Detection threshold of single SPIO-labelled cells with FIESTA

Imaging Research Laboratories, Robarts Research Institute, London, Canada.
Magnetic Resonance in Medicine (Impact Factor: 3.4). 02/2005; 53(2):312-20. DOI: 10.1002/mrm.20356
Source: PubMed

ABSTRACT MRI of superparamagnetic iron oxide (SPIO)-labeled cells has become a valuable tool for studying the in vivo trafficking of transplanted cells. Cellular detection with MRI is generally considered to be orders of magnitude less sensitive than other techniques, such as positron emission tomography (PET), single photon emission-computed tomography (SPECT), or optical fluorescence microscopy. However, an analytic description of the detection threshold for single SPIO-labeled cells and the parameters that govern detection has not been adequately provided. In the present work, the detection threshold for single SPIO-labeled cells and the effect of resolution and SNR were studied for a balanced steady-state free precession (SSFP) sequence (3D-FIESTA). Based on the results from both theoretical and experimental analyses, an expression that predicts the minimum detectable mass of SPIO (m(c)) required to detect a single cell against a uniform signal background was derived: m(c) = 5v/(K(fsl) x SNR), where v is the voxel volume, SNR is the image signal-to-noise ratio, and K(fsl) is an empirical constant measured to be 6.2 +/- 0.5 x 10(-5) microl/pgFe. Using this expression, it was shown that the sensitivity of MRI is not very different from that of PET, requiring femtomole quantities of SPIO iron for detection under typical micro-imaging conditions (100 microm isotropic resolution, SNR = 60). The results of this work will aid in the design of cellular imaging experiments by defining the lower limit of SPIO labeling required for single cell detection at any given resolution and SNR.

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Available from: Chris V Bowen, Apr 15, 2014
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    • "To overcome these limitations and, at the same time, to increase the sensitivity, various other imaging methods have been further developed. Among them, True-Fisp (also known as Fiesta) imaging method is noticeable (Heyn et al., 2005). Compared to the conventional gradient echo pulse sequence, this method is more sensitive to the local field inhomogeneity. "
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    • "By refining the MR hardware (magnetic field intensity, receiver coils, imaging pulse sequences), and cell labeling modalities, some authors have detected single cells, not only in vitro [7] [8] but also in vivo [9]. Detection sensitivity of SPIO labeled cells depend on a number of factors, including static magnetic field strength, SNR, pulse sequence and acquisition parameters such as resolution, echo time (TE), and repetition time (TR), as well as details of the SPIO loading and compartmentalization [8]. In [5], a technique was developed to detect SPIO loaded cells using True-FISP (fast imaging with steady precession) imaging. "
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    • "MRS for brain alcohol kinetics E Adalsteinsson et al A custom-made rat brain quadrature head coil was used for excitation and reception of proton signals. An animal gradient insert (Chronik et al, 2000a; Chronik et al, 2000b; Foster-Gareau et al, 2003; Heyn et al, 2005) with a 20 cm bore, a maximum amplitude of 500 mT/m, and a slew rate of 1875 T/m/s was used in the comparison study of i.g. and i.p. infusion. A 3-plane localizer scan (TE/TR ¼ 2.1/54 ms, FOV ¼ 80 mm, 256 Â 128, 5 mm thick, 10 slices/plane) was used for the prescription of coronal fast spin-echo ( "
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