Dual drive quadrature tool

Topic ID: id_SL5134484-1169977

Personnel requirements

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

Topic ID: id_SL5134486-1169977

Tools and test equipment

Table 2. Tools and Test Equipment
Item	Qty	Effectivity	Part#	Manufacturer
Body Loader with Sphere Phantom	1		2371511	-
Service Foam Positioner	1	-	5554839	-
Head TLT Sphere for 3.0T (Pink Solution)	1	-	2359877	-
Pad for Head Sphere	1	-	46-328383P1	-

Topic ID: id_2012363

Dual drive quadrature tool overview

A dual drive system has two transmit channels. The dual drive (DD) quadrature tool is used to compensate for the amplitude and phase differences in the transmit channels. Amplitude and phase differences between the two channels can begin at the exciter and be carried through to the body coil transmit (the end of the imaging chain). Those differences can also be introduced at any of the intermediate passive components.

The dual drive quadrature tool performs axial scans in three modes.

Combined mode
CH1 transmit, CH2 disabled
CH2 transmit, CH1 disabled

The dual drive quadrature tool calculates amplitude difference between the CH1 and CH2 channels. It also calculates phase difference between the CH1 and CH2 channels. It then updates the system calibration file with the cumulative compensation required.

Test mode without calibration is provided.

Figure 1. Flowchart of dual drive quadrature tool

Figure 2. Dual drive quadrature tool GUI


Locator	Item	Description
1	Calibration Location	Select Head or Center or both.
2	Start	Click Start to start the calibration.
3	Abort	Click Abort to abort the calibration process.
4	Test	Click Test to confirm the test results. The calibration file is not updated.
5	Reset	Reset the initial value to Default(0,0) or the last calibration value.
6	Status	Displays the dialogue of the procedure.
8	Config	The value is the calibration file and is updated when a successful calibration is completed.
9	Initial	Initial value before adjustment.
10	Residual	Residual after the compensation is applied.
11	Data Analysis	This mode allows the user to re-analyze scanned data acquired with the dual drive quadrature tool. It includes the combined image exam, series, image number, and prompts the user for the Pfiles created by the individual channel scans. This mode does not update the calibration file. This mode can also be used for troubleshooting because it provides some freedom in how the data is acquired.
12	Run Analysis	Click Run Analysis to initiate the data analysis process.
13	Quit	Quits the dual drive quadrature tool.

Topic ID: id_v5n_zcb_sfb

Before starting the dual drive quadrature tool procedure

Notice: Before starting a dual drive quadrature calibration scan, confirm that there is no exam in progress. If there is an exam in progress, select End Exam.

If you are calibrating multiple tables, follow these steps:

Complete successful table calibration.
Exit the dual drive quadrature tool by selecting Quit.
Connect the next table to be calibrated.
Restart the dual drive quadrature tool and repeat the steps above.

If you try to calibrate multiple tables without exiting the tool, you will see an error message.

Topic ID: id_2012346

Setting up for head only or both head and center scan

Procedure

At the scanner, remove any surface or head coil from the bore. Confirm that the cradle is at the home position.
From the home position, move the cradle in so that the in-room monitor shows 315 mm. Turn on the alignment lights by pressing the Alignment button on the magnet enclosure.

Figure 3. Buttons on magnet enclosure

Item Description
1 Alignment lights button
2 Landmark button
3 Advance to scan button

Item	Description
1	Alignment lights button
2	Landmark button
3	Advance to scan button

Place the Pad for Head Sphere (46-328383P1) on the table (with flat filler panel) so that its cross hairs align with the laser lines, then place the head phantom (2359877) on the pad making sure the laser lines cross the phantom in the center. Press the Landmark button.

Figure 4. Positioning for head location (phantom and pad)

If scanning only the head location, press Advance to scan. Proceed to Accessing dual drive quadrature tool.
If scanning both head and center locations, move the cradle in an additional 765 mm.
Align the body loader and sphere on the center of the laser light cross hairs. Press Advance to scan, and proceed to Accessing dual drive quadrature tool.

Notice

There should always be a distance of 765 mm between the head location and the center location of the dual drive quadrature tool.

