CT Geometry Calibration and Motion Compensation

System geometry alignment and object motion compensation - algorithms for precise CT Imaging

Excellent image quality and measurement precision start with an accurate definition of the CT geometry. This is why CERA allows to precisely back project the 2D raw data into the volume using projection matrices in addition to parametric descriptions of an ideal CT trajectory. Thus, local deviations from the ideal scan trajectory can be considered in the reconstruction to avoid resolution loss or misalignment artifacts.

The CERA-BASIC add-on modules CERA-CMP and CERA-OMC offer innovative algorithms for CT geometry calibration and object motion compensation. 

CERA module overview
CERA module overview

Phantom-based CT geometry calibration
CERA-CMP offers an easy-to-use phantom-based CT geometry calibration method. Based on the scan data of a steel-pin, the CT projection geometry is estimated. The dynamic geometry calibration approach also takes local offsets from the ideal scan trajectory into account (e.g. a tumbling of the turn table in NDT CT).
The key advantages are

  • Robust geometry calibration
  • High precision via dynamic geometry calibration
  • Inexpensive calibration phantom 

Raw-data based CT misalignment correction (phantom-less)
If the set geometry for the CT reconstruction differs from the actual scan trajectory, this can reduce the effective resolution or even cause image artifacts. CERA-CMP supports an innovative phantom-less CT misalignment correction which estimates the actual CT geometry from the raw-data. Thus, even non-deterministic global geometry deviations can potentially be compensated.


CERA-CMP: CT misalignment correction
CERA-CMP: CT misalignment correction

Object motion compensation for dental CT
Object motion during the CT scan, like patient head motion during a dental scan, can lead to severe misalignment artifacts and can make it necessary to repeat the scan.
The innovative object motion compensation algorithm in CERA-OMC is designed to compensate artifacts due to motion of rigid objects. For this end, an estimate of the time-varying object position is calculated and incorporated in the reconstruction process. Please note that CERA-OMC is not available and to be used for industrial CT.

CERA-OMC: Object motion compensation
CERA-OMC: Object motion compensation