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Lingyi Zhao
BME Ph.D. Thesis Defense
Date: June 13th, 2020
Time: 9:00 PM
Location: Peking University, College of Engineering, Building No 1, Room 210
Webex link: For anyone who would like to audit, please send an email to lzhao91@gatech.edu at least two days prior to the defense to get the link.
Advisor: Changhui Li, Ph.D.
Stanislav Emelianov, Ph.D.
Committee Members:
Changhui Li, Ph.D. (Advisor)
Stanislav Emelianov, Ph.D. (Co-Advisor)
Peng Xi, Ph.D.
Meng Yang, M.D.
Jianwen Luo, Ph.D.
Title: System development and clinical applications of the handheld PA/US dual-mode imaging system
Abstract: As an emerging technology, photoacoustic (PA) imaging (PAI) has gained lots of progress in the past two decades. By combing optical contrast with ultrasound detection, PAI can maintain high spatial resolution in deeper regions. Furthermore, with the aid of multispectral imaging, PAI can reveal functional information such as oxygenation saturation (SO2), which is closely related to tumor malignancy. With the above advantages, nowadays PAI has gained lots of progress in clinically translatable research. These research shows that PAI has the potential to complement existing imaging techniques such as ultrasound (US) imaging for cancer detection, disease evaluation and prognosis monitoring.
This thesis mainly discusses the clinical application of PAI, including system design and clinical research. Particularly, it presents several studies including the development of PA/US imaging system and the clinical evaluation of PA/US imaging in the diagnosis of superficial cancer. The main research results and the major novelties of this thesis include:
1) The collaborative development of the PA/US imaging system for clinical studies, where the author was mainly responsible for the design of the optical path and the trigger method between the laser and the US system.
2) The design of optical fluence compensation strategy based on clinical US structural imaging. This strategy first identifies the tissue type based on US structural imaging and then utilizes the known optical absorption and scattering parameters to simulate the optical fluence map in the imaging region. The simulated optical fluence map can then be used for the correction of original PA images. The effectiveness of this strategy has been verified based on clinical PAI data. The proposed method can improve the accuracy of quantification PAI and restore PA signals in deeper regions.
3) The collaborative study of PA/US imaging on thyroid nodules with the self-developed 2D PA/US handheld imaging system. By comparing PAI results with color Doppler flow imaging (CDFI) results from 10 thyroid nodules, we found that PAI can reveal more abundant vessels than CDFI, and can thus provide valuable information in the diagnosis of thyroid cancer.
4) The design of the method for quantification analysis of 3D PA/US imaging on breast cancer. Specifically, this method first calculates the ellipse enclosing the tumor region with the minimum volume and then automatically segments the tumor regions and tumor surrounding regions. Next, the volumetric mean SO2 of tumor regions and tumor surrounding regions were calculated for quantification analysis. Our results demonstrate that quantification analysis of 3D functional PA/US imaging on breast cancers has the potential to improve the specificity in the diagnosis of breast cancer.
