Author: Jaydev K. Dave, Krzysztof R Gorny, Chunming Gu, Nicholas J. Hangiandreou, Gina K. Hesley, Myung-Ho In, Zaiyang Long, Aiming Lu, Christin A. TiegsHeiden 👨🔬
Affiliation: Mayo Clinic 🌍
Purpose:
MR-guided focused ultrasound (MRgFUS) enables precise tumor ablation with real-time MR-thermometry guidance. Our practice is exploring the potential use of Feraheme (Ferumoxytol), a superparamagnetic iron oxide nanoparticle, to enhance blood vessel visibility through increased T2*-weighting and facilitate their avoidance during treatment for patients with elevated risk. However, its impact on heating and T2*-based MR-thermometry remains unclear, as Feraheme in blood could be taken up by tumors themselves. This study aims to evaluate the feasibility of incorporating Feraheme into MRgFUS treatments.
Methods:
Three phantoms with Feraheme concentrations of 0, 0.25, and 0.5 mM were prepared using a validated recipe for MRI and acoustic properties, based on a clinical Feraheme dose of 4 mg/kg (~1.02 mM in blood). T2 and T2* mapping and MRgFUS experiments were performed on a 1.5T GE 450W scanner with a clinical MR-compatible FUS system (ExAblate 2001, InSightec). Phantoms were positioned in a clear cylindrical container filled with degassed water and covered with a thin film at the base. Sonications targeted a central spot (5 cm depth) at 1000J for 20 seconds, repeated 4 or 5 times with 7-minute cooling intervals. MR thermometry was used to record mean and maximum temperatures. Experiments were repeated for all phantoms and again after two weeks to ensure consistency.
Results:
T2* and T2 values decreased substantially with increasing Feraheme concentration, but MR-thermometry with a signal-to-noise ratio above 50 remained feasible even at 0.5 mM. Phantoms with Feraheme exhibited statistically significant increases of ~4°C and ~5°C in mean and maximum temperatures compared to those without Feraheme, which is consistent across two experiments conducted two weeks apart.
Conclusion:
This study shows that incorporating Feraheme into MRgFUS treatments is feasible. Further studies are needed to better understand its focal thermal effects and to optimize tumor ablation efficiency while preventing unintended damage.