• Object ID: 00000018WIA30501970GYZ
  • Topic ID: id_40021818 Version: 1.10
  • Date: Aug 4, 2022 11:33:08 AM

IDEAL IQ

Before you begin

IDEAL IQ Indications for use

IDEAL IQ is a software option intended for use on GE MR systems. IDEAL IQ is capable of producing transverse, sagittal, coronal, and oblique images of internal structures of the body, including but not limited to, the musculoskeletal, breast, abdominal, and neurological systems. Specific anatomical regions that may be imaged include the abdomen, breast, spine, joints, and extremities. IDEAL IQ is an acquisition and reconstruction technique that simultaneously obtains independent images of hydrogen nuclei that resonate at different frequencies to provide separation of water and triglyceride fat.

IDEAL IQ generates images of separated water and triglyceride fat, relative triglyceride fat fraction map, and tissue transverse magnetization relaxation. In the liver, the relative triglyceride fat fraction map is quantitative; it reflects the proton density (number of protons per unit volume) of triglyceride fat, divided by the sum of the proton density of triglyceride fat and the proton density of water, on a voxel-by-voxel basis.

About this task

Use these steps to acquire a single 3D slab that produces triglyceride fat fraction images and R2* maps in addition to the water and triglyceride fat images from the collected multi-echo images of an IDEAL IQ acquisition.

The combination of the R2* map with the triglyceride fat-signal fraction map enables IDEAL IQ to improve the accuracy of tissue characterization parameters (R2* or triglyceride fat) by removing contamination from multiple chemical components.

Step-by-step instructions

  1. Typical patient orientation: supine, feet-first, arms above the head or beside the body.
    Consider using the respiratory device to monitor the patient's breathing and instruction compliance.
  2. Start a scan session.
  3. From the Workflow Manager, click Add Task > Add Sequence.
  4. From the Protocol screen, select an IDEAL IQ protocol from your site or GE library.
    • At a minimum, include a localizer and IDEAL IQ series.
    • If you cannot locate an IDEAL IQ protocol in either library, then from the Protocol screen:
      1. From the GE protocol library, click the Template tab.
      2. Click the Applications folder.
      3. From the Applications list, click IDEAL IQ and add it to the Multi-Protocol Basket.
      4. Click Accept.
  5. Acquire a 3-Plane localizer.
  6. From the Workflow Manager, select the IDEAL IQ series and click Setup. Make scan parameter adjustments, as needed.
    • Typically select Auto as the Flip Angle option, which maximizes SNR and minimizes T1-bias. The algorithm used to calculate the optimized flip angle uses a typical T1 value for the liver. If IDEAL IQ is used outside the liver, the fixed flip angle value (5 degrees at 1.5 T and 3 degrees at 3.0 T) is recommended; otherwise, fat fraction values may be overestimated.
    • IDEAL IQ uses ARC, which allows for acceleration in both phase and slice directions for supported coils.
    • Typical 1.5T scan parameters include the following:
      • Scan parameters: Scan Plane = Axial, Frequency FOV = 44 cm, Phase FOV =1.0 , Slice Thickness = 8.0 mm, Frequency Direction = R/L, # of slabs = 1, Slices per Slab = 32.
      • Detail parameters: Number Shots = 1, TE = Minimum Full, Flip angle = Auto, Echo Train Length = 6, Frequency = 192, Phase = 192, NEX =0.5, Bandwidth = 83.33, ARC Acceleration factors: see table below for example of a few ARC compatible coils.
  7. Click the Dixon tab.
    Figure 1. IDEAL IQ Dixon tab
    • Select the Dixon images you want reconstructed (in-phase or out-of-phase).
    • Fat, Water and R2* are automatically selected for IDEAL IQ and therefore they cannot be de-selected.
  8. Graphically deposit and position a single slab.
  9. Click the Advanced tab and select User CV values, if needed.
  10. If desired, see Add post-process task. Compatible post-process tasks include:
    • Maximum Intensity Projection
    • Multi Planar Reconstruction
    • Image Enhancement Filters
  11. When the prescription is finished, click Save Rx > Scan.
  12. To view IDEAL IQ images, from the Patient List, select the desired IDEAL IQ series.
    • The IDEAL IQ scan generates images using the following convention.
      Table 1. IDEAL IQ series. Note that all the patient list series text includes the scan plane, for example: R2*: Axial IDEAL IQ
      SeriesDescription
      N, Input series = NTriglyceride fat fraction imagesSeries description in patient list: FatFrac: IDEAL IQ
      100*NR2* mapsSeries description in patient list: R2*: IDEAL IQ
      100*N + 1Water imagesSeries description in patient list: Water: IDEAL IQ
      100*N + 2Triglyceride fat imagesSeries description in patient list: Fat: IDEAL IQ
      100*N + 3In PhaseSeries description in patient list: InPhase: IDEAL IQ
      100*N + 4Out of PhaseSeries description in patient list: OutPhase: IDEAL IQ
    Figure 2. Example of IDEAL IQ images
    Table 2. Image legend
    NumberDescription
    1T2* corrected water IDEAL IQ image
    2T2* corrected triglyceride fat IDEAL IQ image
    3R2* map IDEAL IQ image
    4Triglyceride fat-fraction IDEAL IQ image