Topic ID: id_2012348

Accessing dual drive quadrature tool

Procedure

(For non-proprietary mode) Select Calibration > Calibration Tools > Dual Drive Quadrature, then Click here to start the tool.
(For proprietary mode) Run the Calibration Wizard, and select Dual Drive Quadrature.

Topic ID: id_2012349

Running dual drive quadrature tool

Procedure

Select the calibration locations to include in the scan. Click Head or Center or both.
Click Start for the first iteration.

Scan and analysis begin. It takes about 6 minutes.
The tool runs up to three iterations, attempting to come to specification.

If you have selected both head and center scans, the tool automatically moves to the next location. It reruns iterations for the first location.

When the first iteration is complete, calibration results are passed or failed.
(For passed) Click Quit to complete the calibration. Proceed to Finalization.

Figure 5. Pass case

(For failed) If the head location fails, the calibration scan stops. If you selected head and center locations to be done together, you must manually start the center location calibration scan.

Figure 6. Fail case (at first iteration)

Table 3. Specifications for dual drive quadrature calibration
Phase or Magnitude	Value
Head location phase	30 degrees
Head location magnitude	20 counts (2.0 dB)
Center location phase	30 degrees
Center location magnitude	15 counts (1.5dB)

If the calibration passes within iteration 3, click Quit to exit the tool.

Topic ID: id_13105791

Quadrature calibration troubleshooting

The signals for both channels originate from the exciter and are sent to the dual drive RF amplifier, where they are amplified to a maximum of 15 kW per channel for body coil mode only. The RF output riding on the T/R pulse is sent to the dual transmit receive switch (DTRSW) and then to the RF body coil. Because there are two RF signals, this redundancy can be used to troubleshoot the RF output.

For more information, see:

For information on how dual drive works, see Dual Drive Theory.
For information on dynamic disable and T/R pulse errors, see T/R and DD Troubleshooting .

Warning

Equipment Damage can occur if process and procedures are not followed.

The dual drive Transmit chain has significantly changed.

Take Extra care to familiarize yourself with the Transmit chain and new procedures before attempting to troubleshoot.

Warning

DTRSW and Combiner failures can occur if either channel 1 or channel 2 RF transmission line cables between the DTRSW and RF amplifier are disconnected and RF energy is pulsed to the DTRSW on the remaining connected line.

The damage happens when RF energy is coupled by the RF body coil into the side of the DTRSW deprived of TR bias due to the disconnected line.

These transmission lines should remain connected whenever pulsing any RF energy from RF amplifier to the DTRSW.

Topic ID: id_SL4198489-1137908

Dual drive quadrature calibration failure information

Topic ID: id_SL4198693-1137908

Generic error message

The Dual Drive Quadrature Calibration tool generates the following message when it detects an error that prevents it from executing.

Because the tool reports this generic error message for a variety of reasons, it is important to check the error log when this error message is displayed. Three conditions that can generate this error message are Scan Door Open, No Signal, or Low Signal.

If the Dual Drive Quadrature Calibration tool found a Low Signal condition, the tool generates the following error message in the error log.

The above faults may not be associated with the Dual Drive Quadrature Calibration tool. For example, a poorly calibrated RF amplifier could cause a low signal condition.

Topic ID: id_SL4813105-1137908

Viewing log file

The Dual Drive Quadrature Calibration tool generates a log file. However, there is no GUI viewer for it. To view calibration log files, open a C Shell and type:

>cd /usr/g/service/log/systools/

Note: The Shell window can only be launched when the EA3 user is included in the authorized EA3 group. Users not in this EA3 group will not have access to launch the Shell window. If you are not logged on as the proper logon user, log out and then log back on as the correct EA3 user with the authorized permissions.

An example log file is below:

Iteration 1
Checking landmark location.
Land mark location from home position 1.100100e+03 mm
Setting up combined image scan... Please wait
TG Window = 53
Channel 1 and Channel 2 set to ON
Auto prescan successful...
Phantom offsets (mm) X:L 8, Y:A 24, Z=I -1
Completed scanning for combined image
Last exam: 53651
Extracting image 1 in Exam 53651 complete
Combined image SNR 136.41, Uniformity 87.26
Combined image SNR 136.41 lesser then required SNR 160.00
Compensation PASS
Difference PASS

The log file provides errors for particular issues. For example:

Combined image SNR 136.41 lesser then required SNR 160.00

indicates that test failed due to low SNR.

