1 the necessity of medical image fusion
1. 1 Image fusion is the need of technology update. With the wide application of computer technology in the field of medical imaging, new technology has gradually replaced traditional technology. The application of image archiving and PACS, as well as the realization of telemedicine, marks the establishment of a new mode of image information storage and transmission technology. Image post-processing technology must also develop synchronously, and constantly improve and innovate on the original basis in order to give full play to the advantages of imaging. Image fusion will be a comprehensive update of post-processing technology.
1.2 image fusion makes up for the deficiency of single examination imaging. At present, imaging examination methods range from B-ultrasound and traditional X-ray to DSA, CR, CT, MRI, PET, SPECT and so on. And each examination has its own characteristics and advantages, but it has defects and limitations in imaging. For example, CT examination has high resolution, but it is difficult to distinguish tissues with very close density, which is easy to produce bone artifacts, especially posterior cranial fossa examination, which affects the accuracy of diagnosis; Although MRI examination has superior display ability for soft tissues, it has poor display for bone lesions and calcified lesions. If two images of the same site can be fused together, the normal structure and abnormal changes of tissue can be fully reflected, thus making up for the deficiency of any single examination imaging.
1.3 image fusion is a clinical need, and image diagnosis ultimately serves clinical treatment; Advanced examination methods and clear images are helpful to improve the accuracy of diagnosis, while brand-new images that combine the advantages of various examinations will make the diagnosis more clear and can better assist the clinical diagnosis and treatment of diseases.
2 the feasibility of medical image fusion
2. 1 The existence and complementarity of * * in various image examinations lay the foundation for image fusion. Although the examination methods, imaging principles and imaging characteristics of each examination are different, they have the same morphological basis, and all reflect the morphology, structure and physiological functions of normal tissues and organs, as well as the anatomical, pathological and metabolic changes of lesions through images. Moreover, the defects of each examination and the shortcomings of imaging can be made up and improved in other examinations. For example, traditional X-ray and CT examination can make up for the deficiency of bone imaging; MRI can make up for the deficiency of soft tissue and spinal cord imaging. PET and SPECT can make up for the deficiency of functional measurement.
2.2 The application of medical image digital technology provides methods and means for image fusion. Now, digital technology has been fully applied to important technical links such as image acquisition, storage, post-processing, transmission and replication. The first step, that is, image acquisition, uses a variety of technical means, including: (1) synchronous acquisition and real-time processing of digital information; (2) synchronously collecting analog signals and converting them into digital signals through an analog-to-digital conversion device; (3) Digital conversion of some traditional examinations such as ordinary X-rays by image scanner and digital camera; Convert the collected ordinary images into digital images, and store and transmit them in the form of data files, which provides a prerequisite for further image fusion.
Three key technologies of medical image fusion
The role of information fusion in medical image research is generally described by synergistic effect, and the implementation of image fusion is to realize the synergy of medical images; Image data conversion, image data association, image database and image data understanding are the key technologies of fusion. (1) Image data conversion is the format conversion, three-dimensional orientation adjustment and scale transformation of image information from different acquisition devices, so as to ensure the same size of the image/voxel expression actual space area of multi-source images and the consistency of multi-source images in the spatial description of tissues and organs. It is the basis of image fusion. (2) Image fusion must first realize the counterpoint of related images, that is, one-to-one correspondence from point to point. The higher the resolution of the image, the more details of the image, and the more difficult it is to achieve alignment. Therefore, when aligning high-resolution images (such as CT images and MRI images), external markers are currently used. (3) Establish an image database, and complete the archiving management and information extraction of typical cases and typical image data. It is the data support of fusion. (4) Data understanding is to comprehensively process and apply the information obtained by various imaging devices, and obtain new information that is helpful for clinical diagnosis.