Abstract
In general, only one diffusion model would be applied to whole field-of-view voxels in the intravoxel incoherent motion-magnetic resonance imaging (IVIM-MRI) study. However, the choice of the applied diffusion model can significantly influence the estimated diffusion parameters. The quality of the diffusion analysis can influence the reliability of the perfusion analysis. This study proposed an optimal model mapping method to improve the reliability of the perfusion parameter estimation in the IVIM study. Six healthy volunteers (five males and one female; average age of 38.3 ± 7.5 years). Volunteers were examined using a 3.0 Tesla scanner. IVIM-MRI of the brain was applied at 17 b-values ranging from 0 to 2,500 s/mm2. The Gaussian model, the Kurtosis model, and the Gamma model were found to be optimal for the CSF, white matter (WM), and gray matter (GM), respectively. In the mean perfusion fraction (fp) analysis, the GM/WM ratios were 1.16 (Gaussian model), 1.80 (Kurtosis model), 1.94 (Gamma model), and 1.54 (Optimal model mapping); in the mean pseudo diffusion coefficient (D*) analysis, the GM/WM ratios were 1.18 (Gaussian model), 1.19 (Kurtosis model), 1.56 (Gamma model), and 1.24 (Optimal model mapping). With the optimal model mapping method, the estimated fp and D* were reliable compared with the conventional methods. In addition, the optimal model maps, the associated products of this method, may provide additional information for clinical diagnosis.
Highlights
The theory of intravoxel incoherent motion (IVIM) was first introduced to extend the understanding and usefulness of diffusion-weighted imaging (DWI) with the motion probing gradients (MPG) in the mid-1980s (Le Bihan et al, 1986, 1988)
In the D∗ maps, the gray matter (GM) values were generally higher than the white matter (WM) values
The results estimated by the Gaussian model (Figure 4E) were lower than those of the other two models (Figures 4F,G)
Summary
The theory of intravoxel incoherent motion (IVIM) was first introduced to extend the understanding and usefulness of diffusion-weighted imaging (DWI) with the motion probing gradients (MPG) in the mid-1980s (Le Bihan et al, 1986, 1988). The potential of IVIM-MRI to simultaneously determine perfusion and diffusion information has led to high expectations regarding clinical applications (Le Bihan and Turner, 1992; Paschoal et al, 2018). The feasibility of perfusion measurement with IVIM-MRI has been controversial for a long time. It has been challenging to estimate small blood volumes with a low signal-to-noise ratio (SNR) in IVIM-MRI. IVIM-MRI, especially in the brain, has not been thought to be practically feasible for performing perfusion measurements
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