Multiframe registration of real-time three-dimensional echocardiography time series.

Mosaicing of real-time three-dimensional echocardiography (RT3-DE) images aims at extending the field-of-view of overlapping images. Currently available methods discard most of the temporal information available in the time series. We investigate the added value of simultaneous registration of multiple temporal frames using common similarity metrics. We combine RT3-DE images of the left and right ventricles by registration and fusion. The standard approach of registering single frames, either end-diastolic (ED) or end-systolic (ES), is compared with simultaneous registration of multiple time frames, to evaluate the effect of using the information from all images in the metric. A transformation estimating the protocol-specific misalignment is used to initialize the registration. It is shown that multiframe registration can be as accurate as alignment of the images based on manual annotations. Multiframe registration using normalized cross-correlation outperforms any of the single-frame methods. As opposed to expectations, extending the multiframe registration beyond simultaneous use of ED and ES frames does not further improve registration results.