Figure 1.
T2-weighted fat-suppressed fast-spin-echo anatomical images.
Regions of interest (ROIs) were drawn on primary tumors of nasopharyngeal carcinoma (NPC), metastatic node, spinal cord and muscle and labeled as one to four respectively.
Figure 2.
The measured DWI signals and the best-fit curves within the primary tumor (a), metastatic node (b), spinal cord (c) and muscle (d) according to the mono-exponential and non-Gaussian diffusion models.
The measured DWI signals showed substantial non-Gaussian diffusion behaviors and could be significantly better fitted by non-Gaussian models.
Figure 3.
Maps of the mono-exponential apparent diffusion coefficient (ADC) and non-Gaussian parameters (goodness of fit R2>0.8) for the primary tumor overlaid on the DWI image with b = 0.
Figure 4.
The maps of the mono-exponential apparent diffusion coefficient (ADC) and non-Gaussian parameters (goodness of fit R2>0.8) for the metastatic node overlaid on the DWI image with b = 0.
Figure 5.
The histograms of the extracted voxel-wise diffusion coefficients based on the mono-exponential model (a), diffusion kurtosis model (b), intravoxel incoherent motion (c), stretched exponential model (d) and statistical diffusion model (e) from each model, i.e. Dmono, DDKI, DIVIM, DSEM and DSDM, within the ROIs of the primary tumor in Fig. 3.
Non-Gaussian diffusion coefficients show differences from the mono-exponential ADC in value and distribution pattern. Note that the fitted values around zero for the statistical model were excluded in (e) for better visualization.
Figure 6.
The histograms of the extracted voxel-wise diffusion coefficients based on the mono-exponential model (a), diffusion kurtosis model (b), intravoxel incoherent motion (c), stretched exponential model (d) and statistical diffusion model (e) from each model, i.e. Dmono, DDKI, DIVIM, DSEM and DSDM, within the ROIs of the metastatic node in Fig. 4.
Note that the fitted values around zero for the statistical model were excluded in (e) for better visualization.
Table 1.
The statistics of the extracted mono-exponential ADC and non-Gaussian parameters for primary tumors and metastatic nodes.