• Object ID: 00000018WIA30454970GYZ
  • Topic ID: id_40023572 Version: 1.4
  • Date: Mar 28, 2022 4:31:45 PM

R2Star Optional procedures

About this task

To change R2Star settings, make a selection from the desired R2Star screens.

Step-by-step instructions

  1. From the R2 Star screen, click and drag the left threshold slider until the chest or abdomen is outlined in green and all the anatomy inside the image displays green lines.
    Note: Compute does not update the threshold. As the upper or lower slider is moved or a value entered in the text box, the threshold automatically updates.

    For processing threshold details, see Threshold adjustment.

  2. From the R2 Star screen, click the Skip Image Number arrow and type the images numbers that you do not want to contribute to the R2* or T2* maps. This parameter is only relevant if the Fitting Algorithm is set to 2-Parameter on the Advanced Settings screen.
  3. Click Compute to generate R2Star and T2Star images.
    The R2Star map color scale is displayed in units of Hz and the T2Star map color scale is displayed in units of ms.
  4. From the R2 Star screen title bar, click the Tools icon ().
  5. From the R2 Star screen, click the R2 Star - Advanced Settings arrow to change the fitting algorithm, confidence level or Kernel Spatial Smoothing.
    • The Kernel spatial smoothing default value is 0.
    • As the kernel size increases, voxel averaging occurs and the image maps appear smoother.
    • The 3-parameter algorithm performs a non-linear fit of the input data points. The 3-parameter algorithm is typically used when the input signal has less noise and appears to be of high quality. This algorithm provides higher accuracy but is sensitive to noise in the input data. When the 3-parameter algorithm is selected, all the input data points are used for the fit, regardless of the Skip Images setting.
    • The 2-parameter algorithm performs a linear fit of the input data points. The 2-parameter algorithm is typically used when the input signal is noisy. This algorithm is less susceptible to noise, but provides somewhat lower accuracy. When the 2-parameter algorithm is selected, the Skip Images setting is taken into account and the selected images are omitted when performing the fit.
    • The confidence level indicates how well the final result fits the data: a small value corresponds to high confidence and a large value corresponds to low confidence. You can set a confidence level threshold: pixel locations for which the algorithm returns a confidence level above the threshold are displayed in black on the functional map. By default, the protocol uses a confidence level of 1% (0.01)
      1. Change the desired settings.
      2. Click Compute to generate updated maps.
        • Reset changes the selections to the factory default values.
        • Save All saves your selections as the new default values.
  6. From the R2 Star screen, click the R2 Star - Final Settings arrow to review the settings. If you want to change any of the settings, follow these steps.
    1. Click the appropriate selection from the R2Star screen.
    2. Click Compute to generate updated maps.
  7. To exit READY View, click the Exit icon ().