Research On The Method Of Motion Artifact Correction In Computed Tomography

Medical CT image has become an indispensable diagnostic tool in clinical application.However,artifact caused by patients’ motion in medical CT imaging process is one of the most important obstacles to achieve high-precision diagnosis.Even small motion will have a greater impact on high-resolution CT image.When motion artifact seriously degrades image quality,it may lead to doctors’ misdiagnosis.Therefore,eliminating motion artifact in CT image and improving image quality have become a hot research topic in the field of image processing.The major contribution of this dissertation is summarized as follow:(1)A motion artifact correction method for CT based on frequency-domain amplitude correlation was proposed.According to the relation between motion parameters and fanbeam projections,the translation and rotation motion parameters can be determined by the frequency-domain amplitude correlation.Then,the estimated parameters were applied to compensate for the motion effects in the filtered backprojection reconstruction process.The modified Shepp-Logan head phantom experiments,human head image experiments and clinical data experiments showed that the proposed method is superior to HLCC method in estimation accuracy,real-time performance and motion artifact correction effect.Compared with LLE method,the proposed method has great advantages in real-time performance.(2)A motion artifact correction method for CT based on Radon transform was proposed.Since Radon transform can reduce the two-dimensional translation relation to one-dimensional,the operation was simplified.In order to improve the estimation accuracy,a motion parameter estimation method based on phase correlation was proposed.And a motion parameter estimation method based on extended difference function was proposed to improve the real-time performance.Experiments showed that the phase correlation method improved the accuracy of motion estimation significantly compared with the frequency-domain amplitude correlation method without increasing the computational complexity,while the extended difference function method reduced the computational complexity significantly compared with the frequency-domain amplitude correlation method without reducing the estimation accuracy.(3)A motion artifact correction method for CT based on blind image restoration was proposed.In the image reconstruction,Richardson-Lucy(RL)deconvolution with spatially adaptive total variation(SATV)regularization was inserted into the ordered subsets expectation maximization(OSEM)reconstruction algorithm.The image reconstruction and motion artifact correction were alternately completed in the iteration process.RL iteration algorithm can estimate clear image only based on original data.SATV regularization can effectively preserve image edge and detail information,while removing noise effects.Experiments showed that this method is superior to FDK-based motion compensation method in motion artifact correction effect.