Background and Purpose
Imaging-based tumor grading is highly desirable, but faces challenges in sensitivity, specificity, or diagnostic accuracy. A recently proposed diffusion imaging method using a fractional order calculus (FROC) model offers a set of new parameters to probe not only the diffusion process itself, but also intra-voxel tissue structures, providing new opportunities for non-invasive tumor grading. This study aims at demonstrating the feasibility of using the FROC model to differentiate low- from high-grade gliomas in adult patients and illustrating its improved performance over a conventional diffusion imaging method employing ADC (or D).
Materials and Methods
With approval from the institutional review board (IRB) and written informed consents from all participating patients, 54 adult patients (18–70 years old) with histology-proven gliomas were enrolled and divided into a low-grade (n = 24) and a high-grade group (n = 30). Multi-b-value diffusion MRI was acquired with 17 b-values (0–4000s/mm2) and analyzed using a FROC model. Mean values and standard deviations of three FROC parameters (D, β, and μ) were calculated from the normal contralateral thalamus (NCTH; as control) and the tumors, respectively. Based on these values, the low- and high-grade glioma groups were compared using a Mann-Whitney U-test. Receiver operating characteristic (ROC) analysis was performed to assess the performance of individual parameters as well as the combination of multiple parameters for low- versus high-grade differentiation.
Results
Each of the three FROC parameters exhibited a statistically higher value (p ≤ 0.011) in the low-grade than in the high-grade gliomas, whereas there was no difference in the NCTH (p ≥ 0.706). The ROC analysis showed that β (AUC = 0.853) produced a higher AUC than D (0.781) or μ (0.703), and offered a sensitivity of 87.5%, specificity of 76.7%, and diagnostic accuracy of 82.1%.
Conclusion
The study has demonstrated the feasibility of using a non-Gaussian FROC diffusion model to differentiate low- and high-grade gliomas. While all three FROC parameters showed statistically significant differences between the two groups, β exhibited better performance than the other two parameters, including ADC (or D).