Photoacoustic Tomography
Inflammatory Arthritis
Aiming at a point-of-care device for rheumatology clinics, we developed an automatic 3D imaging system combining the emerging photoacoustic imaging with conventional Doppler ultrasound for detecting human inflammatory arthritis. It can enable early detection and early treatment modification, changing the current procedures in rheumatology clinics.
Chemical Imaging for Cancer Research
The advanced study is focused on PA chemical imaging for guiding cancer therapy. As each chemical status (oxygen, pH and potassium concentrations) is strongly relevant to cancer progress and response to therapy (radio-, chemo- and immuno-therapy), a non-invasive, sensitive, and reliable approach for evaluating their temporal and spatial distributions in the tumor microenvironment (TME) in vivo is desirable. We apply the PA chemical imaging to predict a given tumor’s response to therapy.
Non-organic Metallic Nanoparticles
Gold nanocolloids are particularly useful in optical absorption/scattering applications due to their strong optical responses and their biocompatible nature. The combination of the unique optical and biological properties of gold nanocolloids makes them excellent candidates for biomedical applications. In our study on animal models, the excellent sensitivity of photoacoustic imaging (PAI) to gold nanoparticles, including both gold nanorods and gold nanowonton, has been demonstrated. A novel technique for monitoring the in vivo behaviors of gold particles (AuNPs) using γ-imaging has been developed.
Hydrogel Nanoparticles
Through the collaboration with Prof. Kopelman at UM Chemistry, we are developing a tumor-targeted, biocompatible, biodegradable and bio-eliminable hydrogel-based nanoparticles as contrast agents that enable a combination of structural and functional photoacoustic imaging (PAI). The new technology we used can be used for early detection and diagnosis of cancer, as well as for monitoring the progression of disease and response to therapy. It could also observe phenomena at the molecular level in vivo and allow a better understanding of the pathophysiology of diseases.
Photoacoustic Microscopy
Molecular Imaging of the Eye
The objective of this research is to develop and apply advanced photoacoustic microscopy (PAM) techniques for high-resolution, non-invasive imaging of the eye in real-time. By integrating PAM with optical coherence tomography (OCT) and fluorescence microscopy (FM), the research aims to achieve comprehensive imaging of the eye, providing detailed insights into its structural and functional attributes. This approach enables the visualization of individual blood vessels and abnormal microvasculature, such as neovascularization, essential for diagnosing and monitoring ocular diseases such as age-related macular degeneration, retinal neovascularization, and choroidal neovascularization.
Microscopy and Endoscopy
A part of our research is focused on the development and application of photoacoustic microscopy (PAM) which offers image quality similar to conventional optical microscopic techniques but better imaging depth and unique optical absorption contrast. By collaborating with Prof. Jay Guo at U-M EECS, we have developed an “all optical” PAM system. Instead of using conventional PZT transducers, this PAM system employs an optical microring resonator as the ultrasonic detector. Our PAM system allows excellent depth sectioning and has achieved an axial resolution better than 5 micrometer. The all-optical PAM system has been further developed and miniaturized to satisfy the requirements of clinical endomicroscopy. It is a consensus that endoscopy could one of the most promising application of the emerging biomedical photoacoustic technology. In our lab at Michigan, photoacoustic microscopy is adapted to transurethral imaging of bladder cancer and to transrectal imaging of inflammatory bowel disease.
Ionizing Radiation Acoustic Imaging
Ionizing radiation acoustic imaging (iRAI) is a noninvasive imaging technology that reconstructs the radiation dose using acoustic waves stemming from the absorption of pulsed ionizing radiation beams in soft tissue. iRAI has the potential to map the dose deposition and monitor the dose accumulation at in-depth anatomical structures in real time during RT. In contrast to other dose mapping methods, iRAI is directly proportional to the radiation dose absorbed by the targeted tissue. With pre-calibration of the Grüneisen parameter, medium density, pulse time profile and sensor sensitivity, the linear relationship between the absorbed dose and deposited dose could enable iRAI to both localize and quantify the absolute dose deposition during RT.
Our group was among the pioneers to demonstrate the feasibility of iRAI, as a novel imaging modality, for mapping the radiation dose during RT. Our team was the first to achieve real-time iRAI-ultrasound dual-modality imaging in an animal model in vivo, preparing the technology for clinical applications.
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Photoacoustic Spectroscopy
Spectral Analysis
Almost all of the studies in photoacoustic (PA) imaging have been focused on the intensity of the PA signals as an indication of the optical absorbance of biological tissues. Our group has demonstrated that the frequency domain power distribution of the broadband PA signals also encodes the texture information within the regions-of-interest (ROIs). Similar to ultrasound (US) spectrum analysis, PA spectrum analysis (PASA) could evaluate the intensity and, more importantly, the “pitch” or frequencies of the PA signals. Through a study on mouse model, we have validated the capability of PASA in identifying the microstructure changes corresponding to fat accumulation in livers for the purposes of fatty liver diagnosis. In the study on phantoms, we have demonstrated the close correlation between the PA spectral parameters and the physical properties of the optical absorbers in a tissue.
Physio-Chemical Analysis
By systematically integrating the “optical absorption signature” and the “spatial frequencies of the optical absorbers” in one 2D spectrogram, the PCS presents a unique “physio-chemical signature” for any specific type of tissue. Comprehensive analysis of PCS, termed PA physio-chemical analysis (PAPCA), can lead to rich diagnostic information, including the contents of all relevant molecular and chemical components along with their corresponding histological microfeatures, comparable to those accessible by conventional histology. Ex vivo and in situ studies on mouse models of nonalcoholic fatty liver disease (NAFLD) conditions have demonstrated that, by quantifying the PCS at the optical absorption peaks of major chromophores in liver tissue, including hemoglobin, lipid and collagen, PAPCA can non-invasively characterize the pathological changes correlated to liver steatosis and liver fibrosis.
Prostate Cancer Diagnosis
The objective of this research is to develop a low-cost, minimally invasive, in vivo diagnostic and personalized therapeutic platform for prostate cancer.
Photo-Mediated Ultrasound Therapy
We have developed a novel, selective, localized anti-vascular technique, namely photo-mediated ultrasound therapy (PUT), by applying synchronized nanosecond laser irradiation and ultrasound pulses. Taking advantage of the high optical absorption of hemoglobin, PUT can selectively target microvessels without causing unwanted damages to the surrounding tissue. Moreover, PUT is totally noninvasive and agent-free.
Our group was among the pioneers to demonstrate the feasibility of iRAI, as a novel imaging modality, for mapping the radiation dose during RT. Our team was the first to achieve real-time iRAI-ultrasound dual-modality imaging in an animal model in vivo, preparing the technology for clinical applications.