Results

Considerations

  • Some IDEAL IQ prescriptions may reach system memory limits, resulting in a failure at download. Any of the following methods can be used to resolve this issue.
    • Wait for queued reconstruction jobs to finish.
    • Reduce the Slices per Slab value.
    • Reduce the Phase value.
  • IDEAL IQ image quality depends on the spacing of the IDEAL echoes where the optimal range of spacing is between 0.5p and 0.95p phase shift between triglyceride fat and water. A small echo spacing will result in noisy water-triglyceride fat separation, where as an echo spacing greater than the optimal range is vulnerable to water-triglyceride fat swap. Echo spacing is determined by scan parameters such as receive bandwidth and Frequency resolution (FOV and Frequency value). If your scan parameters force the echo spacing phase shift to be outside the optimum range, the PSD will post one of two messages:
    • "Echo-spacing NN PI is above 0.48PI limit. Increase RBW."
    • "Echo-spacing NN PI is below 0.96PI and 1.5PI. Change ETL/RBW/FOV."
    • "Echo-spacing NN PI is above 1.5PI. Decrease ETL or Increase RBW."

      where NN is the echo spacing phase shift of your prescription. Modify your scan prescription to keep the echo-spacing phase shift within 0.48PI to 0.96PI. If your echo spacing is smaller than 0.48PI, increase your frequency resolution or reduce the receiver bandwidth. If your echo spacing is greater than the range, reduce your frequency resolution or increase the receiver bandwidth. If your echo spacing is outside the advised range and error message is posted advising corrective action.

  • There may be local areas of water-triglyceride fat swap when there is severe Bo field variation due to patient inhomogeneity, air cavity, metal implants, and the presence of iron deposition, etc. The presence of other imaging artifacts may also cause incomplete water-triglyceride fat separation, such as parallel imaging artifact, patient motion and aliasing in the phase encoding direction.
  • When there is sufficient iron overload, T2* can be extremely short (<2ms). In these cases, the source echoes may not possess enough SNR for a good water-triglyceride fat separation. As a result, when R2* in liver is greater than 500 Hz (T2* < 2ms), water/triglyceride fat/triglyceride fat-fraction images may be noisy.
  • Do not use fat fraction and/or R2* map value as a single source for any diagnosis.
  • There may be residual phase error when phase correction fails in IDEAL-IQ. Please always check the fat fraction value from spleen and confirm the value is less or equal to 3%. If the value is greater than 3%, please redo the scan or reach GE representative to check the scanner.