Marcel Beister, Presenter: Nothing to Disclose

Yiannis Kyriakou PhD, Abstract Co-Author: Nothing to Disclose

Robert Brauweiler, Abstract Co-Author: Nothing to Disclose

Willi A. Kalender PhD, Abstract Co-Author: Consultant, Siemens AG Consultant, Bayer AG Founder, CT Imaging GmbH Scientific Advisor, CT Imaging GmbH Shareholder, CT Imaging GmbH Founder, Artemis Imaging GmbH CEO, Artemis Imaging GmbH Shareholder, Artemis Imaging GmbH

Novel robotic C-arm systems with significantly higher rotation speed have the potential for dynamic perfusion CT. The purpose of this work is to further increase temporal resolution for C-arm PCT by means of limited angle reconstruction, in order to approximate a typical clinical PCT temporal sampling of about 1-2 s.

With incomplete data, iterative reconstruction algorithms have significant advantages compared to Filtered Back Projection (FBP) methods. The use of prior information or additional constraints can help to provide acceptable volumetric images in such cases. We propose an iterative algorithm to reconstruct partial scans from our robotic C-arm system (Artis Zeego, Siemens, Forchheim, Germany), implemented on a NVIDIA GTX 285 GPU. Our dynamic data acquisition includes multiple high-speed rotational scans of the C-arm, each covering 220° of rotation angle, carried out in an alternating clock- and counter-clockwise fashion with 133 projections within 2 s. Our SART based algorithm reconstructs half of the scan (110°) using a low temporal resolution prior volume, a dynamic-dependent weighting mask and the total variation norm (TV) as a regularization function. This combination provides more accurate reconstructions of the time-density curves (TDC) in dynamic regions. The proposed method was evaluated with a dynamic FDCT thorax phantom simulation and with measurements of a perfusion phantom on the C-arm system compared to a reference done with a clinical CT (Definition Flash, Siemens, Forchheim, Germany). The simulation results were compared to an identical simulation with much higher temporal resolution.

Limited-angle reconstruction with 110°, corresponding to a temporal sampling of 1 s, reduced the root mean square error (RMSE) of the reconstructed TDC to about 35% of the 220° scan while the error of time-to-peak (TTP) computation was reduced to about 60%. The measurements with the C-arm system were in good accordance with the clinical CT measurements.

Limited angle reconstruction increased temporal resolution for dynamic FDCT whilst preserving quality in static image regions. The optimized implementation on GPU hardware enables routine application.

Increased temporal resolution on a novel robotic C-arm system allows for perfusion measurements in 3D CT mode.

Beister, M, Kyriakou, Y, Brauweiler, R, Kalender, W, Increased Temporal Resolution for Dynamic Perfusion CT (PCT) with C-arm Flat-Detector CT.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9008589.html