Is the T2* Relaxivity of Gadolinium in Brain Microvasculature Linear with Concentration?

Vishal Patil¹, Glyn Johnson¹

Generally, linearity is assumed between T2* relaxation and gadolinium concentration, but it is well known that compartmentalization and secondary magnetic field perturbations generate deviations from linearity in vivo. In this study we test the reliability of both linear and non-linear relaxivity expressions estimating cerebral blood volume in grey and white matter at different field strengths and echo times. Results show that the non-linear expression yields remarkable agreement between tissue measurements while the linear expression systematically over and under estimates blood volume depending on imaging parameters, emphasizing the problem in finding a single linear relaxation relationship that fits multiple field strengths.