MRI setup & programming

Varian 9.4T MRI Tips

• EPI optimization

  • • Shim volume should be inside the brain & away from the ear canal

    • Always use R-L as readout direction

    • Use ramp sampling to reduce echo train length

• Data size limit

  • • Maximum FID file size is 2GB

    • Which means for 10 slices of 256x256 image, you can only acquire < 410 repetitions (using single channel) or < 103 repetitions (using 4 channel).

    • If exceed, the scanner will run but no data will be saved! Have to calculate your data size if you plan to scan high-res and many repetitions.

• Introduction to Varian system (PowerPoint)

Bruker Biospec 9.4T MRI Tips

• Bruker Paravision training video

• EPI optimization by MAPSHIM

  • • Load Field Map protocol and run MAPSHIM macro to acquire field map.

    • Load PRESS protocol and use it to select the voxel for localized shim.

    • Run MAPSHIM with "Local" option.

• Make new sequence

  • • run /opt/PV5.1/bin/CopyMethod

    • make install clean cproto

    • copy *.ppg/*.mod files to /opt/PV5.1/exp/stan/nmr/lists/pp

    • restart PV to see the new sequence

• Artifact

  • • Dark bad in spin-echo:

      • cause: mismatched excitation and refocusing RF pulse bandwidth

      • solution: reduce exc bandwidth to make refoc bandwidth at 10-20% wider

• • "Motion" in phase-encoding direction of EPI

    • • cause: frequency drift due to gradient heating

      • solution: reduce duty cycle by increasing TR or reducing number of slice

Bruker ClinScan 7T Tips

• Orientation

  • • Choose Head First, Supine to ensure the displayed orientation is like what it should be.

• Optimize shimming for EPI

• • Display Adjustment volume (View->Adjustment volume) and reposition inside the ROI (eg, brain).

  • Choose Advanced shim mode in Sequence->Adjustment.

• When "frequency adjustment doesn't converge"...

• • unplug and replug the coil connector

  • may need to do it a few times

• Debug log files

• • Data, HostInstLog, HostLog, MRIRLog

Siemens 3T MRI Tips

• Online manual

IDEA programming Tips

• Install sequence

  • • copy *.dll & *.i86 to \MedComm\MriCustomer\seq (on host)

• Gradient system

  • • ClinScan: 7TZ

    • Trio: TQ-engine

    • Change gradient setting in IDEA: type 'gradconf -h' to see detail.

• External RF file

  • • \n4\MriSitedata\7TZ (or TQ-engine for Trio) (in IDEA)

    • \MedComm\MriSitedata\measurement (on host)

    • perform PAS unload in ideacmdtool every time you add an RF file

• External gradient table for DTI

  • • \n4\x86\prod\bin (in IDEA)

    • \MedComm\MriCustomer\seq (on host)

• Get k-space data

  • • open start menu by CTRL+ESC

    • Programs->Save Meas Data

    • look for data based on date/time

    • Option->copy from RAID

    • k-sapce data will be saved as meas.dat