Discovery MR750w and SIGNA™ Architect T 3.0T System Service Methods
5690002-2EN Revision 4
Object ID: 00000018WIA308EBE20GYZ
Topic ID: id_13106500 Version: 3.2
Date: Dec 9, 2019 1:21:08 PM

MR 750 Body Coil Centering

Prerequisites

Table 1. Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
2	Not Applicable	8 hours each (only if coil alignment is necessary), 3 hours (if no coil alignment is necessary) minutes	Not Applicable

Table 2. Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
Non-Magnetic Level — Non-Magnetic, approximately 90cm (3 ft) in length.	1	-	-	-
Non-Magnetic Level — Small non-magnetic level, approximately 7.5cm (3 inches) in length.	1	-	-	-
3T Uniformity Phantom Kit	1	-	5315746 — Order through your normal pooled tool ordering process.	-
Network Analyzer Service Tool	1	-	5336593-2, or 5336593-3 — Order through your normal pooled tool ordering process.	-
Bridge Height Gauge	1	-	5346292 — Part was shipped with the system. Also available as a FRU.	-
Gap Tool, End bell to Body Coil	1	-	5391159 — Part available as FRU	-
Arc Detection Kit	1	-	5401455-2 — Order through your normal pooled tool ordering process. ONLY if Body Coil Tuning is needed.	-
Field RF Coil Tuning Kit	1	-	5311727 — Order through your normal pooled tool ordering process. ONLY if Body Coil Tuning is needed.	-
Software, RF Tuning Kit	1	-	5352480 or 5535261 — Provided as part of Body Coil Tuning and Arc Detection Stress Test class.	-

Table 3. Consumables
Item	Quantity	Effectivity	Part number	Manufacturer
Tie wraps — Used to secure the elliptical drive cabling.	1	-	-	-

Table 4. Replacement parts
Item	Quantity	Effectivity	Part number	Manufacturer
Body Coil Centering Hardware	1	-	5506884 — Part available as FRU	-

Table 5. Required conditions
Condition	Reference	Effectivity
System must be within specification prior to performing this procedure. Both SPT Body and EPI White Pixel Test must have a PASS result.	-	-

About this task

This document addresses customer complaints related to shading in breast and pelvic imaging on MR750 systems only. It has been shown that the main source of shading in 3T systems is dielectric effect, which distorts the B1 homogeneity.

Performance Baseline
Manual Prescan Projection
End bell/Body coil gap check
RF Tuning check
Coil Alignment (if needed), RF coil tuning (if needed), arc detection stress test (if needed)
Patient Handling checks
RF B1 centering check (uniformity and power check)
Finalization

Note:

Body Coil Tuning requires additional training.

The RF Coil Tuning and Arc Detection Stress Test sections of this procedure can only be performed by trained personnel, who have successfully completed GE Healthcare’s training class for Body Coil tuning and Stress Test (GEHC-TECH-AMSC-MR5037).

This procedure applies ONLY to MR750 magnets operating in normal (forward) ramped polarity.

Use the flowchart to guide you through the various sections of the instructions.

Topic ID: id_SL15485039-1346010

Manual Prescan Projection

Procedure

Place the Elliptical Phantom (2) and phantom holder (1) at the center (S/I) of the cradle. Set the angle of the phantom to 0 degrees. Landmark on the center of the phantom. Press the LANDMARK button at the keypad on the front of the magnet enclosure, then press ADV TO SCAN button.

Figure 2. Elliptical Phantom Positioning

ITEM DESCRIPTION
1 Phantom holder
2 Elliptical phantom
At the console, start the Uniformity Tool using the following steps.
1. Open a C-shell.
2. Type cd /usr/g/service/mclass/uniformity
3. Type touch .uniformity_enable
4. Type run_uniformity_tool
On the Uniformity Tool GUI, select single scan for Data Acquisition mode and select Quadrature Mode under Dual Drive mode. Then select Scan and Analysis to start the scan.
When the single scan completes, two pop-ups appear. One is titled “Profile of ePhantom”; the other is titled “Uniformity Plot of ePhantom.”

