Magnetic Resonance Imaging Guidance of Histotripsy Therapy.

[摘要] Histotripsy is a cavitation based surgical therapy that transmits high amplitude acoustic pulses into a tissue target to stimulate the formation of energetic clouds of microbubbles. These microbubble clouds then exert a mechanical load on the surrounding cellular and extracellular structure, and, eventually, render a precise volume of tissue into a liquid homogenate devoid of any visible cellular structure. This technology has many potential applications including the erosion of intracranial blood clots, deep vein thrombi, liver tumors, and kidney stones.Histotripsy is a non-invasive surgery and cannot ensure the accurate ablation of the target without an accompanying image-based guidance system. The objective of this dissertation is to explore and develop magnetic resonance imaging (MRI) based tools to 1) visualize and monitor the cavitation process within the ablation target and 2) assess the state of the target after ablation.To this end, this dissertation proposes and characterizes a novel cavitation imaging scheme to visualize the histotripsy process. The technique employs synchronized bipolar gradients as a simultaneous temporal and magnitude filter that selectively sensitizes the resulting image to incoherent water flow generated by the histotripsy bubble cloud. It is shown to be easily integrated into various image acquisition schemes. When used with single-shot, fast imaging schemes, the technique can simultaneously localize individual bubble clouds and provide feedback on the ablated state of the target.The dissertation then examines the response of several basic MR signal evolution processes as tissues are ablated by histotripsy. These processes are related to the diffusion and interaction of water molecules within a tissue and are characterized by the time constants T1, and T2, as well as a diffusion coefficient. The work presented here demonstrates that the magnitude of response of these processes is specific to both the tissue target and the treatment history. Further, the response of the process characterized by T2 is shown to depend the ability of the bubble cloud to erode and disperse aggregations of paramagnetic proteins such as hemoglobin and ferritin.Together, this dissertation provides useful magnetic resonance imaging tools for the visualization and assessment of histotripsy therapy.

[发布机构] University of Michigan

[效力级别] Biomedical Engineering

[关键词] Magnetic Resonance Imaging Guidance for Histotripsy Therapy;Biomedical Engineering;Engineering (General);Radiology;Engineering;Health Sciences;Science;Biomedical Engineering