Adaptive MRI-guided liver SBRT planning using superparamagnetic iron oxide nanoparticles (SPION)

Abstract

Background: Ferumoxytol® (Feraheme, AMAG Pharmaceuticals, Waltham, MA) is a super-paramagnetic iron oxide nanoparticle that is increasingly utilized off-label as a liver magnetic resonance imaging (MRI) contrast agent. In addition to its excellent safety profile in patients with impaired kidney function, this agent has the advantage of providing a functional assessment of the liver based upon its uptake within hepatic Kupffer cells proportionate to vascular perfusion, resulting in strong T1, T2 and T2* relaxation effects and enhanced contrast of malignant tumors, which lack Kupffer cells. The latter characteristic is especially important in patients who have undergone prior therapy, in whom the functional liver reserve may be overestimated by conventional imaging techniques. The purpose of this study was to assess visibility of liver tumors and functional hepatic parenchyma utilizing SPION-enhanced 1.5T MRI during per-fraction adaptive stereotactic body radiotherapy (SBRT) planning on Elekta Unity Hybrid MR-Linac (Elekta; Stockholm, Sweden) in patients with pre-existing liver conditions.