Compensation PASS

indicates if channel to channel attenuation passed or failed.

Difference PASS

indicates if channel to channel phase difference passed or failed.

Topic ID: id_SL4198493-1137908

Dual drive quadrature calibration failures due to magnitude: low Signal on one channel

Swapping the RF transmit or receive cables does not cause hardware damage, but it does create a situation known as reverse quadrature. When this occurs, the combined image has a low signal. To determine if this is the problem, generate the three images using the Dual Drive Quadrature Calibration tool.

The illustration below shows the results of a system that has proper quadrature and the proper signal strength from both channel 1 and channel 2.

Figure 8. Scans showing proper quadrature and proper signal strength

Values are approximate and may vary if system gain was not previously executed. The ratio between the combined scan and the single channel scan is approximately 1.41 : 1. If the value for the combined image is 1400, the value for the single channel scans should be approximately 1000.

Table 4. Tools and Test Equipment
Item	Quantity	Part Number
Body TLT sphere phantom (pink solution)	1	2360025
Body TLT short loader	1	2360037

Place the body TLT sphere and loader on the table. If you are using a flat (GEM) table, use the foam holder to contain the phantom.
Landmark the phantom and drive it into the magnet bore.
Click New Patient to set up for a scan.
Under Protocol, select Service. Then select DDquadrature.

Figure 9. Protocol selector screen
Set up and scan the combined image. DO NOT perform Auto Prescan. Perform Manual Prescan and set the values to:
- TG = 150
- R1 = 11
- R2 = 14
After scanning the combined image, removed the RF input cable from RF amplifier channel 2 by disconnecting J21. Leave channel 1 (J14) connected. Repeat the same scan WITHOUT changing any of the values for TG, R1, or R2. This linear scan uses only channel 1.
When the image for channel 1 is complete, reconnect J21 (channel 2 input) and disconnect J14 (channel 1 input). Repeat the same scan WITHOUT changing any of the values for TG, R1, or R2. This linear scan uses only channel 2.

Now there are three images. Review them. Figure 8 shows the results for a system that has proper quadrature and the proper signal strength from both channel 1 and channel 2. Use Table 5 to troubleshoot your images.

Table 5. Troubleshooting Scan Images
Scan result	Problem	Resolution
If the combined image has a weaker signal than either image from the single channels:	The system could be transmitting in reverse quadrature.	Somewhere in the RF transmit chain, the channel 1 and channel 2 cables are swapped. Locate the swapped cables and connect them correctly. Cables between DTRSW and the body coil must always be in the correct locations, or the body receive signal will be poor. Swapping channel 1 and channel 2 cables somewhere else in the transmit chain will not restore the body receive signal quality to normal.
If the signal for one of the channel images is lower than the other channel:	There could be low or no RF signal from one of the channels.	Check the RF output using: RF Amp Power Check tool or Power Measurement Kit (see Body and Head Maximum Power Setup and Calibration).

Topic ID: id_SL5099985-1137908

Phase Troubleshooting

Note: This process can be done for head or center location.

This section is designed to help the FE locate the largest contributor of phase shift in the transmit chain. This is done by swapping cables and hardware between the DTX1 exciter and the RF body coil, and checking for the largest change in phase after every swap. A change in polarity after a cable swap indicates that you have reached one of the cables contributing a majority of the phase shift. Ideally, each channel 1 and 2 transmit chain section should contribute almost no phase shift. In a normal system, swapping channel 1 and 2 cables in any location results in almost no change in phase polarity.

Using a normal system configuration, perform quadrature calibration in Test mode and record the initial residual phase value and polarity as result A.
In Figure 10, The circled numbers show where to swap cables. The numbers progress from the most-likely to the least-likely problem area.
For each action, swap all cable connections identified with swap symbol <—>. For example, for action 1, swap the channel 1 and channel 2 cables (swap J9 and J11 on the PGR cabinet, and swap J22 and J15 on the PEN cabinet).
In each action (except action 5) each end of the cable is swapped so that the entire section of cable is relocated to the other transmit line. Action 5, however, only swaps the cable ends connecting to the DTRSW.

