Stodilka Robert Z, Blackwood Kimberley J, Kong Huafu, Prato Frank S
Imaging Program, Lawson Health Research Institute, University of Western Ontario, Ontario, Canada.
Nucl Med Commun. 2006 Oct;27(10):807-13. doi: 10.1097/01.mnm.0000237987.31597.cf.
A promising SPECT-based method for evaluating stem cells therapy uses (111)In-labelled cells, transfected with a reporter gene. Cells are first transplanted to the infarct, and subsequently interrogated for transgenic expression using a systemic injection of an (131)I-labelled reporter probe. The method is impeded by the physical effects of scatter, (131)I/(111)In cross-talk, and attenuation. We hypothesize that correcting for physical effects improves detection of transgenic expression in transplanted cells when (111)In localization is available.
Canine bone marrow mesenchymal cells (BMMCs), radiolabelled and transfected, were injected into infarcted myocardium. Next, a reporter probe was injected systemically, and 22 SPECT scans were acquired over 20 h. Finally, (99m)Tc-sestamibi was injected and imaged. The animal was killed, the heart sectioned, and counted for (131)I and (111)In in a well-counter ('gold standard'). Canine SPECTs were reconstructed in two ways: with corrections for physical effects and without corrections. The first (111)In reconstruction and the (99m)Tc reconstruction were used to define volumes-of-interest over the transplanted BMMC (VBMMC) and normal myocardium (VNM), respectively.
(131)I reconstructions without corrections for physical effects had negligible differential uptake. With corrections, VBMMC was consistently higher than VNM, demonstrating transgene expression. (131)I had the following VBMMC:VNM activity ratio: without correction for physical effects=0.869; with corrections=1.23; and well-counter=1.21. VNM showed the following (131)I:(111)In activity ratio: without corrections=3.07; with corrections=1.38; and well-counter=1.58.
In dual-isotope SPECT, corrections for physical effects were required to detect transgene expression in cells transplanted into an infarction when localization information was available.
一种基于单光子发射计算机断层扫描（SPECT）的、用于评估干细胞治疗的有前景的方法是使用转染了报告基因的（111）铟标记细胞。首先将细胞移植到梗死区域，随后通过全身注射（131）碘标记的报告探针来检测转基因表达。该方法受到散射、（131）碘/（111）铟串扰和衰减等物理效应的影响。我们假设，当有（111）铟定位信息时，校正物理效应可提高对移植细胞中转基因表达的检测。
将经放射性标记和转染的犬骨髓间充质细胞（BMMC）注射到梗死心肌中。接下来，全身注射报告探针，并在20小时内进行22次SPECT扫描。最后，注射（99m）锝- sestamibi并成像。处死动物，将心脏切片，在井型计数器中对（131）碘和（111）铟进行计数（“金标准”）。犬SPECT图像以两种方式重建：校正物理效应和不校正物理效应。第一次（111）铟重建图像和（99m）锝重建图像分别用于定义移植的BMMC（VBMMC）和正常心肌（VNM）的感兴趣区。
未校正物理效应的（131）碘重建图像中差异摄取可忽略不计。校正后，VBMMC始终高于VNM，表明有转基因表达。（131）碘的VBMMC:VNM活性比为：未校正物理效应=0.869；校正后=1.23；井型计数器测量值=1.21。VNM的（131）碘:（111）铟活性比为：未校正=3.07；校正后=1.38；井型计数器测量值=1.58。
在双同位素SPECT中，当有定位信息时，需要校正物理效应以检测移植到梗死区域的细胞中的转基因表达。
