  In the last decade C-arm-based cone-beam CT became a widely used modality for
intraoperative imaging. Typically a C-arm scan is performed using a circle-like
trajectory around a region of interest. Therefor an angular range of at least
180{\deg} plus fan-angle must be covered to ensure a completely sampled data
set. This fact defines some constraints on the geometry and technical
specifications of a C-arm system, for example a larger C radius or a smaller C
opening respectively. These technical modifications are usually not benificial
in terms of handling and usability of the C-arm during classical 2D
applications like fluoroscopy. The method proposed in this paper relaxes the
constraint of 180{\deg} plus fan-angle rotation to acquire a complete data set.
The proposed C-arm trajectory requires a motorization of the orbital axis of
the C and of ideally two orthogonal axis in the C plane. The trajectory
consists of three parts: A rotation of the C around a defined iso-center and
two translational movements parallel to the detector plane at the begin and at
the end of the rotation. Combining these three parts to one trajectory enables
for the acquisition of a completely sampled dataset using only 180{\deg} minus
fan-angle of rotation. To evaluate the method we show animal scans acquired
with a mobile C-arm prototype. We expect that the transition of this method
into clinical routine will lead to a much broader use of intraoperative 3D
imaging in a wide field of clinical applications.
