A new approach to autocalibrated dynamic parallel imaging based on the Karhunen-Loeve transform: KL-TSENSE and KL-TGRAPPA.
TSENSE and TGRAPPA are autocalibrated parallel imaging techniques that can improve the temporal resolution and/or spatial resolution in dynamic magnetic resonance imaging applications. In its original form, TSENSE uses temporal low-pass filtering of the undersampled frames to create the sensitivity map. TGRAPPA uses a sliding-window moving average when finding the autocalibrating signals. Both filtering methods are suboptimal in the least-squares sense and may give rise to mismatches between the undersampled k-space raw data and the corresponding coil sensitivities. Such mismatches may result in aliasing artifacts when imaging patients with heavy breathing, as in real-time imaging of wall motion by MRI following a treadmill exercise stress test. In this study, we demonstrate the use of an optimal linear filter, i.e., the Karhunen-Loeve transform filter, to estimate the channel sensitivity for TSENSE and acquire the autocalibration signals for TGRAPPA. Phantom experiments show that the new reconstruction method has comparable signal-to-noise ratio performance to traditional TSENSE/TGRAPPA reconstruction. In vivo real-time cardiac cine experiments performed in five healthy volunteers post-exercise during rapid respiration show that the new method significantly reduces the chest wall aliasing artifacts caused by respiratory motion (P < 0.001).
Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA. yu.ding@osumc.edu
Yu
Y
Ding
Yiu-Cho
YC
Chung
Mihaela
M
Jekic
Orlando P
OP
Simonetti
D016477:Artifacts; D002138:Calibration; D005080:Exercise Test; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D009038:Motion; D009200:Myocardial Contraction / Q000502:physiology*; D019047:Phantoms, Imaging; D025341:Principal Component Analysis; D012119:Respiration; D012680:Sensitivity and Specificity; D035441:Thoracic Wall / Q000502:physiology
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