SPECT/CT: Scouting out vulnerable plaques in atherosclerosis

Angiography cannot differentiate between vulnerable and stable plaques, which inform clinicians about a patient’s risk of rupture. Immuno-imaging with SPECT/CT could be a route for marking increased immune response at the site of high-risk vulnerable plaques, but there remain some complications, according to a study published Jan. 21 in Molecular Imaging.

A team of researchers including Leah C.J. Winkel, a PhD candidate at Erasmus Medical Center in Rotterdam, The Netherlands, worked from the premise that more macrophages are active in proximity to vulnerable plaques than those that are stable.

“Macrophages are differentially activated between stable and vulnerable plaques and may provide a specific stable or vulnerable plaque marker,” wrote Winkel et al.

The researchers chose a novel technique of combining a folate biomarker combined with In-111 called In-111 EC0800 and evaluated its effectiveness for singling out vulnerable plaques by locking with folate receptors using preclinical SPECT/CT. Results of the study showed that tracer uptake was significant in both vulnerable and stable plaques, contrary to what was expected. In fact, when the scientists tested for uptake as well as plaque size, there was stronger uptake particularly in smaller, stable plaques.

“We demonstrated that In-111 EC0800 imaging detects both stable and vulnerable atherosclerotic plaques, suggesting that In-111 EC0800 is not a clear-cut marker for the detection of vulnerable plaques, in a mouse model for atherosclerosis,” wrote the authors. “However, combining folate-based imaging with imaging of plaque size might still be an interesting target for differentiating between stable and vulnerable plaques.”

Further research is required to understand whether stable plaques have more macrophage activity, contrary to what was once thought, or whether the macrophages in stable plaques simply have more folate receptor expression.