MR imaging utilizing ultrasmall superparamagnetic iron oxide (USPIO) particles in combination with the current standard of a gadolinium-based contrast agent enabled detection of over 50 percent more multiple sclerosis (MS) lesions than imaging with gadolinium alone, according to research published in the July issue of Radiology.
Study authors Thomas Tourdias, MD, PhD, of Bordeaux Segalen University in Bordeaux, France, and colleagues explained that enhancement with a gadolinium-based contrast agent is the primary sign of MS disease activity, and that it indicates accumulation of the agent due to increased blood-brain barrier permeability. This approach, however, is nonspecific and lacks sensitivity.
“[USPIO] nanoparticles may be used to track iron-laden macrophages in the central nervous system. Previous studies have validated the feasibility of using USPIO in patients with MS, showing that macrophage infiltration obtained with USPIO was distinct and probably complementary to the increased [blood-brain barrier] permeability seen with gadolinium,” wrote the authors.
To test the benefit of USPIO-enhanced MR exams, Tourdias and colleagues studied 24 patients with MS using gadolinium- and USPIO-enhanced MRI at baseline and six-month follow-up.
Results showed that 37 lesions were considered active owing to gadolinium-based enhancement at baseline. The addition of USPIO helped detect 19 additional lesions, a 51 percent increase compared with gadolinium alone, reported Tourdias et al.
Ten patients had a relapsing form of MS and 14 had a progressive form. The authors noted that enhanced lesions were more frequently observed in the relapsing form of MS. “USPIO enhancement, in the form of ringlike patterns, could also be observed on T1-weighted images in patients with progressive MS, enabling the detection of five lesions in addition to the five detected with gadolinium in this phenotype,” they wrote.
Tourdias and colleagues also noted that lesions that enhanced with both contrast agents at baseline were larger, with a mean size of 6.5 mm, and more likely to persistently enhance at follow-up compared with lesions that enhanced only with one of the agents.
While the results suggest USPIO can help assess residual inflammatory activity associated with chronic MS, the authors pointed out this is true only on T1-weighted images, as T2 images were mostly unchanged.