MR Parameter Estimation in MEDx

MR Parameter Estimation is a specialized ImageScript script included with the current release of MEDx, version 3.4.3. It estimates relaxation and diffusion parameters from various MR acquisition schemes.

Summary

Estimates of MR parameters T1-relaxation, T2-relaxation and Apparent Diffusion Coefficient (ADC) can be useful for differentiating physical tissue characteristics in MRI data. Different tissue types have characteristic T1 and T2 values. Values outside the normal range for a given tissue type may indicate pathology. True T1 and T2 maps also yield better tissue segmentation than T1 or T2-weighted images.

Calculated ADC maps from diffusion weighted images estimate the diffusion coefficient of water at each voxel. These maps can be useful for identifying tissue at risk after stroke.

Chi-square (x2) maps measure goodness of fit of the model to (inversion, saturation or multi-echo) data.

Output

T2, Proton Density, x2 (chi-square)
T1, Proton Density, % Inversion, x2
T1, Proton Density, x2
ADC

Graphical User Interface

Simple graphic user interface helps guide the user through map creation while adhering to MEDx interface design.

Estimation Methods

T2 values are estimated via linear least squares fits to multi-echo data. ADC values are calculated from two diffusion-weighted acquisitions. T1 values are estimated via non-linear fitting to either inversion recovery or saturation recovery data.

Models

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