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 T₁ is accurately measured independent of the physics inherent to the method. We used two well-validated but quite different imaging methods to measure T₁ 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 (r²) in phantoms was 0.9996. The r² 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 T₁ 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.