In two of eight recent Siemens PRESS acquisitions, Osprey’s alignment of individual transients from the twix file has made the final aligned and averaged spectrum worse (higher FWHM and worse CRLBs) than the averaged spectrum fit by LCModel using the vendor RDA file. For the other six of our recent PRESS acquisitions, we get much better final spectra using the twix files than using the RDA file.
Below is the Chemical Shift Drift graph showing drift before and after alignment when processed using default settings in the GUI (RobSpecReg, L2Norm, ECC). The tCr FWHM = .082 ppm and the tCr SNR = 102.8. Alignment seems to have made the drift worse. The aligned and averaged spectrum is not very good.
Shown below that is the spectrum from the vendor RDA file. The tCr FWHM = .063 ppm and the tCr SNR = 125.7. These are not great values, but they’re better than the aligned and averaged spectrum generated from the twix file.
So far, I only know how to use Osprey from the GUI. I’ve tried every alternative to the defaults in the GUI for spectral registration and alignment. Only the ProbSpecReg alternative improved the drift pattern and the final spectrum, but it still wasn’t as good as the spectrum from the RDA file.
Does anyone know if I am doing something wrong here, or why this problem is occurring?
Aligned from twix file:
From vendor RDA file:
