Object ID: 00000018WIA30E12970GYZ
Topic ID: id_40025651 Version: 1.3
Date: May 26, 2022 2:02:08 AM

MSDE

MSDE (Motion Sensitized Driven Equilibrium) is a spin echo-based diffusion weighted imaging option played out once per shot to suppress flow in the volume. It ends with a tip-up pulse to return the magnetization to the longitudinal axis (driven equilibrium). MSDE is compatible with Cube.

Use the MSDE Imaging Option for the following:

Blood flow suppression to see the vessel wall.
T1 contrast for segmentation of plaque necrotic core, fibrous cap and hemorrhage.
Fat suppression to distinguish plaque from fat.

Figure 1. Carotid vessel wall image comparison

Table 1. Image legend
Rows	Left column	Middle column	Right column
1 = 3DTOF 2 = Cube 3 = Cube with MSDE (Vessel T1)	Right CCA bifurcation Sagittal reformat	Left CCA bifurcation Sagittal reformat	CCA bifurcation Axial reformat

Consider the comparison of MP-RAGE and Cube with MSDE for T1-weighted acquisitions.

Table 2. MSDE with Cube compared to MP-RAGE for T1-weighted images
PSD	Advantage	Disadvantage
MP-RAGE	High T1 contrast T1 dependent blood suppression	Longer scan time Difficult to adjust T1 and waiting time Incompatible with contrast agents
3D Cube with MSDE	Short scan time Higher SNR Flow dependent blood suppression	Lower T1 contrast

Consider not using MSDE in locally restricted B0 inhomogeneous regions (for example nasal cavity) due to signal suppression.

Figure 2. Images of in locally restricted B0 inhomogeneous regions

Table 3. Image legend
Number	Description
1	MSDE Off and Fast Recovery On.
2	MSDE On and Fast Recovery Off. Note the signal loss.

Imaging Options

Scan time can be reduced with HyperSense.

Fast Recovery controls CSF signal. De-select Fast recovery to increase signal from CSF.

Figure 3. Images with Fast Recovery on and off

Table 4. Image legend
Number	Description
1	Cube with MSDE and Fast Recovery OnCV22 = 3, CV29 = 1
2	Cube with MSDE and Fast Recovery Off CV22= 3, CV29= 1 By turning off Fast Recovery, contrast between vessel wall and vessel lumen became high. On the other hand, contrast between white matter, gray matter and CSF became low.

SAT pulses

Fat Saturation is recommended to reduce fat signal related artifact (for example, ringing artifact or motion artifact).

Figure 4. Cube and MSDE with and without fat saturation

Table 5. Image legend
Number	Description
1	Cube and MSDE without fat saturation. Note the ringing artifact from surface fat.
2	Cube and MSDE with fat saturation. Ringing artifact is eliminated.

MSDE tab

There are two selections from the MSDE tab:

Velocity Suppress Target (VEST)

Range is from 2-10 cm/s.
It is inversely proportional to the gradient strength.

A lower value is optimum for slow blood flow suppression with the tradeoff of lower SNR and suppressed CSF. Typically, use 2cm/s for brain and carotid scans. To avoid CSF flow suppression, a faster value should be selected.

MSDE Directions
- R/L, A/P, S/I, ALL
- Select the value in the direction that matches most of the flow. If most of the vessels are randomly distributed, select ALL.

Table 6. Vest image comparison
Left images	Right images
VEST=2cm/s MSDE Direction=ALL	VEST=10cm/s MSDE Direction=SI
Pros (+) of low VEST: Slow blood flow suppression (green) Cons (-) of low VEST: CSF is suppressed if it flows (red)

Advanced User CV tab and Fast Recovery Imaging Option

CV22 Cube Enhance
- Select 3 when acquiring brain T1-weighted images.
CV29 SAR optimization
- The MSDE RF pulse increases SAR. Select CV29 = 1 to reduce TR.

MSDE Annotation

It appears on the image in the lower left corner.
Figure 7. MSDE Imaging Option
It is on the Series Text page.
Figure 8. Series text page
The MSDE Direction appear in the upper left corner
Figure 9. Example of: VS and MSDE direction
The Velocity Suppress Target (VS) value is written to DICOM.
Figure 10. Phase contrast DICOM tags used for MSDE