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mDIXON is developed to simplify and accelerate liver MRI

White Paper
Prof. Hussain, Shahid, M.D., Ph.D. Omaha, Nebraska, The Nebraska Medical Center
Perkins, Tom, Ph.D. Philips Healthcare

The Philips mDIXON scan creates four image types in one breath hold

A liver MRI exam typically includes T2-weighted imaging, chemical shift imaging, pre-contrast T1-weighted, and dynamic post-contrast imaging. Currently, two separate scans are required to create these four image datasets. The mDIXON sequence provides four image types in one breath hold: water and fat images as well as in-phase and opposed-phase images.
The mDIXON sequence provides images as the pre-contrast and chemical shift sequences, in only one single scan that fits in a breath hold of about 20 seconds.

Because this mDIXON scan is designed to be faster, it allows using higher in-plane and through-plane spatial resolution within one breath hold. Shahid Hussain, MD, PhD, University of Nebraska Medical Center, USA and Thomas Perkins, PhD, Senior Clinical Scientist at Philips, are cooperating to optimize the mDIXON sequence for liver MRI.


Schematic comparison of mDIXON and standard methods. The Philips mDIXON scan creates four image types in one breath hold.The original Dixon technique requires a time-consuming acquisition of in-phase and opposed.

Philips mDIXON differs from previous Dixon techniques

The original Dixon technique requires a time-consuming acquisition of in-phase and opposed-phase gradient echo images. The in-phase and opposed-phase images are then added together to get water-only images, and subtracted to get fat-only images. These imaging sequences have limited possibilities to simultaneously optimize for spatial resolution, slice thickness, and scan time, and still fit in a single breath hold in the case of liver imaging.

The Philips mDIXON sequence is based on a unique reconstruction algorithm, offering freedom in echo time setting, so that it does allow for optimization of key imaging parameters and still fits in one breath hold. Arbitrary echo times are used to generate reconstructed water-only images, fat-only images, in-phase images and opposed-phase images.

Time-consuming fat-suppression RF pulses are not needed, and this gain in speed allows to select better spatial resolution for mDIXON than for e-THRIVE within the same breath hold time. In addition, mDIXON performs a special optimization designed to obtain more uniform fat suppression than with e-THRIVE. On 3.0T systems, a two-point mDIXON sequence may be ideal, because at higher field strengths, the frequency difference between fat and water increases, shortening the fat-water amplitude modulation period such that the two acquired mDIXON echo times can be short, thus enabling a higher data sampling rate.

Example of mDIXON in liver

In one breath hold, four different image types are obtained with mDIXON in a patient with two liver lesions. This 3D axial 2-point multi-echo FFE mDIXON scan was performed using the Achieva 3.0T TX with MultiTransmit and the 16-channel SENSE Torso coil.


First breath hold
 mDIXON in-phase mDIXON opposed phase
mDIXON in-phase
mDIXON opposed phase
 mDIXON water mDIXON fat
mDIXON water
mDIXON fat


Second and third breath hold:
 mDIXON water<br> 
Arterial (2nd  breath hold) mDIXON water<br> 
Delayed (3rd breath hold)
mDIXON water
Arterial (2nd breath hold)
mDIXON water
Delayed (3rd breath hold)


References

1. S Hussain, T Perkins
Preliminary Clinical Experience with a Multiecho 2-Point DIXON (mDIXON)
Sequence at 3T as an Efficient Alternative for Both the SAR-Intensive Acquired In- And Out-Of-Phase Chemical Shift Imaging as Well as for 3D Fat-Suppressed T1-Weighted Sequences Used for Dynamic Gadolinium-enhanced Imaging

Proc. Intl. Soc. Mag. Reson. Med, 18:556 (2010)

2. WT Dixon
Simple Proton Spectroscopic Imaging
Radiology, 153:189-194 (1984)

3. H Eggers, B Brendel, G Herigault
Comparison of Dixon Methods for Fat Suppression in Single Breath-Hold 3D Gradient-Echo Abdominal MRI
Proc. Intl. Soc. Mag. Reson. Med., 17:2705 (2009)

4. S Hussain
Liver MRI: Correlation with Other Modalities and Histopathology
Springer-Verlag, Berlin Heidelberg 2007.


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Achieva 3.0T, Achieva 3.0T TX, Ingenia 1.5T, Ingenia 3.0T
Release 2.5, Release 2.6, Release 3.2, Release 4.1
Quasar, Quasar Dual
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