Purpose

As one novel Diffusion weighted imaging (DWI) model, fractional order calculus (FROC) can offer a set of new parameters to assess not only the diffusion process itself but also intravoxel tissue structure, which provides new potential for noninvasive tumor assessment. This study aimed to evaluate the feasibility of utilizing a new set of imaging parameters (D, β and μ) obtained from FROC diffusion model to diagnose salivary gland tumors.

Materials and Methods

All participants in this prospective institutional review board approved this study and provided written informed consent. Fifteen b value (0–2000 sec/mm2) DWI was performed in 62 patients with salivary gland tumors. Diffusion coefficient D, fractional order parameter, β, (which correlates with tissue heterogeneity), and a microstructural quantity, μ, were calculated by fitting the multi-b-value DWI to a FROC model. D, β and μ were measured in the solid portion, as well as in normal appearing salivary gland as a control. These FROC parameters were compared between benign and malignant salivary gland tumors, and among pleomorphic adenoma (PA), Warthin tumors (WT), and malignant tumors (MT). The performance of FROC parameters for differentiation among different patients groups was assessed by using receiver operating characteristic analysis.

Results

A total of 47 benign and 15 malignant salivary gland tumors were enrolled in this study. None of the FROC parameters exhibited significant differences in the normal salivary gland (D, p = 0.883; β, p = 0.141; μ = 0.667) and in the tumors between benign and malignant group (D, p = 0.150; β, p = 0.967; μ = 0.693). WT showed significantly lower D (p < 0.001) and β (p < 0.001), while higher μ (p = 0.001) than PA. The combination of D, β and μ showed optimal diagnostic performance during this group of differentiation (AUC, 0.998). MT tumors showed significantly lower D (p = 0.001) and β (p = 0.025) than PA, while no significant difference was found on μ (p = 0.064). The combination of D and β showed optimal diagnostic performance during this group of differentiation (AUC, 0.933). Significant difference was only found on β (p = 0.027) between MT and WT, while not found on D (p = 0.806) and μ (p = 0.789). Setting a β value of 0.615 as the cut-off value, optimal diagnostic performance could be obtained (AUC = 0.806).

Conclusion

A non-Gaussian FROC diffusion parameters can serve as a noninvasive and quantitative imaging markers for differentiating salivary gland tumors.

Acknowledgements

No acknowledgement found.