Quantification of superparamagnetic iron oxide with large dynamic range using TurboSPI

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• 作者：James A. Rioux^a ; ^b ; ^{James.Rioux@nrc-cnrc.gc.ca} ; Kimberly D. Brewer^c ; ^{kbrewer@imvaccine.com} ; Steven D. Beyea^a ; ^b ; ^{Steven.Beyea@nrc-cnrc.gc.ca} ; Chris V. Bowen^a ; ^b ; ^{Chris.Bowen@nrc-cnrc.gc.ca}
• 关键词：Quantification ; Relaxometry ; Single point imaging ; Iron oxide ; Static dephasing
• 刊名：Journal of Magnetic Resonance
• 出版年：2012
• 期刊代码：126_10907807
• 类别：ch
• 出版时间：March, 2012
• 卷：216
• 期：Complete
• 页码：152-160
• 文件大小：1201 K

摘要

This work proposes the use of TurboSPI, a multi-echo single point imaging sequence, for the quantification of labeled cells containing moderate to high concentrations of iron oxide contrast agent. At each k-space location, TurboSPI acquires several hundred time points during a spin echo, permitting reliable relaxation rate mapping of large- materials. An automatic calibration routine optimizes image quality by promoting coherent alignment of spin and stimulated echoes throughout the multi-echo train, and this calibration is sufficiently robust for in vivo applications. In vitro relaxation rate measurements of SPIO-loaded cervical cancer cells exhibit behavior consistent with theoretical predictions of the static dephasing regime in the spin echo case; the relaxivity measured with TurboSPI was 10.47 卤 2.3 s^鈭?/mG, comparable to the theoretical value of 10.78 s^鈭?/mG. Similar measurements of micron-sized iron oxide particles (0.96 渭m and 1.63 渭m diameter) show a reduced relaxivity of 8.06 卤 0.68 s^鈭?/mG and 7.13 卤 0.31 s^鈭?/mG respectively, indicating that the static dephasing criterion was not met. Nonetheless, accurate quantification of such particles is demonstrated up to  s^鈭?, with a potentially higher upper limit for loaded cells having a more favorable ratio. Based on the cells used in this study, reliable quantification of cells loaded with 10 pg of iron per cell should be possible up to a density of 27 million cells/mL. Such quantification will be of crucial importance to the development of longitudinal monitoring for cellular therapy and other procedures using iron-labeled cells.