Differentiating between Recurrent Tumor & Post-Treatment Radiation Effects using High-Order Diffusion Imaging

Chu-Yu Lee¹, Leland Hu², Leslie C. Baxter³, Josef P. Debbins³

Resolving the regions of recurrent tumor from post-treatment radiation effects (PTRE) can be challenging, because both can appear enhancing on the contrast enhanced T1 imaging, as shown in Fig. 1a and 1e. Diffusion-weighted Imaging (DWI) was shown to correlate with tumor cellularity [1]. Recently, DWI with a higher b-value was found to have greater sensitivity to the changes in tumor cellularity [2, 3]. While the complications of treatment-bed changes involve tumor growth, radiation- and operation-induced lesions [4, 5], the intra-voxel diffusion heterogeneity measured by the high b-value DWI may be useful in differentiating between pathological mechanisms. In this study, two multiple b-value diffusion models: the stretched exponential model (α-DWI) [6] and diffusion kurtosis imaging (DKI) [7] were used to assess the recurrent tumor and the PTRE. Their fitted parameters: α and Kapp quantify the diffusion heterogeneity without information about the number of water compartments.