Figure 3. Profile of ePhantom

Figure 4. Uniformity Plot of ePhantom
Record the Projection Value (PV).

Is Projection Value (PV) Percentage (%) greater than or equal to 96%?

Yes ___________

No ____________

Note:
Make a note of the type of projection obtained at this point. The type of projection obtained will dictate whether additional shims are needed to align the body coil. Continue with End Bell/Body Coil Gap Check.

ITEM	DESCRIPTION
1	Phantom holder
2	Elliptical phantom

Topic ID: id_SL15485040-1346010

End Bell/Body Coil Gap Check

Procedure

Follow Lockout/Tagout procedure per the LOTO for RF Amplifier and PEN Cabinet (Magnet Room Electronics) in the MR Service Safety Manual.
Remove the split bridge. See Bridge and Longitudinal Drive Belt Replacement.
Check the gap between the front end bell and the RF body coil using the gap tool. Check the gap at several locations across the circumference to ensure it is uniform all around. The gaps should be between 2 – 2.5 mm (ideal gap is 2 mm).
Check the gap between the rear end bell and the RF body coil using the gap tool. Check the gap at several locations across the circumference to ensure it is uniform all around. The gap should be between 2 – 2.5 mm (ideal gap is 2 mm).

Figure 5. Gap Check Using Gap Tool

Figure 6. Example of Proper Gap Between Front/Rear End bells and RF Body Coil

Figure 7. Examples of Improper Gap Between Front/Rear End bells and RF Body Coil
If proper gaps are achieved based on the gap tool (gaps are within the 2 – 2.5 mm specification), proceed to RF Coil Tuning Check. If one or both of the gaps are outside of the 2 – 2.5 mm specification, proceed to RF Body Coil Alignment.

Note:
If the results in the Manual Prescan Projection section were unacceptable and the gaps described in the End Bell/Body Coil Gap Check section passed, proceed to RF Body Coil Alignment to properly center the body coil and end bells.

Topic ID: id_SL15492646-1346010

RF Coil Tuning Check

Procedure

Note:
This procedure should only be performed by trained personnel, who have successfully completed GE Healthcare's training class for the Body Coil Stress Test.

Refer to the Field Service RF Tuning Instructions by downloading ltest from the online documentation library for the steps necessary to take and analyze frequency measurements.
If the tuning check passes, proceed to Patient Handling Checks. If the tuning check fails, proceed to RF Coil Tuning.

Topic ID: id_SL15492666-1346010

Patient Handling Checks

Procedure

Restore the split bridge. See Bridge and Longitudinal Drive Belt Replacement.
Check the bridge height at the front and rear of the magnet using the bridge height gauge that was originally shipped with the dock assembly. This measurement should be taken from the bottom surface of the belt groove in the center of the bridge. The bridge height specification range is 502 – 505 mm (although a bridge height of 505 mm is preferred).
Figure 8. Bridge Height Check
- If the bridge height is not within specification, adjust the M10 nylon nuts at the bottom of the bridge support upper bracket to raise and lower the bridge to attain the 502 – 505 mm specification (a height of 505 mm is preferred). The rear pedestal feet can also be adjusted to attain the bridge height specification of 502 – 505 mm (a height of 505 mm is preferred).
- At bridge height of 502-505 mm check to make sure that the bottom of the bridge is not in contact with any RF coil component (like the bulkhead).
- The bridge height gauge is also available as a FRU in case you’re unable to locate the original one shipped with the dock assembly.
Check the bridge alignment in the z-direction (in/out of the bore) and ensure it is flush with the end bells +/-3 mm. Adjustments can made at the L-brackets.

Figure 9. Bridge Alignment in the z-direction

ITEM DESCRIPTION
1 +/- 3mm
2 L-brackets
Check the bridge alignment in the x-direction (left/right of the bore) and ensure it is centered evenly at the front and rear of the magnet. Adjustments can be made by loosening the phenolic washers at the magnet feet and shifting the bridge left/right.
If not previously installed, install the front and rear end bells. See Front End Bell Removal and Installation and Rear End Bell Removal and Installation. If the gap specification of 2 – 2.5 mm cannot be achieved, see RF Body Coil Alignment.
Perform RF Coil B1 Centering Check (Uniformity and Power Check).

