• Discovery MR750 3.0T System Service Methods
  • 5690009-2EN Revision 4
  • Object ID: 00000018WIA30E1DE20GYZ
  • Topic ID: id_13107004 Version: 2.0
  • Date: Feb 22, 2021 1:47:09 AM

Multi-Coil Quality Assurance Tool

Prerequisites

Table 1. Personnel requirements
Required personsPreliminary requirementsProcedureFinalization
1Not Applicable20 minutes per coil minutesNot Applicable
Table 2. Tools and test equipment
ItemQuantityEffectivityPart numberManufacturer
Coils and Phantoms for all coils to be tested are required.----
Body System Gain tool----
Isocalibration----

About this task

The Multi-Coil Quality Assurance (MCQA) Tool simplifies data acquisition and analysis of SNR for surface coils. It helps detect dead coil elements as well as develop improved ISNR specifications for all Multi-coils, independent of scanner instabilities. The tool does not rely on ROI placement as other SNR tools have in the past. Instead, it chooses slice locations based on coil geometry, acquires one Spin Echo Image, and turns off RF to gather a noise image. The noise mean of the 2D-noise-only image is subtracted from the 2D intermediate image.

The summed signal (2D intermediate image – noise mean) is calculated, and then the signal is divided by the Standard Deviation of the Noise of all pixels of the noise-only-image to give the ISNR. See the formulas below.

Figure 1. ISNR Formula
Topic ID: id_SL1798174-1050993

Setting Up and Starting the Multi-Coil QA Tool

Procedure

  1. On the Common Service Desktop (CSD), click Image Quality, then click Multi-Coil QA Tool, and then click Click here to start this tool. The Coil Log Viewer appears.
    Figure 2. Multi-Coil QA Tool Example
    Note:

    If possible, run the Coil Datapath Diagnostic tool before the MCQA to validate the receive chain functionality. If the MCRV tool has missing or failed results, the MCQA tool detects it. If popup appears either select Yes to proceed anyway with scan or No to end MCQA and exit to run Coil Datapath Diagnostic.

  2. The Current Coil field is automatically populated based on the ID of the coil connected to the LPCA. The listed names are the physical coil names for each coil.
    Note:

    Coil names are specific to the coil connector. Legacy coils should not have reference to the connector, but any new coil with the Bendix connector will have an HDx identifier in the coil name. During download, the tool should detect if the wrong coil was selected and give an error. The user then has the ability to pick again.

  3. Enter a number in the Coil Serial #: field if desired, or if the site has more then one of the same coil type.
  4. Position the coil and phantoms according to the QA test in the coil’s vendor manual, then Landmark on the coil or physical mark as directed by the QA test, and then Advance to Scan.
    Note:

    For the 8 and 12-channel Body array coils, Landmark on the middle cross hair on the coil.

  5. In the MCQA Tool window, press the Start button to begin the test. A warning dialog queries the user to verify the coil/phantom setup and position. Select Yes to continue.
    1. The Status window of the MCQA Tool GUI continuously updates to provide information on what the tool is doing at any point in time.
    2. A progress indicator displays approximate total test time, elapsed time and percentage complete, as shown in Illustration 3.
      Figure 3. Status and Time Bar
  6. After the test finishes, the name of the Results file is listed, along with the Pass/Fail status of the test.
Topic ID: id_SL1798177-1050993

Viewing Report Results

Procedure

  1. After running the Multi-Coil QA test, select View Report Details to see the results. To review past results, select File, Open Results File and then select the desired coil results file. The Results Viewer opens as shown in Illustration 4. The Results file name and Pass/Fail Results are listed across the top of the viewer.
    Figure 4. Results Viewer Example
  2. The Results appear in the Results window on the left side of the GUI.
  3. To review the results of a different test for this same coil, select the appropriate Test # from the scroll box at the lower middle portion of the screen.
  4. To graph the data, select one of the following three choices Isig, Noise, or Isnr, and the corresponding results will be displayed in the window to the right. The signal, noise, or integrated SNR values will be listed on the vertical axis, with the images along the horizontal axis.
  5. To graph the Isnr Specification values in addition to the data, select the Isnr Specs check box below the Test # box in the lower middle portion of the screen.
  6. The graph results will automatically scale according to the data values. To manually scale the data, enter Ymax and/or Ymin values into the boxes at the top right of the GUI.
  7. To view all the Signal or Noise Images, select View Signal Imgs or View Noise Imgs respectively, and an image viewer will appear with one image per coil element, ordered left–to-right and top-to-bottom. See Illustration 5.
    Figure 5. Signal and Noise Images
  8. From the MCQA Viewer, select the Plot noise CC to display a 3D plot of the noise correlation data for the results being viewed. The data shows the relative cross correlation of noise between receiver channels. Green data is a one-to-one correlation. Red data are correlations above the threshold.
    Figure 6. Signal and Noise Images
    Note:

    There are currently no spec for the cross correlation data. It may be possible to determine patterns per coil and set specs as more data is collected.

  9. Past Multi-Coil QA results are stored on the system that allow for the ISNR data to be trended over time. On the Multi-Coil QA Results Viewer window, select the Trend Data button, and the MCQA Trend Viewer displays as shown in Illustration 7.
    Figure 7. MCQA Trend Viewer
Topic ID: id_SL1816441-1050993

MCQA Trend Viewer

About this task

Every time the MCQA test finishes, a new Results file is generated. These results can be graphically trended within the MCQA Trend Viewer. All the Results Files available for trending are listed in the window to the left of the screen.

Procedure

  1. Select the Test and Image numbers of the data you would like to review from the middle scroll boxes.
  2. Choose the Isig, Noise, or Isnr radio button that corresponds with the desired graph.
  3. The data will be displayed over time (# of tests run). To change the vertical scale, enter new values into the Ymax and Ymin boxes at the top of the screen.
  4. Statistics pertaining to the existing data will be given in the box in the lower center section of the GUI.
Topic ID: id_14984778

Finalization

Procedure

  1. To exit the MCQA Trend Viewer and Results Viewer, select the Close button.
  2. Close all image files.
  3. Remove all coils and phantoms from the system bore.