MedE Ph.D. Defense: May (Zi Yu) Huang

https://caltech.zoom.us/j/85279487746

Vulnerable atherosclerotic lesions, widely characterized by a thin fibrous cap and a high content of oxidized low-density-lipoprotein-laden (oxLDL) macrophages, are prone to rupture. These events can have serious consequences such as blood clots or even a heart attack. Diagnostic methods that quantify the lipid content within the arterial wall are needed in the clinical setting. Electrical impedance spectroscopy (EIS) has been shown to detect oxLDL, a key marker for metabolically active plaques. Therefore, we propose a new method, EIS-derived 3D conductivity tomography, for endoluminal mapping of oxLDL-laden arterial walls. This method utilizes impedance values at a fixed frequency to solve for the conductivity distribution. This approach circumvents the mathematically ill-posed problem found when performing tradition electrical impedance tomography (EIT) methods. We designed a 6-point EIS electrode array that was circumferentially configured to a balloon catheter and deployed in Yorkshire mini-pigs with induced stenosis in the right carotid artery. The EIS spectra demonstrated an elevated impedance in the right carotid arteries and the EIS-derived conductivity tomography were reconstructed. The low conductivity regions in the EIS-derived conductivity tomography were correlated with the positive E06 immunostaining for oxLDL-laden regions. Thus, we establish the capability of 3D EIS-derived conductivity tomography to detect oxLDL-laden arterial walls with translational implication to predict metabolically active plaques prone to acute coronary syndromes.

Advisor: YC Tai