Ludwig Ritschl, Presenter: Employee, Ziehm Imaging GmbH

Jan Kuntz, Abstract Co-Author: Nothing to Disclose

Marc Kachelriess PhD, Abstract Co-Author: Nothing to Disclose

The proposed method enables for the acquisition of a complete dataset for 3D reconstruction of C-Arm data using less than 180° rotation.

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. Therefore an angular range of at least 180° 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. To overcome these limitations we propose a new trajectory which requires only 180° minus fan–angle of rotation for a complete data set. Therefore the orbital axis of the C and ideally two orthogonal axis in the C plane need to be motorized. 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° minus fan–angle of rotation. We denote this trajectory as rotate plus shift trajectory.

For the evaluation of the method a pig was scanned using a motorized mobile C-arm prototype. Both, a short scan over 196° and a rotate plus shift scan using only 165° rotation were acquired. Additionally the data were compared to a limited angle circular scan of only 165°. The results show, that the rotate plus shift scan yields equivalent image quality compared to the short scan which is assumed to be the gold standard for C-arm CT today. Compared to the pure rotational scan over only 165°, the rotate plus shift scan shows strong improvements in image quality. If an automatic collimation is used during the scan, patient dose of the rotate plus shift scan is lower or at least equivalent compared to the short scan.

The proposed method makes 3D imaging using C–arms with less than 180° rotation range possible. This enables for integrating the 3D functionality into a C- arm device without any loss of handling and usability for 2D imaging.

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.

Ritschl, L, Kuntz, J, Kachelriess, M, The Rotate Plus Shift C–arm Trajectory: Complete Data with Less than 180° Rotation.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018510.html