Quantification of liver blood volume: comparison of ultra short ti inversion recovery echo planar imaging (ulstir‐epi), with dynamic 3d‐gradient recalled echo imaging

Abstract

An ultra-short TI inversion recovery echo-planar imaging (ULSTIR-EPI) sequence was designed to reduce the influence of water exchange on fractional tissue blood volume (BV) estimation by measurement of T1-changes induced by a gadolinium-based macromolecular contrast medium (MMCM). Fractional liver BV in rats, estimated by ULSTIR-EPI was compared for accuracy to a fast T1-weighted three-dimensional gradient-echo (3D-SPGR, 3D-spoiled gradient recalled acquisition in a steady state) sequence using an in vitro inductively coupled plasma atomic emission spectroscopy (ICP-AES) assay for BV as a standard. Liver images for fractional BV estimation were acquired in eight rats using both ULSTIR-EPI and 3D-SPGR before and after (within 3 to 12 min) intravenous bolus administration of albumin-Gd-DTPA30 (0.05 mmol Gd/kg). Whereas both MR techniques may be useful for fractional tissue BV estimation, ULSTIR-EPI offers certain advantages including greater accuracy, direct T1 maps, and minimization of transendothelial proton exchange effects. 3D-SPGR imaging offers better spatial resolution, current availability on standard clinical MR systems, and acceptable accuracy.

Quantification of the effect of water exchange in dynamic contrast MRI perfusion measurements in the brain and heart

“…[4]) and also the slow-exchange regime with b ϭ 1 3 s (two-site model) for different combinations of TI and E. This was carried out twice, either with F set to 100 or 500 ml/100 g/min. The high value of F was chosen in order to illustrate the situation in the heart during maximal perfusion, such as after administration of dipyridamole.…”

“…Several studies have indicated that this could affect the results of such perfusion measurements (1)(2)(3)(4)(5)(6). However, contrast-enhanced MRI using T 1 -weighted imaging has been developed in order to measure perfusion or perfusion-related parameters of the heart in vivo without explicitly considering the effect of water exchange.…”

“…The lower of the two equations in Eq. [4] indicates that the expression for the MR signal intensity (Eq. [5]) is used twice, describing the MR signal from the vascular compartment and from the extravascular compartment, respectively, and that the weighted sum of these signals is compatible with a noexchange situation between these compartments.…”

Assessment of hepatic perfusion parameters with dynamic MRI

“…Liver blood volume has been quantified with MRI and macromolecular agents (14,15). More recently, hepatic perfusion has been assessed by pharmacokinetic analysis of dynamic MR images obtained after bolus injection of a commercially available extravascular agent (16).…”

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

“…Since most living tissues do not exhibit such extreme exchange characteristics (6,(12)(13)(14), neither of these assumptions accurately describes the biological system. However, it was predicted that the sources of error due to physiologic variations can be minimized by carefully selecting pulse sequence and calculation methods (5).…”