ABSTRACT
Objective:To measure CT linearity and evaluate if it would show linear relationship between coefficient and attenuation.Methods:The Catphan phantom was used to measure CT linearity in 18 computed tomography equipments,and the results were calculated.Results:(1)The CT linearity were qualified in 14 equipment but 4.Conclusion:(1)There are many factors which affect CT linearity.The artifact will be produced if the CT linearity is unqualified.(2)CT linearity must be calibrated periodically to assure the stability of the CT linearity and to make for the accurate diagnoses.
ABSTRACT
Objective To investigate the influence of physiological motions on three-dimensional (3D) CT images and the rules of motion artifacts.Methods A mathematical model of motion artifact was set up based on the principle of spiral scanning, hereby the geometrical distortion of 3D image was analyzed.Experiments were carried out with home-made phantoms on a CT scanner.Results The details of 3D images with trivial distortion were legible under static condition.On the contrary, distinct distortion occured under moving condition, and its degree increased with the pitch and motion period. The 3D images were varied with difference of the motion initial phases.Conclusion The distortion of 3D-CT image depends on the motion characters of scanned objects and scanning parameters such as pitch and slice thickness.
ABSTRACT
Objective:To measure CT linearity and evaluate if it would show linear relationship between coefficient and attenuation.Methods:The Catphan phantom was used to measure CT linearity in 18 computed tomography equipments,and the results were calculated.Results:(1)The CT linearity were qualified in 14 equipment but 4.Conclusion:(1)There are many factors which affect CT linearity.The artifact will be produced if the CT linearity is unqualified.(2)CT linearity must be calibrated periodically to assure the stability of the CT linearity and to make for the accurate diagnoses.
ABSTRACT
Objective To investigate the Ring Artifact Location Algorithm based on edge detection to eliminate the ring artifact.Methods The Sobel operator was used to extract the ring edge,and then an algorithm,which combined scan line searching with line fitting,was applied to determining the ring center and its size.Finally the linear interpolation algorithm was used to get rid of the ring artifact.Results This method was very effective to eliminate the ring artifact of both phantom and clinical images.Conclusion This algorithm is faster and more effective than the usual one and its speed and accuracy are improved.