• SIGNA MR355 / SIGNA MR360
  • Service Manual
  • 5856356-3EN Revision 5.0
  • Basic Service Documentation. Copyright General Electric Company.
  • Object ID: 00000018WIA30FB5E20GYZ
  • Topic ID: id_13106121 Version: 4.0
  • Date: Feb 14, 2020 4:02:30 PM

DQA II Tool Troubleshooting

DQA II Tool

See Table 2 to determine action if there are failures when using DQA II Tool.

Table 1. DQA Phantom Depending on System
System Type Phantom Illustration Part Number
1.5T with old style head coilGreen solution, no loader Figure 2 2131027-2
1.5T with new style head/split top coilGreen solution with loader Figure 1 2322997-2
3.0T long bore magnet (E2)Clear solution, no loader Figure 2 2258365
3.0T short bore magnetGreen solution with loader Figure 1 2322997-2
Figure 1. Phantom Positioning for New Style (Split Top) Head Coil
Figure 2. Phantom Positioning for Old Style Head Coil
Figure 3. Directional Gradient Information in Bore
Table 2. Potential Errors When Using DQA II Tool
Symptom in DQA II Tool Actions Required Window Recommendations
One or more gradients appear not to be functioning at all. Verify the system can properly scan the head image. See Review DQA II Images to Verify Proper Head Scan.
Z gradient coil appears to be driven by the wrong gradient input.

  1. Check coil type (Figure 1 or Figure 2), phantom type (Table 1), and positioning, coil latches/clamps, landmarking, etc. (Figure 3). If an issue is found, correct it and run the DQA II Tool again.

  2. Review the most recent DQA exam in the image browser.

    1. If the latest exam has images labeled Axial (Coronal), make sure at least one of those images looks similar (shape and position of phantom features) to Figure 4 or Figure 5.

    2. If the acquired axial (coronal) image looks similar to Figure 4 or Figure 5 (even if degraded via low SNR, ghosting, distortion, etc.), suboptimal image quality may have confused the DQA II Tool. Resolve the IQ related issues before running DQA II Calibration.

    3. If the axial (coronal) image does not look similar to Figure 4 or Figure 5, there may be a gradient wiring/setup problem. Proceed to the next step to resolve.

  3. See Gradient Cabling.

Z gradient polarity appears to be inverted.

  1. Check coil type, phantom type and positioning, coil latches/clamps, landmarking, etc. If an issue is found, correct it and run the DQA II Tool again.

  2. Review the most recent DQA exam in the image browser.

    1. If the latest exam has images labeled Coronal, make sure at least one of those images looks similar (shape and position of phantom features) to Figure 5.

    2. If the acquired coronal image looks similar to Figure 5 (even if degraded via low SNR, ghosting, distortion, etc.), suboptimal image quality may have confused the DQA II Tool. Resolve the IQ related issues before running DQA II Calibration.

    3. If the acquired coronal image does not look similar to Figure 5, there may be a gradient wiring/setup problem. Proceed to the next step to resolve.

  3. If the latest exam contains an image labeled Axial, the DQA II Tool made an early detection of a Z gradient polarity problem from the set of multi-slice images.

    1. If the central bar feature (above arrow in Figure 4) moves toward the GE logo and comb features as the slice location moves from INFERIOR to SUPERIOR, the Z gradient may be polarity flipped. Proceed to the next step.

    2. If the bar moves away from the GE logo and comb features, the suboptimal image quality may have confused the DQA II Tool. Resolve the IQ related issues before running DQA II Calibration.

  4. Review the images in the browser, checking for an error caused by image degradation such as noise, distortion, etc. See Figure 4 and Figure 5 for proper images.

  5. See Gradient Cabling.

Phantom used appears to be wrong and/or severely mispositioned.

  1. Check coil type, phantom type and positioning, coil latches/clamps, landmarking, etc. If an issue is found, correct it and run the DQA II Tool again.

  2. Visually verify the phantom is positioned approximately in the center of the bore before scanning.

Phantom is offset more than ±36 mm along Z.

