• Discovery MR750w and SIGNA™ Architect T 3.0T System Service Methods
  • 5690002-2EN Revision 4
  • Object ID: 00000018WIA3091CE20GYZ
  • Topic ID: id_13106529 Version: 3.2
  • Date: Feb 4, 2021 7:52:09 PM

Body coil tuning (network analyzer kit 5336593-2)

Prerequisites

Table 1. Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
1 - - -
Table 2. Tools and test equipment
ItemQuantityEffectivityPart numberManufacturer
Network Analyzer Service Tool Kit1-5336593 (5336593-2, 5336593-3 or 5336593-4)-
Body Loader with Sphere Phantom1-2371511-
Table 3. Safety
Table 4. Required conditions
ConditionReferenceEffectivity

Body Coil Isolation is done.

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System must be in scanning condition

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About this task

Body coil tuning is completed by adjusting variable capacitors (VC1, VC2, VC3) to tune fS11, fS22, fS21, and MagS21 so that these parameters are within specification. If it is difficult to adjust parameters by variable capacitors, replacement of dielectric material might be required, as described in Adjustment by dielectric material.
Figure 1. Body coil tuning flowchart
Topic ID: id_SL3911442-1128973

Hardware setup

Procedure

  1. Do the following sub-steps to set up any body coil scan on scan window to set up driver module body BIAS mode.
    1. On the Exciter/Ref Clock module located in the Pen cabinet, set the RF ENB switch to DOWN (Disable).
      Figure 2. Exciter/Ref clock module
    2. Dock the patient table.
    3. At the magnet control panel, press [In] to advance the cradle into the bore until the display reads 800 mm.
    4. Press [Alignment Light]. Then, press [Landmark] and [Advance to Scan] sequentially to advance the empty cradle to the magnet isocenter.
    5. At the operator console, set up any body coil scan to set up driver module bias mode. The following steps are an example of a body coil scan setup:
      Note: The driver module should now be supplying the correct DC bias for tuning the body coil (-13.6 VDC).
      1. Click New Patient.
      2. For Patient ID, enter geservice. For Weight, enter 111. Click [Start Exam].
      3. In the Protocol Selector, select Service from Protocol Library. Select snr_check and SNR Body Axial, FuncChk:Sys. Then, click [>] (right arrow) icon to transfer the protocol to the right (Multi Protocol Basket).
      4. Click [Accept] for Protocol Selector.
      5. Click [Save Rx] to download body coil scan parameter.
      6. Click [Scan] and select Manual Prescan from the menu.
      7. Allow the scanner to pulse once, then select [Done] in the Manual Prescan window.
    6. Use the emergency release latch on the cradle to unlatch the cradle from the LPCA, and then pull the cradle back onto the patient table so that it is at the Home position.
    7. At the magnet control panel, press the In button to drive the LPCA out of the magnet bore to the end of the rear bridge.
    8. Undock the patient table and place it off to the side.
  2. Remove the bridge cover, right center cover, and right rear cover.
    Figure 3. Remove covers
  3. Place the body loader with phantom on the bridge, and push it to the magnet center so that it is centered right-to-left on the bridge. The front edge of the body loader is 835 mm (33 inches) away from the front edge of the bridge.
    Figure 4. Body loader setup
Topic ID: id_SL3911426-1128973

Calibration of network analyzer

Procedure

  1. Connect bias T at port 1 and port 2. Do not connect the bias cable at this time.
    Figure 5. Bias T Installation
  2. Note:

    It is recommended that you connect a mouse to one of the USB ports on the network analyzer.

    If you do not use a mouse, use the hard keys. For example, select [Menu] hard key and then use arrow (<, >) hard keys to navigate and highlight, and [ENTER] hard key to select from menu.

    Power ON the network analyzer.
    Figure 6. Power ON
  3. From the Nwa-Setup menu, select External Tools > Calibration.lnk.
    Figure 7. Nwa-Setup menu
  4. Connect N(m) to N(m) coaxial cable to bias T of port 1.
    Figure 8. Cable connection 1

    Do not touch cable ends. Minimize human interaction during network analyzer calibration, because this can change the impedance of the calibration setup.

    Do not cross the cables. Route the cables so they are parallel and separated from each other as much as possible.