Figure 10. Phase troubleshooting
Starting with action 1, swap both ends of cables as shown to relocate the entire cable onto the other transmit line. (For action 5, swap cables only at the DTRSW.)
For action 2, try the cable ends at the PGR and DTRSW first. If the problem continues, try the cable ends at the pen panel.
After swapping the cables, repeat quadrature calibration in Test mode for the given action, and record the new initial residual phase value and polarity as result B.
Compare the values recorded as result A and result B:
1. If the polarities are the same, neither of the cables are the cause of phase failure. Return the cables to the normal positions and repeat the steps above with the next numbered action, until you find the problem or all actions are done.
2. If the polarities are different and this is action 5, stop and replace the DTRSW because it is the source of most of the additional phase.
3. If the polarities are different and result A is positive, then most of the additional phase is in the channel 2 transmit cable that was swapped. Inspect the cable and confirm that it is the correct cable for the system. Reseat the cable.
4. If the polarities are different and result A is negative, then most of the additional phase is in the channel 1 transmit cable that was swapped. Inspect the cable and confirm that it is the correct cable for the system. Reseat the cable.
5. If the situation remains unchanged, the only items left are the DTX1 exciter and the body coil. Contact support before continuing.

Topic ID: id_SL12119089-1137908

Magnitude troubleshooting

Cable swapping can also be utilized to isolate magnitude issues with dual drive systems. The magnitude change between channels should not vary more than 5 counts when the RF transmit cables are swapped. The following process tests the entire transmit chain from the output of the exciter to the output of the DTRSW. The only cables that are not be tested are the cables that run between the DTRSW and the body coil.

Using a normal system configuration, perform quadrature calibration in Test mode and record the initial residual magnitude value and polarity as result A.
Swap cables between exciter outputs at J12 and J13 at the exciter, and swap cables between J2 and J3 at the DTRSW.

Figure 11. Magnitude troubleshooting
After swapping the cables, repeat quadrature calibration in Test mode for the given action, and record the new initial residual magnitude value and polarity as result B.
Compare the results. If there is a 5 count difference between the two magnitude values, the transmit chain is contributing to the magnitude error.

Topic ID: id_SL4198862-1137908

Using RFA tool to troubleshoot DD quadrature calibration failures

The RFA Loopback Test can be used to measure deviations in magnitude and phase for channel 1 and channel 2 anywhere in the transmit chain between the DTX exciter and the DTRSW. It cannot be used to accurately measure magnitude and phase for channel 1 and channel 2 from the RF body coil.

It is recommended that RFA be executed first at the output of the DTRSW. This will determine if an issue is either with the system electronics leading up to the DTRSW or if the issue is with the body coil. If the failure is determined to be before the DTRSW, RFA can be used to isolate the failure location.

Warning

Equipment Damage!

RF dummy load contains ferrous components. RF dummy load cooling fans can be permanently damaged by exposure to high magnetic fields.

RF dummy load MUST remain outside the magnet room at all times during RFA testing.

Topic ID: id_SL4198867-1137908

Tools and test equipment

Table 6. Tools and test equipment
Item	Quantity	Part Number
Power measurement kit	1	5307511
SST kit	1	5110731-4
70 dB, with 10 dB step, attenuator (from 3.0T Grafidy kit, part 2386042)	1	46-255838P2

Topic ID: id_SL5309362-1137908

Determining “Hot” channel

Either channel 1 or channel 2 could be the “hot” channel (that is, the channel with largest gain). First determine which channel is the hot, then use that channel to set the initial value of the attenuators. If you use the wrong channel to set up the attenuators, the values may be over-ranged, causing inaccurate results.

To determine which channel has larger gain, examine the results from the DD Quadrature Calibration tool. The channel with the larger attenuation value reported in the calibration tool is the hot channel.

Based on which channel is hot, follow the correct instructions below (Running RFA: channel 1 First or Running RFA: Channel 2 First).

Topic ID: id_SL4738776-1137908

Running RFA: channel 1 First

Complete these steps if you have determined that channel 1 is the hot channel (see Determining “Hot” channel). If channel 2 is the hot channel, refer instead to Running RFA: Channel 2 First.

Topic ID: id_SL4738777-1137908

Setup for channel 1

Note:

See Setup for Channel 2 for information on setting up channel 2.

