Direct comparison of two methods to measure T1: in vitro and in vivo values by echo-planar imaging and by segmented k-space imaging.
We test a hypothesis that proton T(1) is accurately measured independent of the physics inherent to the method. We used two well-validated but quite different imaging methods to measure T(1) in phantoms and in humans; an echo-planar imaging T-one measurement (EPITOME) method, and a segmented k-space acquisition precise and accurate inversion recovery (TurboPAIR) method. Agreement between the methods was generally excellent; the square of the correlation coefficient (r(2)) in phantoms was 0.9996. The r(2) in brain tissue of volunteers was 0.79 overall, and 0.85 if cortical gray matter and corpus callosum were excluded. Nevertheless, small but significant differences were observed between methods in vivo and T(1) measurements were sensitive to tissue type, although measurements could be made comparable. The major difference between the methods is that EPITOME takes 97 s to image 15 slices at low resolution, while TurboPAIR takes 240 s to image one slice at high resolution.