Choice of the regularization parameter for perfusion quantification with MRI.
Truncated singular value decomposition (TSVD) is an effective method for the deconvolution of dynamic contrast enhanced (DCE) MRI. Two robust methods for the selection of the truncation threshold on a pixel-by-pixel basis--generalized cross validation (GCV) and the L-curve criterion (LCC)--were optimized and compared to paradigms in the literature. GCV and LCC were found to perform optimally when applied with a smooth version of TSVD, known as standard form Tikhonov regularization (SFTR). The methods lead to improvements in the estimate of the residue function and of its maximum, and converge properly with SNR. The oscillations typically observed in the solution vanish entirely, and perfusion is more accurately estimated at small mean transit times. This results in improved image contrast and increased sensitivity to perfusion abnormalities, at the cost of 1-2 min in calculation time and hyperintense clusters in the image. Preliminary experience with clinical data suggests that the latter problem can be resolved using spatial continuity and/or hybrid thresholding methods. In the simulations GCV and LCC are equivalent in terms of performance, but GCV thresholding is faster.
Sourbron
S
S
Magnetic Resonance Centre, Department of Radiology, Academic Hospital, Vrije Universiteit Brussel, Laarbeeklaan 101, 1090 Brussels, Belgium. ssourbro@vub.ac.be
Luypaert
R
R
Van Schuerbeek
P
P
Dujardin
M
M
Stadnik
T
T
D001158:Arteries / Q000473:pathology; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D002560:Cerebrovascular Circulation; D003198:Computer Simulation; D003287:Contrast Media; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D008962:Models, Theoretical; D009991:Oscillometry; D010477:Perfusion; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D020521:Stroke / Q000473:pathology; D013997:Time Factors
D003287:Contrast Media