    Note: It is recommended that the 50 ohm load (Match Standard) be measured with a DVM to confirm that it is operational.
  5. When the following message is displayed, connect female barrel and “BNC female to N male” to the end port 1 cable and press Enter (or click OK). Do not make any changes until prompted.
    Figure 9. Connect OPEN message

    It takes about 15 seconds for the next message to display.

  6. When the following message is displayed, connect short to “BNC female to N male” and press Enter (or click OK).
    Figure 10. Connect SHORT Message
  7. When the following message is displayed, remove short. Connect 50 ohm load and press Enter (or click OK).
    Figure 11. Connect MATCH Message (50 Ohm Load)
  8. Repeat Step 4 through Step 7 for port 2.
  9. Connect port 1 and port 2 cables through female barrel.
    Figure 12. Cable connection 2
  10. When the following message is displayed, press Enter (or click OK).
    Figure 13. Connect THROUGH message

    Calibration is complete.

    The buttons at the right side of the screen are displayed after calibration is completed.

    Figure 14. Buttons at screen right
  11. Connect the cables to the network analyzer as shown below.
    Figure 15. Hardware setup
Topic ID: id_SL3911454-1128973

S-Parameter measurement

Topic ID: id_SL4213598-1128973

Operation check

Procedure

  1. From the Nwa-Setup menu, select External Tools > Rough Tuning.lnk.
    Figure 16. Rough tuning selection
  2. Check that plots are shown as follows. If not, check the bias cables.
    Figure 17. Rough tuning plots
  3. Remove one bias cable at the network analyzer bias T (port 1). Confirm that there is a significant change in the plots for fS11.
  4. Remove the other bias cable at the network analyzer bias T (port 2). Confirm that there is a significant change in the plots for fS22.
  5. Restore two bias cable to the network analyzer bias T (port 1 and port 2).
Topic ID: id_SL4213281-1128973

Confirmation measurement

Procedure

  1. From the Nwa-Setup menu, select External Tools > Confirmation Measurement.lnk.

    It takes about 30 seconds for the Measurement Results screen to display.

    Figure 18. Measurement results
  2. Write down the fS11, fS22, fS21, and MagS21 values.

    If frequencies are in specification, MagS21 should be in specification.

    Table 5. Data Sheet
    ParameterSpecificationMeasured Value
    Upper conditionLower condition
    Ch1 S11 notch frequency128.05 MHz127.75 MHz
    Ch2 S22 notch frequency128.05 MHz127.75 MHz
    |fS11 - fS22|50 KHzN/A
    S21 notch frequencyN/AN/A
    |(fS11 + fS22)/2–fS21|50 KHzN/A
    MagS21 -20 dBN/A
Topic ID: id_SL4202286-1128973

Data analysis

Procedure

  1. Download the following Data Analysis Tool (PDF), open the file in Adobe Acrobat Reader 9.0 or later, and follow the instructions in the tool.
    The file cannot be used in a web browser.
  2. In the PDF, click the screen once to activate the tool.

    This tool analyzes the following:

    1. If fS11 and fS22 are within 127.6 MHz ~ 128.2 MHz for first measurement. If fS11 or fS22 is out of 127.6 MHz ~ 128.2 MHz:
    2. If all measured values satisfy specifications (PASS indication) the tool shows the message “All Pass. End of Tuning”. This concludes body coil tuning. Go to Step 2.
    3. If any measured values are out of specification and all of VC do not reach the end of rotation, the tool navigates to adjust body coil by VC1, VC2, or VC3 as described in Tuning.
    4. If any measured value is out of specification and VC reaches the end of rotation, the tool determines whether it is possible to tune by VC, or if dielectric material replacement is required. If tuning by VC1, VC2, or VC3 is possible, the tool navigates to adjust body coil by VC1, VC2, or VC3 as described in Tuning. If replacement of dielectric material is required, the tool navigates to Adjustment by dielectric material.
Topic ID: id_SL4202224-1128973

Tuning

About this task

This section describes how to adjust fS11, fS22, or fS21 according to the Data Analysis Tool results so that all measured values are within specification.

Procedure

  1. From Nwa-Setup menu, select External Tools > Rough Tuning.lnk.
    Figure 19. Rough tuning
  2. Read fS11, fS22, or fS21/MagS21 values.
    Figure 20. Rough tuning plots

    To show a single waveform window in a display, double-click on the desired window to expand it. To return to the four-window display, double-click again on the window.

