Table 1 Definitions of the muscle perfusion variables (DCE-MRI)

Highly Perfused Voxels

Nvoxel

The number of voxels with “plateau” or “washout” enhancement patterns, i.e. the highest perfused voxels, the most perfused tissue.

Proportion of Highly Perfused Voxels (%)

Nvoxel%

The proportion of highly perfused voxels reaching either a “plateau” or “washout” enhancement pattern (Nvoxel) in percentage of the total number of voxels within the VOI.

Initial Rate of Enhancement

IRE

The upslope on the Time intensity curve measured as the mean relative increase in signal intensity per second from enhancement onset until ME is reached(%/s). A surrogate of the degree of perfusion.

Maximal Enhancement

ME

The highest mean signal intensity value relative to the baseline intensity. A surrogate of the degree of perfusion.

Initial Rate of Enhancement Composite Score

IRExNvoxel

The mean relative increase in signal intensity per second (%/s) (IRE) multiplied by the number of highly perfused voxels (Nvoxel). The variable becomes a composite parameter reflecting both the volume (voxels) and the degree of perfusion.

Initial Rate of Enhancement Index

IRExNvoxel%

The mean relative increase in signal intensity per second (%/s) (IRE) multiplied by the proportion of highly perfused voxels (Nvoxel%).

Maximal Enhancement Composite Score

MExNvoxel

The highest mean signal intensity value relative to the baseline intensity (ME) multiplied by the number Highly Perfused Voxels. The variable becomes a composite parameter reflecting both the volume (voxels) and the degree of perfusion.

Maximal Enhancement index

MExNvoxel%

The highest mean signal intensity value relative to the baseline intensity (ME) multiplied by the Proportion of Highly Perfused Voxels.