• SIGNA MR355 / SIGNA MR360
  • Service Manual
  • 5856356-3EN Revision 5.0
  • Basic Service Documentation. Copyright General Electric Company.
  • Object ID: 00000018WIA300F8F20GYZ
  • Topic ID: id_13106275 Version: 3.0
  • Date: Feb 21, 2021 9:09:32 PM

Probe-P Calibration and SNR Tests

Prerequisites

Table 1. Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
15 minutes45 minutesNot Applicable
Table 2. Tools and test equipment
ItemQuantityEffectivityPart numberManufacturer
MRS Phantom (without loader)1-

2152220

-
Table 3. Safety
Table 4. Required conditions
ConditionReferenceEffectivity

PROBE-P option (M3333WG) is required at site to perform PROBE-P Cal & SNR Check or PROBE-P SNR Check.

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About this task

The Probe Tuning and SNR Check Tool is an essential part of conditioning a system for performing spectroscopy, to optimize both SNR and phasing. All tests can be run in one session, and no interaction is needed during the calibration. The Probe-p sequence is a version of the point-resolved spectroscopy (PRESS) pulse sequence. The PRESS sequence provides twice the SNR of the STEAM sequence but at the expense of slightly longer minimum TEs

There are two Probe/SV pulse sequences: Probe-s and Probe-p.

This document describes two separate hydrogen only spectroscopy (PROBE/SV) procedures:

  • Echo Peak Location calibration (automated PROBE tuning script)

  • PROBE signal-to-noise ratio (SNR) performance test

Scan Setup

About this task

This section provides instructions for centering the phantom. There is no need to run a 3-plane localizer before scanning, because the tool automatically performs a phantom centering check. The tool also has a built in wait time to allow the phantom to settle before scanning.

Procedure

  1. If there is an exam running, end the current exam (unless the exam was started with the “geservice” patient ID).
  2. Check the MRS phantom temperature shown on the surface of the phantom, and record it.
    Figure 1. MRS Phantom Temperature
  3. Position the MRS phantom in the single channel head coil. Do NOT use the head loader with the MRS phantom. Use foam support pads for quick alignment to center the phantom in the head coil. Phantom centering (up/down/left/right/in/out) within 25 mm of the isocenter in all directions is important.
    Figure 2. Position MRS Phantom
  4. Landmark on the center of the phantom and advance to scan.
  5. Start the PROBE Tuning and SNR Check Tool:
    1. (For non-proprietary service tools) From the Service Desktop, open the Calibration tab, and select Calibration > PROBE Tuning & SNR Check > Click here to start this tool.

    The probeTune window appears.

    Figure 3. PROBE Tuning and SNR Check Tool
  6. By default, only Probe P is run, select the checkbox for the desired test.
  7. (For MRS phantom) Enter the phantom temperature recorded above.
  8. Click Start.

    The test will start after 5 minutes (to allow the phantom time to stablize). the Probe P test takes about 30 minutes to complete.

    If you need to stop the test before it is finished, click Abort.

    If the phantom is off-center by more than 25 mm, an error message is displayed. Correct the phantom setup, click [OK] in the message, and click [Start] again.

  9. The tool provides a visual Pass/Fail result. If the test fails, run Grafidy 3 Eddy Current Calibration , then try the Probe tool again.

Reviewing Results

About this task

The probeTune tool also generates log files, which can be viewed from the tool or manually. There are four log files (one for each probe calibration and SNR check). The log files are stored in /usr/g/service/data and are named to indicate which test they result from (for example, *****_CAL.PRB and *****_SNR.PRB). There is no need for data sheets as in previous probe tuning applications. The files are always on the system, and saved on the SaveInfo media (if SaveInfo is performed after calibrations).

Procedure

  1. To view the log files from the tool, select File > Open in the probeTune window, select the log file you want to view, and click Open.
    Figure 4. Example of Probe Log File
  2. The specification criteria is as follows.

    PROBE-P Calibration (absolute value):

    Single delta parameter < 0.8 (Single delta parameters are “deltay_val”, “deltax_val”, and “deltaz_val”.)

    Sum of all delta parameters < 1.0

    PROBE-P SNR (Average of 3 SNR scans):