ITEM	DESCRIPTION
1	+/- 3mm
2	L-brackets

Topic ID: id_SL15494195-1346010

RF Coil B1 Centering Check (Uniformity and Power Check)

Procedure

Note:
If the RF Body Coil was aligned as part of any of the previous sections, run a new Manual Prescan Projection to verify the system is ready to proceed.

Place the elliptical phantom and test fixture at the center (S/I) of the cradle. Set the angle of the phantom to 0 degrees.
Note:
Allow the phantom solution to settle for 5 minutes prior to scanning. This will prevent flow-related artifacts, which may affect the test results.

Landmark on the center of the phantom. Press LANDMARK at the keypad on the front of the magnet enclosure, then press ADV TO SCAN.

Figure 10. Elliptical Phantom Positioning
Install a service key.
In a command window type the following: cd /usr/g/service/mclass/uniformity touch .uniformity_enable run_uniformity_tool.

The Uniformity Tool GUI pops up.

Note:
The scan status and result are displayed on Uniformity Tool GUI Status dialog box. All buttons are inhibited during scan. Only Abort Scan button is available during scan. All buttons are available when scan is idle. Abort Scan button is inhibited when scan is idle. Do not re-lANDMARK between scans.

Figure 11. Uniformity GUI and Status
Choose Four scans mode.
Select Scan and Analysis.
Choose Yes when asked if user has landmarked.

Figure 12. Landmark Message
During the scan, record the RF amplifier Peak Forward Power value in the table below.

Note:
Use the printPower function to read the Peak Forward Power in each orientation: open a C-shell, type mgd_term to bring up the SCP window, type printPower and record the Body Peak value listed in the window in the table below.
Select Continue when asked to position the phantom at horizontal position.

Figure 13. Horizontal Position
When asked to position the phantom, rotate phantom to 45-degree plane and choose Continue.

Figure 14. 45 Degree Position
During the scan, record the RF amplifier Peak Forward Power value in the table below.

Note:
Use the printPower function to read the Peak Forward Power in each orientation: open a C-shell, type mgd_term to bring up the SCP window, type printPower and record the Body Peak value listed in the window in the table below.
After the second scan completes, confirm that a dialog appears requesting the user to re-position the phantom.
When asked to position the phantom, rotate phantom to 90-degree plane and choose Continue.

Figure 15. 90 Degree Position
During the scan, record the RF amplifier Peak Forward Power value in the table below.

Note:
Use the printPower function to read the Peak Forward Power in each orientation: open a C-shell, type mgd_term to bring up the SCP window, type printPower and record the Body Peak value listed in the window in the table below.
After the third scan completes confirm that a dialog appears requesting the user to re-position the phantom.
When asked to position the phantom, rotate phantom to 135-degree plane and choose Continue .

Figure 16. 135 Degree Position
During the scan, record the RF amplifier Peak Forward Power value in the table below. Scanner should stop after scanning 135-degree position and automatically process results.

Note:
Use the printPower function to read the Peak Forward Power in each orientation: open a C-shell, type mgd_term to bring up the SCP window, type printPower and record the Body Peak value listed in the window in the table below.

Figure 17. Result Plot

Record TG, Min Signal, Max Signal, and Uniformity values displayed on the GUI Status box in the table below.

Note:

TG Values can be obtained from the Uniformity Tool GUI.

Table 6. Pre-alignment Phantom Data
Elliptical phantom position	Exam/Series/Image	TG	Power FWpk	Uniformity			Uniformity Spec
Elliptical phantom position	Exam/Series/Image	TG	Power FWpk	Min	Max	U	Target
0							U > 15
45							-
90							-
135							-

Note:

Make sure that the TG, FWpk, and Uniformity values are recorded in the table. You will refer back to the table after completing the Power Measurements and Reflected Power Check.

Go to Reflected Power Check.

