Relaxivity of gadolinium complexes detected by atomic magnetometry

Laser atomic magnetometry is a portable and low-cost yet highly sensitive method for low magnetic field detection. In this work, the atomic magnetometer was used in a remote-detection geometry to measure the relaxivity of aqueous gadolinium-diethylenetriamine pentaacetic acid Gd(DTPA) at the Earth's magnetic field (40 μT). The measured relaxivity of 9.7 ± 2.0 s−1 mM−1 is consistent with field-cycling experiments measured at slightly higher magnetic fields, but no cryogens or strong and homogeneous magnetic field were required for this experiment. The field-independent sensitivity of 80 fT Hz–1/2 allowed an in vitro detection limit of ∼ 10 μM Gd(DTPA) to be measured in aqueous buffer solution. The low detection limit and enhanced relaxivity of Gd-containing complexes at Earth's field motivate continued development of atomic magnetometry toward medical applications. Magn Reson Med 66:603–606, 2011. © 2011 Wiley-Liss, Inc.