Running LVShim for 3TG3

LVShim rough

LVShim Rough is done at new site installations only.

The objective is to improve the homogeneity to a point where Grafidy and other calibrations can be done. Use the three-piece LVShim phantom. The LVShim Rough process is done with the sampling diameter of 45 cm DSV.

LVShim Rough is usually required at new sites that were never previously shimmed. For a new magnet installation, the magnet ATR shim currents are used for LVShim Rough.

LVShim fine

The objective is to further improve and tune the homogeneity as compared to LVShim Rough.Use the three-piece LVShim phantom. The LVShim Fine process is done with a sampling diameter of 45 cm DSV.

LVShim gradshim

The objective is to complete fine tuning of the homogeneity of the magnet.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.

During LVShim procedures, the system performs a Body SPT SNR to verify system integrity. If the Body SPT SNR fails, troubleshoot the SNR issue (in particular, check the I and Q drive cable connections) before continuing with LVShim.