Abstract
BackgroundAs a dual-modality contrast agent, magnetic microbubbles (MMBs) can not only improve contrast of ultrasound (US) image, but can also serve as a contrast agent of magnetic resonance image (MRI). With the help of MMBs, a new registration method between US image and MRI is presented.MethodsIn this method, MMBs were used in both ultrasound and magnetic resonance imaging process to enhance the most important information of interest. In order to reduce the influence of the speckle noise to registration, semi-automatic segmentations of US image and MRI were carried out by using active contour model. After that, a robust optical flow model between US image segmentation (floating image) and MRI segmentation (reference image) was built, and the vector flow field was estimated by using the Coarse-to-fine Gaussian pyramid and graduated non-convexity (GNC) schemes.ResultsQualitative and quantitative analyses of multiple group comparison experiments showed that registration results using all methods tested in this paper without MMBs were unsatisfactory. On the contrary, the proposed method combined with MMBs led to the best registration results.ConclusionThe proposed algorithm combined with MMBs contends with larger deformation and performs well not only for local deformation but also for global deformation. The comparison experiments also demonstrated that ultrasound-MRI registration using the above-mentioned method might be a promising method for obtaining more accurate image information.
Highlights
As a dual-modality contrast agent, magnetic microbubbles (MMBs) can improve contrast of ultrasound (US) image, but can serve as a contrast agent of magnetic resonance image (MRI)
A robust optical flow model between US image segmentation and MRI segmentation was built, and the vector flow field was estimated by the Coarse-to-fine Gaussian pyramid and graduated non-convexity (GNC) schemes
Materials and data acquisition Dual modality contrast agent MMBs were obtained from Jiangsu Laboratory for Biomaterials and Devices
Summary
As a dual-modality contrast agent, magnetic microbubbles (MMBs) can improve contrast of ultrasound (US) image, but can serve as a contrast agent of magnetic resonance image (MRI). Compared with other medical imaging modalities, ultrasound imaging has been widely used in diagnosis and clinical applications owning to its merits of low-cost, real-time, high safety, and no documented side effects. Ultrasound imaging is still limited because of the following reasons. Ultrasound is reflected very strongly when passing from tissue to gas, and vice versa. The method is of limited use in diagnosing fractures because ultrasound does not pass well through bones. The quality of ultrasound imaging is mediocre when its contrast is lower than that of MRI or computed tomography (CT) [3,4]
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