CEST - Roaming Intensities

Once you have set up the CEST Analysis tool to perform an analysis, you can visualise the Z-spectrum interactively. You can:

• Click on the image to show the Z-spectrum at the mouse point, or
• Show the Z-spectrum within a region of interest. The Z-spectrum that is shown is from the the mean pixel intensities within the ROI.

The Z-spectrum and associated analysis are viewed in a pop-up graph.

First, set up the CEST Analysis tool tool exactly as you would to perform a whole-image analysis, as in sections 3-5. Next, load an image into Jim's display. The image you load can be any of the input images (or the input image if you have just a single input image).

To view the Z-spectrum, select Roam ... from the View menu of the CEST Analysis tool: . Both the ROI Toolkit, and the Roaming Z-spectrum dialog will pop up.

Then, either:

• Click on the image with the mouse. The intensities for each independent variable value will be extracted from the image(s) at the mouse position.
• Using the ROI Toolkit, create a region of interest on the image you are viewing in Jim. The mean intensity values will be extracted from the input images within the ROI you just created). If you select more than one ROI, the mean intensities from the combined ROIs will be used.

The Z-spectrum will now be displayed in the Roaming Z-spectrum dialog. Along with the Z-spectrum, the dialog may also shows the result of the selected CEST analsysis. These are:

• When WASSR analysis is selected, the shifted Z-spectrum (corrected for B₀ inhomogeneity) is also shown.
• When Lorentzian Fitting is selected, the fitted Lorentzians are also shown.

Z-spectrum and fitted Lorentzians

The y- data range of the graph is automatically scaled to match the data. If you want to fix the range of data on the y-axis, select the "Fix range" check box, and type in a range that you want to be displayed.

You can write the data and the graph to a disk file by selecting Write from the File menu:
The graph data is written in a tab-separated table with two columns: the first is the frequency offset and the second is the pixel intensity. See also the File Formats section.

Note: If you change any settings in the Roaming Z-spectrum Dialog, you may need to de-select and re-select the ROI before the graph is updated.