Correction algorithm for singular value decomposition artifact in quantitative cerebral perfusion images using SCALE-PWI

INTRODUCTION Quantitative cerebral perfusion has been achieved via the Bookend technique [1,2] using dynamic susceptibility contrast (DSC) MRI and T1 changes in normal white matter (WM) in relation to the changes in the blood pool in a calibration slice, after contrast injection. Quantitative cerebral blood flow (qCBF), quantitative cerebral blood volume (qCBV) and mean transit time (MTT) measured by the Bookend technique have been proven reproducible, reliable and accurate [3]. An accelerated and simplified version of the Bookend protocol has been achieved through a Self-CALibrated Epi Perfusion Weighted Imaging (SCALE-PWI) MRI pulse sequence [4], which combines three Bookend scans into one. Improvements to SCALE-PWI imaging protocol and perfusion image reconstruction have just been reported [5]. A correction method for an additional artifact is presented in this work. This consists of a singular value decomposition (SVD) algorithmic artifact due to the interleaved (odd/even) order of slice acquisition of the dynamic susceptibility contrast (DSC) images, which introduces apparent changes, by fractions of TR, in the arrival time of the contrast bolus to each slice in the brain with respect to the arterial input function (AIF). It normally causes alternating signal intensity modulation in the reconstructed quantitative perfusion (qCBF, qCBV and MTT) maps of consecutive slices. This artifact could be unnoticeable when looking at relative perfusion maps, but it is more of a problem when dealing with quantitative perfusion parameters, and could be misleading in some cases whereby accurate patient diagnosis is needed.