Before running RFA, zero out any residual values in the DD Quadrature tool as follows:
1. On the Common Service Desktop, select Calibration then select DD Quadrature Calibration.
2. Select Reset.
3. Select Defaults (0,0).
4. Exit the DD Quadrature tool.
Ensure that the system is idle, and remove all portable coils from the bore.
Place the body TLT sphere and loader on the table. If you are using a GEM (flat) table, use the foam holder to contain the phantom.
Landmark the phantom.
On the driver module in the PEN cabinet, set switch 2 (SW2) to TR DISABLE and SW3 to DD DISABLE.
Figure 12. Setting TR and DD Disable
On the exciter/ref clock module located in the PEN cabinet, set the RF Enb switch to down (Disable).
Figure 13. Exciter/Ref Clock Module
To gather data from the first channel, set up the test configuration using the diagram and steps below.
Figure 14. DTRSW Troubleshooting for Channel 1
Disconnect the Ch2 transmit cable from the RF amplifier at J22. Connect the cable from J22 to the 3.0T 35 kW (50Ω) dummy load.
Disconnect J7 and J8 at DTRSW. Leave cables disconnected.
Remove Ch1 RF output cable to body coil from the DTRSW at J2. Leave the cable disconnected.
Place a 60 dB BNC element, labeled 2372868-22, into the Forward port of the 5010G RF power sensor. Install a metal element blank or any other sense element into the open port labeled Reflected on the power sensor. The Reflected port is not measured, so the type of element used to fill this port is not critical.
Connect the power sensor to J2 of the DTRSW.
Install two adjustable attenuators in series with the 60 dB element in the RF power sensor. Set up the attenuators. Set the 1 dB step attenuator to 4 dB, and the 10 dB step attenuator to 40 dB. Total additional attenuation provided by the step attenuators should be 44 dB.
Remove the body receive cable from the preamp combiner at J11. Connect a DC block at the end of this cable and connect the other end of the DC block to the step attenuator.
Disconnect the Ch2 RF transmit to body coil cable at J3 of the DTRSW. Leave the cable disconnected.

Remove the Ch2 RF transmit cable at J4 of the DTRSW. Connect this end to the output side of the RF power sensor using the RF cable from the SST kit and the two RF connectors from the RF power measurement kit.

Table 7. Required Connectors and Cables
Part Name	Part Number	Kit Name
RF Connector, 7/16 (Female) -> N (Male)	2372868-16	3.0T RF Power Measurement Kit
RF Connector, N-FEMALE -> HN (Male)	46-2211865P16	SST Kit
RF Connector, HN (Female) -> 7/16 (Male)	2372868-17	3.0T RF Power Measurement Kit

Disconnect the input cables to the preamp combiner at J9 and J10.
Disconnect J21 cable at the RF amplifier. Leave cable disconnected.

Topic ID: id_SL4738794-1137908

Data Analysis

Notice

When running RFA, select Ascending Mode because this mode provides the proper phase and magnitude information.

On the exciter/ref clock module located in the PEN cabinet, set the RF Enb switch to Enable (UP).
Insert the service key into the PC.
From the Common Service Desktop, select the Image Quality tab, and then select RFA.
Set Loopback Mode to Body Dummy, RF Pulse Type to Ascending, Dual Drive Output to Ch1 output only looped back and Disable Ch2 exciter output.
- For channel 1, set Dual Drive Output to Ch1 output only looped back and Disable Ch2 exciter output.
- For channel 2, set Dual Drive Output to Ch2 output only looped back and Disable Ch1 exciter output.
Figure 15. RF Analysis Tool Menu
Click Start.

Note: SVAT errors usually indicate a setup problem such as landmark, 32-channel patient table connector not connected, TR or DD fault, etc. Check the error log.
Check the loopback setup according to the pop-up request. Click Continue and then click Yes.
After 60 seconds, a message box appears. Do NOT respond to the message box at this point. Click the Patient icon in the upper right of the display.
Figure 16. Patient Icon
Slowly increase TG to 160 while adjusting the rotary attenuators (to prevent receiver over-range indicated by R1%>100 or R2% >100) until you achieve an R1% and R2% display on the manual prescan page of 84-94% with TG=160.

When using RFA to troubleshoot Dual Drive Quadrature Calibration issues, the transmit gain (TG) should be set to 160 for both channels because this is the nominal prescan value.

