Visualisation of normal and abnormal brain vasculature with different ferumoxytol doses.

Abstract

e13517 Background: Ferumoxytol is an iron oxide nanoparticle, marketed for iron replacement therapy. Off label use as an MRI contrast agent allows visualization of cerebral vasculature in the early blood pool phase without early contrast enhancement obscuring the vessels as seen with small molecular gadolinium. This study tested the optimal ferumoxytol dose for visualization of normal and abnormal cerebral vasculature. Methods: MRI images of 75 subjects enrolled in imaging research protocols were analyzed. Vascular visualization was tested in high resolution gradient echo T2*-weighted images acquired after 1mg/kg, 3mg/kg and 7mg/kg (up to 510mg) ferumoxytol doses. Visualization of normal and abnormal vasculature was separately evaluated as “poor, moderate or clear”. Degree of blooming artifact was graded as “none, mild and marked”. Overall clarity of the image was visually assessed as “poor, moderate and very clear”. The probability of abnormal vasculature visualization being “moderate” or “clear” was tested among the three Fe dosages with a mixed effects model while taking correlation among different dosages into account. Results: Visualization of normal brain vasculature was poor with 1mg/kg, moderate with 3mg/kg and very clear with 7mg/kg in 97% of the cases. However, blooming with 7 mg/kg was already marked for all cases causing confluence of larger veins and even smaller vessels close to each other, while images with 3mg/kg showed only mild blooming in all cases, resulting in altogether a better quality/clarity of the images (very clear in 93.3%) with good contrast between normal vessels and brain parenchyma. Not all subjects had abnormal vasculature due to prior surgery. However, when considering all subjects, visualization of abnormal vasculature was moderately or clearly visible in 23% of subjects when using1mg/kg, significantly less than 3mg/kg (42.7%, P = 0.0012) and 7mg/kg (43.9%, P = 0.0007). Conclusions: 3mg/kg ferumoxytol allows adequate visualization of normal and abnormal vasculature with acceptable degree of blooming artifact. Visualization of tumor vasculature may help targeting the most malignant area for surgery/radiotherapy and may help differentiating tumor progression from pseudoprogression. Clinical trial information: NCT00659776, NCT02359097.