Topic ID: id_SL15499259-1346010

RF Body Coil Alignment

Procedure

Perform Front End Bell Gap Adjustment. See Front End Bell Adjustment.
Perform Rear End Bell Gap Adjustment. See Rear End Bell Adjustment.
Perform Manual Pre-Scan Projection - Image Test. See Manual Pre-Scan Projection - Image Test.
Perform RF Body Coil Alignment - Centering Pads.

Note:
Older style body coils might have a one-piece strip that was used for centering. This strip must be removed and the new feet that are provided in the FRU kit will be utilized. If the strip is not present and feet are used, follow the instructions in RF Body Coil Alignment - Centering Pads but do not proceed to Finalization. When complete, proceed to RF Coil Tuning Check RF Coil Tuning Check.
Figure 18. Old Style Shims

ITEM DESCRIPTION
1 Coil shim placement
2 Close-up view

Remove any shim and centering spacer adhesive before installing feet.
Figure 19. Shim Feet Preparation
Figure 20. Installed Shim Feet

ITEM	DESCRIPTION
1	Coil shim placement
2	Close-up view

Topic ID: id_SL15499578-1346010

RF Coil Tuning

About this task

RF Coil Tuning procedure:

This procedure should only be performed by trained personnel, who have successfully completed GE Healthcare's training class for the Body Coil Stress Test.
Please refer to the Field Service RF Tuning Instructions for the steps necessary to tune the RF Body Coil. Once the RF Coil Tuning is complete, proceed to Arc Detection Stress Test (Arc Detection Stress Test).

Topic ID: id_SL15499579-1346010

Arc Detection Stress Test

About this task

Arc Detection Stress Test procedure:

This procedure should only be performed by trained personnel, who have successfully completed GE Healthcare's training class for the Body Coil Stress Test.
Please refer to latest Service Methods for the 3.0T Arc Detection Test With Body Coil Stress procedure.
After the Arc Detection Stress Test is completed, re-check the gap between the endbells and RF Body Coil. Re-install the front and rear endbells. If you cannot achieve the gap spec of 2 – 2.5 mm, see RF Body Coil Alignment. If the gap is acceptable, proceed to Patient Handling Checks.

Topic ID: id_SL15506708-1346010

Reflected Power Check

Procedure

Place the SPT phantom and short loader into the cradle. Landmark on the approximate S/I center of the cradle and press the Advance to Scan button. Prepare the system to scan in Body mode:
1. Click on New Pt.
2. ID: Type geservice then hit Enter.
3. Name: Type apb cal body then hit Enter.
4. Weight (lb): Type 300 then hit Enter.
Set Patient Protocols to Service.
Scroll through the protocol field until the protocol 3.0T apb cal is found.
Select Series 1, Body. Select Accept.
Select Start Exam.
Select Save Rx.
Click on down arrow next to scan option. Click Research, then select Setup Params. Set TG to 50 and select Done.
Click on down arrow next to scan option. Click Research then select Display CVs from the drop-down menu.
Enter calmode under the name field and hit Enter. Set the current value field of CV calmode to 5 then click Accept.
Right click on Research then select Download.
Select Manual Prescan.
Select Scan TR.
Note:
The manual prescan must be started first and TG set to 170 before the SCP command mgd_term is executed. If you encounter any problems, restart from step 1 of this section.

Slowly bring the Transmit Gain up to 170. Make sure everything is functioning normally and there is a reading on the RF amp display.
Pulse for approximately 5 minutes to allow for proper RF amp warm up, and then record the Peak RF power from the RF amplifier display. Keep the RF amp pulsing for the next step.

