On the measurement of absolute cerebral blood volume (CBV) using vascular-space-occupancy (VASO) MRI

✍ Scribed by Jinsoo Uh; Kelly Lewis-Amezcua; Rani Varghese; Hanzhang Lu

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 970 KB
• Volume: 61
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.21872

✦ Synopsis

Abstract

Recently, a vascular‐space‐occupancy (VASO) MRI technique was developed for quantitative assessment of cerebral blood volume (CBV). This method uses the T~1~‐shortening effect of gadolinium diethylenetriamine pentaacetic acid (Gd‐DTPA) with imaging parameters chosen that null the precontrast blood magnetization but allow the postcontrast blood magnetization to recover to equilibrium. A key advantage of VASO CBV estimation is that it provides a straightforward procedure for converting MR signals to absolute physiologic values. However, as with other T~1~‐based steady‐state approaches, several important factors need to be considered that influence the accuracy of CBV values obtained with VASO MRI. Here, the transverse relaxation (T~2~/T) effect in VASO MRI was investigated using multiecho spin‐echo and gradient‐echo experiments, resulting in underestimation of CBV by 14.9% ± 1.1% and 16.0% ± 2.5% for spin echo (TE = 10 ms) and gradient echo (TE = 6 ms), respectively. In addition, the influence of contrast agent clearance was studied by acquiring multiple postcontrast VASO images at 2.2‐min intervals, which showed that the concentration of Gd‐DTPA in the first 14 min (single dose) was sufficient for the blood magnetization to fully recover to equilibrium. Finally, the effect of vascular Gd‐DTPA leakage was assessed for scalp tissue, and signal extrapolation as a function of postinjection time was demonstrated to be useful in minimizing the associated errors. Specific recommendations for VASO MRI acquisition and processing strategies are provided. Magn Reson Med, 2009. © 2008 Wiley‐Liss, Inc.