Quantification of CBF without M0 and without control images without background suppression

[Victor Mazereel]

Dear

I'm working on an PCASL dataset acquired from a Philips scanner (2D readout)  and have run into some problems. 

Our PCASl scan unfortunately does not have a M0 scan. I tried using the mean control image as a pseudo-M0, but then found out that background suppression was utilized, so this method cannot be used.

By reading the settings of ExploreASL I believe a possible solution for this is almost within reach, but i'm missing some key info.

The Philips exam card lists "auto 2 pulse" as info under background suppression without the actual timings of the pulses. The pulse times are not to be found in the dicom headers as well (not by me in any case), nor in a dcm2niix conversion accompanying json file. 

I think I understand that in any case a GM scale factor should also be applied. But I can't find out what this factor is for the Philips scanner. 

I'm thus wondering if perhaps you know what this "auto 2 pulse" and GM scale factor would be for Philips scanners? I've seen some mention of it in a previous google group discussion for Siemens scanners, and for Philips scanners, but without a final solution.

As a more general question, to understand what the program does: is the GM scale factor only applied to the pseudo-M0 (so the mean control image) or to the whole asl sequence (controls+labels)? 

If you need more info on scanning parameters or testdata, I'd be glad to send them over!

Thank you for your time!
Best wishes
Victor Mazereel
PhD Student KU Leuven, Belgium