Optima MR450w BASE 1.5T System Service Methods
5690012-2EN Revision 3
Object ID: 00000018WIA3026CE20GYZ
Topic ID: id_13106168 Version: 3.3
Date: Nov 5, 2020 1:38:56 PM

Probe Tuning and SNR Check Tool (DV24 and later)

Prerequisites

Table 1. Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	5 minutes	45 minutes	Not Applicable

Table 2. Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
MRS Phantom (without loader)	1	-	2152220	-
1.5T TR Split-Top Head Coil	1	-	5182594	-
Curved Adapter Panel for Flat Table (GEM)	1	Flat (GEM) table	5395828	-
Service Filler Panels	2	Curved table	5344577	-

Table 3. Safety

Warning

POISON HAZARD!

1.5T Phantoms CONTAIN NICKEL, A SUSPECT CARCINOGEN.

DO NOT INGEST. DISPOSE OF AS A HAZARDOUS WASTE ACCORDING TO STATE AND FEDERAL REGULATIONS.

Table 4. Required conditions
Condition	Reference	Effectivity
PROBE-S option (M3333WH) is required at site to perform PROBE-S Cal & SNR Check or PROBE-P Cal & SNR Check.	-	-
PROBE-P option (M3333WG) is required at site to perform PROBE-P Cal & SNR Check or PROBE-P SNR Check.	-	-

About this task

This tool is available in systems with DV24 and later software.

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.

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

The Probe-s sequence is a version of the stimulated echo acquisition mode (STEAM). This sequence is used for short echo time, single-voxel spectroscopy; that is, TEs shorter than 35 milliseconds.
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.

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

If there is an exam running, end the current exam (unless the exam was started with the “geservice” patient ID).
Set up the table as follows.
- (For flat (GEM) table) Insert the curved adapter panel into the table.
- (For curved table on wide bore system) Place the service filler panels under the two cradle top panels.
Figure 1. Table Setup
Check the MRS phantom temperature shown on the surface of the phantom, and record it.

Figure 2. MRS Phantom Temperature
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 3. Position MRS Phantom
Landmark on the center of the phantom and advance to scan.
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 4. PROBE Tuning and SNR Check Tool
By default, both Probe P and Probe S are run. To change this default, select the checkbox for the desired test.
(For MRS phantom) Enter the phantom temperature recorded above.
Click Start.

The test will start after 5 minutes (to allow the phantom time to stabilize). If both Probe P and Probe S are run, the test takes about 45 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.
The tool provides a visual Pass/Fail result. If the test fails, run Calibrating grafidy, 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

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 5. Example of Probe Log File
The specification criteria is as follows.

PROBE-P/PROBE-S 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):

Cr SNR > 60 for 1.5T

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

Cr SNR > 30 for 1.5T

Finalization

If not performing this test as part of an installation, perform a SaveInfo to save the calibration file.
Remove all service equipment from the system, including filler panels if applicable.