• Object ID: 00000018WIA305EE870GYZ
  • Topic ID: id_40026685 Version: 1.6
  • Date: Aug 21, 2022 3:13:56 PM

MERGE scan

MERGE is a 2D or 3D fast GRE pulse sequence that acquires multiple echoes at several different TEs and then averages those echoes to form a single T2*-weighted image. MERGE uses a larger receive bandwidth (31.25 kHz), which reduces chemical and susceptibility artifacts and improves image quality.

Use MERGE in the C-spine to minimize susceptibility and chemical shift artifact and in the knee for high resolution extremity imaging when increased T2* weighting is desired.

Figure 1. Sagittal 3D MERGE knee

2D MERGE can minimize susceptibility and chemical shift artifact in the C-spine and due to the excellent gray/white matter conspicuity in the spinal cord, it improves visualization of cord compression and parenchymal disease.

Figure 2. MERGE oblique C-spine

Consider this information when modifying MERGE scan parameters. For specific scan parameter values, select a protocol from your GE or Site library

  • Scan selections: 2D or 3D Mode, Gradient Echo family, MERGE pulse.

General considerations

  • Compared to 2D MERGE, 3D MERGE provides higher SNR at similar resolution.
  • For C-spine applications, use CTL 12 and not TOP.

Scan parameters

  • Bandwidth: If a sagittal or coronal or sagittal/coronal oblique plane is prescribed, the RBw lower limit is 62 kHz to minimize susceptibility artifact. If you prescribe a value less than 62 kHz on 3.0T, a message displays advising you to increase the RBw.
  • Flip Angle: Select Auto to select the optimum flip angle for the selected TR.
  • Frequency: Place Frequency in the S/I direction and not A/P direction.
  • No Phase Wrap: Set the value to > 1.0.
  • # of echoes: It is determined by the receive bandwidth and frequency value. As receive bandwidth increases, more echoes are acquired and thus the susceptibility and chemical shift artifacts decrease. The multiple echoes provide additional SNR that is needed with a higher receive bandwidth because as bandwidth increases SNR decreases.
  • No Phase Wrap: Set the value to > 1.0.
  • SAT: To minimize swallowing motion-related artifact, place an anterior SAT pulse that covers anatomy anterior to the vertebral column, including the esophagus.
  • TE: It is set to Min Full and cannot be changed. The effective TE value (averaged echo time) is approximately:
    • 15 ms for 1.5T
  • TR: From the TR menu, select a TR value.

Imaging Options

  • SSRF: SSRF is available for 3D MERGE to suppress fat signal.

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.

2D MERGE User CVs

3D MERGE User CVs

Post-process tasks

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

  • Maximum Intensity Projection
  • Multi Planar Reconstruction
  • Image Enhancement Filters
  • Pasting