Gradient Calibration (GradCal) - Auto Mode

Prerequisites

1 Preparation for Scan

In this procedure, the strength of the gradient fields are calibrated by modifying the control variables cfxfull, cfyfull, and cfzfull. A separate scan will be taken to calibrate each of the three gradient fields (x, y, and z). For TwinSpeed, the whole procedure must be repeated for each gradient mode (GradMode) separately, Whole-Body (WB) and Zoom (ZM) gradients.

Procedure

  1. Place head coil on cradle and plug coil in.
  2. Place the DQA phantom in head coil.
  3. Turn on alignment lights.
  4. Move the cradle to center the phantom with the alignment light.
  5. With laser light on center of phantom, press the Landmark button.
  6. Press Move to Scan. (Head Coil should automatically move to the center of the magnet.
  7. Go back to the GOC and resume scan setup.

2 Start the DQA Analysis Tool- Prepare for DQA Analysis (GradCal)

The Daily Quality tool analyzes the DQA image to determine if the image is skewed in the x direction (x-y planes). Analysis performed on an image with a few degrees of skew will still give an accurate GradCal value.

Procedure

  1. Select Utilities Desktop. Refer to Figure 1

    Figure 1. Utilities Desktop

  2. Select Service Browser from the Service Desktop Manager (CSD).
  3. Select the Calibration tab.
  4. Select the DQA Calibration from the calibration list.
  5. Select Start the DQA Calibration by clicking on the Click here to start this tool. Refer to Figure 2.

    Figure 2. Starting Gradient Calibration

    note:

    The Daily Quality Assurance Test tool should appear. Refer See Figure 3.

  6. Select Test Mode Option: Type 2 [2= Auto Mode], Enter.

    Figure 3. DQA Calibration Tool

  7. Select Test Option: Type 5 [5= GradCal All Three Axis], Enter.
  8. The Calibration tool will begin and pause requiring that you to make a gradient coil choice. Refer to Figure 4.

    Figure 4. DQA Calibration Tool

  9. Select appropriate mode for Twin Speed Systems (recommend to use option B = Both the Modes). The tool will scan and adjust in the following order: X-Whole; X-Zoom; Y-Whole; Y-Zoom; Z-Whole; Z-Zoom.

    The system will start scanning. The sequence of events is prescan, then scan. The system will re scan if adjustments are necessary. Select Y to update GradientConfig.cfg. See Figure 5.

    Figure 5. DQA Calibration Tool

  10. You must select Y to perform the final test scan. See Figure 6.

    Figure 6. DQA Calibration Tool

  11. When complete, you will see the main menu. Type 6 to select option [6=Quit], Enter. Then press Enter at the prompt press Enter to quit ->. See Figure 7.

    Figure 7. DQA Calibration Tool

3 Finalization

Procedure

  1. Remove all phantoms and coils from the magnet
  2. Return the scanner to normal operation