Fig 6. A, Simulated signal-intensity enhancement curve versus time by using the steady-state T1 method for tissue with different permeability, corresponding to a meningioma (K_trans = 0.5/min), a glioma (K_trans = 0.05/min), and a chronic multiple sclerosis (MS) lesion (K_trans = 0.005/min). v_e of 0.3 is assumed. Proton density is assumed to be 1,000 arbitrary units (au) for all tissue, T1 before contrast is 1.2 seconds, and a typical spin-echo T1-weighted sequence with a TR of 500 ms is assumed. Note the rapid rise and subsequent fall of signal intensity in the highly leaky meningioma compared with the more gradual onset of contrast enhancement in the MS lesion. As is typical for the ssT1 method, contribution from the intravascular space is neglected. B, An example of gradual enhancement on T1-weighted imaging in a high-grade glioma at several time points following contrast administration by using the ssT1 method. The fitted K_trans permeability map is shown at the right. Image courtesy of Dr. Soonmee Cha, University of California, San Francisco.