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Take advantage of mDIXON TSE in MSK imaging without time penalty

Application Tip
van Meel, Marius Philips Healthcare • Netherlands
Elanchezhian, Vijayasarathy, B.Sc. Philips Healthcare • Netherlands

mDIXON provides excellent fat suppression and can save time
by providing images with and without fat suppression in one scan

Philips mDIXON provides images with and without fat suppression in a time efficient manner. The patented 2-echo implementation, versus conventional 3-point techniques, is key to delivering superb fat suppression at routine scan times.

 

 

The fast and robust fat suppression provided by mDIXON TSE makes the method well suited for enhancing routine musculoskeletal (MSK) MR imaging. These tips are intended to help you implement mDIXON TSE in your MSK protocols and ExamCards.
 

Tip 1: Choose a good starting point

Use a fat suppressed protocol as starting point. Choose a protocol in which SNR, resolution and scan time are already well balanced for your purpose.
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Tip 2: Contrast adjustments

mDIXON TSE is compatible with all common profile orders, however protocol optimization is easiest with an asymmetric profile order as it gives full control over TE, TR, BW and echo spacing.
 
On the Contrast tab, set ‘profile order’ to asymmetric. TE and TR may be adjusted according to your preference. Use a TR range for convenience. The table provides some recommended settings.

Click on picture to enlarge
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Tip 3: Switch on mDIXON

On the Contrast tab:

  • Set ‘Fat suppression’ to No to switch off SPIR or SPAIR.
  • Set ‘mDIXON’ to yes.
  • If volume shim is present, set to Auto to reduce workflow steps.
  • Set ‘WFS’ to user defined, select 1.3 (pixels).
 <br>Scan time first increases by switching on mDIXON

Scan time first increases by switching on mDIXON

Tip 4: Adjust NSA to balance scan time and SNR

mDIXON uses 2 echoes (2-point mDIXON) to calculate the inphase (IP) and water (W) images. This effectively doubles scan time but also increases the signal-to-noise ratio, similar to doubling NSA which doubles scan time and increases SNR by 41% (factor √2).

 

After switching to mDIXON, the easiest way to revert to the original scan time is by reducing NSA on the Motion tab to use less averages. If a scan has only 1 NSA, use SENSE to reduce scan time

 <br> Scan time reduces again by changing NSA

Scan time reduces again by changing NSA

Tip 5: Adjusting to partial fat suppression

Specifically in MSK imaging, some radiologists prefer a partial fat suppression. This is easy to obtain with mDIXON. 

 

To achieve this, also the fat (F) images need to be reconstructed. On the Postproc tab, expand the parameter ‘mDIXON images’ and add the fat image



When the mDIXON scan is finished:

  • Load the scan into the ‘Image Algebra’ post processing package.

  • Choose Addition: (A+B).

  • In viewport A (lower left) scroll to the fat (F) image using the left and right arrow keys.

  • Viewport B (lower right) should contain the water (W) image.

  • Use the ratio slider to adjust the amount of fat added. In general, a ratio of 0.05 to 0.10 is advised  for MSK. The upper right viewport displays a preview, helping the user to fine-tune the level of fat suppression interactively.

  • Create the series by clicking the ‘Generate’ button.

  • After performing this once, this postprocessing step will be saved in the ExamCard as a SmartLine step. It can be copied to other mDIXON scans.

                                Viewport A, fat image (F)                     Viewport B, water image (W)

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Tip 6: Ideas to simplify your ExamCards with mDIXON TSE

 ExamCards without mDIXON TSE
ExamCards without mDIXON TSE

  
mDIXON TSE can help to simplify an ExamCard by replacing two or more separate sequences. This can reduce redundancy and support standardization.
 


Why not take advantage of mDIXON for each

TSE scan to double the information in the same scan?



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Mar 26, 2014

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Application Tip
Ingenia 1.5T, Ingenia 3.0T
Release 4.1.3
dStream, Fat suppression, Knee, mDIXON, Musculoskeletal, Shoulder
 

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