Abstract
Objective. To demonstrate a novel approach of compensating overexposure artifacts in CT scans of the knees without attaching any supporting appliances to the patient. C-Arm CT systems offer the opportunity to perform weight-bearing knee scans on standing patients to diagnose diseases like osteoarthritis. However, one serious issue is overexposure of the detector in regions close to the patella, which can not be tackled with common techniques. Methods. A Kinect camera is used to algorithmically remove overexposure artifacts close to the knee surface. Overexposed near-surface knee regions are corrected by extrapolating the absorption values from more reliable projection data. To achieve this, we develop a cross-calibration procedure to transform surface points from the Kinect to CT voxel coordinates. Results. Artifacts at both knee phantoms are reduced significantly in the reconstructed data and a major part of the truncated regions is restored. Conclusion. The results emphasize the feasibility of the proposed approach. The accuracy of the cross-calibration procedure can be increased to further improve correction results. Significance. The correction method can be extended to a multi-Kinect setup for use in real-world scenarios. Using depth cameras does not require prior scans and offers the possibility of a temporally synchronized correction of overexposure artifacts. To achieve this, we develop a cross-calibration procedure to transform surface points from the Kinect to CT voxel coordinates.
Highlights
C-arm CT systems (Figure 1(a)), in contrast to conventional CT systems, have a high mechanical flexibility which gives radiologists the opportunity to perform CT scans in a variety of spatial positions
It is possible to rotate the CT system around a vertical axis [1]. This enables imaging of patients with knee diseases such as osteoarthritis while they are standing in an upright position, while the knee is bearing the weight of the patient [2]
Using a C-arm CT acquisition protocol with the patient lying in supine position, several approaches are available to avoid or compensate overexposure artifacts
Summary
C-arm CT systems (Figure 1(a)), in contrast to conventional CT systems, have a high mechanical flexibility which gives radiologists the opportunity to perform CT scans in a variety of spatial positions. It is possible to rotate the CT system around a vertical axis [1]. This enables imaging of patients with knee diseases such as osteoarthritis while they are standing in an upright position, while the knee is bearing the weight of the patient [2]. Using a C-arm CT acquisition protocol with the patient lying in supine position, several approaches are available to avoid or compensate overexposure artifacts. One way to avoid overexposure artifacts during acquisition is by covering the knees with an additional absorber, for example, a rubber belt [2, 3]. Extra weight of the belt can cause great discomfort for an upright patient with pains in the knees
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