Water exchange and inflow affect the accuracy of T₁‐GRE blood volume measurements: Implications for the evaluation of tumor angiogenesis

Abstract

The goal of this study was to determine the degree to which vascular water exchange and blood flowing into an imaging slice affect the accuracy of blood volume measurements of brain and tumor tissue when using intravascular T 1 contrast agents. The study was performed using 2D and 3D gradientecho imaging sequences, since these are two of the most commonly used MRI methods used to evaluate tissue blood volume fraction. Computer simulations were performed and measurements made in a rat 9L gliosarcoma brain tumor model. The computer simulations demonstrate that, with either water exchange or inflow effects alone, the dependence on the physiologic and imaging parameters can be well characterized and therefore potentially offset. In the exchange only case, the parametric dependence of 3D simulations suggest that the best accuracy is achieved with high flip angles, short TR, and low blood contrast agent concentrations. However, for a 2D GRE sequence which is influenced by both water exchange and inflow, the simulations predict that the error trend as a function of the imaging and physiologic parameters is unpredictable and therefore difficult to compensate. With both 2D and 3D GRE the measured blood volume data in rat brain and tumor tissue demonstrate tissue-specific trends, which reflect differences in the considered physiologic parameters. The experimental data strongly support the computer simulations and also indicate that minimization of the physiological effects by proper selection of imaging parameters, contrast concentration, and volume calculation methods is crucial for accurate assessment of absolute blood volume fraction. Magn Reson Med 47: 1110 -1120, 2002.

Diagnostic Accuracy of Dynamic Contrast-Enhanced MR Imaging Using a Phase-Derived Vascular Input Function in the Preoperative Grading of Gliomas

“…16 While saturation of signal intensity could lead to an underestimation of the contrast agent concentration, the presence of inflow effects could lead to an overestimation. 17 Our magnitude-VIF based K trans and V p estimates were higher than those derived from the phase method. This might be due to an underestimation of the contrast agent concentration in the VIF.…”

Dynamic NMR effects in breast cancer dynamic-contrast-enhanced MRI

“…Even so, exchange effects seem to facilitate very high discrimination of malignant from benign breast tumors (17). In recent years, there has been considerable effort devoted to decreasing DCE-MRI pulse sequence exchange sensitivity (25). Our results suggest that there could be significant profit, not the least for cancer screening, in working to increase exchange sensitivity, by adjusting not only ␣ and TR, but also TE (a small increase may improve specificity).…”

The magnetic resonance shutter speed discriminates vascular properties of malignant and benign breast tumors in vivo

“…Even so, exchange effects seem to facilitate very high discrimination of malignant from benign breast tumors. In recent years, there has been considerable effort devoted to decreasing the exchange sensitivity of DCE-MRI pulse sequences (29 …”