Christian T McHugh1, Phillip G Durham2, Michele Kelley1, Paul A Dayton3, and Rosa T Branca1
1Physics & Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 3Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
1Physics & Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 2Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States, 3Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
Gas microbubbles have the potential to be a dual modality contrast agent for US and MRI, but the MR detection sensitivity to microbubbles must improve. Here we show that microbubbles, at clinically relevant doses, can be detected by using hyperCEST.
Figure 2. Zoom-in of experimental Z-spectra around the gas-phase peak. Z-spectra for (A, 340 fM) small and (B, 40 fM) medium MBs at different B1 strengths. Z spectra obtained with a constant B1 (5 μT) at different gas-volume concentrations with (C) small, (D) medium, and (E) large MBs. (F) Z-spectra of MBs with different sizes at a constant concentration of 400 fM. Signal loss increases with B1 as well as with gas-volume concentration. HyperCEST efficiency is maximized for MBs with a 2 μm diameter.
Figure 1. Simulations of MBs hyperCEST contrast. MB samples are characterized by the gas-volume concentration (μL/L) and average diameter (μm). These characteristics are directly related to the exchange rate and participation rate of 129Xe. Using the FHC solution, signal loss at different B1 strengths is shown. Signal loss generally increases with B1 and gas-volume concentration. The MB size must be optimized, and MBs lose efficiency as hyperCEST agents at sizes in excess of 2 μm.
