Phillip Zhe Sun, PH.D.
|Title||Assistant Professor of Radiology|
|Institution||Massachusetts General Hospital|
|Address||Massachusetts General Hospital|
Radiology, Rm. 2301
149 13th Street
Charlestown MA 02129
My research is to develop and apply novel MRI technique to improve our understanding of human diseases for early diagnosis and treatment. In particular, I have been focusing on imaging ischemic penumbra (the viable tissue under the risk of infarction if not reperfused promptly) using the recently developed pH sensitive endogenous amide proton transfer (APT) MRI. Conventionally, perfusion (PWI) and diffusion (DWI) imaging can demarcate ischemic core from hypoperfused area, which contains both ischemic penumbra and benign oligaemia. As the thrombolytic treatment increases the risk of hemorrhage and has neurotoxic side effects, it is crucial to detect the ischemic penumbra to assist treatment decision. Previously, we showed that pH MRI, in complimentary to PWI and DWI can delineate the ischemic tissue into core, penumbra and benign oligaemia, and the pH lesion is closely correlated with the 24hr infarction using a permanent animal stroke model. Encouraged by the animal study, we have implemented and optimized the APT imaging on clinical scanners, and are currently evaluating its effectiveness in detecting salvageable ischemic tissue on acute and subacute stroke patients. We will also develop and validate an infarction prediction model that integrates multi-parametric MRI of the hemodynamic, metabolic, structural and temporal status of ischemic tissue, and the ultimate goal is to develop MRI guided acute stroke therapy.
I am also interested in advancing the new chemical exchange dependent saturation transfer (CEST) imaging for specific molecular and cellular MRI. In comparison with conventional relaxation based contrast agents, the CEST agents can be incorporated into cellular proteins and provide enormous amplification of dilute labile groups. We will develop sensitive CEST agents that specifically bind to cell surface markers and explore the CEST imaging as a new method for cell tracking and functional imaging.
Moreover, I am developing advanced diffusion MRI technique such as diffusion imaging with ultra-short diffusion time. Although diffusion MRI has found tremendous applications such as white matter fiber tracking and detection of early stroke lesion, one of the technical limits is that the diffusion time is usually very long, tens of milliseconds, therefore the diffusion imaging is susceptible to transmembrane exchange and displacement restriction. By developing a diffusion MRI of ultra-short diffusion time, we can provide “genuine” diffusion contrast of microscopic water mobility and therefore improve our understanding of diffusion change in response tissue damage. In addition, I am also exploring a hybrid MRI technique that integrates the magnetization transfer and intravoxel incoherent motion (IVIM) mechanism as a new technique for endogenous cerebral blood volume (CBV) imaging.
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