Coregistration of Magnetic Resonance and Single Photon Emission Computed Tomography Images for Noninvasive Localization of Stem Cells Grafted in the Infarcted Rat Myocardium

Abstract

This paper demonstrates the application of mutual information based coregistration of radionuclide and magnetic resonance imaging (MRI) in an effort to use multimodality imaging for noninvasive localization of stem cells grafted in the infarcted myocardium in rats. Radionuclide imaging such as single photon emission computed tomography (SPECT) or positron emission tomography (PET) inherently has high sensitivity and is suitable for tracking of labeled stem cells, while high-resolution MRI is able to provide detailed anatomical and functional information of myocardium. Thus, coregistration of PET or SPECT images with MRI will map the location and distribution of stem cells on detailed myocardium structures. To validate this coregistration method, SPECT data were simulated by using a Monte Carlo-based projector that modeled the pinhole-imaging physics assuming nonzero diameter and photon penetration at the edge. Translational and rotational errors of the coregistration were examined with respect to various SPECT activities, and they are on average about 0.50 mm and 0.82°, respectively. Only the rotational error is dependent on activity of SPECT data. Stem cells were labeled with 111 Indium oxyquinoline and grafted in the ischemic myocardium of a rat model. Dual-tracer small-animal SPECT images were acquired, which allowed simultaneous detection of 111 In-labeled stem cells and of [ 99m Tc]sestamibi to assess myocardial perfusion deficit. The same animals were subjected to cardiac MRI. A mutual-information-based coregistration method was then applied to the SPECT and MRIs. By coregistration, the 111 In signal from labeled cells was mapped into the akinetic region identified on cine MRIs; the regional perfusion deficit on the SPECT images also coincided with the akinetic region on the MR image.

Imaging Stem Cells Implanted in Infarcted Myocardium

“…(113); the autoradiographic confirmation of In-111 signal with the histological staining of stem cells are presented inFigures 3B to 3D. As a step further from…”

Lost signature: progress and failures in in vivo tracking of implanted stem cells

“…Besides advantages and disadvantages of the applied labeling method, 99m Tc with a half-life of 6 h is not applicable for long-term in vivo studies but can be used in higher doses. 99m Tchexamethylpropylene amine oxime ( 99m Tc-HMPAO) is the most commonly applied 99m Tc-containing labeling agent, as it does not affect the cell viability of MSCs (Shen et al 2007). However, after transplantation of 99m Tc-HMPAO, 99m Tc accumulation was observed in the lung and kidney (Barbash et al 2003).…”

Cell delivery and tracking in post-myocardial infarction cardiac stem cell therapy: an introduction for clinical researchers

“…In addition, SPECT/CT has also been tested [90]. Moreover, the application of SPECT/MRI has been explored in an animal study by a mutual-information-based co-registration method by co-registrating the SPECT (111)In signal from labeled cells with the akinetic region identified on cine MRIs [91].…”