Do NOT change the attenuator settings for channel 2. The attenuator settings must be the same for both channels.
When done, click the Toolbelt icon to return to service window. Start the scan by selecting Proceed & auto-scan.

Figure 17. Message Box
After the scan and analysis ends, view the results. Compare the results to the typical normal plots shown in Figure 18.

Real failures exceed the example plot values by 2 or more times. Minor differences are not failures. Select the popup choice to erase the displays. The plots are saved as JPG files under /usr/g/service/cclass/RFA/.

Figure 18. Sample RFA Plot Results
From the RFA Intra-Pulse Phase Linearity Plot Analysis 1, record the Topavg (magnitude) value and the Avg Phase deg (Phase) values for channel 1. You may need to resize to view values. Use Table 9 to record these values.

Note:
If the plots are closed, they can be reopened. Go to directory /usr/g/service/cclass/RFA and open file with the suffix phafit.jpg.

For example: display P28160.7.RFA.bodydummy.2.phafit.jpg

Topic ID: id_SL4839405-1137908

Setup for Channel 2

On the exciter/ref clock module located in the PEN cabinet, set the RF Enb switch down (Disable).
To gather data from channel 2, set up the test configuration using the diagram and steps in the following illustration.
Figure 19. DTRSW Troubleshooting for Channel 2
Reconnect Ch2 transmit cable at RF amplifier (J22).
Disconnect Ch1 transmit cable from the RF amplifier at J4. Connect the cable removed from J4 to the 3.0T 35 kW (50Ω) dummy load.
Remove the Ch2 RF output cable to body coil from the DTRSW at J3. Leave the cable disconnected.
Move the RF power sensor input (currently connected to J2) to J3.
Leave variable attenuators set in the same values as channel 1.
Remove the body receive cable from the preamp combiner at J11. Connect a DC block at the end of this cable and connect the other end of the DC block to the step attenuator.
Remove the Ch1 RF transmit cable at J1 of the DTRSW. Connect this end of the cable to the output side of the RF power sensor using the RF cable from the SST kit and several RF connectors from the RF power measurement kit.
Disconnect J14 at the input of the RF amp.
On the exciter/ref clock module, set the RF Enb switch to up (Enable).
Repeat the steps in Data Analysis, changing the following on the RFA Analysis Tool (Figure 15):
- Set Loopback Mode to Body Dummy
- Set RF Pulse Type to Ascending
- Set Dual Drive Output to Ch2 output only looped back and Disable Ch1 exciter output
After the scan is complete, reconnect J14 at the RF amplifier.
From the RFA Intra-Pulse Phase Linearity Plot Analysis 1, record the Topavg (or magnitude) value and the Avg Phase deg (or Phase) values for channel 2. You may need to resize to view values. Use Table 9 to record these values.

Note:
If the plots are closed, they can be reopened from the JPG files where they are stored. Go to directory /usr/g/service/cclass/RFA and open the file with the suffix phafit.jpg.

For example: display P28160.7.RFA.bodydummy.2.phafit.jpg.

Topic ID: id_SL5309357-1137908

Running RFA: Channel 2 First

Complete these steps if channel 2 is the hot channel (see Determining “Hot” channel). If channel 1 is the hot channel, refer instead to Running RFA: channel 1 First.

Topic ID: id_SL5309653-1137908

Setup for Channel 2

Before running RFA, zero out any residual values in the DD Quadrature tool as follows:
1. On the Common Service Desktop, select Calibration then select DD Quadrature Calibration.
2. Select Reset.
3. Select Defaults (0,0).
4. Exit the DD Quadrature tool.
Ensure that the system is idle, and remove all portable coils from the bore.
Place the body TLT sphere and loader on the table. If you are using a GEM (flat) table, use the foam holder to contain the phantom.
Landmark the phantom.
On the driver module in the PEN cabinet, set switch 2 (SW2) to TR DISABLE and SW3 to DD DISABLE.

Figure 20. Setting TR and DD Disable
On the exciter/ref clock module located in the PEN cabinet, set the RF Enb switch down (Disable).
To gather data from channel 2, set up the test configuration using the diagram and steps in the following illustration.

