure tissue perfusion linked to microcirculation, to validate it against from perfusion-related parameters derived from intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced (DCE) magnetic resonance (MR) imaging, and to investigate its utility to differentiate low- from high-grade gliomas. Materials and Methods: The prospective study was approved by the local institutional review board and written informed consent was obtained from all patients. From May 2016 and May 2017, 50 patients confirmed with glioma were assessed with multi-b-value DWI and DCE MR imaging at 3.0 T. Besides conventional apparent diffusion coefficient (ADC_0,1000) map, perfusion-related parametric maps for IVIM-derived perfusion fraction (f) and pseudodiffusion coefficient (D*), DCE MR imaging-derived pharmacokinetic metrics, including K^trans, v_e and v_p, as well as a metric named simplified perfusion fraction (SPF), were generated. Correlation between perfusion-related parameters was analyzed by using the Spearman rank correlation. All imaging parameters were compared between the low-grade (n = 19) and high-grade (n = 31) groups by using the Mann-Whitney U test. The diagnostic performance for tumor grading was evaluated with receiver operating characteristic (ROC) analysis. Results: SPF showed strong correlation with IVIM-derived f and D* (ρ = 0.732 and 0.716, respectively; both P < 0.001). Compared with f, SPF was more correlated with DCE MR imaging-derived K^trans (ρ = 0.607; P < 0.001) and v_p (ρ = 0.397; P = 0.004). Among all parameters, SPF achieved the highest accuracy for differentiating low- from high-grade gliomas, with an area under the ROC curve value of 0.942, which was significantly higher than that of ADC_0,1000 (P = 0.004). By using SPF as a discriminative index, the diagnostic sensitivity and specificity were 87.1% and 94.7%, respectively, at the optimal cut-off value of 19.26%. Conclusion: The simplified method to measure tissue perfusion based on DWI by using three b-values may be helpful to differentiate low- from high-grade gliomas. SPF may serve as a valuable alternative to measure tumor perfusion in gliomas in a noninvasive, convenient and efficient way.

Keywords: diffusion-weighted MRI; dynamic contrast-enhanced MRI; glioma grading; glioma perfusion; intravoxel incoherent motion.

Figure 1

Scatterplot matrix of measured simplified perfusion fraction (SPF), intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced (DCE) MR imaging parameters. Spearman rank correlation (ρ) was included in each scatterplot with significant correlation marked with (*). Adjusted level of significance was set at P = 0.004 with Bonferroni correction for 12 comparisons.

Figure 2

Images obtained in a 67-year-old woman with oligodendroglioma (WHO grade II). (A) T2-weighted image shows a hyperintense lesion with massive edema in the right hemisphere. (B) ADC_0,1000 map shows increased apparent diffusion coefficient (ADC) value in the edema and slightly decreased ADC value in the corresponding area of the contrast-enhanced lesion as shown in (E). (C,D) IVIM f and SPF maps show relatively increased f and SPF values in the corresponding low-diffusion tumoral area compared with surrounding edema. (E) Contrast-enhanced T1-weighted image shows faint enhancement in the tumor. (F,G) DCE MR imaging parametric maps of K^trans and v_e show almost isointensity in the corresponding area of the contrast-enhanced lesion. (H) DCE MR imaging parametric map of v_p shows increased v_p value in the corresponding area of the contrast-enhanced lesion. Note that the tumoral hyperperfusion area on v_p map is consistent with the region on f and SPF maps. Round-shaped regions of interest are marked on parametric maps.

Figure 3

Images obtained in a 56-year-old man with glioblastoma (WHO grade IV). (A) T2-weighted image shows a heterogeneous hyperintense lesion in the left hemisphere. (B) ADC_0,1000 map shows markedly decreased ADC value in the lesion. (C,D) IVIM f and SPF maps show increased f and SPF values in the corresponding area of the contrast-enhanced lesion as shown in (E). (E) On contrast-enhanced T1-weighted image, a rim-enhanced mass with central necrotic changes is seen correspondingly. (F–H) DCE MR imaging parametric maps of K^trans, v_e and v_p show markedly increased values in the corresponding area of the contrast-enhanced lesion. When focusing on f and SPF maps, we can notice that the tumoral hyperperfusion area on SPF map is more visually obvious and more similar to that on DCE maps. Round-shaped regions of interest are marked on parametric maps.

Figure 4

Receiver operating characteristic (ROC) curves and corresponding area under the curve values for diffusion-weighted imaging (DWI) parameters (ADC_0,1000, SPF, f, D and D*) and DCE MR imaging parameters (K^trans, v_e and v_p) in the differentiation of low- and high-grade gliomas. SPF showed the highest diagnostic performance with the area under the curve value of 0.942.