Note:
Use the printPower function to read the Peak Forward Power in each orientation: open a C-shell, type mgd_term to bring up the SCP window, type printPower and record the Body Peak value listed in the window.
While the system is still scanning from the previous step, open a C-shell and type mgd_term to open up the SCP window.
In the SCP window type: Upm_Data_Capture "upmdata",1,1 then hit Enter. This string is case sensitive.
After approximately 10 seconds, two files will be generated and saved under the /usr/g/service/log directory:
- upmdata_upm1.txt
- upmdata_upm2.txt
The output of the command above will look similar to the following:

Upm_Data_Capture "upmdata",1,1
0x3dcaa98 (tShell): Dumping data done
value = 0 = 0x0
SCP_LX->0x3dcaa98 (tShell): Dumping data done
End Manual Prescan by clicking Done. Click on End Exam from the left hand-side of the screen. When prompted, click Confirm to end exam.
Confirm that the two upmdata files are present under the /usr/g/service/log directory. In a C-Shell, type: cd /usr/g/service/log ls –la upmdata_upm*.

Sample output:

-rw-rw-rw- 1 sdc 32116 39665 Jun 15 16:50 upmdata_upm1.txt
-rw-rw-rw- 1 sdc 32116 39665 Jun 15 16:50 upmdata_upm2.txt
From the C-Shell, view the first upmdata file, by typing: view upmdata_upm1.txt then hit Enter.

The first upmdata file will be displayed. Scroll down towards the end of the file until you find the Body Channel section.

Figure 21. UPM Data File

ITEM DESCRIPTION
1 Body Channel section
2 Data

Upm_Data_Capture "upmdata",1,1
0x3dcaa98 (tShell): Dumping data done
value = 0 = 0x0
SCP_LX->0x3dcaa98 (tShell): Dumping data done

-rw-rw-rw- 1 sdc 32116 39665 Jun 15 16:50 upmdata_upm1.txt
-rw-rw-rw- 1 sdc 32116 39665 Jun 15 16:50 upmdata_upm2.txt

ITEM	DESCRIPTION
1	Body Channel section
2	Data

Complete the table below with the necessary info. You will need to make note of “forward” (column 2), and “reflected” (column 3) for rows number 10, 30, 50, 70, and 90.

Copy the values for forward and reflected for rows number 10, 30, 50, 70, and 90 from the file into the UPMDATA File 1 table.
Calculate the ratio of the reflected to the forward power for each row and enter that percentage into column 4 of the UPMDATA File 1 table.
Calculate the average of the values in column 4 and record value in the last row of the UPMDATA File 1 table.

Table 7. UPMDATA File 1
UPMDATA FILE 1 TABLE
Column 1 (Num)	Column 2 (Forward)	Column 3 (Reflected)	Column 4 = (Reflected / Forward) * 100
10
30
50
70
90
		AVERAGE OF COLUMN 4 =

When you have completed filling in Table 2, quit the file viewer in the C-shell by typing: :q.
View the second upmdata file by typing: view upmdata_upm2.txt then hit Enter.

Gather the data for the second upmdata file and note these values in the UPMDATA File 2 table.

Table 8. UPMDATA File 2
UPMDATA FILE 2 TABLE
Column 1 (Num)	Column 2 (Forward)	Column 3 (Reflected)	Column 4 = (Reflected / Forward) * 100
10
30
50
70
90
		AVERAGE OF COLUMN 4 =

Compare the average values calculated in both tables. Take the higher of the two averages.
(For systems with original hybrid and cables) Confirm that reflected is less than or equall to 2%. If your value is greater than 2%, contact Online Center (OLC) Engineering.
(For systems with added elliptical hardware with new hybrid and cables) Confirm that reflected is less than or equal to 7%. If your value is greater than 7%, contact Online Center (OLC) Engineering.

Topic ID: id_SL15500366-1346010

Uniformity Measurements

About this task

Repeat the Baseline Uniformity Measurements for only the Elliptical Phantom Position of 0 degrees following the steps in Uniformity Test and record the data in the Final Phantom Scan Data Table.

Table 9. Final Phantom Scan Data
Elliptical phantom position	Exam/Series/Image	TG	Power	Uniformity			Uniformity Spec
Elliptical phantom position	Exam/Series/Image	TG		Min	Max	U	Target	Absolute min
0							U > 30 If elliptical hardware is installed.
0							U > 15 If elliptical hardware is not installed.

Topic ID: id_14984164

Finalization

Procedure

Return system to normal operating configuration.