Figure 21. DTRSW Troubleshooting to Channel 2
Disconnect Ch1 transmit cable from the RF amplifier at J4. Connect the cable removed from J4 to the 3.0T 35 kW (50Ω) dummy load.
Disconnect J7 and J8 at DTRSW. Leave cables disconnected.
Remove the Ch2 RF output cable to body coil from the DTRSW at J3. Leave the cable disconnected.
Place a 60 dB BNC element, labeled 2372868-22, into the Forward port of the 5010G RF power sensor. Install a metal element blank or any other sense element into the open port labeled Reflected on the power sensor. The Reflected port is not measured, so the type of element used to fill this port is not critical.
Connect the power sensor to J3 of the DTRSW.
Install two adjustable attenuators in series with the 60 dB element in the RF power sensor. Set up the attenuators. Set the 1 dB step attenuator to 4 dB, and the 10 dB step attenuator to 40 dB. Total additional attenuation provided by the step attenuators should be 44 dB.
Remove the body receive cable from the preamp combiner at J11. Connect a DC block at the end of this cable and connect the other end of the DC block to the step attenuator.
Disconnect the Ch1 RF transmit to body coil cable at J2 of the DTRSW. Leave the cable disconnected.

Disconnect the Ch1 RF transmit cable at J1 of the DTRSW. Connect this end of the cable to the output side of the RF power sensor using the RF cable from the SST kit and several RF connectors from the RF power measurement kit.

Table 8. Required Connectors and Cables
Part Name	Part Number	Kit Name
RF Connector, 7/16 (Female) -> N (Male)	2372868-16	3.0T RF Power Measurement Kit
RF Connector, N-FEMALE -> HN (Male)	46-2211865P16	SST Kit
RF Connector, HN (Female) -> 7/16 (Male)	2372868-17	3.0T RF Power Measurement Kit

Disconnect the input cables to the preamp combiner at J9 and J10.
Disconnect J21 cable at the RF amplifier. Leave cable disconnected.

Topic ID: id_SL5309677-1137908

Data analysis

Notice

When running RFA, select Ascending Mode because this mode provides the proper phase and magnitude information.

On the exciter/ref clock module located in the PEN cabinet, set the RF Enb switch to Enable (UP).
Insert the service key into the PC.
From the Common Service Desktop, select the Image Quality tab, and then select RFA.
Set Loopback Mode to Body Dummy, RF Pulse Type to Ascending, Dual Drive Output to Ch1 output only looped back and Disable Ch2 exciter output.
- For channel 1, set Dual Drive Output to Ch1 output only looped back and Disable Ch2 exciter output.
- For channel 2, set Dual Drive Output to Ch2 output only looped back and Disable Ch1 exciter output.
Click Start.
Note:
SVAT errors usually indicate a setup problem such as landmark, 32-channel patient table connector not connected, TR or DD fault, etc. Check the error log.
Check the loopback setup according to the pop-up request. Click Continue and then click Yes.
After 60 seconds, a message box appears. Do NOT respond to the message box at this point. Click the Patient icon in the upper right of the display.

Figure 22. Patient Icon
Slowly increase TG to 160 while adjusting the rotary attenuators (to prevent receiver over-range indicated by R1%>100 or R2% >100) until you achieve an R1% and R2% display on the manual prescan page of 84-94% with TG=160.
When using RFA to troubleshoot Dual Drive Quadrature Calibration issues, the transmit gain (TG) should be set to 160 for both channels because this is the nominal prescan value.
Do NOT change the attenuator settings for channel 2. The attenuator settings must be the same for both channels.
When done, click the Toolbelt icon to return to service window. Start the scan by selecting Proceed & auto-scan.

Figure 23. Message Box
After the scan and analysis ends, view the results. Compare the results to the sample normal plots shown in Figure 24.
Real failures exceed the example plot values by 2 or more times. Minor differences are not failures. Select the popup choice to erase the displays. The plots are saved as JPG files under /usr/g/service/cclass/RFA/.

Figure 24. Sample RFA Plot Results
From the RFA Intra-Pulse Phase Linearity Plot Analysis 1, record the Topavg (magnitude) value and the Avg Phase deg (Phase) values for channel 1. You may need to re-size to view values. Use Table 9 to record these values.
Note:
If the plots are closed, they can be reopened. Go to directory /usr/g/service/cclass/RFA and open file with the suffix phafit.jpg.

