Cationic CT contrast agents are more sensitive for imaging joint cartilage compared with most commercially available contrast agents, according to a study published online Sept. 1 in the Journal of the American Chemical Society .
To diagnose cartilage disease like osteoarthritis—which afflicts more than 27 million people in the U.S.—physicians need to assess the local variations in glycosaminoglycans (GAGs). The loss of GAGs from joints is an indicator of osteoarthritis.
According to Mark W. Grinstaff, PhD, professor of chemistry and biomedical engineering at Boston University and colleagues, although contrast agents are needed to assess GAG content, those that are now being used with CT or MRI “rely on limited diffusion of the anionic or negative ion-charged contrast agents into the target tissue.”
The authors hypothesized they could get a more sensitive technique for imaging cartilage by using cationic contrast agents that would electostatically attract to anionic GAGs. They synthesized three cationic ion-charged iodine-based x-ray contrast agents. The scientists imaged the femur of a rabbit after utilizing their contrast agents and reported obtaining more specific images than with the negative ion-charged contrast agents.
"Compared with commercially available contrast agents under the same experimental conditions, these new cationic agents are three times more sensitive for imaging cartilage," said Grinstaff.
The authors warned that while the results make a case for continuing to develop cationic contrast agents, future studies will have to focus on toxicity and radiation dose levels.
"However, the ability to characterize ex vivo cartilage samples is clearly evident," the study concluded. "Currently obtaining data about the spatial distribution of biochemical components in tissue samples is largely accomplished using histology, which is destructive and time consuming, and thus the use of contrast agents in conjunction with CT imaging will result in readily available, nondestructive alternative to histology."