The Adelaide MR Web Site
How to collect Siemens SE 135 SVS (The easy way)

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Prepared by Greg Brown    Royal Adelaide Hospital North Terrace Adelaide South Australia 5000   January 24th 2001 Back to MRS Page

Find The Lesion Sequence Selection & Voxel Positioning Prepare to Shim Voxel Shimming Frequency Adjust
Water Suppression Prepare the Sequence Water Reference Data The Other Side

I think this set of notes gets you through the process of collecting a single voxel spectrum as fast as possible, with a Numaris 3 Proton Spectroscopy package.
Read the Spectroscopy manual too, but it distills down to this
Practice it and send me any more shortcuts you can find

· Find the lesion on diagnostic images

· If necessary move the table to get the lesion within 7 cm of the magnet isocentre
· Use the fast orthogonal T2 images
· Place an axial, sagittal and coronal with no angulations through the lesion
· Adjust the slice thickness between 6 10 mm to get at least 3 slices through the lesion.

Sequence selection and voxel positioning

· Protocol Select
· Siemens side head / spec. Select SVS_SE135
· Change
· Position (you cant go straight to Position from Protocol Select )
· Position the voxel in three planes to be within the lesion and clear of bone, air or containing large areas of CSF
· You can increase the voxel to include all the lesion.  This increases SNR but makes shimming harder
· Use the Series and image controls in the bottom right of the screen to control images.  You cannot use the keys
· When positioned click exit to return to protocol change

Prepare to shim

· Adjust
· Receiver
· Set water suppression pulse to 0 (Transmitter Amplitude [No. 1])
· Start to get total receiver gain  to set to 115 db
· Exit

Voxel shimming

· Main menu Measurement Shim
· Measure
· Adjust the X ,Y, Z shim currents in appropriate steps to get  FWHM < 10 Hz (preferably < 9Hz) AND Integral value maximized within the FWHM measurement
· Stop
· Adjust

Frequency adjust

· Frequency
· Start until  diff = 0
· Apply to return to the adjust platform

Optimizing the water suppression pulse voltage

· Receiver
· Start
· This sets total Rx gain to maximum (115)
· Start again and note ADC voltage for the Transmitter Amplitude [No. 1] value at max receiver gain
· Alter Transmitter Amplitude [No. 1] value until ADC is less than 0.1V as low as possible and preferably below 0.06V
· Apply (returns to adjust platform)
· Change

Preparing the sequence

· Set the Acquisitions to 192 256 (based on an 8 cc voxel with good shim and water suppression pulse)
· Start

Water reference data

If water suppression was difficult or voxel contains CSF or oedema, do a water reference acquisition
· When the first sequence is finished
· Adjust
· Receiver
· Set water suppression pulse to 0
· Start
· Apply
· Change
· Set acquisitions to 8 and start the sequence.

The other side

When doing the contra lateral voxel
· From Protocol Change platform, click Position
· Click inside the voxel and drag to the contra lateral location
· Recheck the shim but use small increments (5 mA)
· When you go to optimise the water suppression pulse, enter the value used for the first sequence and Start twice, noting the ADC voltage on the second measurement.
· Use small increments to optimise the pulse setting should be close.