For example: display P28160.7.RFA.bodydummy.2.phafit.jpg.

Topic ID: id_SL5309693-1137908

Setup for Channel 1

On the exciter/ref clock module located in the PEN cabinet, set the RF Enb switch to down (Disable).

Figure 25. Exciter/Ref Clock Module
To gather data from the first channel, set up the test configuration using the diagram and steps below.

Figure 26. DTRSW Troubleshooting for Channel 1
Reconnect the Ch1 transmit cable at the RF amplifier (J4).
Disconnect the Ch2 transmit cable from the RF amplifier at J22. Connect the cable from J22 to the 3.0T 35 kW (50Ω) dummy load.
Remove the Ch1 RF output to body coil cable from the DTRSW at J2. Leave the cable disconnected.
Move the RF power sensor input (currently connected to J3) to J2.
Leave the variable attenuators set to the same values as channel 2.
Remove the body receive cable from the preamp combiner at J11. Connect a DC block at the end of this cable and connect the other end of the DC block to the step attenuator.
Remove the Ch2 RF transmit cable at J4 of the DTRSW. Connect this end to the output side of the RF power sensor using the RF cable from the SST kit and the two RF connectors from the RF power measurement kit.
Disconnect J21 at the input of the RF amp.
On the exciter/ref clock module, set the RF Enb switch to up (Enable).
Repeat the steps in Data analysis, changing the following on the RFA Analysis Tool:
- Set Loopback Mode to bodydummy
- Set RF Pulse Type to Exp (Ascending)
- Set Dual Drive Output to Ch1 output only looped back and Disable Ch2 exciter output
Figure 27. RF Analysis Tool Menu
After the scan is complete, reconnect J21 at the RF Amplifier.
From the RFA Intra-Pulse Phase Linearity Plot Analysis 1, record the Topavg (or magnitude) value and the Avg Phase deg (or Phase) values for channel 1. You may need to resize to view valves. Use Table 9 to record these values.
Note:
If the plots are closed, they can be reopened from the JPG files where they are stored. Go to directory /usr/g/service/cclass/RFA and open the file with the suffix phafit.jpg.

For example: display P28160.7.RFA.bodydummy.2.phafit.jpg

Topic ID: id_SL5309715-1137908

Calculating dB difference

Table 9. Record values
	Channel 1	Channel 2
Topavg
Avg Phase deg

Calculate the dB difference using the following formula:

If the MagBal delta is greater than 0.5 dB (either positive or negative), there could be an issue with the system electronics. Check RF output. It is also recommended to run RFA at the output of the RF amplifier and the exciter to isolate cause of high MagBal.
However, if the MagBal delta is less than 0.5 dB, there could be an issue with the body coil tuning.
Note:
If the plots are closed, they can be reopened from JPG files where they are stored. Go to directory /usr/g/service/cclass/RFA and open the file with the suffix phafit.jpg.

For example: display P28160.7.RFA.bodydummy.2.phafit.jpg

Note: When setting the variable attenuators for this test, do not change the settings. Channel 1 and channel 2 must be set at the same attenuation values for this test.
If the phase difference between channel 1 and channel 2 is greater than 90 degrees, ±15 degrees (or 75 to 105 degrees), there could be an issue with the system electronics. It is recommended to run RFA at the output of the RF amplifier and the exciter to isolate the cause of the phase issue.
In the RFA results, channel 1 should lead channel 2. The phase of channel 1 should be +90 degrees relative to the phase of channel 2.
For example, if the phase for channel 1 is 110.0 degrees and the phase for channel 2 is -160.0 degrees, the actual phase difference is 90 degrees.
Figure 28. Polar Chart
If both the magnitude and phase results for the DTRSW output are acceptable, the problem is possibly in part of RF chain that is not included in RFA test loop, such as the RF body coil.

Topic ID: id_SL5309716-1137908

Finalization for RFA check

Return the system to the normal operating configuration.

Topic ID: id_SL4199215-1137908

Check Body Coil Tuning with Network Analyzer

If the RF transmission from channel 1 and channel 2 is good, order a Network Analyzer (part #5336593-2).

Topic ID: id_2012351

Finalization

Procedure

Remove the phantoms, pads, and body loader from the cradle and return them to the assigned storage.