I-value

I-value fit 

There is an empirical linear relation between Zeff and I-value (read the reference papers for more information). As the relation is not continuous, the user has to define:

•  The number of segments (2 in the image below)

• The Zeff superior limit for each segment. Note that if 2 segments are defined the user only needs to input the upper limit of the first segment (e.g. 8.5) as everything above that value will be in the second segment. 

Press the plot to display the values (from the main table) then press Calculate Fit.

"Special case"

Often this fit is performed using the composition of human tissues from the literature (not the tissue-mimicking inserts). If that is the case, the user should load the tissue compositions, perform the fit and write down the coefficients.  When performing the calibration using acquired phantom data the coefficient can then be filled in manually.  The fit can be visualized by pressing "Plot" and then "Pre-calculated Fit".  Note that pressing "Calculate fit" will replace values entered by the user. 

If the information above makes no sense to you please read the reference:  10.1088/0031-9155/59/1/83