骨表微小血管脉冲逆转微泡小波变换超声造影成像及血流灌注评价

Two problems will arise for ultrasound imaging of musculoskeletal system with oblique incidence angles: Firstly, the quality of the micro-vessels imaging near the bone surface will be disturbed by the multi-mode leaky lamb waves (LLWs) from the bone surface of diaphysis and joint. Secondly, detection the perfusion information of the micro-vessels near the bone surface will be difficult due to the LLWs dispersion properties. Considering the above limitations, the major works of our project are as follows: (1) The dispersion and propagation properties of LLWs from the bone surface of diaphysis and joint are studied which are excited by ultrasonic beam modulated by frequency and phase; the influences mechanism of LLWs dispersion properties on the vibration and scattering characteristics of micro-bubbles and the ultrasound contrast imaging of micro-vessels near the bone surface are clarified in this work. (2) In order to restrain such influences and acquire the superficial and deeper contrast and perfusion images with higher Contrast-to-Tissue and Contrast-to-Bone Ratios, a new method of ultrasound contrast signal separation detection, and sub-harmonic (f=7-12MHz) and second-harmonic (f=3-5MHz) imaging of micro-vessels near the bone surface is presented based on the pulse inversion with bubble wavelet transform. (3) For the micro-vessels near the femur and vertebrae with higher incidence of bone tumors, above imaging method is performed on the imported and domestic ultrasound platform, and a new way is provided for high resolution imaging, perfusion detection, early diagnosis and post-operative evaluation of bone tumor.

肌骨系统超声斜入射时，存在超声波激励骨体（局部近似平面）/关节（凸/凹面）骨表产生多模式漏Lamb波（LLWs）干扰骨表微小血管造影成像和难以准确提取血流灌注信息的问题。本项目（1）提出并研究频率/相位调制的骨体/关节骨表LLWs的频散特性，澄清骨表LLWs频散特性对造影微泡振动与散射特性及对微小血管超声成像的影响机制；（2）针对浅表/深部成像，构建频率/相位调制的母小波，提出骨表微小血管脉冲逆转微泡小波变换造影信号多尺度分解和次谐波（7-12MHz）/谐波（3-5MHz）成像方法，以抑制LLWs对造影成像和血流灌注评价的混叠干扰，得到高造影组织比(CTR）、造影骨导比(CBR)的骨表微小血管造影与灌注参量图像；（3）并针对骨肿瘤发病率高且存在关节侵犯的股骨与椎骨附近微小血管，在B超设备上实施上述算法，为骨肿瘤新生血管高分辨成像与血流灌注评价、早期诊治提供新方法。

骨表微血管造影成像及评价对肌骨系统的疾病诊断具有重要价值。骨导波对造影微泡的振动和散射特性的影响作用以及得到高CTR、高分辨的造影图像是其中的关键性问题，本项目针对这些问题展开了研究工作。主要研究内容和结果包括：（1）构建了骨表-血管-微泡的理论研究实验仿体系统，研究并澄清了骨导波对造影微泡的作用机制，发现骨导波的影响会增加微泡的次谐波分量，同时造影图像的分辨率会有所降低。（2）发展了基于平面波的微泡小波解相关造影成像技术，获得了高CTR、长时间灌注的超声造影图像，相比脉冲逆转谐波成像，仿体实验所得图像CTR 提高了10.09 ± 2.96 dB，微泡检测灵敏度提高了12.52 ± 2.10 dB。（3）研究了单像素分辨水平的微血管灌注参量成像技术，将血流灌注的高分辨、高信杂比的定量化成像及评价技术推进一大步；（4）此外，研究了基于压缩感知技术的快速造影成像技术及基于互相关筛选的灌注参量成像技术，同时采用了四分法和DFA技术解决了灌注中呼吸运动补偿等问题，将造影成像及灌注评价技术的性能进一步提高。