Ultrashort T 2 relaxometry for quantitation of highly concentrated superparamagnetic iron oxide (SPIO) nanoparticle labeled cells

• Published in: Magnetic resonance in medicine 2009-04, Vol.61 (4), p.761-766
• Main Authors: Liu, Wei, Dahnke, Hannes, Rahmer, Juergen, Jordan, E. Kay, Frank, Joseph A.
• Format: Article
• Language: English
• Subjects: cell labeling; superparamagnetic iron oxide nanoparticles; T 2 relaxometry
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.21923

A new method was developed to measure ultrashort T 2* relaxation in tissues containing a focal area of superparamagnetic iron oxide (SPIO) nanoparticle‐labeled cells in which the T 2* decay is too short to be accurately measured using regular gradient echo T 2* mapping. The proposed method utilizes the relatively long T2 relaxation of SPIO‐labeled cells and acquires a series of spin echo images with the readout echo shifted to sample the T 2* decay curve. MRI experiments in phantoms and rats with SPIO‐labeled tumors demonstrated that it can detect ultrashort T 2* down to 1 ms or less. The measured T 2* values were about 10% higher than those from the ultrashort TE (UTE) technique. The shorter the TE, the less the measurements deviated from the UTE T 2* mapping. Combined with the regular T 2* mapping, this technique is expected to provide quantitation of highly concentrated iron‐labeled cells from direct cell transplantation. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.