A similarity measure for nonrigid volume registration using known joint distribution of targeted tissue: Application to dynamic CT data of the liver

A similarity measure for nonrigid volume registration with known joint distribution of a targeted tissue is developed to process tissue slide at the boundaries between the targeted and non-targeted tissues. Pre-segmentation of the targeted tissue is unnecessary. This measure is applied to registering volumes acquired at different time-phases in dynamic CT scans of the liver using contrast materials and can be derived for the case where only the joint distribution of the targeted tissue is known. The similarity measure is formulated as a likelihood by introducing a concept termed ‘exclusivity condition’ and embedded into a cost function for nonrigid registration to be combined with the smoothness term. In addition, a practical method for estimating the joint distribution of the liver from unregistered clinical CT data is described. We demonstrate experimentally that tissue slide is effectively processed by this proposed measure using simulated dynamic CT data generated from a software phantom and clinical CT data of eight patients.