Quantification of endothelial permeability, leakage space, and blood volume in brain tumors using combined T1 and T2* contrast-enhanced dynamic MR imaging

First order correction for T2*‐relaxation in determining contrast agent concentration from spoiled gradient echo pulse sequence signal intensity

“…[9] is approximated by a first order Taylor expansion around T E r 2 C ¼ 0, which agrees with the assumption that E Ã 2 % E Ã 20 . This yields the final first order solution for the CA concentration C fo :…”

“…While for most pulse sequences, this range covers the physiological concentrations found in tumor tissue, it does not comprise the typical blood concentrations encountered when measuring the AIF. Nevertheless many DCE-MRI studies neglect the T 2 *-effect to convert the signal intensity variation into concentration curves as it yields an analytical solution linking a relative signal enhancement to a single CA concentration (8)(9)(10)(11)(12)(13). The most accurate conversion method C num , comprising T 2 *-effects, is more difficult to perform as it requires numerical solution of strongly non-linear equation (4).…”

“…Several authors assumed a linear relationship between the relative signal enhancement and the CA concentration (2,5,6), which causes severe error in kinetic parameter estimation (7). Currently, many authors use a nonlinear method as described by Dale et al (8) or by Zhu et al (9) in which T 2 *-relaxation of the MR-signal, caused by the presence of the CA, is neglected (10)(11)(12)(13). The advantage of this approach is that an analytical solution exists, linking a measured signal intensity to a single concentration.…”

Comparison of errors associated with single‐ and multi‐bolus injection protocols in low‐temporal‐resolution dynamic contrast‐enhanced tracer kinetic analysis

“…Figure 2 illustrates the process of data simulation. Signal intensity (SI) data were calculated for each simulated tissue and blood plasma concentration time course, based on a 3D spoiled gradient-echo (FLASH/fast field echo) DCE-MRI protocol (22) with tissue and blood T 1 assumed to be 1000 ms and 1400 ms, respectively (23). Each time course consisted of 1600 volumes covering 6 min with a temporal resolution of 0.23 s, a flip angle of 20°, and a TR of 2.5 ms. Two AIF injection protocols were simulated for subsequent use as input to the data simulation process.…”

Jeannette Wilkins Award: Can Locally Delivered Gadolinium Be Visualized on MRI? A Pilot Study

“…Second, we were able to visualize the area to which Gd-DTPA had distributed, but we have not been successful in converting T1 values for each pixel to concentration values. Calculation of Gd-DTPA concentration requires measurement of T1 value for each pixel before and after the contrast agent is introduced [30]. Because the rabbit is moved and tissues are distorted during implantation of the local depots, precisely identifying the same pixels before and after local delivery of Gd-DTPA has not yet been achieved.…”