Image quality analysis of vibration effects in C-arm flat panel X-ray imaging
The motion of C-arm scanning X-ray systems may result in vibrations of the imaging sub-system. In this paper, we connect C-arm system vibrations to Image Quality (IQ) deterioration for 2D angiography and 3D cone beam X-ray imaging, using large Flat Panel detectors. Vibrations will affect the projected image sharpness and the projected image position. The former will appear as blur and the latter as image shift for the 2D projection radiography process. If this phenomenon is not corrected in the post processing (pixel shift), it will manifest as subtraction registration artifacts. We will model and verify the effect of vibrations in 2D subtracted and non-subtracted flat panel imaging. Two effects on 3D IQ are modeled: (1) vibrations during an actual acquisition run inducing movement blur and (2) C-arm movement calibration errors in the iso-center giving remnant blur. The model establishes a relation between vibration amplitudes and image quality for dominant system Eigen-frequencies. The validity and accuracy of the model for 2D and 3D imaging modes is supported and demonstrated by experiments and even provides sufficient quality for defining image quality requirements.