CONTEXT: MR imaging enhanced with ultrasmall superparamagnetic iron oxide (USPIO) particles can noninvasively monitor the behavior of novel anti-angiogenesis drugs, according to researchers at the University of Munster in Germany. The group is investigating USPIO-enhanced MR measurements of vascular volume fraction as a surrogate marker for tumor angiogenesis. Results, compiled by Dr. Thorsten Persigehl and colleagues at the university's Institute for Clinical Radiology, were summarized in a scientific poster at the European Congress of Radiology in March.
RESULTS: Tumor-bearing mice were treated intravenously with either an agent inducing thrombosis in selective tumor vasculature (11 mice) or saline (13 mice). All animals underwent MR imaging at 1.5T with a long-circulating USPIO (SHU 555C, Schering) four to eight hours after treatment. USPIO-induced changes to relaxation ( delta R2*) to determine the vascular volume fraction were measured using a T2-weighted dual echo-planar MR sequence.
Parametric delta R2* maps revealed a noticeable reduction in tumor perfusion in the treatment group compared with controls. This change was observed as early as four hours after injection with the anti-angiogenesis agent. Histological analysis confirmed the MR findings, showing extensive tumor thrombosis in the treatment group.
IMPLICATIONS: The study confirmed that USPIO-enhanced MR imaging measures early tumor response to anti-angiogenesis treatment, according to Persigehl. Radiologists will readily adopt this class of MR contrast media when it is introduced for clinical use, he said.