Siemens syngo MR E11 Operator's Manual - Page 29

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MAGNETOM Family, Biograph mMR | syngo MR D11, syngo MR D13, syngo MR B19, syngo MR B20P,

syngo MR E11

Print No. MR-06020G.640.08.04.02

Image scale

Numerical values on a linear scale of 0 to 8 kilopascals (kPa) are repre

sented by a color scale ranging from violet to red, when using the

default window/level of the relative stiffness image. The scale defines

estimated tissue stiffness: very soft tissues in the 0-2 kPa range are

shown with a color range of violet to blue, whereas stiffer tissues above

4 kPa are depicted with colors ranging from green through yellow to

red.

The numerical values corresponding to the color scale are obtained by a

mathematical analysis of wave images with a locally homogeneous, lin

ear elastic model that represents tissue stiffness as directly proportional

to the square of the local wavelength. Since the local wavelength at a

given pixel is calculated from a region surrounding it, the stiffness esti

mate is most valid when the tissue is uniform for at least 1 cm in all

directions to avoid partial volume effects. The validity of the local stiff

ness estimate depends on the presence of waves of sufficient quality (as

indicated in the "Relative Stiffness Map 95 %" images). Other factors

that can affect the quality of the stiffness images are patient motion

during the acquisition, failure to place the passive driver in the recom

mended location for liver imaging, and failure to acquire liver imaging

data during end expiration.

This scale is meant to provide you with a guide to distinguish between

the stiffness variations of the tissue within each acquired image.

Wave Image

Before applying the Helmholtz equation, the phase difference images

are unwrapped. A least squares fit is applied to remove global displace

ments due to bulk motion, leaving just the shear waves. The unwrapped

and corrected wave displacements are displayed in this series.

In addition, two other result image types can be loaded from the

database.

Examination