Indeed. Martin's a great name in the field -- the thing that has actually made most clinical proton MRI substantially better over the last twenty years has been parallel imaging (acquiring the magnetic resonance signal from different spatially separated devices known as RF coils) and associated reconstruction techniques such as compressed sensing.
Given the fact that macrocyclic gadolinium complexes accumulate in the brain and the linear ones dechelate I think very few companies are pursuing new agents. I've done some work with different ions (like Dy, which has Curie paramagnetism) but a lot of focus in the field is trying to find alternatives to gad and reduce its use. There are plenty of great ways of getting more info out of a machine that spans quantum mechanics to medicine, from the established but now actually useful and routine (like advanced diffusion models) to the sort of utterly mad techniques I work on... [0]
[0] https://www.science.org/doi/10.1126/sciadv.adz4334