Gadodiamide T1 relaxivity in brain tissue in vivo is lower than in saline

✍ Scribed by Stephen Pickup; Andrew K. W. Wood; Harold L. Kundel

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 330 KB
• Volume: 53
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.20336

✦ Synopsis

Abstract

In vivo measurements of gadodiamide (Gd‐DTPA‐BMA) T~1~ relaxivity were performed at 4.7 T in injured and normal rat brains. Cerebral lesions were induced in nine rats by a localized freezing method. T~1~ maps of the lesions were generated before and after injection of Gd‐DTPA‐BMA (0.1–0.6 mmol/kg). Samples of normal and necrotic brain were collected postmortem; the wet and dry weights were determined, and Gd content was measured by inductively coupled plasma mass spectroscopy. The in vivo relaxivity was determined by a linear fit of a plot of the change in relaxation rate following injection of the contrast agent as a function of Gd content. This analysis yielded a relaxivity in the injured brain of 2.8 sec^−1^ mmol^−1^ kg tissue water at 36°C. The water weight fraction was 0.90 ± SD 0.02 wt/wt in injured brain and 0.79 ± 0.02 in normal brain. Relaxivity measurements were also performed on solutions of Gd‐DTPA‐BMA (0.0–0.6 mmol) and albumin (0–30% wt/wt) in normal saline at room and physiologic temperatures. The relaxivity in the albumin/saline increased with increasing solids content with values of 4.0–4.9 sec^−1^ mmol^−1^kg at 21°C and 3.4–4.5 sec^−1^ mmol^−1^ kg at 37°C. The relaxivity of the tissues differed significantly from that of the saline solutions of comparable solids content, suggesting that the solids content of a tissue is not the only factor that determines in vivo relaxivity. Magn Reson Med 53:35–40, 2005. © 2004 Wiley‐Liss, Inc.