  1. Check coil type, phantom type and positioning, coil latches/clamps, landmarking, etc. If an issue is found, correct it and run the DQA II Tool again.

  2. Make sure the correct phantom is used, properly positioned and centered in the head coil and landmarked.

  3. Check Laser Light Alignment to ensure that the axial alignment light aims straight down and lines up with the crosshairs on the DQA phantom.

  4. Make sure the isocenter Z value is close to the default for the magnet type, and verify that the proper magnet and magnet cover options are properly set in the MR confess file.

For any of the following:

  • X and Y gradient coil inputs appear to be swapped.

  • X and Y gradient polarities appear to be inverted.

  • X gradient polarity appears to be inverted.

  • Y gradient polarity appears to be inverted.

  • X and Z gradient polarities appear to be inverted

  • X gradient polarities appear to be inverted.

  1. Check coil type, phantom type and positioning, coil latches/clamps, landmarking, etc. If an issue is found, correct it and run the DQA II Tool again.

  2. Review the images in the browser, checking for an error caused by image degradation such as noise, distortion, etc. See Figure 4 and Figure 5 for proper images.

  3. See Gradient Cabling.

For any of the following:

  • Phantom appears to be rotated 16 degrees about the physical Z axis.

  • Phantom appears to be rotated 16 degrees about the physical Y axis.

  1. Check coil type, phantom type and positioning, coil latches/clamps, landmarking, etc. If an issue is found, correct it and run the DQA II Tool again.

  2. Make sure the correct phantom is used, properly positioned and centered in the head coil and landmarked.

  3. Visually inspect the phantom in the head coil to verify it is not rotated.

    Note:

    If a positive value is observed for phantom rotation in the Z direction, rotate the phantom clockwise (when viewing from the front).

  4. Avoid misaligning the phantom (Figure 9) when repositioning. See Figure 3 for axes information.

For any of the following:

  • Phantom center appears to be offset 20 mm along physical X.

  • Phantom center appears to be offset 20 mm along physical Y.

  1. Check coil type, phantom type and positioning, coil latches/clamps, landmarking, etc. If an issue is found, correct it and run the DQA II Tool again.

  2. Visually inspect the phantom in the head coil to verify it is not rotated.

    1. If a positive value is observed for the phantom position in the X direction, move the phantom to the left (when viewing from the front).

    2. If a positive value is observed for the phantom position in the Y direction, move the phantom down (when viewing from the front).

  3. Avoid misaligning the phantom (Figure 9) when repositioning. See Figure 3 for axes information.

Review DQA II Images to Verify Proper Head Scan

  1. Open the browser.

  2. Review the last exam.

The DQA II Tool scans axial images (example in Figure 4) in one study, and creates a new exam or study (example in Figure 5) for the coronal images. A similar axial should appear, but it may not be the center image.

Figure 4. Axial Image
Figure 5. Coronal Image

Gradient Cabling

  1. Before checking gradient cabling, verify that the gradient polarities in the Gradient Config file are properly set.

    • For magnets ramped positive (red to + and black to -), all values should be positive.

    • For magnets ramped negative or reverse ramped (red to - and black to +), all values should be negative.

  2. To view gradient config values:

    1. Open a C-shell and type cd /w/config.

    2. Type more GradientConfig.cfg.

    3. Scroll down and highlight the desired file: xfull, yfull, zfull.

    4. To review the entire contents of the file, type more out.

    Note:

    For all TwinSpeed systems, review these files: GradientConfig.cfg.WHOLE and GradientConfig.cfg.ZOOM.

Gradient Cabling for BRM

Figure 6. Gradient Cabling for BRM/CRM

Gradient Cabling for TRM

Figure 7. Gradient Cabling for TRM in Equipment Room
Figure 8. Gradient Cabling for TRM in Magnet Room

Example of Rotated Image

The illustration below is an example of a phantom rotated counterclockwise and grossly offset in the +X position.

Figure 9. Example of Rotated and Offset Axial Image