Volume-constrained image registration for pre- and post-operative CT liver data

The resection of a tumor is one of the most common tasks in liver surgery. Here, it is of particular importance to resect the tumor and a safety margin on the one hand and on the other hand to preserve as much healthy liver tissue as possible. To this end, a preoperative CT scan is taken in order to come up with a sound resection strategy. It is the purpose of this paper to compare the preoperative planning with the actual resection result. Obviously the pre- and postoperative data is not straightforward comparable, a meaningful registration is required. In the literature one may find a rigid and a landmark-based approach for this task. Whereas the rigid registration does not compensate for nonlinear deformation the landmark approach may lead to an unwanted overregistration. Here we propose a fully automatic nonlinear registration with volume constraints which seems to overcome both aforementioned problems and does lead to satisfactory results in our test cases.