  3. Turn VC1, VC2, or VC3 using stick to tune fS11, fS22, or fS21, respectively, so that fS11, fS22, fS21 are as close as the target frequency in the Data Analysis Tool.

    1 clockwise turn of VC1 => -10 kHz to -20 kHz of fS11, 1 clockwise turn of VC2 => -10 kHz to -20 kHz of fS22

    1 clockwise turn of VC3 => +15 kHz to +40 kHz of fS21. fS11 and fS22 are slightly decreased by tuning VC3 clockwise. Reconfirm fS11 and fS22 values after VC3 adjustment.

    Figure 21. Tuning
  4. After adjustment is complete, go to Confirmation measurement to confirm fS11, fS22, fS21, and MagS21.

    Tips for fine tuning: If fS11, fS22, and fS21 are within target frequency +/– 150 KHz but some results are still out of specification, use Confirmation Measurement.lnk described in Confirmation measurement to check frequency instead of Rough Tuning.lnk.

    The difference between Rough Tuning Mode and Confirmation Measurement Mode is as follows.

    • Rough Tuning Mode: Real time measurement, but the measured value is not stable enough for fine tuning.
    • Confirmation Measurement Mode: Accurate measurement value is shown by single sweep, but it takes time to show result.
Topic ID: id_SL4135914-1128973

Further adjustment

Topic ID: id_SL4206076-1128973

Adjustment by dielectric material

About this task

Under the following conditions, adjustment of dielectric material is needed.
  • fS11, fS22, or fS21 < 127.6 MHz at the first measurement of S-Parameter measurement.
  • fS11, fS22, or fS21 > 128.2 MHz at the first measurement of S-Parameter measurement.
  • VC1, VC2, or VC3 reached the end of rotation and the Data Analysis Tool indicates you should perform adjustment by dielectric material.

Procedure

  1. Select End Exam from the scan window menu (End/End Exam).
  2. Note: Perform LOTO on the PGR PDU/gradient subsystem before body coil removal. See the MR Service Safety Manual, PN 5452735.
    Remove the body coil. Refer to RF Body Coil Replacement for body coil removal instructions.

    If there is no body coil FRU case available, place the body coil on two pads, making sure they protect the drive cables of body coil from damage. Make sure the body coil does not roll over.

  3. Change dielectric material according to the site conditions.
    • fS11 or fS22 > 128.2 MHz: Increase dielectric material by one step.
    • VC reached end of rotation and fS11 or fS22 >128.05 MHz, or fS21 > (fS11 + fS22)/2 + 0.05 MHz: Increase dielectric material by one step.
      Figure 22. Increase dielectric material by one step
    • fS11 or fS22 < 127.6 MHz: Decrease dielectric material by one step.
    • VC reached the end of rotation and fS11 or fS22 < 127.75 MHz, or fS21 < (fS11 + fS22)/2 – 0.05 MHz: Decrease dielectric material by one step.
      Figure 23. Decrease dielectric material by one step

    If 16 lower shift pieces are attached on body coil, no additional material is needed for replacement.

    The body coil FRU includes dielectric materials for adjustment. There is no need to order the dielectric material FRU kit. If dielectric material is required after XRMw replacement, order the dielectric material FRU kit (5423650).

    When replacing dielectric material to “Standard x 8 pieces” or “Standard x 8 pieces + Lower Shift x 8 pieces”, the order is important. Follow the illustration below.

    Figure 24. Dielectric Material Order
  4. Inspect airflow gaskets (5404530 and 5404530-2). Gaskets should be bonded along entire length.
    Figure 25. Air flow gasket
  5. After changing the dielectric material, install the body coil by reversing the steps of removal. Refer to RF Body Coil Replacement.
  6. Verify that LOTO is removed and TPS reset is done.
  7. Set VC1, VC2, and VC3 to the center of rotation by turning VC counter-clockwise until it reaches the end, and then turning VC clockwise by 23 turns.
  8. Return to Hardware setup.
Topic ID: id_SL4206078-1128973

Adjustment of MagS21

Procedure

  1. If MagS21 fails but other values are within specification, perform Body Coil Isolation.
  2. If MagS21 fails after body coil isolation and body coil tuning, replace the body coil.