• Discovery MR750 3.0T System Service Methods
  • 5690009-2EN Revision 4
  • Object ID: 00000018WIA3095A650GYZ
  • Topic ID: id_2024932 Version: 2.5
  • Date: Nov 3, 2021 6:29:06 PM

Running LVShim - Gradshim

Prerequisites

Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
1-30 minutes10 minutes
Tools and test equipment
ItemQuantityPart numberManufacturer
LVShim Phantom Inner Sphere12274476-
LV Phantom Small Half Assembly12306642-
LV Phantom Big Half Assembly12306645-
Required conditions
Confirm that passive shimming is complete and is within specification.
Remove all coils from the cradle and phantoms from the bore.
Safety

Before working in any GE Healthcare MR suite or performing any GE Healthcare service procedure, you must:

  • Have read and understood all hazard conditions and safety requirements in the latest revision of the GE Healthcare MR Service Safety Manual (5452735).
  • Have successfully completed all relevant GE Healthcare Environmental Health and Safety (EHS) courses (or for non-GE employees, equivalent workplace training courses).
  • Comply with all site-specific training and workplace safety requirements.

If you have any safety concerns at any time, do not begin work or immediately stop work and move to a safe location. Immediately contact your supervisor or site safety officer for instructions on how to proceed.

About this task

The Gradshim process is done with a sampling diameter of 22 cm DSV and the same bandwidth as LVShim Fine, which depends on the quality (good/bad) of the fine tuning. When the scan passes and all harmonics are within specification, the magnetic field is reanalyzed in Test mode automatically at 45 DSV for customer acceptance.

The gradshim process includes LVShim - test. The objective of this test is to analyze completed scans at 45 DSV without calculating currents.

Note:

For DV systems 22.x and earlier, 1.5T LVShim uses green phantoms and 3.0T LVShim uses pink phantoms.

For DV systems 23.x and later, 1.5T LVShim uses green phantoms and 3.0T LVShim uses either green or pink phantoms.

Note: If you are running LVShim - Gradshim as part of Planned Maintenance:
  1. On the MR Service Desktop, select the PM tab.
  2. Select PM > PM Assist > LVShim (Prerequisite) > Click here to start this tool.