The best chelators are agents that possess the highest stability constant (same as thermodynamic stability) and also kinetic stability with Gd, or whatever else to be chelated. DTPA has the highest stability of currently available agents - other ligands for GBCAs may even be better. Stability of the GBCA is only part of the problem with these agents, otherwise why would the macrocyclics cause it when they should remain intact? Neutrophils are recognized as assuming an ameoboid shape when encountering an adversary, I suspect the others can as well (macrophages). I think they can crawl along the surface of Gd molecular forms, including intact chelate, and recognize the Gd within, and release a cytokine storm (as well as other inflammatory products). DTPA has the lowest re-release of Gd in the body of what we have available, and whatever else is involved with GDD it is important to get as much Gd out as is feasible.