# CalculateMath using parent object measurements

Hi,

I have Images of Cells that have bright spots (foci) in the nuclei. I have identified both objects using IdentifyPrimaryObjects and related using RelateObjects. I also performed MeasureObjectIntensity on both types of Object.

I would now like to filter the foci and only keep those with an mean intenity of at least 1.3 times the mean intensity of the parent nucleus.
Is there a way to use the parent intensity measurement in the CalculateMath that i could use to calculate this ratio for each foci?
Or is there a way to copy a measurement value from a parent to each child object?

Christoph

Hi Christoph,

You can do this through an indirect method:
[ul][li]Use the RelateObjects module to relate the nuclei as children and the foci as parents. This is the opposite of what is normally done but the key is to associate the nuclei measurements with the foci, not the other way around.[/li]
[li]Also in RelateObjects, check the “Calculate per-parent means…” box. If you have measured the nuclei intensity beforehand, the mean nuclei intensity is the same as the nuclei intensity itself, since there’s just one nuclei per foci.[/li]
[li]Use the CalculateMath module to subtract two foci object measurements in this order: [list][]The foci MeanIntensity[/li][li]The mean nuclei MeanIntensity with 1.3 as the multiplication factor[/li][/ul]The result of this is a new foci measurement that will be positive where the foci mean intensity > 1.3nuclei mean intensity and negative otherwise.[/*:m]
[li]Use FilterObjects to filter the foci using Limits as the filtering method, the new Math measurement as the measure to filter by, leaving the minimum measurement value box checked and maximum measurement value unchecked, and the minimum value as 0.[/li][/list:u]
I believe this procedure should give you the results you want.

Regards,
-Mark

Dear Mark,

thanks a for the help. Your approach seems to work fine as long as there is only one foci per nucleus.
Unfortunately In the pictures I am working with there are often more than one foci in a single nucleus. In this case the nucleus gets asigned as a child only to one of the foci. As a result the Mean_Nuclei_Intensity_MeanIntensity_CorrGreen is only calculated for those foci. The rest of the foci have NaN as a value and are not filtered correctly.
Do you see another way or would I have to modify the CalculateMath module?

Best Christoph

Hi Christoph,

Thanks for the feedback. Unfortunately, I don’t think there’s a way to do this task currently. I’ve added this to our requested feature list, either (1) a per-parent operation to CalculateMath, or (2) add a per-object measurement threshold method to the Identify* modules (currently, only image measurement thresholding is supported).

Regards,
-Mark