Abstract
The effects of calibration phantoms on the correction results of the empirical artifacts correction method (ECCU) for the case of tube modulation were investigated. To improve the validity of the ECCU method, the effect of the geometry parameter of a typical single-material calibration phantom (water calibration phantom) on the ECCU algorithm was investigated. Dual-material calibration phantoms (such as water-bone calibration phantom), geometry arrangement, and the area-ratio of dual-material calibration phantoms were also studied. Preliminary results implied that, to assure the effectiveness of the ECCU algorithm, the polychromatic projections of calibration phantoms must cover the polychromatic projection data of the scanning object. However, the projection range of a water calibration phantom is limited by the scan field of view (SFOV), thus leading to methodological limitations. A dual-material phantom of a proper size and material can overcome the limitations of a single-material phantom and achieve good correction effects.
Highlights
In conventional computed tomography (CT) tube voltages are fixed while CT scans are carried out
Tube voltage modulation is very helpful in CT scanning, but when the voltage is modulated at different views during a CT scan, images reconstructed through commonly used reconstruction methods may contain various artifacts leading to inaccuracy and degradation of image quality
Calibration phantoms for CT scanners with tube voltage modulation are investigated through computer simulation
Summary
In conventional computed tomography (CT) tube voltages are fixed (constant) while CT scans are carried out. Different polychromatic X-ray beams are used through tube voltage modulating at different scanning views. The reconstruction algorithm is based on the assumption of the monochromatic property of the X-ray beam that just computed the average attenuation coefficient and leads to the appearance of cupping artifacts or beam hardening artifacts within conventionally reconstructed images. “Water calibration for CT scanners with tube voltage modulation” in 2010, in which the ECCU algorithm for cupping artifact correction was provided, showed excellent simulation results. The effects of calibration phantoms for CT scanners with tube voltage modulation are investigated by a numerical simulation method.
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