Object ID: 00000018WIA30FF3970GYZ
Topic ID: id_40026757 Version: 1.6
Date: Mar 2, 2022 9:45:20 AM

Multi-echo FGRE/FSPGR scan

Gradient Echo pulse sequences are sensitive to magnetic susceptibility effects. When anatomical regions that have increased ferromagnetic matter (such as iron) are scanned, the result is a dark or low signal intensity in the iron containing region. As TE increases, the SNR decreases significantly.

It is possible to quantify susceptibility effects by measuring T2* relaxation time via at least two sets of images that have different TE times. 2D Multi-Echo FGRE/FSPGR enables allows selection of 3-16 echoes. These images can be post-processed in READY View to measure the relaxation time variants using READY View: R2Star workflow.

Use Multi-echo FGRE/FSPGR:

to acquire images to analyze iron-load for blood-transfused patients
in the clinical management of patients with iron overload diseases such as Thalassemia
in liver and myocardium examinations

Consider this information when modifying Multi-echo FGRE/FSPGR scan parameters for images to be post-processed in R2Star READY View application. For specific scan parameter values, select a protocol from your GE or Site library.

Warning

Computed R2* values are affected by the presence of contrast agents in tissue, and results may be incorrect. Do not utilize post-contrast images for generating R2* maps. Affected applications include multi-echo FGRE/FSPGR acquisitions such as IDEAL IQ, and any post process applications that create R2 star maps such as StarMap and READY View R2 Star.

CAUTION

Measurement of relaxation time by Multi-Echo FGRE/FSPGR is very sensitive to the result of gradient shim (Auto-Shim) in the slice direction. Auto-Shim with shim-volume setting is recommended.

Important: When using Multi-echo FGRE/FSPGR for tissues with short T2* relaxation times, the echo spacing and first echo should be as small as possible (around 1 ms for the first echo time) to ensure confidence in the fit of the R2* value. The best way to achieve this is to use a high band width and low matrix values. For liver exams, set User CV 17 (Interleave Mode) to a value greater than 1 (the higher the value, the shorter the echo-space).

Scan selections: 2D Mode, Gradient Echo family, Multi-echo Fast GRE or Multi-echo Fast SPGR pulse.

Scan parameters

# of echoes: The number of echoes range is 3-16. Typically select a minimum of 4 or 5.
SAT: To minimize Fat/Water in-phase/out-of-phase effect, select Chemical Saturation for liver scans.
TE: It is automatically calculated.
- Select Minimum TE for liver scans in order to get a short TE time for the first echo.

Imaging Options

The following imaging options are available with Multi-Echo FGRE/FSPGR

ASSET
ARC with ARC compatible coils
Cardiac Gating/Triggering
Extended Dynamic Range
Flow Compensation
Square Pixel
Respiratory Gating/Triggering
ZIP 512

User CVs

Click the Advance tab to view the available User CVs. The CVs may vary based on the field strength and selected scan and imaging parameters.

Post-process tasks

There are multiple compatible post-process tasks. For details, see Add post-process task.

Image Enhancement Filters

Parameters (Lower Threshold, Confidence level, Kernel size, Fitting algorithm) and Functional maps R2* and T2*). For details, see READY View R2Star Optional procedures

CAUTION

It is possible that READY View results of the calculated T2* and R2* values have an error with acquisitions that have a large slice number value.