A posteriori navigator echo for perfusion imaging of the liver with contrast ultrasound

This paper proposes a strategy to minimize respiratory motion artifacts in ultrasound contrast imaging sequences, and to enable parametric imaging from time sequences. This strategy, originated from navigator-echo techniques in MRI, has been tested on contrast ultrasound sequences, to study perfusion of the liver. A respiratory component is first estimated by an independent component analysis (ICA), then two subsets of frames corresponding to the minima and maxima of the respiratory cycle are selected. Finally, factor analysis is applied to each resulting sequence - two main perfusion kinetics are estimated: one is related to the early contrast uptake in the tumor, the other one is related to the normal perfusion of the liver. In conclusion this preliminary approach makes possible parametric imaging, and should facilitate quantification.