Motion compensation for cone-beam CT using Fourier consistency conditions

Abstract

In cone-beam CT, involuntary patient motion and inaccurate or irreproducible scanner motion substantially degrades image quality. To avoid artifacts this motion needs to be estimated and compensated during image reconstruction. In previous work we showed that Fourier Consistency Conditions (FCC) can be used in fan-beam CT to estimate motion in the sinogram domain. This work extends the FCC to 3-D cone-beam CT. We derive an efficient cost function to compensate for 3-D motion using 2-D detector translations. The extended FCC method have been tested with five translational motion patterns, using a challenging numerical phantom. We evaluated the root-mean-square-error (RMSE) and the structural-similarity-index (SSIM) between motion corrected and motion-free reconstructions. Additionally, we computed the mean-absolute-difference (MAD) between the estimated and the ground-truth motion. The practical applicability of the method is demonstrated by application to respiratory motion estimation in rotational angiography, but also to motion correction for weight-bearing imaging of knees. Where the latter makes use of specifically modified FCC version which is robust to axial truncation. The results show a great reduction of motion artifacts. Accurate estimation results were achieved with a maximum MAD value of 708 µm and 1184 µm for motion along the vertical and horizontal detector direction, respectively. The image quality of reconstructions obtained with the proposed method is close to that of motion corrected reconstructions based on the ground-truth motion. Simulations using noise-free and noisy data demonstrate that FCC are robust to noise. Even high-frequency motion was accurately estimated leading to a considerable reduction of streaking artifacts. The method is purely image-based and therefore independent of any auxiliary data.

Motion Reduction for C-Arm Computed Tomography of the Pulmonary Arteries: Image Quality of a Motion Correction Algorithm in Patients with Chronic Thromboembolic Hypertension During Balloon Pulmonary Angioplasty

“…Different attempts to reduce CACT motion artifacts are reported in the literature [24][25][26]. Berger et al introduced a theoretical concept using dedicated phantoms with artificially induced motion artifacts [24].…”

“…Different attempts to reduce CACT motion artifacts are reported in the literature [24][25][26]. Berger et al introduced a theoretical concept using dedicated phantoms with artificially induced motion artifacts [24]. The method described by Klugmann et al is time-consuming as it requires manual vessel segmentation of the whole vascular tree [25].…”

Flat-panel conebeam CT in the clinic: history and current state

“…Interestingly, system geometric calibration (discussed above) and motion compensation are closely related, with use of an “objective image quality” metric between simulated and measured projections or iterative correction approaches using image-based metrics such as gradients or entropy to measure artifact levels. An alternative approach exploits redundancies in the projection images, identified via application of epipolar geometry, 26 , 108 , 109 and has been applied with success to C-arm CT images of the head, as shown in Fig. 20 .…”

Motion correction for separate mandibular and cranial movements in cone beam CT reconstructions

“…24 Cases are also observed in which only the mandible is moved against the remaining (resting) skull. 24 Techniques, which are applicable in scenarios more similar to ours, include methods of autofocus, [25][26][27][28] consistency conditions [29][30][31] and learning based approaches. [32][33][34] However, methods using consistency conditions are currently not able to correct separate cranial and mandibular motions, which is the goal of our work.…”