“Quantitative Susceptibility Mapping (QSM): tissue magnetism physics, mathematical algorithm and clinical applications”
Background: Dr. Yi Wang, Ph.D., holds the Faculty Distinguished Professorship at the Department of Radiology, and is a tenured Professor of Physics in Radiology, Professor of Biomedical Engineering, and the Principal Investigator of the 3T MRI facility at Cornell University. Professor Wang has invented multiple MRI technologies that are very important to the clinical and scientific communities: i) the cardiac navigator method to compensate for motion artifacts that has been adapted by most major academic centers as a basic approach in cardiac MRI; ii) the time-resolved acquisition method to solve the critical problem of timing acquisition to contrast bolus arrival in clinical contrast enhanced MRA and the multiple-station stepping-table platform to offer high throughput imaging of various body parts; iii) the quantitative susceptibility mapping (QSM) method that has broken ground for a new field in MRI for studying tissue magnetism.
Abstract: Tissue magnetism refers to the electron–proton interaction, which is macroscopic and long range with its effects on MRI being treated as static dephasing. In contrast, traditional tissue relaxation refers to the proton–proton (commonly known as spin-spin) interaction, which is microenvironment-sensitive and short range with its effect on MRI being treated quantum-mechanically. The long-range magnetism implies nonlocal blooming artifacts in both T2* hypointensity and phase of MRI signal. Quantitative susceptibility mapping (QSM) is to study magnetism by deconvolving the blooming artifacts. The Bayesian approach has been established to address the main QSM challenge, which is the ill posedness of the magnetic field to susceptibility source inverse problem.
QSM has become sufficiently accurate and robust for routine applications. QSM is advancing MRI study of tissue magnetic susceptibility from simple qualitative detection of its hypointense blooming artifacts to precise measurement of its biodistributions. Tissue susceptibility contains rich functional and structural information pertinent to molecular electron cloud properties. The dominant susceptibility sources in tissue are biometals, which are vital participants in cellular functions and pathologies. QSM can be useful for diseases that involve neurodegeneration, inflammation, hemorrhage, abnormal oxygen consumption, substantial alterations in highly paramagnetic cellular iron, bone mineralization, or pathologic calcification; and for all MRI with contrast agent injection. Clinicians should consider integrating QSM into their routine imaging practices by including susceptibility-sensitive gradient echo sequences in all relevant MRI protocols.
For inquiries contact Cathy Gezella.